Non-structural modification of agricultural water distribution systems in large scale irrigation districts

Abstract

The present study's primary objective is to investigate non-structural alternatives' effectiveness in providing a reliable agricultural water distribution in large scale irrigation districts. Accordingly, the following activities were conducted to accomplish the objective: i) developing an operation model of non-structural alternatives in MATLAB; ii) developing a simplified hydraulic flow simulation model in MATLAB, capable of being integrated the operation model. iii) operational performance appraisal of the developed model under the normal and water shortages scenarios, iv) spatial analysis of the obtained results with GIS to determine each alternatives' effectiveness. The developed model was tested on a real test case, extensive irrigation districts located in central Iran. Analysis of the obtained results reveals that employing the first to third non-structural alternative improved the mean value of the daily water distribution adequacy index by 6–8%, 10–11%, and 5–7% in the normal scenario, 4–5%, 8–7%, and 3–4% in the water scarcity scenario, compared to the water distribution process in the status quo. Besides, the alternatives lead to improving water distribution equity even under the water scarcity scenarios, where the equity improved by 10, 12, and 8% for the first through third alternatives compared to the status quo. Besides the technical assessment, a comprehensive evaluation concerning the non-structural alternatives' effectiveness was conducted, based on the environmental, agricultural, and social effects of these alternatives, to provide practical results. The latter assessment reveals that the second alternative's implementation is expected to lead to a remarkable 12% annual water extraction reduction from the aquifer, decommissioning about 1694 of the 14,440 authorized tube-wells within the district, and a 14.3% reduction in energy consumption. The results showed acceptable improvement in irrigation water distribution by employing non-structural alternatives under normal operating conditions and little improvement under water scarcity scenarios. It was shown that, given the limited infrastructure available in the irrigation districts in developing countries, improving operation management does not necessarily need massive investments in renovating and modernizing these districts.