Calculating effective irrigation water use efficiency of Zhongjiang County using head-tail and whole-process methods

Abstract

【Objective】 Irrigation water use efficiency is an important parameter in irrigation design. It depends on various factors. In this paper, we compared irrigation water use efficiency calculated using the whole-process method and the head-tail method, from which we further studied the factors that influence water loss in irrigation districts. 【Method】 The study area was Zhongjiang County in Sichuan province. We divided the county into four regions (represented by TW, TH, ON and FO), each region having its typical canal systems and field conditions. The whole-process method calculated the irrigation water use efficiency in each region using a combination of hydrodynamic method, empirical formula and irrigation experiments. The head-tail method calculated the total irrigation amount in each region first by measuring the water flowing into and out of the region at the heads and tails, respectively, as well as other water sources flowing into and out of the region; these, along with the irrigation water consumed by crops, were used to calculate the irrigation water use efficiency. 【Result】 The canal water use efficiency in the largest TW regions was 0.596 and the smallest TH regions was 0.564, with a weight-average of 0.580. The water use coefficient in ON and TW regions in the north of the county was 0.90, thanks to their good hydraulic engineering projects. Affected by their topography, the water use coefficient in the TH and FO regions was 0.85. When the required irrigation guarantee was 75%, the irrigation water use efficiency calculated by the whole-process method was 0.503, compared to 0.492 calculated by the head-tail method. 【Conclusion】 The irrigation water use efficiency calculated by the two methods is comparable and their results are reasonable. The proposed method and the results can help to improve irrigation water use efficiency in regions where the irrigation water use efficiency is currently lower than the national average.

Keywords

• water efficiency of irrigation
• dynamic water discharge method
• kostiakov empirical formula
• head-tail method
• whole-process method