Effect of an improved agricultural irrigation scheme with a hydraulic structure for crop cultivation in arid northern Afghanistan using the Soil and Water Assessment Tool (SWAT)

The current study focuses on water scarcity, water shortages, and inequal water allocation for downstream water users in the Balkhab River basin (BRB) in northern Afghanistan. The Soil and Water Assessment Tool (SWAT) was utilized to determine the hydrological process in the watershed and assess the water resource capacity. The model was calibrated and validated to ensure proper model setup for the entire watershed. The analysis of the current water management and allocation scheme indicated inadequate water distributions for the downstream irrigation canals. The current water allocation approach was modified based on crop water requirements and the available agricultural lands. A new irrigation scheme was proposed and included in the SWAT model that does not decrease upstream water allocation. The annual streamflow in the Balkhab River can supply the extra allocated water downstream without influencing the upstream water. Notably, a dam was proposed in the middle stream to store water during the winter and early spring seasons, as well as floodwater. The model outcomes showed that the existing annual streamflow in the river can fully support the irrigation of currently available land and an extra 18,470.6 ha of agricultural lands in the BRB. The results of this study can contribute to scientific evidence-based policy and decision-making processes for sustainable agricultural water resource management and flood control in the study region.