Upstream-downstream linkages of hydrological processes in the Himalayan region

Understanding the upstream-downstream linkages in hydrological processes is essential for water resources planning in river basins. Although there are many studies of individual aspects of these processes in the Himalayan region, studies along the length of the basins are limited. This study summarizes the present state of knowledge about linkages in hydrological processes between upstream and downstream areas of river basins in the Himalayan region based on a literature review. The paper studies the linkages between the changes in the physical environment of upstream areas (land use, snow storage, and soil erosion) and of climate change on the downstream water availability, flood and dry season flow, and erosion and sedimentation. It is argued that these linkages are complex due to the extreme altitudinal range associated with the young and fragile geology, extreme seasonal and spatial variation in rainfall, and diversity of anthropogenic processes. Based on the findings, the paper concludes that integrated systems analysis is required to understand the holistic complexity of upstream-downstream linkages of hydrological processes in the river basin context. The integrated land and water resources management (ILWRM) approach can be instrumental in developing adaptive solutions to problems and can also enable stakeholders of upstream and downstream areas with various interests and needs to work together for the better utilization and management of land and water resources. As a part of this, the specific circumstances of the upstream communities, who live in fragile and inaccessible mountain areas with limited resource opportunities, should be taken into account so that incentive mechanisms can be established to encourage and acknowledge their contribution.