The selection of general circulation models (GCMs) with high capability to represent the past and likely future climate for a specific geographical location is a crucial step to assess impacts of climate change on different sectors. This study included pool of 105 and 78 GCMs for representative concentration pathways (RCPs) 4.5 and 8.5, respectively, from Coupled Model Intercomparison Project-Phase 5, applied an advanced envelope-based selection approach to select representative GCMs for the Koshi river basin in China and Nepal at short-term (2016-2045), mid-century (2036-2065) and end-of-century (2071-2100) periods, and developed range of possible future precipitation and temperature scenarios with high resolution downscaled data (10 × 10 km 2), which is the novelty contribution of the study. Considering RCP4.5, average annual precipitation is expected to increase by 0-16%, 4-23% and 4-24% in the short-term, mid-century and end-of-century periods, respectively. Using RCP8.5, equivalent predictions are 6-20%, 6-36% and 13-49% in the shortterm, mid-century and end-of-century periods, respectively. Average annual temperature is expected to increase, but with higher increases during winter than in the monsoon period. Considering RCP4.5, average annual temperature is expected to increase by 1-1.4 C, 1.3-1.9 C and 1.6-2.8 C in the short-term, mid-century and end-of-century periods, respectively. Similarly, using RCP8.5, equivalent predictions are 1-1.6 C, 1.8-2.9 C and 3.1-5.6 C in the short-term, mid-century and end-ofcentury periods, respectively. The ensemble mean of absolute change in average precipitation and temperature projects that High Himalaya and Tibet regions are more sensitive to climate change considering precipitation and temperature, respectively. The results also suggest that GCMs selection for a catchment varies with climate scenarios and specific future time periods.

This study assesses climate change impacts on the hydrological regime of a river basin and its implications for future irrigation water availability in the Koshi River basin using RCPs 4.5 and 8.5 over short-term (2016-2045), mid-century (2036-2065) and end-of-century (2071-2100) periods. Average flow in the Koshi River is projected to increase. Projections of average minimum monthly river flow suggest that the areas of winter wheat and monsoon paddy rice could be increased. However, the planting period of paddy rice should be delayed by one month (July to August) to capture the expected increased water availability in the river.

An increase of cropping intensity of irrigation schemes is required to address the challenge of global food security. Socio‐economic factors also have a significant impact on the cropping intensity within an irrigated area. This research is focused on understanding the impact of socio‐economic factors on cropping intensity in an irrigation scheme. To assess the socio‐economic factors and cropping intensity, a framework was developed, which we believe can be adopted in other irrigation schemes in developing countries. The framework was applied to an irrigation area in Nepal. An interview checklist and observation techniques were used as the primary data‐gathering method, which followed the concepts articulated in the developed framework. A census survey was also conducted in 72 farmer households. The results showed that farmers' socio‐economic status and their socio‐cultural practices affected cropping intensity. The research also highlighted that mechanization in agricultural practices, coordination between irrigation and agricultural district offices with farmers, market facilities for agricultural inputs and agricultural products, and land tenancy agreements all significantly influenced agricultural intensification. Based on the findings of this research, an approach to intensify cropping intensity by farm owners and farming tenants has been developed, which can be applied in irrigated areas in the developing world. © 2020 John Wiley & Sons, Ltd.

The Nepalese Sunsari Morang Irrigation district is the lifeblood of millions of people in the Koshi River basin. Despite its fundamental importance to food security, little is known about the impacts of climate change on future irrigation demand and grain yields in this region. Here, we examined the impacts of climate change on the irrigation demand and grain yield of wheat crop. Climate change was simulated using Representative Concentration Pathways (RCPs) of 4.5 and 8.5 for three time horizons (2016–2045, 2036–2065, and 2071–2100) in the Agricultural Production Systems Simulator (APSIM). For the field data’s measured period (2018–2020), we showed that farmers applied only 25% of the irrigation water required to achieve the maximum potential grain yield. Actual yields were less than 50% of the potential yields. Projected irrigation water demand is likely to increase for RCP4.5 (3%) but likely to decrease under RCP8.5 (8%) due to the truncated crop duration and lower maturity biomass by the end of the 21st century. However, simulated yields declined by 20%, suggesting that even irrigation will not be enough to mitigate the severe and detrimental effects of climate change on crop production. While our results herald positive implications for irrigation demand in the region, the implications for regional food security may be dire.