Developing a centralized automatic control system to increase flexibility of water delivery within predictable and unpredictable irrigation water demands

摘要

Irrigation districts modernization has become a key strategy to address unreliable water resources and improve water use efficiency in irrigated regions. However, improving water use efficiency will be achieved when off farm water distribution systems are integrated with on-farm practices within irrigation districts. In the present study a modernization alternative for irrigation canal operation, a centralized automated control system, was designed to handle both of known and unknown patterns of demanded water dictating by different irrigation systems in the farms. This alternative was developed in response to on-farm water management transitions from traditional, surface irrigation methods, to modern irrigation systems including the pressurized systems. The capability of Centralized Model Predictive Control (CMPC) was investigated for dealing with a set of complex water distribution test scenarios including predictable and unpredictable +/- 50% demand variations through the irrigation canal. Altus canal of the Lugert-Altus Irrigation District in southwest Oklahoma, USA is selected as the test case due to the recent challenges occurred in water distribution management in the Altus canal. The transition from traditional irrigation methods (i.e., furrow irrigation) to modern pressurized systems of subsurface drip irrigation (SDI) systems in large regions of the district caused the mentioned challenges. The results showed that when the demands were predictable, the controller successfully regulated water levels so that no off-take within the entire canal suffered from inadequate water delivery. Although the changes in the demand were considerable, stable canal operation was provided using the CMPC for this scenario. The designed controller also had an outstanding performance in dealing with extreme, unpredictable irrigation water taking test scenarios. The controller performed well with a quick hydraulic response to the changes, especially in the downstream canal reaches. The developed system started storing extra water within the canal reaches and employed it as a local inline reservoir to compensate delay times of water traveling within the irrigation canal. The stored water within the canal was entirely used after a sudden increase in any unknown demands.