Estimating the potential for in-line hydropower in the Himalayas: from global remote sensing data to local flow duration curves

Adopting multi-use systems in rural water infrastructure is a promising strategy to improve the sustainability of water utilities. For example, in-line hydropower - an infrastructure concept that combines water supply and micro-hydropower - has been successfully implemented in Switzerland for a century. Net profit from electricity is used to cross-subsidize water supply, improving the financial sustainability of water utilities. The concept is transferable to mountainous regions of developing countries, where it promises to alleviate the financial constraints that currently inhibit water supply development. Yet field attempts are missing to evaluate the success of trial in-line hydropower implementations, and a dearth of distributed hydrological and meteorological data complicates evaluations of the potential for future development. In this context, remote sensing offers a powerful technique to overcome data-scarcity issues in developing nations to facilitate the development of appropriate water supply technology. To utilize remotely sensed data for infrastructure planning, however, downscaling and regionalization challenges have to be addressed, especially in the mountainous regions where in-line hydropower would be applicable. Nepal offers an excellent test-bed to explore the potential for incorporating remote-sensing data into water resources planning. Here we present initial downscaling of TRMM daily precipitation data to a 5 x 5 km grid, including bias correction and explicit consideration of elevation effects. Several complementary approaches, including fractal downscaling, statistical downscaling and CDF-matching bias correction are evaluated through a cross-validation process. The results are used to drive different regionalization approaches for flow duration curves of Nepalese rivers. Finally, the relevance of in-line hydropower in rural mountainous communities is briefly discussed, based on feasibility assessments recently conducted in Central Nepal.