Integrated Basin and Aquifer Management (IBAM)
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Item Which machine learning algorithm is best suited for estimating reference evapotranspiration in humid subtropical climate?(Journal Article, 2025-01) Deb, P.; Kumar, V.; Urfels, A.; Lautze, Jonathan; Kamboj, B. R.; Sharma, J. R.; Yadav, S.Timely and reliable estimates of reference evapotranspiration (ET0) are imperative for robust water resources planning and management. Applying machine learning (ML) algorithms for estimating ET0 has been evolving, and their applicability in different sectors is still a compelling field of research. In this study, four Gaussian process regression (GPR) algorithms—polynomial kernel (PK), polynomial universal function kernel (PUK), normalized poly kernel (NPK), and radial basis function (RBF)—were compared against widely used random forest (RF) and a simpler locally weighted linear regression (LWLR) algorithm at a humid subtropical region in India. The sensitivity analysis of the input variables was followed by application of the best combination of variables in algorithm testing and training for generating ET0. The results were then compared against the Penman–Monteith method at both daily and monthly time steps. The results indicated that ET0 is least sensitive to wind speed at 2 m height. Additionally, at a daily time step, RF, followed by PUK, generated the best results during both training and testing phases. In contrast, at a monthly time step, using multiple model evaluation matrices, PUK followed by RF performed best. These results demonstrate the application of the ML algorithms is subjected to user-required time steps. Although this study focused on Northwest India, the findings are relevant to all humid subtropical regions across the world.Item Assessing the contribution of managed aquifer recharge programs on groundwater storage in the Ramganga Basin(Journal Article, 2025-08) Alam, Mohammad Faiz; Pavelic, Paul; Sharma, Navneet; Sikka, AlokGroundwater, which supports nearly two-thirds of irrigation and underpins food security in India, faces depletion due to unsustainable abstraction. Managed aquifer recharge (MAR) programs, which replenish aquifers during periods of surplus surface water, have emerged as a national strategy to bolster groundwater security. This study evaluates the contribution of government-led aquifer recharge programs to groundwater storage in the alluvial aquifers of the Ramganga basin, whilst taking account of factors such as climate variability and agricultural water demand. The analysis, drawing on district-level MAR development data, field monitoring of recharge structures, and trends in rainfall, irrigation, and groundwater levels, reveals that MAR initiatives have a positive impact on groundwater storage. However, at their current scale, their contribution is modest accounting for an estimated 2.5–7.5 % of rainfall-recharge in 2023. Thus, groundwater levels continue to decline across districts, with average annual depletion rates of 0.21–0.29 m/year, indicating that current MAR contributions remain insufficient to counter the supply-demand imbalance. Scaling of MAR has been assessed to require >40,000 additional recharge ponds. Moreover, the recharge efficiency of existing structures, averaging 48 mm/day, falls well below that of optimized MAR systems that incorporate recharge wells. Beyond supply-side measures, this study highlights the need for integrated demand management strategies in the Ganges basin. It underscores the pressing need for a comprehensive, science-based approach to MAR implementation, coupled with demand-side interventions, to ensure sustainable groundwater management.Item Direct seeded rice in Haryana (India) ABY districts: impact and lessons for scaling(Report, 2025-05-30) Mutum, Lamnganbi; Mizan, Syed Adil; Bhatpuria, Dhyey; Taneja, Garima; Mitra, Archisman; Gupta, S. K.; Sikka, AlokRice is a staple crop in India, traditionally cultivated using the Transplanted Puddled Rice (TPR) method. This traditional method, while effective and very popular amongst farmers, is highly labour, water, and energy-intensive, that leads to significant groundwater depletion and higher energy usage in pumping groundwater. In response to these challenges, the Direct Seeded Rice (DSR) method has been introduced as a more sustainable alternative. DSR involves sowing seeds directly into the field, eliminating the need for growing and transplanting seedlings. This method, tested in various field trials, promises to have several benefits, including water savings, reduced labour and production costs, higher economic returns, and lower methane emissions. However, the success in farmer fields when adopted at scale outside trials remains to be analysed critically. In that context, this study was commissioned through a MoU with National Project Management Unit (NPMU), Atal Bhujal Yojana (ABY). ABY, also known as Atal Jal, is a central sector scheme aimed at sustainable groundwater management with community participation. Launched in December 2019, ABY focuses on improving groundwater management in water-stressed areas across seven states, including Haryana. The adoption of DSR in Haryana has been gradual but promising. The area under rice cultivation in the state has increased significantly over the years, with initial efforts to introduce DSR beginning around 2009. The state government has played a crucial role in promoting DSR by offering financial incentives to farmers. In 2022, an incentive of INR 4000 per acre1 was introduced to encourage farmers to adopt DSR. Given its uptake in Haryana, the objective of this study is to assess the socio-economic and environmental benefits of DSR, identify the challenges, and offer recommendations for scaling up this technology in Haryana and other regions. The study employed a multi-faceted approach including qualitative surveys with stakeholders, focus group discussions, field visits, and a large-scale quantitative survey (sample size is 809) of DSR and TPR farmers across selected districts in Haryana to assess the impact of DSR. These farmer-level sources were complemented by water flow meter data analysis and remote sensing analysis.Item Key insights from a community-based solar water pumping system in southern Laos. [In Lao](Brief, 2024-08-30) Pavelic, Paul; Sinavong, P.; Phompackdee, S.; Sinavong, S.Item Key insights from a community-based solar water pumping system in southern Laos(Brief, 2024-08-30) Pavelic, Paul; Sinavong, P.; Phompackdee, S.; Sinavong, S.Item Detecting potential community fish refuges (CFRs) of southeast Cambodia and assessing their vulnerability(Report, 2024-12-30) Vo, M. Q.; Truong, Q. C.; Vuong, S. T.This study investigates water dynamics and identifies potential Community Fish Refuges (CFRs) in Cambodia's Prey Veng and Svay Rieng provinces using multi-year satellite imagery (2018–2023), GIS data, and field data. The analysis focuses on stable surface water regions and their suitability for CFR establishment to support aquatic biodiversity and community livelihoods.Item Community fish refuge (CFR) pond monitoring: surface and groundwater study at Sras Ang CFR, Prey Veng Province, Cambodia(Report, 2024-12-30) Oeurng, C.; Sok, T.; Hout, M. H.; Ich, I.This technical report delves into the essential task of gathering validation data, focusing on surface and groundwater related data monitoring through the deployment of field equipment. The primary objective is to comprehensively monitor surface water and groundwater levels, along with rainfall, on a regular basis. This hydrologic monitoring initiative is conducted within the context of a case study centered on rice-fish systems, specifically community fish refuges (CFRs) in Prey Veng Province, Cambodia. The selected study area, Prey Veng Province, features a network of community fish refuges. The chosen pond, "Sras Ang", was converted into a fish refuge in 2010 and has a protected status during both wet and dry seasons. The monitoring approach included the installation of instrumentation for continuous monitoring of surface water and groundwater levels, as well as rainfall. Groundwater gradient assessments were conducted, and soil data was collected for further analysis. The collected data was used to create a preliminary water balance assessment, considering factors such as effective rainfall, surface water runoff and groundwater recharge. The study also incorporated anthropogenic influences, like water abstractions and discharges. The project involved site visits, community meetings, and the establishment of monitoring plans. Rainfall data, potential evaporation rates, groundwater levels, and pond water levels were collected and analyzed to understand the hydrological dynamics of the area.Item Mapping the potential of managed aquifer recharge in Africa: GIS-based multi-criteria decision analysis approach(Journal Article, 2024-11) Ebrahim, Girma Yimer; Stefan, C.; Sallwey, J.; Lautze, JonathanAfrica faces numerous challenges related to rainfall variability, droughts, water scarcity, and climate change. Managed Aquifer Recharge (MAR)- groundwater recharge and underground water storage for later use or environmental support presents a viable alternative for water storage and may provide an effective tool for coping with such challenges. However, the potential area where MAR can be feasibly implemented has not been identified. This study mapped MAR feasibility using a Geographic Information System-based Multi-Criteria Decision Analysis (GIS-MCDA) and assessed MAR potential in Africa. The methodology focused on three key pillars of MAR feasibility: intrinsic suitability based on biophysical parameters, water source availability, and water demand. Maps responding to these pillars were developed and combined to create a composite MAR feasibility map. Results show that 18% of the continental area falls into the low feasibility class, 73% into the moderate feasibility class, and 7% into the high feasibility class. The feasibility map was validated against 17 existing MAR schemes in Africa, demonstrating a good correlation between their locations and areas with MAR potential. Results of sensitivity analysis of criteria weights of the biophysical parameters show that geology is the most influential criterion, followed by slope. In general, this first feasibility assessment shows good potential for MAR implementation in Africa. Therefore, MAR should be considered prominently among other water storage options for resilience building in Africa and policymakers should ensure adequate resource allocation for its implementation. The feasibility map can be used to guide MAR planning and investment decisions.Item Enhancing smallholder agricultural production through sustainable use of shallow groundwater in the Borkena Catchment, Awash River Basin, Ethiopia(Journal Article, 2024-10-01) Ebrahim, Girma Yimer; Taye, Meron Teferi; Seid, Abdulkarim; Tekleab, S.With increasing shallow groundwater use for agricultural purposes, understanding the spatiotemporal variability in recharge rates, storage capacity, and its interaction with surface waters becomes crucial for its sustainable management. An integrated SWAT–MODFLOW model is developed to assess shallow groundwater availability in the Borkena catchment. The model is calibrated using streamflow and static groundwater level data. Results show that groundwater recharge in the catchment is 85 mm/a, representing 11% of the mean annual rainfall. Shallow groundwater resources exist across nearly 42% of the Borkena catchment. The percentage of shallow groundwater withdrawal to groundwater recharge is very low (0.1%), signifying the potential for increased shallow groundwater development. However, caution must be taken as its uncontrolled expansion may result in a high risk of depletion. This integrated modeling is one of the few efforts conducted to provide important information regarding shallow groundwater potential in the Borkena catchment, which is essential for the resilience of small-scale producers in the continued growing water demand and climate change.Item Modelling groundwater futures under climatic uncertainty for local policy and planning: a case of quantification of groundwater resources at sub-regional level in the Ganges basin(Journal Article, 2025-06) Mizan, Syed Adil; Sikka, Alok K.; Chakraborty, Shreya; Laing, Alison M.; Urfels, Anton; Krupnik, Timothy J.Study region: Nalanda district, Bihar, India, a sub-tropical region, and part of middle Ganga River basin. Study focus: Assessing the impacts of climate change on aquifers' seasonal replenishment is thus crucial for planning for future local food and water security. This study looks at how future groundwater levels will be affected by climate change in relation to important functioning thresholds that are typical for aquifers that replenish periodically. New hydrological insights for the region The result shows the projected groundwater levels from 2018 to 2060 using the CMIP6 global climate model, using rainfall data from three GCMs selected based on their different projected scenarios of levels of high intensity rainfall. Given the key role of low intensity rainfall in groundwater recharge, we find that incorporating rainfall intensity in groundwater models can be crucial for more robust projections. Our findings also show that higher total rainfall does not necessarily equate to higher groundwater recharge or lesser groundwater declines. Instead, the least groundwater declines were found in projections, where relatively higher total rainfall was also associated with lower high intensity rainfall periods, highlighting the need for combining and comparing varied SSPs and climate models for accurate future trends. At the sub-regional level, we find that climate change could lead to maximum groundwater loss of ∼ 0.8 km3 in 42 years in Nalanda district. Current trend analysis (2000–2018) already shows a negative annual groundwater balance. Even assuming no changes to current groundwater extraction rates, climate change will result in decreased groundwater levels and storage. The projection trends also reveal distinct short-term, medium-term, and long-term shifts which offer different policy windows for managing and governing the groundwater resources.Item NEXUS Gains in the Incomati and Limpopo basins: Botswana, Eswatini, Mozambique, South Africa, and Zimbabwe.(Brief, 2024-12-30) CGIAR Initiative on NEXUS GainsA NEXUS Gains transboundary river basin brief shares examples of the Initiative’s work across five work packages in the Incomati Basin and Limpopo Basin – specifically the Shashe sub-basin – covering Botswana, Eswatini, Mozambique, South Africa, and Zimbabwe.Item Moving toward implementation: basin-wide modeling and stakeholder platforms in the Incomati Basin(News Item, 2024-12-16) Joaquim, D.; van der Merwe, S.; Nehring, Ryan; Lautze, JonathanNEXUS Gains has been in partnership with INMACOM for more than two years, providing technical support for integrated management of the Incomati’s natural resources. One key focus of this collaboration is a basin-wide decision-support system, with another being the development of a multi-stakeholder platform. Both were the subject of a workshop in South Africa in November 2024, where discussions with stakeholders highlighted the significant impact of NEXUS Gains’ work.Item The environmental fallout of illegal mining in Southern Ghana: the environmental toll of illegal mining is undeniable, but forward-thinking initiatives are forging a path to recovery(Blog Post, 2024-12-05) Tilahun, Seifu A.; Atampugre, Gerald; Nartey, Eric; Gelaye, K.; Adusei-Gyamfi, J.; Herzog, J.; Barron, J.Item A community of practice for water modeling in Nepal(News Item, 2024-11-27) Pradhananga, Saurav; Nepal, Santosh; Aryal, Mamata; Parajuli, D.Item Social-ecological landscape sustainability in West Africa: applying the driver pressure state impact response framework in Ghana and Nigeria(Journal Article, 2024-11) Atampugre, Gerald; Tilahun, Seifu Admassu; Oke, Adebayo; Mabhaudhi, T.; Cofie, Olufunke; Igbadun, H. E.; Olaleye, A. O.This study interrogates the state of social-ecological landscapes (SEL) in West Africa, focusing on two case studies: the Mankran SEL in Ghana (case study 1) and the Doma–Rutu SEL in Nigeria (case study 2). Using a mix of methods, the assessment was framed by the Drivers Pressure State Impact Response (DPSIR) model tailored for SEL evaluation (DPSIR-SEL). In the Mankran landscape, land use patterns shifted significantly from 2008 to 2018, with cash crop cultivation peaking at 30% in 2015 before declining to 14.5% by 2018. Water quality assessments in the Mankran micro-watershed indicated that several parameters, including Total Suspended Solids (TSS) at 914.41 ± 1974 mg/L, lead at 18.73 ± 17.26 µg/L, and arsenic at 53.41 ± 86.66 µg/L, exceeded World Health Organization (WHO) standards, raising concerns about potential contamination. In contrast, the Doma–Rutu landscape in Nigeria experienced land use and land cover (LULC) changes from 2000 to 2022, characterized by the expansion of residential and agricultural areas alongside modifications to natural water bodies and vegetation. Water quality issues have emerged, with elevated levels of electrical conductivity, total dissolved solids, and salinity. Furthermore, Focus Group Discussions (FGDs) revealed persistent herder-farmer conflicts in Nigeria, which have historically constrained crop production due to various environmental and social factors. The intertwined challenges faced by both the Mankran and Doma–Rutu landscapes underscore the urgent need for sustainable and inclusive resource management, adaptive land-use strategies, and proactive measures to safeguard water quality.Item Stakeholders converge on integrated water storage in the Shashe Catchment(News Item, 2024-11-14) Sibanda, B. M.A workshop on advancing integrated water storage in the Shashe Catchment, a sub-basin of the Limpopo Basin shared by Zimbabwe and Botswana, organized by Dabane and IWMI, demonstrated the transformative potential of collaborative efforts and innovative approaches in water storage.Item The potential of Cambodia’s solar technology market to support farmer-led irrigation(Opinion Piece, 2024-10-11) Minh, Thai Thi; Buntong, B.; Pavelic, Paul; Hin, L.; Flor, R. J.Traditional irrigation systems in Cambodia, such as reservoirs, as well as river and canal systems, have limitations, leading to the emergence of farmer-led irrigation management. Meanwhile, solar irrigation has gained attention as a solution. However, challenges exist in matching demand with supply, as the solar irrigation market structure in Cambodia is monopolistic and limited in product choices. This article highlights the need for evidence-based targeting, stronger market demand-supply linkages, innovative marketing strategies and financing solutions to enable the uptake of solar irrigation and expand its potential benefits to farmers.Item Integrating groundwater recharge solutions across the Ramganga Basin, India: a rural-urban approach(Brief, 2024-10-30) Angou, G.; Alam, Mohammad Faiz; Sharma, Navneet; Pavelic, Paul; Sikka, AlokA study carried out by IWMI, TU Delft and Wageningen University looked at how groundwater recharge can help meet growing demands in both rural and urban parts of the Ramganga Basin, India.Item नेपालमा जलवायु संकट र व्यवस्थापनका विकल्प- विविधा - कान्तिपुर समाचार(Newsletter, 2024-10-07) Nepal, Santosh; Phuyal, Surendraकञ्चनपुरमा इतिहासकै सबैभन्दा बढी (२४ घण्टामा ६२४ मिलिमिटर) वर्षाको चपेटामा परेको अढाई महिनामै मध्य नेपालले त्यस्तै प्रकृतिको वर्षाजन्य विपद् भोग्नुपरेको छ । ४० घण्टाको अवधिमा मध्य नेपालमा ३०० मिलिमिटरभन्दा बढी वर्षा भएपछि आइपरेका बाढी, डुबान र पहिरोका कारण देशले कम्तीमा १७ अर्ब रुपैयाँ बराबरको आर्थिक क्षति बेहोरेको प्रारम्भिक आकलन छ ।Item The climate crisis is a water crisis(Blog Post, 2024-11-06) Nepal, SantoshThe climate crisis is marked by rapid changes that lead to more severe disasters, often resulting in irreversible impacts. Nepal faces this crisis, evident in rising temperatures, erratic rainfall patterns, and fast-melting glaciers. The climate crisis in Nepal is closely tied to an impending water crisis, affecting various sectors and communities across the country. A 2017 report from the Department of Hydrology and Meteorology reveals that Nepal has experienced a maximum temperature increase of 2.2°C over the last four decades, at a rate of 0.56°C per decade. The future appears even bleaker, with a 2019 Ministry of Forests and Environment report predicting an average annual temperature rise of 1.7 to 3.6°C by the end of the century under various scenarios. Average annual precipitation may increase by 11-23%, though pre-monsoon rainfall could decrease. Both reports suggest that extreme weather events, such as heavy rainfall and dry spells, will likely become more common due to climate change. These changes could significantly impact the hydrological cycle and sectors like water resources, agriculture, energy, forests and biodiversity.