Hydraulic simulation of Al-Badaa regulator operation and its impact on the flow of Al- Gharraf river

Surface irrigation is a widely used method for agricultural practices; however, it often suffers from low conveyance efficiency. The research investigates the hydraulic performance of a specific reach of Al-Gharraf River near Al-Badaa regulator located in Nasiriya city in southern Iraq. The primary objective of the present study is to simulate the operational mechanism of Al-Badaa regulator and evaluate its influence on upstream offtake operations. The research employs the Simulation of an Irrigation Canal (SIC) model, which is carefully calibrated and verified using values for the Manning coefficient and the discharge coefficient, alongside real-world operating scenarios. Five distinct flow conditions (100, 90, 80, 70, and 60% of design flow, Qd) were simulated, with cross regulators, head regulator gates, and offtakes fully opened. The findings indicate that Al-Badaa regulator significantly influences the hydraulic dynamics of Al-Gharraf River. Full opening of the gates results in a decrease in upstream water levels, causing reduced discharge at some water intake stations. This study provides critical insights into the hydraulic dynamics interaction between Al-Badaa   Regulator and the upstream offtakes serving Al-Dawaya, Shatt Al-Shatra, and Al-Basra water projects, located approximately 200 m, 300 m, and 2 km upstream of Al-Badaa regulator, respectively. A key outcome of this work is to partially open two out of six gates, to a height of less than 1 m, to maintain sufficient water levels. This operational strategy significantly improves the hydraulic performance of the irrigation network and ensures equitable water distribution to critical upstream offtakes.