IFPRI Discussion Paper 02178 
April 2023 
Is Irrigation Fit for Purpose? 
A Review of the Relationships between Scheme Size and Performance 
of Irrigation Systems 
Nancy McCarthy 
Claudia Ringler 
Mure Agbonlahor 
A.B. Pandya 
Biniam Iyob 
Nicostrato Perez 
Natural Resources and Resilience Unit 
INTERNATIONAL FOOD POLICY RESEARCH INSTITUTE 
The International Food Policy Research Institute (IFPRI), a CGIAR Research Center established in 1975, 
provides research-based policy solutions to sustainably reduce poverty and end hunger and malnutrition. 
IFPRI’s strategic research aims to foster a climate-resilient and sustainable food supply; promote healthy 
diets and nutrition for all; build inclusive and efficient markets, trade systems, and food industries; 
transform agricultural and rural economies; and strengthen institutions and governance. Gender is 
integrated in all the Institute’s work. Partnerships, communications, capacity strengthening, and data and 
knowledge management are essential components to translate IFPRI’s research from action to impact. 
The Institute’s regional and country programs play a critical role in responding to demand for food policy 
research and in delivering holistic support for country-led development. IFPRI collaborates with partners 
around the world.  
 
AUTHORS 
Nancy McCarthy (nmccarthy@leadanalyticsinc.com) is CEO of Lead Analytics. 
 
Claudia Ringler (c.ringler@cgiar.org) is Director of the Natural Resources and Resilience Unit of the 
International Food Policy Research Institute (IFPRI), Washington DC. 
 
Nicostrato Perez (n.perez@cgiar.org) is a Research Fellow in IFPRI’s Natural Resources and Resilience 
Unit, Washington DC. 
 
Mure Agbonlahor (agbonlahoru@africa-union.org) is Senior Agricultural Production and Marketing 
Officer at the Africa Union Commission, Addis Ababa, Ethiopia. 
 
A.B. Pandya (abpandya@yahoo.co.uk) is Secretary General of the International Commission on Irrigation 
and Drainage (ICID), New Delhi, India. 
 
Biniam Iyob (biyob@usaid.gov) is Senior Policy Advisor, Office of Policy, Analysis and Engagement, 
Bureau for Resilience and Food Security, U.S. Agency for International Development, Washington DC. 
 
 
 
 
 
 
 
Notices  
 
1 IFPRI Discussion Papers contain preliminary material and research results and are circulated in order to stimulate discussion and 
critical comment. They have not been subject to a formal external review via IFPRI’s Publications Review Committee. Any opinions 
stated herein are those of the author(s) and are not necessarily representative of or endorsed by IFPRI.  
 
2 The boundaries and names shown and the designations used on the map(s) herein do not imply official endorsement or 
acceptance by the International Food Policy Research Institute (IFPRI) or its partners and contributors. 
 
3 Copyright remains with the authors. The authors are free to proceed, without further IFPRI permission, to publish this paper, or any 
revised version of it, in outlets such as journals, books, and other publications. 
 
 
Abstract  
Irrigation is increasingly being called upon to help stabilize and grow food and water security in the face 
of multiple crises; these crises include climate change, but also recent global food and energy price crises, 
including the 2007/08 food and energy price crises, and the more recent crises triggered by the COVID-
19 pandemic and the war on Ukraine. While irrigation development used to focus on public, large-scale, 
surface- and reservoir-fed systems, over the last several decades, private small-scale investments in 
groundwater irrigation have grown in importance and are expected to see rapid future growth, particularly 
in connection with solar-powered pumping systems. But is irrigation ‘fit-for-purpose’ to support 
population growth, economic development, and multiple food, energy and climate crises? This paper 
reviews how fit-for-purpose irrigation is with a focus on economies of scale of surface and groundwater 
systems, and a particular examination of systems in Sub-Saharan Africa where the need for expansion is 
largest. The review finds challenges for both larger surface and smaller groundwater systems in the face 
of growing demand for irrigated agriculture and dwindling and less reliable water supplies. To support 
resilience of the sector, we propose both a holistic design and management improvement agenda for 
larger surface systems, and a series of suggestions to improve sustainability concerns of groundwater 
systems. 
 
The design of large-scale irrigation systems, and particularly those that are built and managed to support 
basic food security, needs to include more flexibility for farmers to adjust cropping patterns to today’s 
more rapidly changing food prices, and agricultural input costs. Large-scale systems that support smaller 
irrigated areas with more decentralized management have shown most promise, as they combine lower 
individual design cost per system unit with more flexible irrigation management. In water-scarce systems, 
the design should include low-cost, precision water application systems to address increased competition 
for limited water resources, actively support multiple uses of irrigation water (such as livestock watering 
and domestic uses) and should ensure timely delivery of water supplies. It is unrealistic to expect 
recovery of irrigation investment costs in systems that limit farmers to growing food security crops.  
 
In groundwater systems, land size and growing costs of digging deeper wells, as well as associated higher 
pumping costs, are key investment considerations that might price smaller farmers out of irrigation 
development opportunities. For groundwater systems, more research is needed to locate “weather-
independent” groundwater resources, that is groundwater sources that are renewable and support an entire 
production season. Moreover, for groundwater development to flourish the development of regulatory and 
management frameworks that enable smallholders to benefit from irrigation beyond the near term will be 
key. Additionally, support to accessing technologies needs to improve; requiring scale economies in 
equipment and other services. While large-scale systems are often less dependent on area rainfall than 
smaller systems, providing greater resilience to weather extremes, smaller surface and groundwater 
systems are often located in closer proximity to input and output markets that increase incentives for 
farmers to make a profit. There is no doubt that irrigation will need to expand in places where water 
resources are accessible, food insecurity levels critical and climate extremes render rainfed systems 
increasingly challenging. Given the growing number of recent crises and the worsening levels of 
undernutrition over almost a decade, it is essential that the sector’s full potential is developed, while 
increasing sustainability and reducing environmental externalities.  
 
But the future of irrigation cannot repeat the past; systems will need to be developed with greater fit-for-
purpose, that is, more flexibility of cropping patterns, with more incentives and agency for farmers, 
including women farmers, and with more productive water use in mind. Sustainable irrigation contributes 
greatly to reducing global, national and local food prices and, if intentionally designed and managed, can 
shield farmers from energy price fluctuations as well thus growing resilience to multiple crises.  
 
iii 
 
 
 
Acknowledgments  
This paper was made possible through support provided by the Office of Policy, Analysis and 
Engagement, Bureau for Resilience and Food Security, U.S. Agency for International Development, 
under the terms of the Strengthen Evidence-based Policy Making in Africa, Asia, Latin America and the 
Caribbean (IFPRI/ReSAKSS), Award # AID-BFS-I0-17-00001, and under the umbrella of the NEXUS 
Gains initiative that works at the critical intersection of food, energy, and water security while preserving 
the ecosystems underlying food systems in selected transboundary river basins. 
 
The opinions expressed in this publication are those of the authors and do not necessarily reflect the views 
of the CGIAR or the U.S. Agency for International Development. 
iv 
 
 
 
1. Introduction 
Irrigation development has been essential for both people and the planet. Irrigation has increased food 
production, productivity and therefore increased the availability and access to food by lowering prices of 
key staple crops, particularly rice and wheat.  Irrigation has also been essential for the production of 
other key crops, such as sugarcane, maize, fruits and vegetables and cotton (Ringler and Zhu, 2015, 
Figure 1). Irrigation has thus been an important contributor to reducing the number of people at risk of 
hunger.   
Figure 1 Water consumption of key crops from irrigation and field precipitation, in billion cubic meters, 
calculated for 2020 
 
Source: Authors based on IFPRI-IMPACT simulations. 
 
Through higher yields and through more intense use of existing crop areas, in the form of double- or 
triple-cropping, irrigation has reduced pressure to expand land areas into fragile tropical forest and 
savannah systems. Without irrigation, dramatic additional conversion of forest to crop areas would have 
been required to achieve current food production levels (Evenson and Rosegrant 2003). Our own 
analysis, developed as part of this paper, finds that if no additional irrigation development takes place 
during 2010-2050 beyond maintenance of current systems, an additional 32 million hectares (ha) of 
forest and other lands would need to be converted to crop production, an area similar to the arable area 
of Ukraine.  
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Asia accounts for about 70% of irrigated area, while the share of area irrigated is lowest in Sub-Saharan 
Africa (Figure 2). While rainfed agriculture dominates in most countries, food production in some 
countries, such as Egypt and Pakistan, relies almost entirely on access to irrigation. 
 
Figure 2: Distribution of irrigated area across the globe  
 
Note: Data from various recent years. 
Source: Authors based on FAO AQUASTAT data. 
 
Irrigation development can, however, not continue as in the past. Population and economic growth have 
multiplied demands on quasi-static freshwater resources, with growth in the domestic and industrial 
sectors, as well as for renewable energy production, outpacing growth in the agriculture sector 
(Rosegrant et al. 2002). There are also increased demands for preserving at least some environmental 
uses of water to counteract rapid freshwater and other biodiversity loss. Environmental water uses are 
critical as freshwater-related ecosystems host around one third of all vertebrate species and 10 percent 
of all species in wetlands, rivers, aquifers and lakes, all severely threatened by water depletion, pollution 
and other degradation (Stayer and Dudgeon, 2010).  Population and economic growth factors are not 
only increasing demands for domestic, industrial and environmental uses of water but are also putting 
pressure on developing additional irrigation to meet increases in food demand.  Irrigation is also 
increasingly called upon to stabilize food production in the face of growing climate variability and 
climate change.  Finally, water and food systems need to jointly adjust to other crises, such as the 
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COVID-19 pandemic, which has interrupted global supply chains, leading to calls for increased local and 
national food self-sufficiencies supported by irrigation, or the war on Ukraine which has led to energy 
and food price spikes and the disruption of wheat and vegetable oil markets and further calls for more 
localized food production, even in countries with limited land and water resources.  As an example, to 
address wheat import shortages as a result of the war on Ukraine, Egypt announced plans to expand 
irrigated wheat area by 2 million acres (AL Monitor, March 3, 2022).  
Irrigation is considered a key climate action area, which is reflected in the many nationally determined 
contributions that propose the expansion of irrigation as an adaptation strategy. As an example, 16 out 
of 20 Feed-the-Future countries list irrigation as an adaptation and sometimes also as a mitigation 
strategy (in the latter case, focusing on solar irrigation or the system of rice intensification).  
At the same time, all of these crises, and particularly climate change, affect the ability of irrigation to 
support food security and various other water uses. As an example, Biemans et al. (2019) note that in 
the pre-monsoon season up to 60 percent of irrigation withdrawals in the Indus River Basin depend on 
snow and glacier melt, accounting for 11 percent of crop production. While dependence on glacier melt 
is more limited in the Ganges basin, they find that a total of 129 million farmers in both basins depend 
on meltwater that will eventually dry up with advancing climate change. Other river systems depending 
on glacier flows from the Himalayan Water Tower include the Yangtze and Brahmaputra (Immerzeel et 
al. 2010). 
At the same time, irrigation contributes to, and can even be the origin of local conflicts and some 
diseases. Examples are local conflicts between pastoralists and irrigators over areas that pastoralists 
used for grazing in the past but are now being used for dry-season irrigation (for example, Mbonile, 
2005). Moreover, in some cases, irrigation water has been a source of water harboring new diseases, 
such as the West Nile virus or malaria carrying mosquitoes (for example, Mangani et al., 2022).  
Given these new realities, irrigation development, more than ever before, needs to be “fit-for-purpose.” 
With food insecurity, water shortages and climate extreme events on the rise, irrigation needs to jointly 
contribute to food security and nutrition, to income generation and poverty alleviation, and to climate 
resilience and environmental sustainability by using water more efficiently. The ability of the irrigation 
development and practice to meet these triple roles will determine how “fit-for-purpose” it is.  We know 
that many previous irrigation investments have not delivered hoped-for benefits, often leading costly 
failures (Higginbottom et al., 2021; McCarthy & Winters, 2022). Moreover, levels of food insecurity, 
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economic and other crisis and climate extremes also affect policy decisions on investing or not in 
irrigation as well as on the types and size of irrigation that will be promoted.   
We posit that irrigation investments that take into account irrigators’ preferences and constraints – are 
more likely to be sustained.  However, oftentimes there is a mismatch between the government and 
donors’ stated purpose (on which estimated benefits are calculated) and what the irrigators prefer given 
their constraints.  So, assumptions driving irrigation system investments are often not met.  A major 
aspect to consider is the size of the investment, because in many irrigation systems, there are likely to 
be both economies of scale and scope over certain investment decisions, and diseconomies over others.  
Different types of irrigation are also likely to be linked to different non-irrigation benefits from irrigation 
development, such as livestock watering or domestic uses of water.  
Choices on system size, water delivery technologies, and management structures will affect the extent 
to which irrigators’ benefit from the system and their incentives to contribute to system performance.  
There is a gap in empirical evidence on the link between irrigation system size and performance, and the 
link between performance and the investors’ stated purpose of the system fills a gap in the literature.  
Here, we attempt to partially fill that gap. 
Following a review of the evolution of major types of irrigation systems since the 1970s, we discuss 
evidence on the economies (or diseconomies) of scale and scope in irrigation system investments. This is 
followed, in turn, by an assessment of the performance of irrigation systems of different sizes and 
scopes. In the analysis, we consider multiple benefit streams and impacts from irrigation, including for 
poverty alleviation, environmental sustainability, food security and nutrition. 
2. Evolution of types and sizes of irrigation systems 
We distinguish between two major types of systems: surface and groundwater systems. 
2.1 Surface water systems 
Surface water schemes are generally owned and operated by the government, by irrigator associations, 
and to a lesser extent, by private businesses.  Although there are differences in technologies and 
institutions for water storage and delivery amongst the different surface water schemes, they are 
sufficiently similar to consider likely economies of scale in the construction, operation and maintenance 
of such schemes.   
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Several authors have described the “build-deteriorate-rebuild” cycle that characterize many government 
and donor-funded surface-water irrigation schemes in both sub-Saharan Africa (SSA) and Southeast Asia 
(SEA) during the 1970s and 1980s (Alam, 1991; Higginbottom et al., 2021; Inocencio et al., 2007; Kikuchi 
et all., 2021; Shah, 2011; Suhardiman & Giordano, 2014).  Evidence suggests that this cycle was in part 
caused by the particularities of large-scale systems, many of which were requested by national 
governments to grow staple crops with the goal of increasing food security (Darko et al., 2016), rather 
than for profit maximization. State ownership of irrigation and land resources, and limited control of 
farmers over cropping schedules and timing and quantity of water access, moreover, limited the 
incentives of irrigating farmers to improve water productivity (Meinzen-Dick, 2014). The relatively 
greater ease of multilateral banks of investing in rehabilitating systems over financing new systems as 
well as the limited generation of irrigation service fees has also contributed to the neglect of 
maintaining surface systems by national irrigation agencies.  Other surface investments failed or 
deteriorated due to the focus on expensive, complex imported technology that could not readily be 
maintained or repaired on site (Darko et al., 2016) and possibly because of the capture by outside 
investors or national elites of irrigated land (Adamczewski et al., 2015).  Yet other factors that 
contributed to the secular decline in publicly funded surface irrigation projects included growing 
environmental concerns over water depletion and the adverse impacts of large reservoirs associated 
with large-scale irrigation systems on aquatic ecosystems, such as migrating fish, and downstream water 
users (Wisser et al., 2013; World Commission on Dams, 2000).   
Svendsen and Rosegrant (1994) note that during the 1980s external support to large irrigation 
development in Asia, the region with by far the largest developed area, declined by half compared to 
levels in the 1970s. Decline in funding, driven by declining food prices and growing investment costs, 
directly translated into a decline in irrigated area growth from 2.0-2.5 percent per year in the 1970s to 
less than 0.5 percent per year in the 1980s.  
This then led to a focus on investments in smaller-scale schemes in the 1990s, in line with lower food 
prices and a more limited set of areas that could be profitably developed for irrigation.  But these too 
followed a similar cycle and by the turn of the millennium many donors had dramatically reduced 
investments in surface water schemes (Fanadzo & Ncube; 2018; Inocencio et al., 2007; van Koppen et 
al., 2017; Venot et al., 2012).   
Despite these documented difficulties, given the experience of the 2007/2008 food price spikes, 
continued and growing rates of poverty and food insecurity, and climate change related increases in the 
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frequency and severity of weather events, governments and donors have renewed interest in both small 
and large irrigation schemes. As an example, the World Bank (2013) has called for a doubling of irrigated 
area in Africa and the G-8 Statement on Global Food Security1 asked for substantial investment in food 
production on the continent including through expanding irrigation.  
2.2 Groundwater irrigation 
Groundwater irrigation relies on extracting water from underground, either shallow groundwater or 
deeper aquifer sources.  Individual groundwater irrigation took off with the advent of affordable, 
individual pump sets and cheaper well drilling technology in the 1970s and 1980s.  Groundwater 
irrigation expanded most rapidly in South Asia as a result of the availability of high water tables due to 
runoff and seepage and percolation from canal systems; and due to electricity subsidies in several Indian 
states (Lee et al., 2018; Shah, 2011; Shivakoti et al., 2019; Sikdar, 2019; Mukherji, 2022).  Groundwater 
extraction’s negative environmental impact, such as groundwater mining, that is extraction of 
groundwater beyond return flows, soon became apparent (Stratton Syre and Taraz, 2019).  
Groundwater irrigation has also expanded in SSA, although at a slower pace (c.f. Cobbing & Hiller, 2019; 
Gaye & Tindimugaya, 2019; Laube et al., 2008; Pavelic et al., 2013; Ringler et al., 2020; Shah et al., 2020; 
Villhoth, 2013).  Policies that favored the expansion of groundwater in Asia included reducing or 
eliminating tariffs on pumping equipment, the subsequent development of domestic production of 
pumping equipment in some Asian countries, the fact that large-scale surface water schemes were 
inefficient, and the provision of fuel subsidies or free electricity for pumping (Balasubramanya & Lele, 
2021; Shah et al., 2020).  Given population densities and the longer history of intensive groundwater 
irrigation, many countries in SA are concerned with the negative impacts of over-extraction, particularly 
negative impacts on the environment, land subsidence, and water quality.  In SSA, however, with lower 
population densities, and shorter and slower history of groundwater irrigation, many researchers argue 
that poverty and food insecurity concerns should shift the overly cautious approach to groundwater 
irrigation toward the adoption of policies and investments that support a more rapid expansion of 
groundwater use (Cobbing & Hiller, 2019). 
Groundwater irrigation generally affords more flexibility for farmers, since they can control the timing of 
extraction as well as the crops they choose to grow. On the other hand, well drilling and pumping can be 
highly expensive. While most groundwater development has been smallholder driven, there are still 
 
1 https://georgewbush-whitehouse.archives.gov/news/releases/2008/07/20080708-6.htm l 
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significant gaps between relatively richer smallholders who have been able to draw down groundwater 
sources and smallholders who cannot afford deeper wells.  The most recent technological change of 
solar-driven motor pumps is expected to further accelerate groundwater irrigation, particularly if initial 
high capital costs can be overcome (Xie et al., 2021). The key challenge with groundwater irrigation is its 
governance due to the invisibility of the resource, and the large numbers of smallholder farmers that 
depend on groundwater systems.  Progress in groundwater governance is urgently needed to avoid 
large groundwater table declines in local areas.  
Economies of scale and scope of groundwater systems are generally different from those applicable to 
surface water schemes, and relate to size of pumping equipment available to farmers in the market, and 
to groundwater irrigation-related service provision, where service costs decline as the number of 
irrigators increase.   
3.  Economies and Diseconomies of Scales 
It is useful to consider the conditions under which economies, or diseconomies, of scale and scope arise, 
and their influence on investment decisions.  For surface water schemes, economies of scale may 
operate at all stages of irrigation development and operations, and to a lesser extent, management.  
While economies of scale are well-documented in terms of construction, the economies of scale in 
irrigation scheme design have been less well documented. Inocencio et al. (2007) note that professional 
human resources are indivisible, scarce resources that drive economies of scale in irrigation schemes.  
Building on the Inocencio et al. (2007) work, Fujiie (2011) document very large economies of scale in 
design, noting that in most cases, design expenditures go towards high opportunity cost human 
resources, often recruited internationally.   
There can be large economies of scale in operations and management as well, though these likely differ 
depending on the management structure. As an example, a public irrigation management entity, a 
parastatal firm, or Water User Associations might have full O&M responsibilities, or responsibilities can 
be shared between WUAs, the government or the parastatal firm.  For WUA managed schemes, 
evidence suggests that economies of scale will operate over operations (such as administrative and 
financial tasks), and potentially maintenance and repair activities per unit of irrigable area.  However, 
transactions costs associated with coordination, cooperation, monitoring and enforcement may actually 
increase at an increasing rate (diseconomies of scale) and thus may overwhelm economies of scale in 
other O&M activities at larger schemes.  For public irrigation management and parastatals, there can 
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also be administrative and financial economies of scale in managing as scheme size increases; such as 
costs of maintenance and repair. This is particularly true if only larger schemes can support a full-time 
on-site manager and/or investments in equipment needed for maintenance.  However, public irrigation 
managers and parastatals might face challenges communicating with farmers who often do not trust 
government agencies, as compared to WUAs, and as such transaction costs on collecting irrigation fees 
and information on system breakage might be even higher with parastatal management as scheme size 
increases.  Joint management seeks to harness economies of scale in administrative, financial, 
maintenance and repair works at the main and often secondary infrastructure levels, while minimizing 
diseconomies of scale in monitoring, coordination and cooperation by shifting responsibility for O&M of 
tertiary infrastructure to the WUA level.  In very large schemes, even WUAs are often broken into 
smaller blocks of user associations, to minimize diseconomies of scale.   
For groundwater, the main issues related to scale are really only relevant for small landholdings, where 
unit costs of irrigation equipment can be relatively cheaper as landholdings increase.  A related issue 
concerns threshold cropland sizes.  The costs (and risks) of drilling a well, investing in a pump and 
constructing water delivery structures, combined with operating and maintenance/repair costs, means 
that both fixed and variable costs may swamp gross revenues for farmers with landholdings below a 
certain threshold, especially those that grow relatively low value crops (Shah et al., 2020).  
Unsurprisingly, many studies have shown that costs of individual irrigation equipment (or lack of access 
to finance) are the key factor reducing uptake of solar and other irrigation pumps (for example, Xie et 
al., 2021). 
Diseconomies of scale in groundwater management often result once over-extraction becomes a 
concern.  The SA experience, as well as experiences from other countries around the world, documents 
that when extraction rates become high enough for water tables to drop, land to subside, and water 
quality to decline (pollution, salinity), there are significant diseconomies of scale in managing this 
“invisible” resource across the relevant area, e.g. aquifer.  The more users within a given, contiguous 
aquifer, the more difficult it is to negotiate, coordinate, monitor and enforce extraction rates.  
Technology, especially for monitoring groundwater observation wells, continues to advance and become 
less expensive which can help alleviate these costs.  But enforcement of groundwater management has 
been challenging all over the world. While one would not want to be accused of being overly cautious, it 
stands to reason that resources should be dedicated to understanding what sustainable management of 
the aquifer would look like as the number of irrigators increase in the SSA context, to avoid the negative 
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consequences of over-withdrawals in many SA contexts, but also in parts of China, Iran, and the United 
States, among others. 
The stated purpose of the irrigation system investment can influence the type of irrigation system 
investment (surface water, groundwater), and the extent to which assumptions underpinning the stated 
purpose can then affect system performance.  For instance, achieving national food security has been 
the stated purpose of a number of investments in large-scale surface water irrigation scheme 
investments, primarily for rice production (Kenya, Mali, Senegal, most Asian systems). For schemes with 
a national food security purpose, the primary assumption is that meeting that objective is possible while 
at the same time guaranteeing that irrigators’ returns are sufficient to attract farmers to irrigate across 
all relevant seasons, and participate in maintenance as required.  Such schemes tend to be inflexible 
with respect to crop choices (often rice only), in timing of cropping activities, in water access, and in 
method of aggregation, amongst others (for example, Office du Niger, Mali).  Where such schemes are 
not well managed (water delivery is unreliable; timing of complimentary services (land preparation) and 
inputs (fertilizer) are not available or delayed; or primary and secondary infrastructure not maintained, 
farmers may choose not to irrigate and to not participate in maintenance of tertiary infrastructure.  This 
then leads to the build-deteriorate-rebuild cycle.   
On the other hand, food security of irrigating households is often the stated purpose for supporting 
many individual investments in groundwater (Ethiopia, Ghana, Zambia, India, etc.).  For food security at 
the household level, the primary assumption is that the benefits from producing irrigated crops for sale 
or home consumption, such as vegetables, are high enough to justify the costs.  Where pumping 
technology and diesel costs are high and/or irrigators do not have the resources or skills to maintain the 
pumping equipment, or cannot obtain complementary inputs, the incentives to adopt and sustain 
irrigation might be limited.  For investments that seek to increase nutritional quality of household diets, 
the primary assumption is that the irrigation technology and other conditions are suitable for producing 
more nutrient-dense crops for home consumption or irrigated crops that can be sold on the market with 
funds being used to purchase other food items. Women play important roles in ensuring that irrigated 
production supports household nutrition.  Manual water application, which is often used in household 
irrigation application, is often very labor intensive, which dissuades adoption of irrigation beyond very 
small plots.  In other cases, the stated purpose is to support the adoption of high-value crops for sale.  
Due to economies of scope in aggregating crop production for sale, such investments would need to be 
large enough to attract purchasers, and often require complementary investments in market-related 
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infrastructure (for example, tomatoes for Ghana and Mozambique; and onion and tomatoes in Niger 
and Nigeria).    
Groundwater irrigation, which allows for the farmer to choose what and when to cultivate can also help 
farm households achieve more diverse and nutritious diets (Namara et al., 2014; Shah et al., 2013; van 
Koppen, Hope, & Colenbrander, 2013).  However, as with irrigation scheme participation, a number of 
authors also document that it is generally wealthier farmers who invest in groundwater equipment 
(Kafle et al., 2022 for Ethiopia; Giordano et al., 2012 for Ghana; Shah et al., 2013 covering 9 countries in 
SSA).  To ensure equitable access to groundwater resources, Shah et al. (2020) note that government 
support to groundwater irrigation expansion was very strong in many South Asian countries, including 
enabling imports of affordable pumps and tubewells, and even free drilling.  Free drilling would 
considerably lower the costs and the risks faced by smallholders where siting the well is difficult.  The 
authors argue that different packages of subsidies and government investment and services helped 
many countries in South Asia to avoid elite capture of groundwater resources.  Of course, fuel subsidies 
also increase access by poorer farmers but can also have severe negative consequences on the 
environment from overextraction (Shah et al., 2020; Balasubramanya & Lele, 2022; Chauduri et al., 2021 
and references cited therein).  
For high value crops, the primary assumption is that irrigators are sufficiently integrated into the value 
chain so that they can purchase the necessary complimentary inputs, produce high quality crops, have 
sufficient bargaining power and reliable connections with purchasers.  Schemes with high-value crops 
and national food security purposes often also expect irrigators to crop multiple seasons within the year, 
which is based on the assumption that irrigators’ opportunity costs of allocating labor to irrigation are 
relatively low throughout the seasons.  Where irrigators have high opportunity costs of labor in the dry 
season(s), cropping rates may fall well below the project implementers’ expectations. 
The stated purpose may also be to specifically support household nutrition and women’s bargaining 
power; these investments tend to also focus on supporting the adoption of relatively low-cost irrigation 
technology for home gardens.  The Irrigation Innovation Laboratory for Small-Scale Irrigation (ILSSI) has 
identified several potential pathways through which irrigation can positively influence food security, 
nutrition, and health outcomes, including 1) a production pathway, 2) an income pathway, 3) a water 
supply path-way, and 4) a women’s empowerment pathway, while also noting a fifth, negative pathway 
that links irrigation to water pollution and disease via the application of fertilizers and pesticides and via 
supporting vector-borne diseases, such as malaria or schistosomiasis, respectively (Domènech, 2015; 
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Passarelli et al., 2018). Several studies undertaken with support of ILSSI have confirmed the existence of 
the production and income pathways (for example, Baye et al., 2022; Mekonnen et al., 2022; Mekonnen 
et al., 2019) whereas increased availability of irrigation technology and irrigation water sources do not, 
on their own, lead to increased women’s empowerment (Bryan and Mekonnen, 2023) or improved 
WASH outcomes.  
4.  Economies and Diseconomies of Scale: Evidence from the literature 
4.1. Economies of Scale for Surface Water Schemes 
Inocencio et al. (2007) collected data on 314 irrigation schemes based on information provided in 
project completion reports for irrigation projects funded by the World Bank, the African Development 
Bank (AfDB), and the International Fund for Agricultural Development (IFAD), covering schemes in SSA, 
SEA, the Middle East and North Africa (MENA), Latin America and the Caribbean (LAC), SA and East Asia.  
Data were available on total project cost, irrigated area, whether new construction versus rehabilitation, 
time and cost overruns, whether the primary crops to be grown were staples or high-value cash crops 
and major irrigation source and delivery mechanisms, amongst other variables.  Many of the projects 
actually consisted of constructing and rehabilitating multiple schemes, so the authors collected 
information on the total irrigation scheme area and the average size of sub-schemes.  From the 
information, the authors constructed the economic internal rate of return (EIRR) for each project.  The 
authors found that irrigation projects in SSA tended to be much smaller than those in other regions, but 
that staff weeks spent on project development and implementation supervision were about the same, 
indicating high, and relatively fixed, professional costs per hectare irrigated for SSA projects.  On the 
other hand, SSA projects did not face higher time and cost overruns, compared to other regions, but 
these were relatively high in all cases.  Nonetheless, SSA projects faced the highest total and hardware 
unit costs – more than double unit costs of SEA projects.  The authors then define “success” projects as 
those with an EIRR greater than 10% and “failure” projects as those with EIRRs less than 10%.  The 
results show that average total costs for SSA are close to other regions.  But, costs of failed projects are 
much higher than other regions, and a lower proportion of projects are deemed as successful, though 
SSA and SEA are relatively similar at 56% and 59%, respectively.  Finally, simple descriptive statistics 
indicate that successful projects are likely to be far larger than failure projects in both SSA and all other 
regions, likely in part due to the fact that such projects have lower unit costs (project size and unit total 
costs have a correlation coefficient of -.77).  The regressions of EIRR and project costs reinforce the 
11 
 
 
 
descriptive analysis. Yet, it is difficult to determine if economies of scale in irrigation scheme size were at 
play because many projects included multiple activities, including construction of a number of new and 
rehabilitated schemes of different sizes under one project.  They use both project size and average size 
of irrigation schemes; combined, the results suggest that larger projects with several, smaller-sized 
irrigation schemes lead to higher EIRR’s2.  Finally, the regression results suggest that schemes where the 
primary crops grown are high-value cash crops perform better than those where staple crops are mainly 
grown.   
Building on Inocencio et al. (2007), Fujiie et al. (2011) also gather data from project completion reports, 
but focus only on SSA projects.  Because schemes in SSA tend to be smaller than in other regions, the 
authors consider schemes to be “large” if they are over 100 hectares (ha), small if they fall between 5-
100 ha3.  The authors also use the EIRR as their measure of project performance.  As in Inocencio (2007), 
the authors use project size to examine returns to scale.  One of the more interesting results is that both 
small and large projects exhibit decreasing unit costs when looked at separately.  Thus, they find 
economies of scale within each category, but also diseconomies across scales.  As noted in footnote 2 
however, these results should be interpreted cautiously due to very few observations for small projects 
that are concentrated in one country and implemented by one donor; almost all projects are in the large 
category.  The authors then look at construction cost, high-value overhead cost (professionals involved 
in design and supervision, for example), and low-value overhead costs.  The observed relationship 
between and within scheme size is reflected in construction and overhead costs.  However, the share of 
overhead costs to total costs is much higher for small versus large projects.  Their evidence also suggests 
that the economic viability of irrigation schemes under 10,000 ha is very weak, and “it appears kind of 
crazy” to invest in projects between 100 – 1000 ha (Fujiie et al., 2011, page 51).  For small projects to be 
economically viable, overhead costs must be driven down, consistent with results found in Inocencio et 
al. (2007).  Unfortunately, Fujiie et al. (2011) did not include data on primary crops grown, or other 
metrics of project purpose.   
 
2 The authors use the Fadama project in Nigeria as an example of successful large project funding many small-scale 
irrigation investments, mainly tubewell-based systems to secure water from shallow aquifers.  However, 
subsequent studies found much smaller benefits in general, and declining benefits over time (Dayo et al., 2020; 
Villacis et al., 2022).  
3Unfortunately, there are just four small projects and seven micro projects; with 8 projects being implemented by 
JIICA in Uganda, which limits the generalizability significantly. 
12 
 
 
 
A potentially important cost missing from the analyses in Inocencio et al. (2007) and Fujiie et al. (2011) 
are environmental costs associated with poor design and/or management, both within the irrigation 
scheme and externally.  Negative environmental impacts of surface water schemes, particularly those 
that rely on large reservoirs created by dams on major rivers, include reduced sediment transport 
leading to erosion on lands downstream (Lebdi, 2016; Penvenne, 1996), soil salinization (FAO, 2011; 
Lebdi, 2016; Rengassamy, 2006), loss in biodiversity (Avellán et al., 2018; Majoro et al., 2016), greater 
intensity of use of fertilizer and pesticides that negatively impacts water quality (Lefore et al., 2019), 
and, higher rates of water-borne or related diseases (Derne et al., 2015; Majoro et al., 2016).  Though 
we have found no studies that explicitly compare negative environmental impacts across different 
surface water scheme sizes, it is likely that the larger schemes that significantly divert and store water 
generate relatively greater negative environmental impacts. 
4.2.  Economies of Scale for Groundwater Irrigation 
A number of studies review the evidence on groundwater volumes and current withdrawal rates, and 
most show that almost all countries in SSA have significant potential to expand groundwater irrigation, 
though determining the extent of “optimal” withdrawals is hampered by severe lack of data at higher 
resolutions (Cobbing & Hiller, 2019; McDonald et al., 2012; Pavelic et al., 2013; Wijnen et al., 2018; Xie 
et al., 2014; You et al., 2011).  Pavelic et al. (2013) evaluate the groundwater potential for 13 countries 
in SSA associated with the Alliance for a Green Revolution in Africa (AGRA), taking into account water 
needs for irrigation as well as domestic use, industrial use, livestock and ecosystem services.  The 
authors note that groundwater irrigation constitutes less than 0.5% of recharge currently across the 13 
countries, so even with conservative assumptions, they argue that groundwater irrigation can be 
developed on 13.5 million ha – a dramatic expansion from the 109,000 ha estimated to be irrigated by 
groundwater at that time.  Many authors argue that the vast groundwater resources combined with 
high poverty and vulnerability mean that policies and programs should rapidly foster extensive 
development while simultaneously developing the monitoring, research capacity, and institutional 
frameworks to manage groundwater resources at local (basin) levels (Cobbing & Hiller, 2019; Ringler et 
al., 2021; Xu et al., 2019).  Simultaneously expanding groundwater irrigation and developing the 
regulatory and management framework is essential to enable smallholders to benefit from irrigation 
and to reduce or avoid problems associated with over-use.  Given the lack of functioning regulatory 
systems, negative impacts of overdrafting (higher pump costs, lower water quality, etc.) have also 
already been felt in local areas of SSA despite limited overall development, such as Mauritania and 
13 
 
 
 
Djibouti (Cobbing & Hiller, 2019), eastern Ethiopia (Hagos et al., 2011), and Nigeria (Altchenko & 
Villholth, 2015). 
Evidence of economies of scale in groundwater irrigation in SSA is very limited.  Dhawan (1978) finds 
large economies of scale for tubewell-based systems in India, when considering 7 different cost 
components from equipment to administrative costs.  Mushtaq, Khan and Hafeez (2008) evaluate 
economies of scale in pond water storage for small, medium and large-scale ponds in China.  They find 
diseconomies of scale for small ponds, and economies of scale for medium and large-scale ponds.  Small 
ponds, even the lowest cost, are not profitable, however, so the authors suggest group or community 
ponds as a way to achieve economies of scale associated with large ponds.  On the other hand, Villholth 
(2013, and references cited therein) discuss the evidence for diseconomies of scale in well drilling, as 
unit costs of excavation tend to increase as the depth increases.   
There is more evidence of cropland threshold barriers, where available equipment or operational costs 
are too expensive for those with landholdings of less than 1 or 2 ha (Agrawal & Jain, 2018; Namara et al., 
2014; Ringler, 2021; Shah et al., 2020; Villholth, 2013).  A series of World Bank projects in Niger suggests 
that economies of scale motivated the project team to switch from targeting subsistence smallholders 
cropping staples to commercially-oriented farmers with cropland between one and six ha as well as a 
switch to high-value crops such as onions and tomatoes (Abric et al., 2011).  A number of studies also 
find that farmers with larger landholdings were more likely to adopt groundwater irrigation and high-
value crops, except for use of buckets to irrigate small gardens (Owusu et al., 2013; Serote et al., 2021).  
Technological advancements should continue to lower unit costs of pumps and tubewells and 
potentially increase the range of pump systems available to increase “divisibility” of the asset, while 
alternative fuel sources can reduce pumping costs (Agrawal & Jain, 2018; Shah et al., 2020).  For 
instance, solar-powered pumps do require a relatively high fixed-cost investment, though pumping costs 
are then limited to maintenance and repair.  Where diesel costs are high, solar can provide an attractive 
alternative if financing modalities can be developed (Shah et al., 2020; Xie et al., 2021).  
There can also be economies of scale and/or scope in expanding groundwater irrigation for groundwater 
service and equipment providers, such as well drillers, pumps (Wang et al., 2007), equipment repair 
tradespeople and MFIs to supply credit (Abric et al., 2011; Agrawal & Jain, 2018; Villholth, 2013 and 
references cited therein; Shah et al., 2020; Soumaila, 2021).  Irrigation equipment providers may also 
find it more profitable to devise alternative financing mechanisms to reach clients that are otherwise 
priced out of the market, such as pay-as-you go financing (Mukherji et al., 2017) and rent-to-own 
14 
 
 
 
financing (Kunen et al., 2015; Bastakoti et al., 2019).  These economies may be even more likely if 
government and/or donor projects to support groundwater investment also invest in complementary 
services, such as roads or cold storage facilities, etc. (Abric et al., 2011; You et al, 2011; Mwamakamba 
et al., 2017; Pittock et al., 2017; Ringler et al., 2020).    
Greater numbers of groundwater irrigators may additionally help to alleviate the barriers to smallholder 
adoption.  With sufficient demand, pump owners could provide pumping services, so that smallholders 
would only need to invest in well drilling.  Providing pumping services has been observed in some 
African countries, particularly those who import relatively cheaper pump sets from India and China 
(Agrawal & Jain, 2018; de Fraiture & Clayton, 2019; Merrey & Lefore, 2018; Shah et al., 2020).  In some 
South Asian countries, arrangements to sell excess capacity to neighbors have also arisen, though no 
such cases had been observed by Shah et al. (2020) in Africa.  Selling excess water is common in some 
SA countries, such as in Bangladesh, where buying in groundwater from neighboring farmers leads to 
benefits equivalent to owning the irrigation equipment (Bell et al., 2015). 
4.3.  Evidence from datasets looking at the correlation between size and performance, surface 
irrigation schemes 
For irrigation schemes – as opposed to groundwater-based irrigation – we can also evaluate evidence 
from two small datasets on irrigation project performance from McCarthy and Winters (2022) (30 
observations) and Higgenbottom et al. (2021) (75 observations).  The McCarthy & Winters’ dataset 
captures all irrigation projects in SSA that were implemented by the World Bank, IFAD, and Millennium 
Challenge Corporation (MCC) since 2000 and for which program completion reports were available.  The 
authors collected data on basic project characteristics (funding, irrigated area, source of irrigation water, 
primary crops grown, amongst others), on problems identified in the completion reports, and various 
measures related to scheme performance including quality of infrastructure at endline.  Unfortunately, 
in many cases, the irrigation infrastructure itself was not completed until close to the end of the project, 
meaning that quality assessments are not likely to pick up potential issues with sustainability, as other 
authors have noted (Redicker et al., 2022; Higginbottom et al., 2021). For our purposes, we instead use a 
dichotomous variable capturing threats to sustainability as a project performance indicator; the index 
takes a value of 1 when major threats to sustainability are discussed in the completion reports, and a 
value of 0 when threats to sustainability are discussed as minor. 
15 
 
 
 
Given the dataset, it made sense to split the sample into irrigated area terciles, where small schemes 
range from 100 – 2250 ha, medium schemes range from 2500 – 6400 ha, and large schemes range from 
7,000 to 161,000 ha.  The largest project by far is a World Bank project in Tanzania covering just under 
161,000 ha, the next largest is an MCC project with 28,000 ha in Senegal.  
Table 1 below gives descriptive statistics by size of the irrigated area.  Our first observation is the very 
high cost per irrigated hectare in small irrigation projects, at nearly $17,600.  This observation is quite 
consistent with the figures provided in Fujiie et al. (2011).  Small projects tend to invest in very costly 
infrastructure.  For instance, the MCC project in Cabo Verde spent over US$4 million to develop 111 
hectares, with a very extensive and expensive system of dikes, boreholes, reservoirs and pumping 
stations.  Cabo Verde has very low annual rainfall, and is often subject to multi-year droughts.  Even so, 
this sophisticated system, which also relies on drip irrigation, is considered to have high threats to 
sustainability, and farmers have not been able to switch to high-value crops as foreseen in the project 
proposal due to transportation and other market-related barriers.  A World Bank project in Senegal, 
with an irrigated area of 1320 ha at project completion, cost of over US$27,000 per hectare.  At least 
some of the spending went towards the development of an additional 3680 ha that were not completed 
by the end of the project, thereby driving up costs per hectare completed.  Funding per irrigated hectare 
for medium projects was US$8535, while it was just US$2430 for large-scale projects, again consistent 
with evidence in Fujiie et al. (2011) and Inocencio et al. (2007).  Interestingly, for 50% of small-scale 
schemes, the primary crops cultivated are high-value crops, whereas only 10% of medium and large-
scale schemes produced such crops. High value crops can be vegetables consumed by the household, 
increasing dietary diversity and nutritional quality, or they can be mainly sold for cash in markets.  The 
large schemes mainly focus on rice production in support of food self-sufficiency objectives.  
Major threats to sustainability are identified for 90% of small projects, 60% of medium projects, and for 
50% of large projects.  We have seven indicators of problems identified in the completion reports, for 
which we create seven dichotomous variables.  These include variables that take the value of 1 if the 
respective document mentions project delays, project design problems, thin or absent markets for crop 
inputs and outputs and/or for goods and services to maintain irrigation infrastructure, and problems 
related to collective action.  Problems related to fee payments take a value of one if documents noted 
low rates of fee recovery, and/or that water fees are too low to cover repairs and maintenance, and/or 
if irrigators revenue is simply too low to cover repair and maintenance fees.  Problems related to 
conflicts takes a value of 1 if conflicts between head and tail irrigators, tenure insecurity, or land 
16 
 
 
 
conflicts more broadly were mentioned.  Finally, problems associated with use and enforcement of 
regulations takes a value of 1 if irrigation water is used by non-irrigators, unregulated water 
withdrawals, and/or sedimentation are mentioned as problems4.  As shown in Table 1, many problems 
occur at similar rates across the size categories, with some differences.  For instance, project delays 
occur in 100% of medium- and large-scale projects, but “only” in 70% of small projects.  Interestingly, 
project design issues plague both small and medium projects, but only 20% of large projects.  This 
suggests that more effort is spent in the feasibility and preparation stages for larger projects.  Both 
Redicker et al. (2022) and Higginbottom (2021) discuss the impact of the lack of solid planning and 
preparation on irrigation system performance, though they do not break this observation down by 
scheme size.  Medium projects face greater difficulties with fee payments than small or large projects.  
This would be consistent with greater benefits from cash cropping at small schemes, and integration 
into staple value chains at large schemes.  Large projects are more likely to face land-related conflicts 
than small and medium projects.   
Few of the projects in this database directly support farmer-led irrigation development (FLID).  There are 
only four projects where groundwater is the primary source of irrigation water, and only some activities 
under the World Bank’s Fadama II project supports FLID as groundwater irrigation adopted and 
practiced at the individual, or small group, irrigator level (the other projects have groups of farmers 
irrigating within perimeters organized similarly to small surface water schemes).  The costs per hectare 
for the Fadama II project are quite low at US$265, and, in 2012, the completion report found only minor 
threats to sustainability.  And yet, Dayo et al. (2020) document that 81.5% of Fadama beneficiary 
households indicated that irrigation canals were not functional when interviewed in 2019, and nearly 
100% indicated that sprinklers were not functional5.  Villacis et al. (2022) use nationally representative, 
three-period panel data for Nigeria collected by the World Bank’s LSMS-ISA, and find that irrigation 
covered just 2.5% of cropland nationally, on average, over the three periods.  Their data covers three 
waves between 2010 – 2016.  We complement the Villacis et al. (2022) analysis by adding the 2019 
LSMS round data and find that just 2.25% of households irrigated at least one plot in the previous year.   
 
4 We include use by non-irrigators as a potential problem when it is explicitly mentioned by the reviewer as a 
potential threat to sustainability of the system per se.  However, irrigators themselves might prefer multiple uses 
of irrigation water, even if this does threaten sustainability in the long run.  These benefits tend not to be included 
in assessments at the irrigation system level, while costs to the environment are also often ignored.  Benefits and 
costs are more likely to be assessed at the household or natural resource level.  
5 It is unclear what proportion of all households surveyed had acquired sprinklers or had access to irrigation canals 
with Fadama project support. 
17 
 
 
 
Table 1:   Irrigation Schemes and Threats to Sustainability 
  Small Medium Large 
Mea
  # Obs. Mean # Obs. n # Obs. Mean 
Major Threats to 
Sustainability 10 90% 10 60% 10 50% 
2935
Irrigated Area (ha) 10 954 10 3824 10 3 
Cost per ha (USD/ha) 10 17592 9 8535 10 2430 
Cash-Crop Focus  10 50% 10 10% 10 10% 
Project Delays 10 70% 10 100% 10 100% 
Project Design Flaws 10 60% 10 50% 10 20% 
Problems with Fee Collection 10 50% 10 80% 10 50% 
Thin Markets 10 40% 10 60% 10 60% 
Collective Action Problems 10 60% 10 60% 10 70% 
Land Conflicts 10 40% 10 50% 10 70% 
Inappropriate Scheme Use 10 60% 10 50% 10 30% 
 
Source: McCarthy and Winters (2022). 
 
Higginbottom et al. (2021) use data from project completion reports and other irrigation scheme-related 
documentation for schemes constructed in SSA, to put together a database that includes data on the 
proposed size of the scheme when the project was approved, country and year of project completion.  
They also identified the area currently being used for irrigation using geo-spatial techniques to generate 
the proportion of currently irrigated area relative to project proposal size, which they use as a measure 
of project performance.  They included irrigation projects completed between 1947 and 2010, with 
about 80% of projects completed between 1970 and 1995.  They also matched other geo-spatial 
information to the dataset, including the mean and coefficient of variation of precipitation and potential 
evapotranspiration, population within a 20 km2 radius of each scheme in 2015, travel time to nearest 
major town in 2015, and the average of the World Bank’s Doing Business Government Effectiveness 
index over the period 1996-2017. 
Using their database, we create three categories of project proposal size: small schemes that range from 
200 to 2250 ha (26 observations); medium schemes that range from 2500 to 10000 ha (21 
observations); and large schemes that are greater than 10000 ha (32 observations).  Because scheme 
size has declined over the decades (pairwise correlation coefficient of year completed and proposal size 
is  -.37), we exclude projects implemented before 1970 (8 schemes) and after 1995 (8 schemes), leaving 
18 
 
 
 
63 observations.  Table 2 below presents descriptive statistics for these schemes by proposal size 
category. 
We first note that current irrigation is 63% of proposal size for small schemes, which drops to 19% for 
medium schemes and then increases to 32% for large schemes.  Small schemes were actually more likely 
to expand from original proposal size (5 of 23 schemes) than medium-scale schemes, followed by large 
schemes. However, large-scale schemes were much less likely to suffer from design flaws and 
inappropriate use.  The stronger performance of small schemes in terms of area still in operation is at 
first glance somewhat contradictory to the evidence in Inocencio et al. (2007) and Fujiie et al. (2011) 
though it is worth recalling that these two papers used net benefits as a performance metric, while 
actual area still irrigated mainly captures benefits alone.  The results are also somewhat at odds with 
McCarthy & Winters (2022), where threats to sustainability were considered major for 90% of small 
schemes.  The primary difference between the datasets is that the Higginbottom data pertain to 
schemes completed between 1970 and 1995, whereas the McCarthy & Winters dataset covers projects 
completed from 2001 – 2021.  The better performance of earlier schemes may be due to “selection”, 
where areas most suitable for small-scale irrigation infrastructure were selected as project sites at 
earlier dates. However, there is not enough evidence to establish whether selection is the key driver of 
this difference.  Medium schemes have the lowest average current irrigation proportion, at just 19%, 
and no schemes expanded to be larger than the proposed area.  Large schemes fall in between, with 
32% average current irrigation proportion.  However, even though small schemes have higher percent of 
area still irrigated, the average absolute area is much smaller than large schemes (670 ha vs. 16,395 ha), 
and even medium schemes (970 ha).   
Looking at other scheme characteristics, we note that small schemes were more likely to be constructed 
in areas that subsequently had relatively large populations, followed by medium and then large 
schemes, consistent with the patterns for travel times to major urban centers.  The governance 
effectiveness index is also highest (least negative) for small schemes, with medium schemes having the 
lowest score.  Small schemes are also located in areas with relatively high rainfall and low rainfall 
variability.  These results suggest that greater market access and higher population densities combined 
with relatively high government effectiveness at the national level enabled small schemes to endure 
longer than medium and large schemes that are located in more isolated areas, and for medium 
schemes located in countries with particularly poor government effectiveness.  Additionally, more 
favorable rainfall environments – higher average and more stable rainfall where small scale schemes are 
19 
 
 
 
located – suggests these factors contribute to better performance vis-à-vis medium schemes; both small 
and medium schemes are often reliant on surface water storage that varies with rainfall.  Large 
schemes, on the other hand, are more likely to be constructed in areas with lower rainfall, but generally 
with access to water for irrigation that is less correlated with rainfall patterns.   
 
Table 2: Irrigation System Performance 
  Small Medium Large 
  # Obs. Mean # Obs. Mean # Obs. Mean 
Proposal Size (ha) 23 1057 18 4883 22 51234 
16,39
Actually Irrigated Size (ha) 23 671 18 935 22 5 
% Currently Irrigated 23 63% 18 19% 22 32% 
Population  23 354648 18 12302
7 22 80433 
Travel Time, Urban Center 23 30 18 76 22 113 
Government Effectiveness Index 23 -0.62 18 -1.06 22 -0.91 
Mean Annual Rainfall 23 881 18 785 22 712 
Coef. Variation, Annual Rainfall 23 1.71 18 2.06 22 2.09 
 
Source: Higginbottom et al. (2021). 
 
5. Other Factors Affecting Performance of Irrigation Schemes and Groundwater Irrigation6 
5.1 Irrigation System Design  
As captured in Table 1, project delays and design flaws are documented as ubiquitous problems that 
threaten scheme sustainability captured in project completion reports. For irrigation schemes, there are 
two distinct issues, quality of the built infrastructure and whether the irrigation system – even if well-
built – is capable of being financially viable.  A number of authors document poor quality infrastructure, 
including poorly placed intake valves, improper drainage, and use of poor-quality materials (World Bank, 
2015 (ICR for Niger project); Adekunle et al., 2015; Saïdou & Kossou, 2009; Osman, 2015; Webb, 1991).  
Additionally, some designs make it particularly difficult to monitor water use, avoid illegal irrigation 
(diverting water to non-scheme plots), and ensure distribution is fair and according to schedule 
 
6 This section draws heavily on a literature review of irrigation scheme performance provided in McCarthy & 
Winters (2022).   
20 
 
 
 
(Adekunle et al., 2015).  Design flaws can severely affect incentives for irrigators to pay fees and/or 
engage in collective maintenance.   
5.2 Financial Viability 
Financial viability is related to whether the scheme is fit for purpose.  For instance, van Averbeke et al. 
(2011) document the transfer of sophisticated pumping and overhead irrigation systems in South Africa 
to WUAs where members were relatively poor, irrigating less than 2 ha of mainly subsistence crops, and 
also relatively isolated from markets in which to sell cash crops.  Obviously, such schemes were never 
going to be financially viable and many subsequently collapsed.  Chidenga (2003) documents the 
Irrigation Management Transfer (IMT) process in Zimbabwe, where irrigators were rather suddenly 
expected to absorb all pumping costs previously borne by the government; the rationale provided was 
that smallholders would then be able to switch to high-value crops and thus be able to afford pumping 
costs.  Overly optimistic assumptions about small irrigator profitability has plagued, and continues to 
plague, irrigation project proposals, so that schemes with high O&M costs continue to be built or 
rehabilitated (Higginbottom et al., 2021; Redicker et al., 2022).  More emphasis on designs that lower 
O&M costs but ensure reliable delivery of water of good quality would more likely lead to improved 
scheme performance, fee payment rates and adequate labor contributions to collective maintenance.  A 
wide range of papers provide evidence that lack of market access – for crop production inputs, crop 
outputs (particularly for high value cash crops), irrigation maintenance goods and services, and irrigation 
water service providers – have severe negative impacts on irrigation scheme performance and adoption 
of groundwater irrigation (Emaleaf, 2017; Sonda & Ngaruko, 2017; Maleza and Nishimura, 2017; 
Sharaunga & Mudhara, 2018; World Bank, 2021).  For irrigation schemes reliant on irrigator fees and 
collective action for maintenance, a number of authors also document that greater access to markets, 
especially for cash crop sales, increases fee payment rates and collective labor for maintenance (Nhundu 
& Mushunje, 2010; Poulton, Dorward & Kydd, 2010; Totin et al, 2014; Fanadzo & Ncube, 2018; Masasi & 
Ng’ombe, 2019).  Irrigation scheme performance is also related to opportunity costs of labor; where 
alternative labor opportunities are relatively unremunerative in the dry season, irrigation rates are more 
likely to reach project goals and irrigators are more likely to provide labor for maintenance (Emaleaf, 
2017; Kahuro, 2012; Saidu et al., 2019). 
 
21 
 
 
 
5.3 Tenure Security 
For irrigation schemes, tenure security increases incentives to pay fees and contribute to repair and 
maintenance activities that provide benefits over multiple cropping seasons.  For groundwater 
irrigation, tenure security will increase incentives to make on-farm investments, such as digging wells 
and boreholes, constructing channels, and laying pipes.  A number of articles find that tenure security 
over plots in irrigation schemes increases collective contributions to O&M, and increases incentives to 
adopt groundwater irrigation equipment (Damianos & Giannakopoulos, 2002; Meinzen-Dick, 2014; 
Mutambara et al., 2016; Fanadzo & Ncube, 2018; Sharaunga & Mudhara, 2018; Wijnen et al, 2018). 
 
5.4 Water Scarcity and Reliability of Irrigation Water Supply  
Incentives to abide by scheme operation regulations and contribute to maintenance or to maintain 
groundwater irrigation equipment and conveyance structures should be higher where rainfall is 
relatively scarce but irrigation water supply is relatively stable.  Extreme water scarcity in North African 
countries is mentioned as a critical factor motivating irrigator participation in maintenance and fee 
payment (World Bank, 2021).  On the other hand, Vandersypen et al. (2015) argue that abundant water 
supplies in the Office du Niger irrigation scheme reduces incentives for irrigators to perform 
maintenance activities.  However, Akuriba et al. (2020) find that small-scale schemes with relatively high 
average rainfall in Ghana performed better across a range of performance metrics.  Schemes where 
water availability is more directly tied to rainfall, such as the small dam schemes in the north of Ghana, 
may thus perform better in areas with higher and less variable rainfall.   Greater reliability of water 
delivery has been associated with better scheme performance in a number of cases (Chidenga, 2003; 
Kahuro, 2012; Maleza & Nishimura, 2007; World Bank, 2021).  For groundwater irrigation, Wijnen et al. 
(2018) note that more research is needed to locate “weather-independent” groundwater resources that 
can still be exploited cost effectively.  Similar to the small dams in Ghana case, many groundwater 
irrigators rely on shallow aquifers that are rainfall dependent and thus highly variable, discouraging 
adoption.   
 
5.5 Operational Capacity  
A large number of studies and project completion reports suggest that under-performance of irrigation 
schemes is often associated with lack of requisite skills and knowledge needed to operate the system, 
ensure timely maintenance and repairs, ensure irrigators comply with their obligations, and solve 
22 
 
 
 
conflicts when they arise.  As noted above, in most cases, surface water schemes generally rely on WUAs 
for O&M at the tertiary level, with the state or parastatals having responsibility for bulk water provision 
and usually secondary infrastructure.  At the WUA level, especially in the context of IMT, insufficient 
resources to train WUA members in terms of group leadership, financial and administrative skills, and 
the technical expertise required to maintain the scheme often led to poor performance (Chidenga, 2003; 
Kahuro, 2012; van Averbeke et al., 2011).  Many IMT schemes rapidly devolved responsibilities – in some 
cases responsibilities for the entire system – in countries such as Madagascar, South Africa and 
Zimbabwe, primarily to reduce pressures on government budgets rather than to empower irrigators 
with little attention paid to WUA capacity building (Chidenga, 2003; Marcus, 2007; van Averbeke et al., 
2011).  This occurred and continues to occur, despite early research establishing the importance of 
capacity building in IMT (Chancellor & Hide, 1996; Frederiksen & Perry, 1995; Merrey, 1995; Patil & Lele, 
1995; Sargadoy et al., 1985). 
The organizational structure should reflect the principles of “optimal devolution” or subsidiarity, where 
authority, roles and responsibilities are assigned at the administrative level that is most cost-effective at 
providing O&M services (Meinzen-Dick, 1997; Berger et al., 2007; Andersson & Ostrom, 2008; Blomquist 
et al., 2010; Brousseau et al., 2010).  Vaguely defined and/or overlapping responsibilities can 
significantly reduce scheme performance (World Bank, 2021; Meinzen-Dick, 2014).  The ability of WUA 
members, particularly on relatively small schemes in isolated locations, will simply never be able to 
afford major maintenance or repairs; they are much less likely to have the resources to hire private 
sector contractors on reasonable terms (Chidenga, 2003; van Averbeke et al., 2011). 
For groundwater irrigation, O&M issues are less of an issue.  But, irrigation equipment and 
infrastructure still requires routine maintenance and repairs, so that irrigators either have to acquire the 
skills and knowledge required to perform maintenance and repair by themselves, or have the capacity to 
source (and pay for) service providers.  At the supra-irrigator level, however, groundwater irrigation 
systems can impose daunting operational issues of monitoring and “invisible” resource and effectively 
managing extraction rates across multiple irrigators and other water users such as municipalities, 
industry, etc. (Wijnen et al., 2018; World Bank, 2017).  While of limited relevance at this time in most 
African contexts, experiences in South Asia, Latin America and the United States suggest that managing 
over-extraction can be very costly, and often ineffective.   
23 
 
 
 
5.6 Collective Action Capacity 
In most systems, WUAs have roles and responsibilities for O&M, from complete responsibilities 
generally on smaller schemes to responsibilities for tertiary infrastructure O&M at large schemes.  There 
is a large literature on factors that favor collective action, from Ostrom’s design principles (Ostrom, 
1993) to social-ecological frameworks captured in extensions to the Institutional Analysis and 
Development conceptual model applied to irrigation systems (Anderies, et al., 2004; Meinzen-Dick et al., 
2002; Meinzen-Dick et al., 2004; Meinzen-Dick, 2014; Ostrom, 2011).  Factors favoring collective action 
include well-defined resources and well-defined users, the ability to monitor irrigators use and 
management practices, the ability to levy graduated sanctions reflecting the nature of irrigation non-
compliance, trust in leadership, social cohesion to manage social, cultural and economic heterogeneity 
amongst irrigators, and the number of irrigators (which should favor collective action starting from low 
levels, but may hinder collective action after a certain point unless sub-groups are formed within a 
federated structure).  McCarthy et al. (2001) and McCarthy & Winters (2022) also argue that since 
collective action entails transaction costs, the larger gains to collective action versus non-cooperation 
also favor collective action to provide public goods, e.g. locations where rainfall is scarce and erratic but 
irrigation water is sufficient and stable. 
6. Country Case Studies 
6.1  Senegal 
Senegal developed irrigated areas primarily in the 1980s, although limited additional expansion has 
occurred since then, and the total irrigated area is just about 5% of the cultivated area (FAO AQUASTAT). 
The Senegal River Valley (SRV) has both the largest area currently in crop production at 108000 has, and 
also has the largest potential to expand irrigated agriculture, at about 130000 additional ha (Diouf et al., 
2015).  The infrastructure of medium- and large-scale systems completed in the late 1980s and early 
1990s degraded over time, with insufficient water delivery and thus abandonment of fields (Harris et al., 
2021).  The potential problems with long-term sustainability were presaged in an irrigation proposal 
document by CILSS (1979), which identified a number of possible constraints to success that, for the 
most part, were not adequately addressed in the following decades.  Constraints included: extent of salt 
intrusion and difficulties with appropriate drainage (often due to poorly implemented preparatory 
feasibility studies; the fact that, for hydro-engineering reasons, large-scale schemes were sited in 
relatively isolated areas with limited local farmer populations; property rights and tenure issues 
24 
 
 
 
associated with new settlements; lack of familiarity of year-round farming and maintenance 
requirements on the part of irrigators; the intertwined problems associated with lack of parastatal 
management to provide required irrigation services in a timely manner and subsequent low irrigation 
fee payment rates; and, under-resourced and under-skilled management.  These constraints led to low 
cropping intensities and low yields, furthering the cycle of non-fee payment and eventually 
abandonment.  Despite these constraints and limited evidence on how to address these constraints, the 
CILSS document describes the development of two major dams (Diama and Manantali) required for the 
second phase to ensure year-round controlled irrigation – up to 375,000 ha, which has never 
materialized.  Different sources instead suggest that this second phase increased the irrigated area to 
between 110,000 – 120,000 ha (USAID, n.d.; ).  Interestingly the CILSS document notes that small-scale 
village level perimeters were performing better than large-scale schemes in terms of higher rice yields, 
lower construction costs per hectare, and to a lesser extent maintenance7.  There is also some 
discussion of potential negative environmental impacts particularly on mangrove land, but the authors 
do not discuss how these negative impacts could be minimized.  
Harris et al. (2021) provide results of an evaluation of a large-scale irrigation project implemented by the 
Millennium Challenge Corporation five years after it was completed in 2016.  The authors found that 
though targets for building and rehabilitating infrastructure were met, production goals fell far short of 
objectives.  For instance, for the Senegal River Valley (SRV) larger-scale schemes, the project expected to 
increase cropping intensity to 150%, but intensity was just 78% five years after completion, due in part 
to logistical challenges related to land preparation in consecutive seasons.  Additionally, the expansion 
of production of tomatoes and onions – which provide much higher net revenue margins (Manikowski & 
Strapasson, 2016) – remains far below expected levels, at just 20%.  The authors also noted that while 
infrastructure remains in good condition, maintenance of canals through dredging threatens longer-
term sustainability.  In addition to investments in large-scale schemes, the MCC project also invested in 
building and rehabilitating irrigation infrastructure at a smaller scheme; this scheme faced similar 
problems to the larger schemes.  Estimated rates of return for the SRV large schemes was just 1.8%, and 
negative for the smaller-scale scheme.  
A new JICA project (JICA, 2019) also intends to increase rice self-sufficiency to lessen the trade deficit, 
even though other evidence suggests that vegetable crops give higher net revenues and that urban 
 
7 Pump maintenance at these smaller schemes was in the hands of the parastatal at that time.   
25 
 
 
 
consumers apparently prefer imported rice (Manikowski & Strapasson, 2016).  The JICA project targets 
two areas that were also targeted by the MCC project, Dagana and Podor, and intends to fund irrigation 
development and rehabilitation at both small (less than 100 ha) and medium scale schemes.  The project 
document executive summary states that the main constraints to low cropping intensity are 
deteriorating canal networks and lack of drainage systems, while in section 6, constraints due to 
availability of seed, and inappropriate operation and maintenance are also mentioned.  Yet, the project 
activities focus overwhelmingly on technical issues.  Both the CILSS (1979) document and results 
presented in the MCC report suggest that in addition to technical issues, O&M problems and market 
conditions also significantly affected economic rates of return (and thus low fee payments) and 
threatened longer-term sustainability of funded schemes.  Given these experiences in Senegal, plus all of 
the other empirical evidence, it is unlikely that an overwhelming focus on technical details will ensure 
sustainability8. 
Sakurai (2016) evaluated the efficiency of rice production in large and small irrigation schemes operating 
in the SRV.  The author finds that rice farmers in the large schemes receive significantly higher yields and 
net profits than those in small schemes; the author attributes this to more professional management 
and ability to take advantage of economies of scale in O&M at the larger schemes.  This is the only 
research arguing that large scheme management may have improved over time as management shifted 
from a government parastatal to irrigator unions; but, since the analysis focused on household level 
data, this remains a hypothesis regarding the relatively better performance of large-scale schemes.  The 
results also focus on irrigator profitability, and do not consider negative environmental impacts.  For 
instance, Manikowski & Strapasson (2016) document a wide range of negative externalities, including 
large losses from loss of inland fishing, loss of forest products, loss of wetlands and mangrove lands, and 
negative health impacts; the authors argue that the negative impacts far outweigh any positive benefits 
to farmers9.  The authors also show that onion and tomato farming provides much higher net revenues, 
but irrigated crop production still overwhelmingly favors rice production.  The latter may be due to 
 
8 While the document gives more details on the technical work, it may be that the short descriptions of supporting 
farmer groups to undertake O&M and maintenance may be more sophisticated than what appears in the proposal; 
however, the proposal only mentions “tools” to be used by farmers organizations on which they will be trained, 
and four sentences on sub-component 3.2, enhancing the capacity of farmer organizations, and a list of O&M 
Manuals to be produced under sub-component 3.4. 
9 It remains unclear from the literature how much of these losses are actually due to dam construction and 
completely controlled irrigation; CILSS (1979) note that flood recession agriculture had been largely abandoned 
due to the droughts in the 1970’s, which continued into the 1980’s while Manikowski & Strapasson assume that all 
of the land use changes were due to the dams alone.  Likely, it is somewhere in between.   
26 
 
 
 
“lock-in” in terms of value chain development, long-standing contractual relationships, and government 
policies and donor programs to promote rice production for self-sufficiency as identified in the JICA 
(2019) proposal.   
Some recent investments in irrigation by donors have focused on small schemes and even individual 
adoption of pumping equipment, including the promotion of solar-powered pumps and drip irrigation 
kits (Feed the Future, 2022).  Smaller schemes tend to focus on vegetable and fruit production; Paglietti 
& Machado (2016) calculate that these small-scale schemes provide 90% of vegetables sold in the local 
market.  There is limited recent evidence of how these schemes are performing, and the extent to which 
solar powered and/or drip irrigation systems are generating profits and are being maintained over time.  
To date, most evidence suggests that pump-based systems are more likely to be adopted by wealthier, 
male farmers (Kafle et al., 2022; Namara et al., 2014; Ringler et al., 2020), but it is too early to determine 
whether more recent projects have been able to reach a broader range of farmers. More research on 
how to increase women’s access to irrigation systems is needed.  
In summary, there may be opportunities to support large-scale scheme rehabilitation, but the extremely 
limited empirical evidence on their functioning – and any additional negative environmental and social 
externalities that might be generated with rehabilitation – seriously hampers the development of 
credible project proposals.  The strong emphasis on rice-only cultivation in large schemes needs to be 
reconsidered in light of market conditions for rice versus horticulture crops.  More serious attention is 
needed to understand how best to incentive irrigators to pay fees and contribute to maintenance and 
improve the functioning of WUAs, outside of vaguely expressed trainings and operations manuals.  
Secondly, support to smaller-scale pump-based operations is more likely to be successful where 
motorized pumping is combined with affordable energy such as solar and access to maintenance and 
repair service providers.  Water quality monitoring systems should also be in place, to monitor water 
table levels and variability as well as salinization to improve management and use, and to help those 
dependent on groundwater pumping to devise mechanisms to avoid negative environmental impacts of 
over-extraction. 
6.2 Zambia 
Zambia is a landlocked country in Eastern Africa and, outside of its northern province, slated to become 
hotter and drier with climate change (Hamdudu & Ngoma, 2020).  Irrigation has been expanding 
relatively slowly but steadily since the 1980s, increasing from just 20,000 ha in 1985 to about 160,000 
27 
 
 
 
has by 2010 (Akayombokwa et al., 2015), though still well below the 2.75 million ha with irrigation 
potential (MACO/FAO, 2004).  In contrast to Senegal, the largest fraction of irrigated land is irrigated by 
smallholders using private equipment to extract water, primarily from shallow aquifers and wetlands, 
and to a lesser extent, river diversions (Akayombokwa et al., 2015).  Using nationally representative 
survey data, Ngoma et al. (2019) find that 18% of households irrigate at least one plot, often for 
cultivating vegetables and fruit.  However, 85% of irrigators rely on bucket irrigation so that irrigated 
plots are very small.  Survey results also showed that just 4.6%, 3.6% and 2.6% of irrigators used 
motorized pumps, irrigation canals, and hand/treadle pumps, respectively.  van Koppen et al. (2012) 
purposively selected four districts and locations within those districts where irrigation was extensively 
practiced in order to evaluate which technologies were best adapted to local conditions.  The authors 
found that bucket irrigation is still the predominant technology, though river diversion and canal 
systems were adopted by 47% of irrigators in Mpika district, while 28% of irrigators used motor pumps 
in Chibombo district.  Very few irrigators had adopted manual pumps.  It is worth noting that treadle 
pumps have been widely promoted by international donors and NGOs for at least the last two decades 
(Merrey et al., 2008), but adoption of manual pumps remains limited (Ngoma et al., 2019); and are 
unlikely to grow in use as motorized pumps have become more available.   
Van de Zande (2022) find that farmers overwhelmingly prefer motorized pumps in Ethiopia, Kenya and 
Zambia, though they also prefer solar panels to provide energy for those pumps.  The authors also note 
two additional features of pump systems that are attractive to farmers but generally neglected in the 
literature, that the pumps be portable so they can be secured at night preventing theft, and the ability 
of the system to generate sufficient additional electricity for home lighting and charging cellphones.  
Commercially-oriented smallholders also value an irrigation system that can also generate electricity for 
home appliances.  However, the number of people interviewed was quite small, so these remain 
tentative conclusions.   
Ngoma et al. (2019) find that those who practice irrigation are found in areas with relatively high 
seasonal rainfall, consistent with irrigation water availability being dependent on rainfall.  This 
dependence is expected since most irrigators are using water from shallow aquifers and/or wetlands.  
Other household factors included tenure security, as were wealth metrics; however, the data did not 
enable the authors to determine causality between wealth and irrigation.   
With respect to larger irrigation schemes, these are generally associated with private, often outgrower, 
schemes where the private sector is in charge of O&M, involved in sourcing inputs and are often 
28 
 
 
 
vertically integrated with agro-processing (Akayambokwa et al., 2015).  This is quite different from 
Senegal and other countries, where most large schemes began as public schemes that subsequently 
became owned, operated and maintained by the irrigators or irrigators jointly with the government 
through IMT.  Currently, the government is supporting the development of “three tier” irrigation sites 
that would be operated and maintained by a private investor, with a first tier of irrigators being large-
scale commercial farmers using center pivots or other sophisticated water distribution systems, a 
second tier of commercial-oriented small-scale farmers (between 1 – 5 ha) under sprinkler systems, and 
smallholders practicing flood irrigation with pumps (Akayambokwa et al., 2015).  A number of authors 
argue that these public-private partnerships using the three-tier model are most likely to generate the 
greatest net benefits to smallholders and other irrigators, but there is still little hard evidence to support 
this argument (Akayambokwa et al., 2015; Bangwe & van Koppen, 2019; Hambolo et al., 2019).  The 
authors argue that such schemes efficiently capture economies of scale in O&M, in sourcing inputs and 
in securing output markets, while reducing or eliminating the transactions costs of cooperation where 
smallholders are responsible for O&M.  On the other hand, a number of other authors question whether 
the three-tier and similar approaches really reduce poverty and improve food security for the 
smallholders involved (German & Parker, 2019; Harnish et al., 2019; Manda et al., 2018; Manda et al., 
2020; Remy & Cochet, 2019).  Remy & Cochet (2019) provide a very detailed analysis of one sub-project 
under the World Bank’s Irrigation Development Support Program, which was meant to provide irrigation 
and remuneration to smallholders affected by the development of the Kariba dam, constructed in 1959. 
The authors documented the long delays, and argued that the smallholders had not been adequately 
compensated for lost land, equipment and in some cases, houses; additionally, they question whether 
the large commercial irrigators would pay a fair rental, since how rent will be set and shared remains 
unclear eight years after the project began.  Evidence from South Africa suggests that PPP schemes 
often do not provide medium- to long-term benefits, often because the large irrigators and/or the 
private investor pull out of such investments when they themselves do not realize sufficient profits (van 
Averbeke et al., 2011). 
In summary, given this mixed evidence on the performance of PPP’s with respect to productivity and 
poverty reduction – especially for newer PPP schemes – it is critical to generate additional evidence of 
the performance of these schemes, particularly for poorer smallholders, and those that have provided 
their own land to the scheme.  With respect to smallholder private investment in irrigation equipment, 
the evidence suggests that manual pumping options are not attractive to smallholders, but that 
29 
 
 
 
motorized pumps may become attractive as investment and operating costs decline and financing 
mechanisms reach more smallholders.  In addition to labor costs, another factor that makes manual 
pumping less attractive is that the shallow aquifers and wetlands that supply water for pumping are 
highly dependent on rainfall, which is becoming more erratic across most of the country.  Accessing 
somewhat deeper aquifers may provide a more reliable supply, but there is simply too little evidence to 
understand groundwater dynamics and thus where groundwater may be more reliable across the 
country.   
6.3 Nepal 
Nepal has a long history of irrigation systems, including government-built and managed systems, as well 
as many farmer-managed systems.  According to the government’s Irrigation Master Plan 2019 (Ministry 
of Energy, Water Resources and Irrigation (MEWR), 2019), 75% of irrigated land is under farmer-
managed systems.  Area irrigated has increased to 1.435 million ha in 2019 from about 0.93 million ha in 
1990 (MEWR, 2019), most of which is found in the valley areas.  Large schemes are either under agency 
(AMIS) or joint management with the irrigation agency and communities (JMIS), or are farmer managed 
(FMIS), with about 50% under each system – though the land area in FMIS is only about 15% of 
AMIS/JMIS land area (MEWR).  Most AMIS and JMIS are large schemes that tend to be located in the 
valleys; they typically encompass multiple communities. These schemes have high capital requirements 
for maintenance and often face difficulties in fostering community participation in maintenance 
activities.  FMIS tend to be located in the hill and mountainous areas, are much smaller but are also 
developed by and based within a community, which can lead to less costly O&M.  There remains ample 
scope to extend surface and groundwater irrigation, but there is also scope to increase crop intensity 
(MEWR, 2019).  The new irrigation master plan has ambitions to increase area by 535,000 ha, although 
many projects to develop these additional irrigated areas will also include hydropower generation. The 
government of Nepal also intends to continue its Irrigation Management Transfer (IMT) policy, and sees 
four possible organizational entities to which large-scale schemes can be transferred:  local government, 
private operator under contract, water user cooperative (WUC), and joint agency-WUA management.  
Transfers to local government are likely to be preferred when the hydraulic boundaries of the system 
fall with a single local government jurisdiction and where local government have the necessary 
resources or access to resources and both the organizational and technical skills to take over full control; 
for this capacity building and ongoing support might be needed.  Transfers to private operators cannot 
be done at present due to the lack of civil work contractors with proven capacity; however, the 
30 
 
 
 
government intends to explore helping to develop this capacity.  Transfers to WUC are likely to be 
preferred when the system is relatively small-scale and O&M is relatively less intensive, though there is 
limited evidence on how WUCs may perform in the Nepal context.  Transfers to agency – WUA joint 
management has been on-going, but performance is below expectations, with agency 
underperformance inducing WUA underperformance.  As with transfers to private operators, better 
performance will be related to the ability to establish and maintain a transparent monitoring system 
that is not too costly.  
Both government and farmer managed irrigation systems depend on the functioning of WUAs, though 
to different extents; in AMIS, irrigators retain responsibility for O&M over tertiary systems, while in 
JMIS, irrigators generally retain responsibility for O&M at the secondary and tertiary levels, and FMIS 
have full responsibility for the system, though they may receive some government support for high-cost 
repairs or maintenance (MEWR, 2019).  A number of studies have found that farmer managed schemes, 
which are usually “small” schemes (less than 25 ha following government’s definition), are more likely to 
be effective at reducing poverty primarily because head and tail end use conflicts are lower, and poor 
farmers are able to fully control a reliable source of water (Bhatta et al., 2006; IWMI, 2007; IWMI and 
Earthscan, 2007; MEWR, 2019).  ADB (2012) also argues that government managed schemes are more 
likely to suffer from O&M problems than farmer managed systems; the authors also state that both high 
quality design and construction as well as well-functioning O&M systems are required to achieve hoped 
for gains in terms of yields, cropping intensity and poverty reduction.  A number of studies find that 
strong social cohesion, trust in leadership, effective leadership, better quality infrastructure, equitable 
and transparent enforcement of rules and regulations that are seen as fair, and the capacity to levy 
sanctions all led to better system performance and irrigator outcomes (Bastakoti et al. 2010; Khanal et 
al., 2021; Lam, 1998; Ostrom, 2011; Pokharel, 2016; Regmi, 2008; Thapa & Scott, 2019).  These findings 
are quite consistent with the collective action and irrigation literature cited above.  Meinzen-Dick et al. 
(2022) show that there are also additional pressures that may affect performance of farmer-managed 
irrigation schemes both now and in the future, such as migration by men.  The authors show that 
women irrigators have been able to fill responsibilities initially held by men who now migrate, but the 
O&M systems themselves need to adjust to less male labor, e.g. by allowing women irrigators to pay for 
labor services.  It should be noted, however, that few of the studies evaluating the performance of 
farmer managed schemes are based on rigorous research protocols and adequate sample sizes.  And, 
there has been little change in agricultural productivity per hectare over the last few decades, rather, 
31 
 
 
 
production increases have largely been obtained through expanding land (Anik et al., 2017;  MEWR, 
2019; NPC, 2017).   
There is limited empirical evidence on the performance of jointly managed systems.  Mishra & Molden 
(1996) describe the IMT process at the Nepal West Gandak Irrigation System; the authors argue that the 
process appeared to be successful at least in the short term.  The authors argue that this success was 
due the formation of a system-level WUA and civil works at the main, which motivated the tertiary-level 
WUAs to become active and to harness resources to maintain tertiary infrastructure.  However, Roth & 
Vincent (2013) find that the West Gandak system had deteriorated, that only 19% of irrigators joined 
WUAs and that 74% judged that operations were currently poor and worse than before the IMT process 
began.  The authors note that two levels of water user groups were formed, 132 tertiary level groups 
and 11 WUA federations, of which only a few remained by 1992.  Lack of government investment in 
O&M at the main and secondary levels, poor construction quality at the tertiary level, floods and 
siltation making maintenance relatively expensive, and the fact that a full transfer of responsibilities was 
realized soon after all contributed to system decline. On the other hand, the authors argue that joint 
management at another site, the Khageri Irrigation System, was more successful, and it was also smaller 
at 3,900 ha.  The authors argue that the relatively simpler water control technologies and drawing water 
from a silt-free river lowered maintenance costs, while rain water scarcity and relatively knowledgeable 
farmers favored collective action.  Roth & Vincent (2013) argue that the IMT process was too top-down, 
that it was unclear what property would be transferred to the WUAs (land, equipment, forest areas), 
that WUAs lacked the necessary legal support to enforce their authority to collect irrigation fees, uneven 
support to participatory processes combined with dominance of government engineers in the process, 
and the problems created by over-expectations of the extent of government funding for maintenance 
and repairs.  WUAs either evolved over time to manage pressing problems or simply stopped 
functioning.  The authors argue that having design principles based on previous experience for WUA 
development is useful, but they need to accommodate social and political realities to endure that these 
institutions are seen as fair and effective by irrigators.  But, the authors argue that technical designs are 
critical and must be matched to the irrigators capacity to implement O&M through WUAs and be 
consistent with their irrigated farm objectives. Since the early 2010’s, there has been very little research 
to evaluate which factors and processes support successful joint management, despite the continued 
IMT process that will likely continue to be dominated by joint management.   
32 
 
 
 
In summary, large-scale schemes are still the dominant irrigation system in the country and will likely 
remain so for many years.  The government is continuing its IMT process, but very limited evidence 
suggests that results are likely to continue to be disappointing unless new mechanisms are put in place 
to take advantage of economies of scale at the main and secondary levels, but capitalize on the ability of 
WUAs to voice irrigators’ concerns, monitor the condition of tertiary infrastructure, motivate fee 
payment and maintenance labor where relevant, and address local conflicts.  What limited evidence 
there is points to the need to determine what facets of system O&A should be transferred to which 
levels especially in larger, more complex systems.  Farmer managed systems apparently perform better, 
and their support particularly in mountainous and hilly regions should promote food security, but 
outmigration by families and male migration and subsequent land abandonment need to be carefully 
understood if longer-term objectives are to be met.   
7. Research and Management 
Based on the review of various irrigation sizes and types we propose the following management and 
research agenda to strengthen the resilience and sustainability of all types of irrigation systems. 
7.1.  Surface water schemes 
For surface systems, excessively optimistic expectations of irrigator profitability on behalf of project 
proposers should be abandoned as they automatically set up systems for failure, particularly if the 
design and investment incorporate overly complex and expensive system components for which costs 
can never be recovered and whose maintenance is impossible with local resources. Instead, irrigation 
system designers need to adapt systems to local capacities, needs and should also consider broader 
(including multiplier) benefits from irrigation, such as lower local food prices, improved domestic water 
security, and increased employment opportunities from forward and backward linkages of systems. 
Second, for all surface systems, more research and capacity building to explicitly reduce transactions 
costs of collective action capacity is needed.  
Surface water schemes have potentially large economies of scale in design, construction, and 
operations, and for major maintenance and repair works. These economies of scale need to be better 
balanced with potential dis-economies of scale associated with transactions cost of collective action 
where WUAs are part of the management structure (costs of coordination, cooperation, monitoring and 
33 
 
 
 
enforcing use rules).  More research on the appropriate management of large-scale system through 
more empowered groups of women and men farmers is needed.  
For smaller schemes that are more likely to grow a diverse set of more profitable crops, design quality 
needs to improve to reduce system failure, while research needs to focus on reducing cost and 
accessibility of service provision for major maintenance and repairs.  
7.2 Groundwater irrigation 
Contrary to surface systems, groundwater irrigation is more naturally fit-for-purpose from a smallholder 
point of view, except for very small landholdings that might not be able to afford initial investment. 
Technological advances continue to increase the “divisibility” of pump assets and lower unit costs of 
pumping. Moreover, informal groundwater markets are common in SA countries allowing smaller 
farmers to access water pumped by better-off pump owners (Acharyya 2019). Both lower the threshold 
cropland size. To support expansion of groundwater, new business and finance models that allow 
smallholders to access the technologies are needed.  
Evidence strongly suggests that cheaper, non-motorized groundwater extraction is not attractive to 
smallholders, and thus provides limited climate resilience and food production growth.  Key research 
and management challenges relate to better governance of groundwater resources to avoid over-
extraction, groundwater degradation and pollution and to increase replenishment.  In a country like 
Nepal, linkages between springs and ground and surface water supply need to be better understood and 
springs preserved.  More research is also needed to identify current and future renewable locations for 
groundwater extraction and the impacts of alternative groundwater pumping technologies on 
environmental sustainability and equity.   
In almost all – if not all – cases, making and enforcing groundwater regulations has been very costly and 
not very effective; and, costs of doing so are likely to exhibit diseconomies of scale. More research and 
pilots are needed to improve groundwater governance everywhere.  
More research is also needed to incentivize sustainable pumping when farmers switch from fuel to 
solar-operated pumping systems.  
We provide a more detailed checklist that irrigation investors should consider in Appendix 1.   
34 
 
 
 
8. Concluding Comments 
With respect to surface water schemes, the evidence suggests large economies of scale in design, 
construction, operations and major maintenance and repair works.  In particular, smaller schemes are 
unlikely to be able to afford major equipment for maintenance or to hire-in expensive services for 
maintenance and repairs.  At the same time, evidence also suggests that there are diseconomies of scale 
in management and routine maintenance where these activities rely on collective action, and costs of 
collective action can rise substantially as scheme size increase.   Larger schemes can also capture the 
economies of scale by having professional or parastatal organizations manage the main and secondary 
infrastructure, and avoid diseconomies of scale by having WUAs manage blocks of tertiary 
infrastructure.  Overall, the evidence suggests that net benefits are likely to be lowest in the medium 
scale schemes, which fall between 100 – 2250 ha.  These schemes are likely to face higher collective 
action transactions costs than small schemes but are much more expensive to build per ha than larger 
schemes.  A notable caveat is that the net benefits of larger schemes are often calculated without taking 
into account negative environmental impacts, which can be substantial in some cases. 
 
Even when surface water scheme infrastructure is well-built, it may not be fit for purpose.  Large scale 
schemes whose purpose is to ensure national food security are sometimes run by private companies 
with skilled staff, but they are also often run by parastatals that do necessarily have the incentives to 
ensure the schemes are effectively managed and maintained.  They also often impose fairly rigid rules 
on types of crops to grow, crop calendars, etc.  Large scheme rules and regulations  may not align with 
irrigator’ seasonal budget constraints, crop preferences, household food security goals and market 
opportunities, while inefficient operations may dampen income from cropping.   On the other hand, 
irrigation water availability at larger schemes are often less dependent on area rainfall than smaller 
systems, providing greater resilience to weather extremes.  Medium-scale schemes often focus on 
staple crop production.  While irrigators may have more leeway to choose crops than those in large 
systems, when and what to crop are also often regulated.  While this may align better with irrigators 
food security goals, the scheme maintenance needs are often greater than what irrigators can provide 
given the low value of staple crops.  Small schemes allow greater flexibility on cropping activities, and 
they are more likely to involve high-value cropping.  These may better meet irrigators’ objectives, at 
least where irrigators’ returns are sufficient to cover their share of maintenance needs.  However, 
irrigation water availability is often more rainfall dependent and thus riskier in both medium and small 
35 
 
 
 
scale schemes vis-à-vis large schemes, which disincentives irrigators from engaging in water sensitive 
high-value crops and contributing to scheme maintenance.   
 
For individual investments in groundwater, there are limited economies of scale, except over a range of 
very small landholdings that depends on pumping technologies available.  Threshold land sizes may also 
be important when adoption requires cropland to exceed a certain threshold given the currently 
available technologies.  There are potential economies of scale for groundwater service providers, as 
costs per unit of service delivery will decrease relatively steeply as the number of irrigators increases 
from a low level.  Evidence from Asia suggests that widespread adoption of irrigation can crowd-in 
additional service providers, giving further incentives to adopt irrigation.  There is not much evidence of 
this occurring in SSA as yet.  There are also potentially large diseconomies of scale in regulating 
groundwater, particularly when there are multiple users and uses of groundwater.  There is a good deal 
of evidence of the costs of overextraction in South Asia and elsewhere, though many countries in SSA 
are not yet facing such a threat.   
The primary benefit of individual groundwater pumping is the flexibility it provides to the individual 
farmer to choose what and when to irrigate, and thus to choose for themselves the purpose of 
irrigation.  Whether a particular project promoting a specific type of groundwater irrigation is fit for 
purpose depends to a large extent on the net benefits realized from a specific technology.  In particular, 
most evidence suggests that irrigators strongly prefer motorized pumps to manual pumps.  Motorized 
pumps are more likely to require a minimum land size even for high-value crops and thus are more likely 
to be adopted by relatively wealthier farmers.  A project that focuses on manual pumps for affordability 
in order to increase nutrition and dietary diversity will not be fit for purpose if their target group is 
unwilling to adopt manual pumps even to cover relatively small areas.  Fuel costs will also determine the 
extent to which irrigators benefit; solar is more expensive to invest in but cheaper to run, while diesel or 
electric pumps are a cheaper investment but more costly to run (at least without massive subsidies).  
And, more sophisticated pumps require more sophisticated maintenance and repairs.  A project focusing 
on household food security though high-value crops for home consumption and marketing may not be 
fit for purpose if it is located in a relatively isolated area with very costly access to spare parts and skilled 
maintenance people.  Finally, if a project focused on building climate resilience is operating without 
knowledge of the dynamics of the groundwater resource, and there is no effective government 
36 
 
 
 
regulation of extraction, negative impacts of overextraction may overwhelm benefits to irrigation over 
relatively short period of time.  This too would not be fit for purpose. 
Turning to our case study findings, the Senegal experience suggests that recent large-scale rehabilitation 
of surface water schemes has been very expensive, continues to underperform, and faces significant 
threats to sustainability.  This is in part due to the fact that schemes have been asked to recover costs 
and cover O&M while focusing on food security crops, generally rice in West Africa.  Moreover, negative 
environmental and social externalities have been under-estimated.  Irrigation institutions have remained 
weak and are not fit for purpose in terms of fee recovery and O&M of tertiary infrastructure. 
Groundwater irrigation has been under-developed, but has recently started to increase from very low 
levels. While the potential is very high, particularly in Eastern Senegal, appropriate institutions will be 
required to support sustainable and equitable use.  
Unlike elsewhere in Asia or Africa, in Zambia, most of the large-scale irrigation infrastructure is operated 
by the private sector or within the context of public-private partnerships. The government is pursuing a 
three-tier model of irrigation scheme development, where schemes will include smallholders (< 1 ha), 
commercially oriented smallholders (1-5 ha) and larger scale commercial farmers. The objective is to 
capture economies of scale in O&M of main and secondary infrastructure and avoid diseconomies of 
scale in collective action required for maintaining tertiary infrastructure. These schemes often require 
smallholders to provide land, labor and other resources.  Evidence is both scarce, mainly anecdotal, and 
mixed.  To work, the large commercial farmers and private companies must crowd in market 
participants and service providers and generate sufficient profits to ensure their effective O&M at the 
main and secondary levels. With respect to groundwater irrigation, evidence suggests that manual 
pumps are not attractive to smallholders, and their adoption is likely to continue to decrease as motor 
pumps become more affordable. However, expansion of motorized pumping remains slow, hampered 
by the relatively high costs of pumps, fuel and well-drilling, and lack of maintenance and repair services. 
Nepal has a mix of larger irrigation systems in the lowlands or terai while smaller schemes dominate the 
more mountainous regions. The government embarked on an IMT program in the 1990s, which is still in 
progress.  The largest schemes tend to still be operated by the government (agency managed irrigation 
schemes, AMIS), while full transfer has occurred at smaller schemes (farmer managed irrigation 
schemes (FMIS). The legal framework allows for jointly managed systems (JMIS), but there is limited 
evidence on how widespread and/or effective these systems are.  Some research suggests that 
problems with agency maintenance of the main and secondary infrastructure has had negative impacts 
37 
 
 
 
on WUA performance. Some evidence also suggests unclear roles and responsibilities at different 
administrative levels have also hindered performance. There has been almost no research evaluating 
and comparing scheme performance across the AMIS, JMIS and FMIS in the past ten years (at least, no 
research available in English). A unique feature of agriculture and irrigation systems in Nepal is the 
growing number of women responsible for scheme operation due to the high share of men migrating 
abroad for work. Groundwater irrigation continues to expand, mainly via shallow tubewell irrigation.  At 
least in the Terai, there is potential to continue expansion, which is slowed by fuel costs, relatively high 
costs to buy or rent pumps, delays when pumping equipment is shared by a group, and difficulties in 
repairing broken pumpsets. In the mid-hills, lift irrigation is practiced but very costly due the high lift 
that needs to be covered by the pumps.  
Overall, the evidence shows both successes and failures at multiple scales for surface water schemes 
and for projects promoting groundwater adoption, the latter particularly in Africa.  The results also 
suggest the factors that must be included when designing an irrigation investment for systems of both 
types and all sizes.  Broadly speaking, this means rigorously assessing irrigators’ needs and incentives 
and their alignment with the irrigation system’s purpose; relevant market conditions; management 
structure, especially for jointly managed schemes; the skills required of management over a wide range 
of topics (technical knowledge of system operations and maintenance, finance, leadership skills) and 
how these will be built; the extent to which irrigation water is sufficient and reliable (how dependent it 
is on rainfall, for instance); tenure security; and, environmental impact.  
 
38 
 
 
 
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50 
 
 
 
Appendix 1:  Factors that Favor Different Irrigation Types 
 
Factors that Favor: 
Large Schemes:   
a. Large economies of scale in design, construction, and of scope in O&M 
i. More likely with experienced local construction companies, or international companies 
with proven in-country experience 
ii. Lower per unit O&M charges, e.g. equipment needed to repair and maintain 
infrastructure 
b. Ability to attract and pay for professional managers (not too isolated) 
c. Markets for inputs and crop outputs are well-developed, and irrigators can make sufficient 
profit to afford O&M fees under a range of input and crop prices 
d. Where the scheme will be used intensively; irrigators have incentives to crop at least two 
seasons (low opportunity costs of allocating labor to cropping across all relevant seasons) 
e. Where relevant, irrigators have the incentives and management capacity to provide labor for 
maintenance at the tertiary level. 
f. Scheme provides sufficient water on time 
g. Irrigation water availability is sufficient and reliable 
h. Flexibility in system operation to allow farmers some independence in crop choice 
i. Rainfall is low and unreliable 
j. Land and water tenure security 
k. Limited environmental impacts 
l. Equitable access, for example, through inclusive WUAs  
Medium Schemes: 
a. Moderate economies of scale in construction and scope of O&M 
b. Local availability of goods and services to repair and maintain scheme (e.g. equipment for 
desilting) 
c. Markets for inputs and crop outputs are sufficiently developed, and irrigators can make sufficient 
profit to afford O&M fees under most input and crop price realizations 
d. Well-defined and clear roles and responsibilities for polycentric governance, especially where 
schemes must rely on periodic costly maintenance and repair work 
51 
 
 
 
e. Proven capacity of water user groups to pay fees and provide labor for scheme maintenance at 
the tertiary, or perhaps even secondary, levels.   
f. Tenure security for irrigators, any potential land conflicts resolved 
Small Schemes 
a. If constructed for multi-season irrigation, irrigators have incentives to irrigate, e.g. when there 
are limited off-farm opportunities or where irrigation provides relatively high returns 
b. If irrigators mainly crop subsistence crops, the system must be relatively low maintenance by 
design 
c. Availability of materials for routine O&M and small repairs 
d. State willing to retain some responsibility for larger-scale maintenance 
e. Proven capacity of water user groups to pay fees and/or provide labor for routine scheme 
maintenance at all operational levels. 
 
Groundwater 
1. Target irrigator group has the capacity and incentives to invest in groundwater pumping 
equipment 
2. Diesel or electricity needed to operate motorized pump is reliable and affordable; alternatively 
solar pumps are accessible / affordable 
3. Irrigators can be trained in routine pump maintenance 
4. Availability of spare parts, repair service providers 
5. Legal framework for monitoring and managing use of groundwater 
6. Capacity to enforce legal framework 
7. Schemes can support multiple water uses, including domestic uses 
52 
 
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