DefinePK

Abstract

The main objective of this study is to evaluate discernible long term trends in streamflows of four major rivers of Pakistan, namely Kabul, Indus, Jhelum, and Chenab.  For each river, the first hydrological station where flow rate is measured after its entry to Pakistan, has been selected. The stations, thus selected on Kabul, Indus, Jhelum and Chenab are Warsak, Tarbela, Mangla and Marala, respectively.  The average monthly streamflow data for each of the four stations was collected from Irrigation department, Lahore for the period 1962-2011. The annual as well as seasonal analysis of average monthly streamflows was conducted using the Mann Kendall non-parametric test. For each case, the trend slopes were estimated using the Sen's slope method. A trend free pre-whitening (TFPW) approach was used to account for the auto correlation in the time series. Results indicate increasing trends for winter streamflows and decreasing trends for summer streamflows. For the spring season, Warsak exhibited decreasing trend, whereas the other stations showed increasing trends. Annual flow had a decreasing trend at all stations.  The trends identified in this study may be partially attributed to the effects of climate change in Pakistan.