Assessing inflow variability at rim stations of the Indus Basin Irrigation System*

Abstract

AbstractHaving one of the largest interconnected irrigation systems in the world, the distribution of irrigation water in Pakistan is largely dependent on river supplies. Seasonal planning of water distribution in the country ignores day‐to‐day inflow variability which impacts water distribution operations. This study has been carried out to assess the inflow variability at four rim stations of the Indus Basin Irrigation System (IBIS) in Pakistan, namely: Kabul River at Noshera, Indus River at Tarbela, Jhelum River at Mangla, and Chenab River at Marala. Nine vital hydrological parameters, depicting various aspects of variability, were computed using 24 years of daily inflow time series. Analysis indicated that Mangla and Marala stations depicted more instances of high flow pulses, which highlighted their flashy nature compared to Noshera and Tarbela whose contributions were mainly from snowmelt. Mangla and Marala stations also depicted higher variations in terms of number and duration of low flow pulses, whereas least low flow variations were observed at Tarbela. Assessment of variability indicated that Tarbela exhibited minimum variations in inflows in the months of October to January, while Marala showed highest inflow variations among all stations in the same months. This study identified successfully the critical months of high flow variability, in addition to identification of the climate shift in the region—two aspects that need attention in future planning and operations.