Modeling Current and Future Hydrometeorological Variability in the Neelum Basin using HBV-Light model

Abstract

The Neelum river basin which is also a transboundary basin suffers from scarcity of data and research in the field of hydrology and water management. The main objective of the study includes to Calibrate & validate the HBV model in the Neelum basin, project future streamflow using IPCC climate change scenarios (RCP 4.5 & 8.5) in HBV model and analyze the long-term (35 years) observed and future hydrometeorological trend at Neelum basin. The model was forced with in-situ as well as RCP’s (4.5 & 8.5) projected climatic data of temperature and precipitation from the bias corrected CORDEX. Moreover, both historical and projected trends were calculated using Mann-kendall and Sen’s slope estimating methods. Results depicted that model perform fairly well during both calibration and validation (NSE=0.8 & 0.7) in the Neelum catchment. The future projection of the precipitation showed that the winter water availability is projected to drop down from more than 5mm/day to as low as 2mm/day under RCP 8.5 in 2060s. The summer water budget is also reduced in the future projection from 9mm/day to 7mm/day under the RCP 8.5 in 2030s. The temperature projections revealed that the high relief in the monsoon months (July, Aug, Sep) expected to diminish in the future projection with 5 to 6 0C increase under the RCP 8.5 in 2060s. These changes would affect magnitude of the future discharge by dropping it down to 50% especially in the summer months with an increased in the peak flows of monsoon seasons. The trend analysis of the observed data showed a significant increase of upto 2 0C in July temperature, 1.8mm/day decrease in March precipitation and a corresponding 1.8m3/s decrease in the discharge values of the Neelum river basin in July. The future estimations of the temperature showed that it is susceptible to increase by 4.8 0C in the 2060s. whereas, precipitation generally showed no significant increase or decrease in the future projected and is expected to remain unchanged in the future. Although winter discharge in the future projection was increasing significantly with value of 8.4m3/s but the summers discharge exhibits no significant change in the future projection. The present study provides added value to the hydrometeorological characteristics of Neelum river basin in the future scenario for decision and water policy makers.