Development of the Indus River System Model to Evaluate Reservoir Sedimentation Impacts on Water Security in Pakistan

Abstract

Pakistan’s society and economy are highly dependent on the surface and groundwater resources of the Indus River basin. This paper describes the development and implementation of a daily Indus River System Model (IRSM) for the Pakistan Indus Basin Irrigation System (IBIS) to examine the potential impact of reservoir sedimentation on provincial water security. The model considers both the physical and management characteristics of the system. The model’s performance in replicating provincial allocation ratios is within 0.1% on average and the modeling of water flow at barrages and delivered to irrigation canal commands is in agreement with recorded data (major barrage NSE 0.7). The average maximum volumetric error for the Tarbela and Mangla reservoirs are respectively 5.2% and 8.8% of mean annual inflow. The model showed that a 2.3 km3 reduction in storage volume since 1990 equates to approximately 1.3 km3 i.e., a 4–5% reduction in irrigation deliveries, respectively, for Punjab and Sindh in the dry (Rabi) season. This decline indicates that without further augmentation of system storage, the Rabi season supplies will continue to be further impacted in the future. This paper demonstrates the suitability of IRSM for exploring long term planning and operational rules and the associated impacts on water, food and energy security in Pakistan.