Nepal

Climate change is projected to notably impact water requirements and crop yield; therefore, it is imperative to quantify climate risk and devise climate-resilient field management practices. This study applied the AquaCrop model to Tulsipur, a sub-metropolitan city located in Western Nepal. The model was calibrated and validated on a field scale, and various scenarios were analysed for baseline (2010–2020) and future (2021–2100) periods to formulate workable management strategies for irrigation and fertilizer applications. Results showed that a deficit irrigation strategy could lead to 81% fewer requirements for irrigation in rice and 24% in wheat at the cost of a minimal (~1%) reduction in yield. Water requirement is projected to decrease and crop yield to increase for both crops for all future scenarios, except wheat water requirement, where water requirement is projected to increase by up to 13% in the future. Rainfed irrigation leads to extremely high variance in crop yields. Deficit irrigation under the nationally recommended fertilizer dose is recommended as a better option to develop climate resiliency in cereal yield in the study area.

Hydro-climatic extremes, such as floods and droughts, are influenced by climate change and climate variability, significantly affecting natural ecosystems, human lives, and livelihood. It is crucial to advance the understanding of long-term trends of hydro-climatic extremes for effective water resource planning and management. We analyzed 25 climatic extremes-related indices and 33 hydrologic extremes-related indices in a medium-range river basin in western Nepal, the Babai River Basin. We used RClimDex and Indicators for Hydrologic Alterations to analyze extreme climatic and hydrologic parameters. We computed monotonic trends to evaluate temporal changes in extreme events. The results show a positive trend of total precipitation at Kusum (+ 2.2 mm/year) and Bargadaha (+ 17.7 mm/year) stations and a negative trend at Gulariya (- 5.7 mm/year), Nayabasti (- 7.0 mm/year), Luwamjula (- 5.9 mm/year), and Ghorai (- 18.5 mm/year) stations. Similarly, we observe that almost all temperature extreme indices have a rising trend except the percentage of the days when the maximum temperature is less than the 10th percentile index at Rani Jaruwa station, located at a low elevation. Notably, the cold day temperature index falls at 0.13 days per year. Overall, the hydrologic alteration value shows moderate variability and reduction in the median flow for the second half. The findings of this study indicate that the study area is subjected to a reduced flow regime with a medium degree of variability.

Comprehensive flood risk assessment is often constrained by a lack of appropriate data in high-altitude watersheds, particularly in developing countries like Nepal, where institutional capacities are limited for mapping and monitoring flood-prone communities. This study, one of the first of its kind, produced spatial multi-criteria-based flood susceptibility, vulnerability, and risk index maps for the Kathmandu Valley (KV) watershed in Nepal using an Analytical Hierarchy Process (AHP) approach and Geographical Information System (GIS). The result shows that most parts of the KV (around 80%) have moderate to low flood susceptibility around the watershed but susceptibility is prominent in southern areas. Highly flood-susceptible regions (about 14%) are found mainly along the riverbanks. Flood vulnerability, primarily influenced by population density and literacy rate, is moderate to low in most areas of the watershed (around 86%), predominantly higher in the central urban areas, and gradually lower towards the edge of the watershed. Flood risks in the major portion of the watershed (around 72%), mainly in the southern and eastern parts, are estimated as moderate to low risk, whereas higher risk zones are found in the central urban areas. The high contrast in flood vulnerability scores across the watershed has mainly contributed to the variation of flood risk zones, as flood susceptibility scores are fairly distributed over the watershed. The study findings will help policymakers develop location-specific sustainable flood risk management strategies for the flood-vulnerable communities in the KV watershed.