Abstract:
Investigation of continuous daily streamflow of high altitude cryosphere catchment based mainly on both snowmelt- and rainfall-runoff, is particularly challenging in case of limited climatic records. The aim of this study is to compare the accuracy of two different rainfall runoff hydrological models, SWAT (Soil and Water Assessment Tool) and HBV (Hydrologiska Byråns Vattenbalansavdelning model) through performance of continuous simulation of snowmelt and rainfall runoff in Gilgit River basin, northern Pakistan under current and potential climate-change scenarios. We used European Centre for Medium Range Weather Forecasts, ERA Interim (ECMWF) daily temperature, precipitation, evapotranspiration data and Coupled Model Intercomparison Project (CMIP3) daily Solar Radiation, Relative Humidity and Wind Speed datasets to examine the efficiency of both models. The observed streamflow data of thirteen years (1990–2002) was used for the calibration and five years (2003 – 2007) data for validation of models. A good agreement was attended between simulated and observed streamflows for annual snowmelt season in the calibration and validation period (0.93, 0.23) and (0.75, 26.30) for HBV and (0.60, 34.26) and (0.74, 10.73) for SWAT [statistic are (Nash-Sutcliffe efficiency and difference in volume %)], respectively. For potential climate-change scenarios, streamflow was projected using different precipitation and temperature scenarios. For temperature variations of -2 – +4°C HBV and SWAT showed a variation in annual streamflows of -16.92% – 6.6% and -28.71% – 2.96% respectively. While change in precipitation of -10% – +20% showed a variation of -6.65% – 13.3% and -18.13% – 27.5% in HBV and SWAT respectively. End results of the project reveal that HBV has higher efficiency and requires less datasets than SWAT to accurately predict rainfall using Remotely Sensed data. Also, HBV shows more consistent results of streamflow under changing climate conditions in Gilgit basin.
