Water Security In Irrigation District Under The Condition Of Water Supply Limitation

Baotouhu farm was established in 1959.The development of the farm agricultural economy was in an all-round way for more than 50 years. Especially in the decade after 2005,farm land area had a rapid growth at an average rate of 10.0 %,and the demand for water was also increasing.The changing of irrigation mode and the decrease of surface water prompted the farm shift water demand to groundwater and the imbalance between supply and demand of groundwater resources was very outstanding.Chosed Baotouhu farm,where a limited water supply system had put into practice,as the study area. Studied on the groundwater depth and flow field distribution and analyzed the facing problems with field investigation, real-time monitoring and numerical simulation method, etc.In Baotouhu farm, cultivated land took up 81.0 % of the administrative total areas, and 90.2 % of the arable landhad taken high-efficiency water saving technology. With the promotion of high efficiency water saving technology and the rise of the cotton industry, water-saving facilities were improved continuously, of which the construction of the electromechanical well was particularly outstanding.For three years, the number of electromechanical well increased at an annual rate of more than 30.As a result, proportion of groundwater in total agricultural water demand increased rapidly. It was detrimental to the irrigation area groundwater resources and the ecological environment.Took 2007 as the initial year to established hydrogeological conceptual model, mathematical model and the numerical model of groundwater system in the study area and run to calculate through the processing of MODFLOW software. On the basis of the surface water resources in 2009-2014 survey data,set three kinds of different situations for the regional water balance analysis. Then, used the numerical model to predict wether the groundwater depth in the study area could meet the water safety standards.For the situation that did not meet the requirements, returning farmland was needed. Finally,choosed reasonable return farmland scheme respectively, and determined the irrigation water-saving irrigation area, analyzing the economy and feasibility conditions comprehensivly.Analyzing the simulation results, when surface water diversion was 2500.0×104m3/a, groundwater withdrawal was 2273.5×104m3/a,the water could meet the needs of the existing farmland irrigation and ensure the ecological security.When surface water diversion was 1800.0×104m3/a, groundwater withdrawal was 2973.5×104m3/a, groundwater depth surpassed the critical standard of maintains ecological safety. To meet the minimum standards of ecological requirements, it should reduce 30.0 % of the non-responsibility farmland,at least. When surface water diversion was 1300.0×104m3/a, groundwater withdrawal was 3473.5×104m3/a, even the extraction of groundwater was unrestricted. It was difficult to meet the needs of the existing arable land. To alleviate ecological crisis of the irrigation area, it was necessary to return for at least 80.0% of non-responsibility farmland.