Hydroclimatic Assessment of Scarcely Gauged High-Altitude Catchment; A Case of Shigar Catchment of Pakistan

Abstract

The complex glacier dynamics of the third pole of the world makes HKH region challenging for hydrological modelling. The present study was conducted in the Shigar Catchment of Pakistan, with the objective to identify seasonal change on climate variables and to simulate potential changes in streamflow with respect to Projected climate data of CMIP 6 from Global Circulation model ACCESS-CM2 using HBV Light model, calibrated with efficiency value of 0.9. The results indicated the main contribution to streamflow was snow and glacier melt in summer mainly 79-80 % due to rising temperature values and the 20% from the summer rainfall. The catchment has a dry climate with maximum precipitation in the form of winter snow and generates the runoff from the melting of this snow in August- September. The high temperature and precipitation scenarios were found during 2060’s and 2080’s time series scenarios. The results also highlighted the change of temperature by a annual rise of 0.9 oC for 2020’s scenarios, followed by 1.86oC, 1.86 oC, 2.65 oC, 3.30 oC at SSP 245 and 0.98 oC, 2.08 oC, 3.54 oC and 5.10 oC in reference to annual rise in temperature of 0.06 for the historical periods. The precipitation trend in future for the catchment was found haphazard. The projected runoff values were found to increase from 25.6 mm to 38.9 mm for runoff from the changes in projected temperature and precipitation scenario for SSP 245 and SSP 585. Overall, the results of study suggested that catchment hydrology is more influenced by the temperature trend than precipitation trend in the past and future. Further, the Karakoram anomaly phenomenon also plays a significant role in deciding the fate of hydrology of the catchment from the drop of temperature in July from Westerly disturbances in summer and then rise in August and September