Estimation of Flow from Hunza Watershed Under Possibly Changed Climatic Conditions

Abstract

University of British Columbia watershed model is a modelling software which creates a computational representation of watershed behavior of the flows of rivers. The study was oriented to develop a daily watershed outflow of rivers resulting from glacier melt, snowmelt and rainfall for Hunza watershed, to estimate the flows under changed meteorological conditions. The discharge data was obtained from Danyor gauging station. Daily maximum and minimum temperatures and daily precipitation data was obtained from Ziarat meteorological station. The calibration was performed for the year 1999 to get the best coefficients of efficiency and determination. The results recorded for coefficient of efficiency and coefficient of determination were same for year 1999 i.e. 0.94. The calibrated model was then validated for year 1995 & 2000. The results showed that the values of coefficient of efficiencies were 0.92 & 0.87 and coefficient of determination were 0.88 & 0.72 for the years 1995 and 2000 respectively. River flow for year 2080 of Hunza catchment was estimated by assuming 100% glacier meltdown. Arshad in 2006 predicted future increase in daily temperature and precipitation by about 4.67 °C and 3.95% respectively for year 2080. These results were used in this study and scenario modelling was performed for the year 2080 by taking assumed changes in glacier extents i.e. ranging from 0% change (no reduction in glacier) to 100% change (means no glacier). The modelling results showed that there is a decrease in water river flow. The discharge for year 2080 (assuming no glacier) was 64.9% less than the discharge observed for no reduction in glacier in 1999.