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The Koshi Basin, spread across China, Nepal and India, is perceived as having high potential for hydropower and irrigation development, both seen as ways to promote economic development in the region
. This paper quantifies and assesses the past and projected future spatial and temporal water balances in the Koshi Basin. Results show that precipitation and net water yield are lowest in the transmountain region and the Tibetan plateau. The values are highest in the mountain region, followed by the hills and Indo-Gangetic Plains. Approximately 65% of average annual precipitation is converted to flows, indicating high water availability. Actual evapotranspiration is highest in the Indo-Gangetic Plains region due to the presence of irrigated agriculture and a few forested mountain watersheds. As most of the water from the mountain and hill regions eventually flows down to the plains, the mountain and hill regions in Nepal are important for maintaining agriculture in the plains in both Nepal and India. Results from the flow analyses indicate the high temporal variability of flows in the basin. The frequent occurrences of both high- and low-flow events demonstrate the existing vulnerability of the region to both floods and droughts, leading to a very risk-prone livelihood system. Climate change projections show an increasing trend in precipitation and net water yield for most of the basin, except the transmountain region. Therefore, it is important to consider the climate change impacts on water resources in future planning
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The sustainable development goals (SDGs) and the Paris agreement target a global cleaner energy transition with wider adaptation, poverty reduction and climate resilience benefits
. Hydropower development in the transboundary Koshi river basin in the Himalayan region presents an intervention that can support the SDGs whilst meeting the regional commitments to the Paris agreement. This study aims to quantify the benefits of proposed water resource development projects in the transboundary basin (4 storage and 7 run-of-the-river hydropower dams) in terms of hydroelectric power generation, crop production and flood damage reduction. A hydro-economic model is constructed by soft coupling hydrological and crop growth simulation models to an economic optimization model. The model assesses the potential of the interventions to break the vicious cycle of poverty and water, food, and energy insecurity. Unlike previous studies, the model (a) incorporates the possibility of using hydropower to pump groundwater for irrigation as well as flood regulation and (b) quantifies the resilience of the estimated benefits under future climate scenarios from downscaled general circulation models affecting both river flows and crop growth. The results show significant potential economic benefits generated from electricity production, increased agricultural production, and flood damage control at the transboundary basin scale. The estimated annual benefits are around USD 2.3 billion under the baseline scenario and USD 2.4 billion under a future (RCP 4.5) climate scenario, compared to an estimated annual investment cost of USD 0.7 billion. The robustness of the estimated benefits illustrates the climate resilience of the water resource development projects. Contrary to the commonly held view that the benefits of these proposed projects are limited to hydropower, the irrigation and flood regulation benefits account for 40 percent of the total benefits. The simulated scenarios also show substantial irrigation gains from the construction of the ROR schemes, provided the generated power is also used for groundwater irrigation. The integrated modelling framework and results provide useful policy insights for evidence-based decision-making in transboundary river basins around the globe facing the challenges posed by the water-food-energy nexus
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Using biophysical and social analysis methods, this paper evaluated agricultural practices under changing climate in the Koshi Basin and assessed adaptation options
. Agricultural trend analysis showed that in the recent three to four decades, the total cultivated area had declined in all parts of the basin except in the Nepal Mountain Region. Household survey results also confirmed such decline and further revealed shifts towards non-agricultural activities. Climate trend analysis showed changes in the frequency of wet and dry days in study districts, implying an increasing chance of flood and drought events. Household surveys further revealed that, in general, people perceived a decline in agricultural water availability and an increase in drought and flood events. The direct impacts of these changes were reduced crop yield, increased fallow lands, displacement of people from settlement areas, sedimentation of cultivable land and damage to properties. Household surveys showed that despite the perceived impacts on agriculture and livelihoods, only limited adaptation options are currently practised. Adaptation efforts are constrained by several factors, including: finance; technical knowledge; lack of awareness about adaptation options; lack of collective action; unclear property rights; and ineffective role of state agencies
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The water resources of the Koshi Basin (87,311 km2) are largely untapped, and while proposals for their development exist, their impacts on current and future water demand are not quantified
. The current study is the first to evaluate the impacts of 11 proposed development projects for hydropower generation and water storage. We find that 29,733 GWh of hydropower could be generated annually and 8382 million m3 of water could be stored. This could satisfy unmet demand in the current (660 million m3) basin situation and in future scenarios ? i.e. population, agricultural and industrial growth ? that are projected to have 920, 970 and 1003 million m3 of unmet demand, respectively, by 2050
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Sugden, F.; Shrestha, L.; Bharati, L.; Gurung, P.; Maharjan, L.; Janmaat, J.; Price, J. I.; Sherpa, T. Y. C.; Bhattarai, U.; Koirala, S.; Timilsina, B.
Climate change could have a critical impact on agriculture in Nepal due to dry-season water shortages, and changes in the variability of water availability and associated uncertainty
. This makes water storage systems (most notably ponds and tanks) increasingly important. This report explores the potential role of small-scale water storage infrastructure in two subbasins within the larger Koshi River Basin in central and eastern Nepal, yet shows that upscaling such infrastructure requires an appreciation of the other drivers of change in agriculture aside from climate (e.g., rising cost of living and poor terms of trade for agriculture). It also identifies the social relations and dynamics (distribution of land, water and labor) which could mediate the success of future interventions. It is clear from the research that, while small-scale water storage has the potential to significantly strengthen livelihoods in the Nepali hills, it is necessary to tailor projects to the existing political-economic context
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Water has been identified as a key resource for Nepal's economic growth
. Although the country has 225 billion cubic meters of water available annually, less than 7% has been utilized. Climate change is a frequent topic in national development discussions in part because of its possible impact on future water availability. This study assessed the likely impact of climate change on water resources development in the Koshi River basin, Nepal, using the Soil and Water Assessment Tool to generate projections for the 2030s and 2050s. Results suggested that the impacts are likely to be scale dependent. Little impact is projected at annual, full-basin scales; but at sub-basin scale, under both the IPCC's A2 and B1 scenarios, precipitation is projected to increase in the upper transmountain subwatersheds in the 2030s and in most of the basin in the 2050s and to decrease in the lower sub-basins in the 2030s. Water yield is projected to increase in most of the basin except for the A2 scenario for the 2030s. Flow volumes are projected to increase during the monsoon and postmonsoon but decrease during the winter and premonsoon seasons. The impacts of climate change are likely to be higher during certain seasons and in some sub-basins. Thus, if infrastructure is in place that makes it possible to store and transfer water as needed, the water deficit due to any changes in rainfall or flow patterns could be managed and would not be a constraint on water resources development. The risks associated with extreme events such as floods and droughts should, however, also be considered during planning
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