Decreasing Water Availability as a Threat for Traditional Irrigation-Based Land-Use Systems in the Mustang Himalaya/Nepal

Mountain ecosystems, which play a major role in the global water cycle, are extremely sensitive to changes in the climate system. Related modifications in the hydrological system affect both socio-economic structures in mountain regions as well as in the downstream lowlands. This is particularly evident in the northern catchment area of the Kali Gandaki River (Mustang/Nepal), an area in the Trans-Himalaya which is part of the greater Ganges catchment. The region is characterized by an extreme gradient in precipitation from a humid to a semi-arid climate and associated strong spatial-temporal differentiation of annual precipitation distribution over a short horizontal distance. While monsoonal summer precipitation in the south bordering High Himalayas contributes significantly to the annual precipitation, extreme winter snowfall indicates a significant influence of the westerly wind circulation on the hydrology of the study area. However, due to the lack of long-term meteorological datasets, the respective significance of these factors for local and regional water resources and the fluctuations and changes they are subject to is still largely unknown. The livelihood of the rural population in the study region depends to a large extent on agriculture for food security as the main source of income. Therefore, local water availability, access to water resources and its sustainable management are essential to secure local livelihoods. Although, locals have adapted their economic and land-use systems over centuries to the challenges in harsh mountain environments, recent and future climate change requires very short-term reactions to enhanced changes within environmental conditions. Of these, the strongly varying water availability in semi-arid environments will have the greatest impact on local communities.