C41A-0319:
Integrated simulation of snow and glacier melt runoff in a distributed biosphere hydrological modeling framework at Upper Indus Basin, Karakoram region
Thursday, 18 December 2014
Maheswor Shrestha1, Toshio Koike2, Yongkang Xue3, Lei Wang4 and Yukiko Hirabayashi2, (1)University of Tokyo, Bunkyo-ku, Japan, (2)The University of Tokyo, Tokyo, Japan, (3)University of California Los Angeles, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, (4)ITP Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
Abstract:
High mountain river basins in Hindukush Karakoram and Himalaya (HKH) regions are considered as ‘water towers’ of Asia with abundant source of fresh water as snow and glaciers. Upper Indus basin is one of the mega scale river basin in HKH region where snow and glaciermelt runoff is the major contributor to the annual runoff. The hostile climate, remote and extreme rough topography imposes many restraints regarding hydro-meteorological and glaciological observations, leading towards limited understanding of hydrological processes of river basins in this region. It is vital to integrate snow and glacier melt processes in a distributed biosphere hydrological framework to estimate the snow and glacier melt runoff and to quantify the river flow composition (snowmelt, glacier melt and rainfall contribution). An integrated system of distributed biosphere hydrological modeling framework with multilayer energy balance based snow and glaciermelt runoff schemes (WEB-DHM-S model) was implemented at Upper Indus basin (207300 km2) with a spatial resolution of 1 km and temporal resolution of an hour. Model input were meteorological forcing from Global Land Data Assimilation System (GLDAS), APHRODITE precipitation and de-trended gridded air temperature from observations. Simulations were carried out for two hydrological years (2002-2003). Discharge simulation results at multiple gauges showed good agreement with the observed one having Nash efficiency at 0.86. The spatial distribution of snow cover is simulated well as compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) derived eight-day maximum snow-cover extent data (MOD10A2). Model accuracy, overestimation error and underestimation error in snow cover simulation were obtained at 78%, 7% and 15% respectively. Uncertainty in precipitation was the main reason for the biases in seasonal variation of snow pixel errors. The model demonstrated its sound capability in comprehensive simulation of discharge with its flow composition, spatial distribution of snow cover and net mass balance.
