Modeling of Water Fluxes and Budget in Nam Co Basin during 1979–2013

Abstract

AbstractIn this study, we established a hydrologic modeling framework over the Nam Co Lake basin by linking a glacier-melt scheme with a physically based, distributed land surface hydrologic model, and a heat-balance model was used for water surface evaporation. Hydrologic processes including evapotranspiration from land regions, runoff from both glacierized and nonglacierized areas, and lake surface evaporation were continuously modeled for 1979–2013, and then lake level changes were reconstructed. Rainfall runoff, snowmelt runoff, and glacier runoff contributed 59%, 28%, and 13% of total runoff, respectively. For the high-altitude region, runoff was mostly generated from glaciers. The lake had a positive water budget in most of the years with an average lake level depth of 128.8 mm, resulting in a total rise of approximately 4.5 m. Precipitation and precipitation-induced runoff were the main water supplies and played a dominant role in lake growth. Although the glacier runoff only contributed 13% of the total runoff, it played an important role in controlling the water level. The rising temperature led to increasing evaporation in two ways: one was providing an energy source for evaporation, and the second was extending the ice-free period. This mitigated the recent expansion of the lake, but on the other hand, it led to increasing glacier runoff into the lake. Hence, the rising temperature had two diametrically opposed effects on lake water balance.