Towards sustainable 
groundwater 
systems in South Asia 
Data exploration in Nalanda 
district in Bihar, India
Research Note 2, Work Package 2
December 2022
SUMMARY
Groundwater resources and irrigation systems are a fundamental consideration for
sustainable and inclusive food system transitions in South Asia. Over the course of the
latter part of the 20th century and the early 21st century, groundwater has become the
primary source of irrigation water across South Asia and globally. The aquifers in Western
and Peninsula regions in South Asia have faced water scarcity and groundwater depletion.
But in in the Eastern Gangetic Plains, aquifers are still considered underutilized by most
planners and policymakers. This has resulted in increased investments in groundwater
irrigation for water security and climate adaptation. However, the aquifer response to
increasing irrigation water withdrawals remains poorly understood. To address this
knowledge gap, TAFSSA is developing watershed assessment on sustainable groundwater
use. Starting with Nalanda district in Bihar, India, a relatively water scarce district within
the Eastern Gangetic Plains. This research note reports on the initial findings from existing
groundwater data and outlines key steps towards building a groundwater model to
support sustainable groundwater management and planning.
Photo: Irrigation in farmer’s field. Photo credit: Abdul Momin 1
KEY RESULTS farm configurations and cropping
The Indo-Gangetic Plains (IGP) in South patterns might be most suitable for
Asia hosts predominantly cereal-based producing nutritious foods while
farming systems (Aravindakshan et al., sustaining the natural resource base.
2015, Jat et al. 2020). Considered the food Groundwater flow modelling can be used
basked of South Asia, the IGP’s cereal to assist in decision making to more
production is crucial to food security as effectively manage groundwater
well as political and economic stability. resources. It can provide quantitative
However, parts of the IGP are threatened indicators of aquifer characteristics and
by unsustainable groundwater dynamic groundwater behavior. In this
withdrawal – the region extracts one third sense it can ‘making the invisible visible’.
of global groundwater withdrawals – Crucially, groundwater models can
spurred by existing irrigation incentives showcase and predict water deficit and
anchored in a number of key food and water abundant locations within aquifers
energy policies (Arshad et al., 2018, Dorosh over time and varying scenarios of
et al. 2009). Farmers in this region are precipitation and groundwater use. As
vulnerable and exposed to climate such, they can be useful in long-term
change and extreme weather (Lal et al. agricultural resource planning.
2010, Kishore et al. 2021, McDonald et al.
2020), contributing to high risks for Building groundwater models consists of
farmers that can lead to low incomes and two key steps, first building a conceptual
rural out-migration away from agriculture model and second building a numerical
(Aryal et al 2020). As a result, model to examine scenarios based on
governments are investing in expanding Darcy’s law and other fundamental
groundwater irrigation to support hydrogeological equations. The
intensified cropping and climate remainder of this report describes initial
adaptation in agriculture. Interest across findings aquifer systems research in
the region in these efforts collectively Nalanda district – our initial focus district
target nearly 22 million hectares that are in Bihar, India.
currently fallowed during the dry season
(Rasul et al. 2016, Krupnik et al. 2017, Urfels The study area isf 2300 km2 and includes
et al. 2020, Gumma et al. 2016). one of TAFSSA’s research learning
analogue sites. Toposheets (72G/3, 4, 7, 8,
In alignment with these efforts, TAFSSA 11, 12, 15, 16, H/5, 9) were used delineate the
supports coordinated efforts to transform administrative and hydrological
the agrifood system in ways that ensure boundaries of the study area. The
that people can equitably access and topographic elevation ranges from 35 to
consume healthy diets produced within 450 m above sea level (masl). The average
the environmental boundaries (cf. IFAD, annual rainfall is 974.5 mm. The climate is
2021). Work package 2 (WP2) of TAFSSA sub-tropical to sub-humid, and is
emphasizes farm- and landscape-level characterized by a hot summer and mild
interdisciplinary research, including the winter. About 89% of all rainfall takes
assessment of groundwater resources place from June to September.
through numerical modelling Geologically, Nalanda district is mainly
approaches. The objective of groundwater occupied by Quaternary sediments The
modelling is to assess sustainable exemption is a part of the South
groundwater use at the landscape level, in comprised of metasediments of Munger
order to provide information on what group belonging to middle Proterozoic
age (CGWB 2022). 2
Figure 1. Analytical framework being employed in groundwater flow modelling.
Figure 2. The Digital Elevation Model (DEM) and hydrogeological 
conceptual map of Nalanda district in Bihar, India. 
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3
Metasediments include highly folded and whole district is covered by alluvium,
fractured quartzite, phyllite and schist. except the crystalline rock areas in Rajgir.
These are combined with intrusive granite In the alluvial areas, several aquifer layers
and pegmatites. The study district is exist and have been explored to the depth
located within the Mid-Ganga basin, in of 250 m below ground in the northern
the southern margin of the Gangetic part of the district. In the crystalline hard
plains. Flat alluvium terrain is common, rock areas, water well discharges are
with the exception of Rajgir Hill (~ 443 highly variable. The conceptual
masl) in the south (CGWB 2022). hydrogeological map of Nalanda district is
presented in Fig 2.
About 90% of the area is used for
agricultural purposes with cereal-based Lithologically, Nalanda known for clay
farmland far exceeding any other land beds, inter-bedded with sands (Saha,
uses. Built-up area is the second largest 2007). In the northern part of the study
land use category. Nalanda district is part area, aquifers are more fully developed,
of the Harohar Basin, and generally slopes and, four alluvial fills, starting with coarse
towards the northeast. Major rivers sand and gravel at base and clay at the
include the Mohana, Panchane and Sakri top, have been reported within 100- 120 m
rivers. These all flow towards the north bgl.
east and empty into into the Ganges. The
Figure 3. Observed groundwater level trend of Nalanda district.
4
Observed ground water behavior data CONCLUSIONS AND NEXT
across the district’s total 39 National
Hydrograph Monitoring Stations were STEPS
chosen for calibration and validation of Despite being considered part of the
the model. Out of 39 stations only eight groundwater abundant Eastern Gangetic
Dug water wells contain water level data Plains, Nalanda district is already showing
since 1998. Al remaining wells provide signs of groundwater depletion. TAFSSA
data from 2013 to the present. The two is testing the hypothesis that ongoing
decades of water level observations in investments in irrigation infrastructure
dug wells is shows a significant decline in could amplify this trend. Careful
water levels (Fig. 3). Considering the the management of groundwater resources is
current expansion of electrically powered likely to be required to ensure that food
groundwater for irrigation, this declining systems transitions do not endanger
trends signals some concern for the groundwater related ecosystem service
district’s efforts to both develop and provisioning or create inequitable
sustainably manage groundwater. groundwater access across for users.
The overall mean water level is 3.5 m bgl To assist these efforts, conceptual model
with a standard deviation of 1.2. As shown in Figure 1 will need to be
described above, most surface water flows calibrated and validated with observed
towards the north-east following the values to produce a numerical
predominant topography, but several groundwater model. The validated model
local flows are also present in different will subsequently be used for
directions based on the hydraulic participatory and co-creative scenario
gradient (Fig. 4). The Biharsharif block (a runs that – through TAFSSA’s multi-
sub-urban area of the district) has a stakeholder platforms – are expected to
deeper water level following the Rajgir assist planners to ensure that food
area. These represent the crystalline hard security and water security objectives are
rock aquifers. met without breaching local ecological
resource limits.
Figure 4. Mean water level map including estimated groundwater flow direction of 
Nalanda district during the pre- and post monsoon season.
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ABOUT TAFSSA
TAFSSA is a CGIAR regional 
integrated initiative to support 
actions that improve equitable 
access to sustainable healthy 
diets, improve farmers’ 
livelihoods and resilience, and 
conserve land, air, and water 
resources in South Asia.
ABOUT CGIAR
CGIAR is a global research 
partnership for a  food secure 
future. Visit 
https://www.cgiar.org/research/
cgiar-portfolio to learn more 
about the initiatives in the 
CGIAR research portfolio
AUTHORS DISCLAIMER
Syed Adil Mizan, Researcher, IWMI Responsibility for editing, 
Alok Sikka, Country Representative, IWMI proofreading, and layout, 
Timothy J. Krupnik, Country Representative for opinions expressed, and any 
Research and Partnerships and Systems Agronomist possible errors lies with the 
and TAFSSA Lead, CIMMYT authors and not the institutions 
Anton Urfels, Post-Doctoral Fellow Cropping Systems involved. The boundaries and 
Agronomist, CIMMYT names shown, and the 
designations used on maps do 
not imply official endorsement 
or acceptance by CIMMYT, the 
SUGGESTED CITATION CGIAR, our partner institutions, 
or donors.
Mizan, S.A., Sikka, A., Krupnik, T.J., Urfels., A. 2022. 
Towards sustainable groundwater systems in South 
Asia. Work Package 2, Research Note 2. CGIAR research 
initiative on Transforming Agrifood Systems in South 
Asia (TAFSSA). International Maize and Wheat 
Improvement Center. Dhaka, Bangladesh.
FUNDING ACKNOWLEDGEMENT
We would like to thank all funders who supported this 
research through their contributions to the CGIAR Trust 
Fund: https://www.cgiar.org/funders/
To learn more, please contact: 
a.urfels@cigar.org
To learn more about TAFSSA, please contact:
t.krupnik@cgiar.org; p.menon@cgiar.org