ASSESSMENT OF VARIABILITY IN FRESH WATER RESOURCES UNDER CHANGING CLIMATE SCENARIOS: A CASE STUDY OF SOAN RIVER BASIN, POTOWAR REGION, PAKISTAN

Abstract

This study aims to investigate the variations in freshwater resources of the semiarid Soan River Basin (SRB) under changing climate scenarios till mid of the twenty first century. In the present study, state of the art, conceptual, semi-distributed, lumped hydrological model, Hydrologiska Byråns Vattenbalansavdelning (HBV) light, a modified version of the HBV model was implemented to simulate projected flows of two sub-catchments of the SRB namely, the Sihala sub-catchment (SSC) and the Kani sub-catchment (KSC). HBV-light is calibrated for the time period (1984–2008) and validated for (2009–2017) for both the sub-catchments of the SRB. HBV-light exhibited good performance both during calibration and validation for both the subcatchments of the SRB. After calibration and validation, the hydrological model was induced with future climate projections data of the Swedish Meteorological and Hydrological Institute Rossby Centre Regional Atmospheric Model (SMHI RCA4), forced with the two Representative Concentration Pathways (RCPs), i.e. the RCP 4.5 and RCP 8.5 to simulate projected flows of the (SRB) for the time period (2018–2047). Climate changes in the future suggest warming under both the RCPs and a significant increase in precipitation amount (yearly and seasonal basis, while decrease and increase could be seen for monthly basis), and an increase in evapotranspiration (but the magnitude of change in precipitation outweigh the change in evapotranspiration). Mean annual flows of the SSC showed an increase of 467% (593%) and an increase of 270% (316%) for KSC under the RCPs 4.5 (8.5). A decrease of up to 39% and 29% is projected under RCP 4.5 for spring transitioning months for both sub-catchments and a decrease of up to 41% for winter months under RCP 8.5 for the SSC. Highest increase amongst all the seasons is projected for the summer season in the SSC under both the emission scenarios. However the winter flows seems to decrease under the RCP 8.5. Overall an increasing pattern could be observed for the rest of the seasons. This study would be beneficial for multiple stakeholders and sectors including water resource managers, agriculture, hydropower generation, and socioeconomic development.