Reducing losses in earthen agricultural water conveyance and distribution systems by employing automatic control systems

Abstract

Losses in agricultural water conveyance and distribution systems are caused by two main reasons: seepage and improper operation of canal structures. This study examined the potential of Automatic Control Systems (ACS) to simultaneously reduce seepage losses and improve the operational performance of structures. To achieve this goal, a seepage model was integrated with an operational simulation model. The former model simulated the seepage flow throughout the main irrigation canal for different operational conditions imposed by the operational model. The ability of the integrated models to simulate reduction in losses was tested for the main canal of an irrigation district in southwest Oklahoma, United States (U.S.). Three combinations of the ACS and seepage model were studied, where ACS included or lacked inline water storage as an operational strategy and the seepage model simulated seepage rate for existing or maximum potential conditions. Three scenarios of reducing target levels in the canal to reduce seepage losses were considered for each combination. The results showed that without inline storage, considerable reduction in operational and seepage losses could be achieved for variable target levels. However, the adequacy indices for all off-takes were poor and proved water delivery process was unreliable and unacceptable. With inline storage, operational and seepage losses were reduced by 8–9% and 3–7%, respectively, while good adequacy indices were obtained, indicating an appropriate water delivery. The same ACS was able to significantly reduce losses while maintaining acceptable water distribution and hydraulic conditions under maximum seepage that can potentially occur in the studied irrigation canal. The control system proposed in this study can be a reliable and practical solution for reducing two main sources of water losses within irrigation districts and thus improving districts-level water productivity.