Trend analysis of hydrometeorological parameters and reservoir level of Tarbela reservoir, Pakistan

This study identified the trends in monthly temperature, precipitation, & evaporation for Astore, Darosh, Gilgit, Gupis and Skardu and trends in inflow, outflow and reservoir level for Tarbela reservoir. Two non-parametric tests i.e. Man-Kendall and Sen’s Slope and Innovative Trend Analysis (ITA) were used to determine the trend. The first Mann-Kendall test with a significance level 5% was applied to 33-year data of five selected areas from 1990-2022. The results showed an increasing trend in temperature in March for all selected areas. No significant trend was observed in precipitation except negative trends for Darosh in March, May and December and positive trend for Gilgit in January and September. It has been observed that the trend direction given by ITA and Mann-Kendall is similar. Inflows to reservoir were found directly related to the temperature because of glacier melt in rising temperature, thus increasing the inflow, although the precipitation was found decreasing with increase in temperature. Altered snowmelt patterns can influence weather systems, potentially contributing to more extreme weather events.