Construction and empirical analysis of the evaluation index system for the water-saving level of large-sized irrigation districts

Abstract: About 215 billion cubic metres of water has been consumed by large and medium-sized irrigation districts in recent years, particularly over 35% quantity of the total water consumption in China. The irrigation district has been the main field of agricultural water-saving construction. Therefore, it is necessary to accurately assess the water-saving level in modern irrigation districts. In this study, an index system was established to evaluate the water-saving level in large-scale irrigation districts. Five aspects were considered, including engineering water-saving, farmland water-saving, water use management, water resources protection, and water use benefit. Eight standards were selected, such as measurability, vulnerability, predictability, typicality, controllability, integrity, responsiveness, and stability. A screening model was constructed to identify the indexes to be shortlisted or not. Subsequently, 23 indexes from the 70 primary indexes, 86.42% of the information was expressed by 32.86% of the elementary indexes, indicating the concise and adequate index system. The final indexes were formed, including the backbone canal lining ratio, the completion rate of engineering projects, backbone canal intact rate, backbone hydraulic structures intact percentage, water utilization coefficient of canal system, high-efficient water-saving irrigation coverage percentage, field water utilization coefficient, multi-cropping index, gross irrigation water consumption per mu, real collection rate of water charges, water user association coverage rate, allocation rate of water measuring equipment on lateral gate, 2 fees implementation rate, number of management personnel per 10 000 mu, proportion of management personnel with junior college degree or above, informationization coverage rate, proportion of irrigation water in total water consumption, drainage ditch intact rate, water ecological monitoring system coverage rate, proportion of ecological water in the total water consumption, grain yield produced by 1m3 irrigation water, proportion of primary industry production in irrigation district, and water consumption per-10 000-yuan-GDP. Four large-scale irrigation districts (Qucun, Penglou, Guangli, and Dagong) are all located along the Yellow River in Henan Province. The indexe system was then investigated empirically to determine the water-saving level. The water-saving level indexes for the four objective Irrigation Districts were 0.666 (Qucun), 0.730 (Penglou), 0.657 (Guangli), and 0.616 (Dagong), respectively. On the whole, the score of the water-saving level index was ranked in the descending order of Penglou, Qucun, Guangli, and Dagong. The scores of the 5 secondary indexes showed that Penglou achieved the best effect of engineering water-saving, whereas, Dagong was a negative example. This was due to the well-matched infrastructure engineering, where the backbone canal system was of systematic construction and renovation in the past 10 years. Guangli performed relatively lower than the rest because the high-efficient coverage percentage of water-saving irrigation was rather weak and the gross consumption of irrigation water per mu was pretty high, particularly for the long-term goals of farmland water-saving. There was no significant difference in the score of water use management level among the four irrigation districts, but their agriculture water rate, water user association promotion, and water measuring facilities setting, all needed to be rather improved. Water resources protection was the common weakness of the four irrigation districts, indicating the concept of project construction without considering ecological protection over the past years. Consequently, five recommendations can be addressed to further improve the water-saving level in the irrigation districts. 1) To coordinate the backbone and field construction, 2) To establish the new water-saving system under the agricultural water price reform, 3) To strengthen the dredging and transformation of drainage ditches, 4) To improve the water resources and environment monitoring network, 5) To promote the efficient saving on water irrigation, particularly for the planting area of cash crops. The findings can provide an effective way to scientifically evaluate the water-saving construction in large-scale irrigation districts, thereby promoting the process of agricultural water-saving in China.