Cycle 1 (2011 Deadline)
Establishing a collaborative assessment of the impacts of climate change on the hydrological regime of the Langtang River Basin, central Nepal
PI: Rijan Bhakta Kayastha, Kathmandu University
US Partner: Mark W. Williams, University of Colorado
Project Dates: May 2012 - April 2014
The Himalayas display great climatic variability, with the mountains acting as a barrier to atmospheric circulation for both the summer monsoon and winter westerlies. A substantial amount of the annual precipitation falls as snow, particularly at high altitudes, feeding the Himalayan glaciers. While about one-third of the world’s population depends to some degree on freshwater within the High Asia hydrological system, there is not enough data at present on river and stream flows, precipitation, and the contribution of seasonal snow and glacier melt to paint an accurate picture of the water resources there. The High Asia mountains funnel water into such major river basins as the Ganges, Brahmaputra, Indus, Amu Darya, and Syr Darya. The contribution of glacier melt to the major rivers in the region is unknown, with estimates ranging from 2 to 50 percent. Climate change is currently taking place and is projected to compound the pressure on natural resources and the environment associated with rapid urbanization, industrialization, population growth, and economic development. It will potentially have profound and widespread effects on the availability of and access to water resources.
This project focuses on the hydrological regime of the Langtang River Basin in Nepal. It will include data analysis and field measurements of discharge, glacio-hydrological modeling, and estimation of future water availability in the river basin. The modeling results will be verified using geochemical and water isotope tracer techniques studies developed at the National Science Foundation-funded Niwot Ridge Long-Term Ecological Research, which allow researchers to follow water as it courses through mountain landscapes. Expected results of this project will be improved understanding of the hydrological regime of the basin and enhanced prediction of future water availability. It should also promote research capacity building for the Nepalese participants and contribute to helping relevant Nepalese government agencies improve their capabilities in water resources planning and implementation.
Summary of Recent Activities
During the first quarter of 2013, Dr. Kayastha and his team worked on glacio-hydrological model selection and calibration. A simple distributed positive degree-day (PDD) model that requires monthly temperature and precipitation data has been calibrated in the Langtang River basin to estimate snow and ice melt under a debris layer, including the total discharge from the river basin. The Langtang was partitioned into 18 elevation bands for this purpose. The PDD model has been calibrated for the period of 1995 - 2003 using observed temperature, precipitation, and discharge data obtained from the Department of Hydrology and Meteorology, Government of Nepal. While calibrating the model, the researchers used different inputs such as low PDD factors, degree day factors for snow and ice, and other parameters like infiltration, potential evapotranspiration, and base flow. The downscaled data are being used for future discharge predictions for the Langtang river basin. To aid in these projections, the team acquired downscaled climate data and projections for 2010-2030 from the Himalayan Cryosphere, Climate, and Disaster Research Center (HiCCDRC) at Kathmandu University. In addition, they obtained other data sets for 2031-2059 from the Climate Data Portal of the Department of Hydrology and Meteorology. Future plans include additional field visits in April 2013 and an annual workshop in May 2013.