Comprehensive assessment on water-saving renovation of large-scale irrigation districts in Inner Mongolia based on hierarchical analysis- ant colony algorithm

Abstract: Inner Mongolia Autonomous Region is located in northern China and it is characterized by dry，little rainfall, and shortage of water resource. Most farmlands in this region are distributed in arid and semiarid areas, and thus agricultural production is highly dependent on irrigation. There are 14 large-scale irrigation districts in 7 municipalities (leagues) or around 3 river basins. Most of the irrigation districts obtain irrigation water from surface water. The irrigation districts as important agricultural bases of China for spring wheat, maize and sunflower production are constructed in 50 s-70 s of 20th century. The old irrigation districts are found with problems such as disrepair, poor auxiliary works, sever canal seepage and low water use efficiency. The increased population and socio-economic development have greatly aggravated the competition for water among agriculture, industry and domestic users in these irrigation districts. In order to deal with such problems and maintain agricultural production, a project of renewed construction and water saving renovation for irrigation districts was implemented in Inner Mongolia Autonomous Region since 1998. It is necessary to evaluate the effects of the project for better managing and developing future projects of water saving renovation. However, since there is large difference in physical conditions, hydrogeology and climate among irrigation districts, the effect of water saving renovation may vary greatly in different irrigation districts, causing the difficulty in selecting indicators for evaluation. In this study, 10 typical irrigation districts (water diversion from the Yellow River, water diversion from reservoirs, water diversion from other rivers, water lifting from rivers and water lifting from wells) were selected and used for the evaluation of water saving renovation using Hierarchical Analysis-Ant Colony method. From the perspective of plant species, irrigation methods, operating management level and economic benefits of different environment, the evaluation indicator system was constructed with 4 parameters for crop cultivation, operation, management and benefit. The Hierarchical Analysis was used to assign the weights to each indicator for each irrigation district and the Ant Colony Algorithm was used to determine the optimal degrees indicating goodness of the water saving renovation in each district. The results showed that the 10 irrigation districts were ranked by optimal degree as Mountain bay (0.91), Dengkou (0.95), Hetao (0.97), the South Bank of Yellow River (0.98), Dian Zi (1.005), Chaer Sen (1.01), Yingjin River (1.115), West Liaohe River (1.14), Madi Hao (1.165), and Moli Temple (1.185) irrigation area. It indicated that of the 10 typical irrigation districts, the water-saving renovation effect of San Wanzi Irrigation District and Dengkou Irrigation District were remarkable but that of Mo Limiao Irrigation District was not desirable. The evaluation was in agreement with the real situations of these irrigation districts, suggesting that the assessment based on the Hierarchical Analysis-Ant Colony method was reliable. The Hierarchical Analysis-Ant Colony method was simple and easy to operate and reliable for evaluation of large-scale irrigation districts. The study introduced a new method for assessment of water-saving renovation effects of large-scale irrigation districts.