Study On The Evolution Of Groundwater System Under The Large-scale Water-saving Irrigation In The Irrigation Area Of Hejing County

Hejing County is located in northwestern Yanqi basin, since the mid-1990 s, for making the irrigation area of the basin to get rid of soil secondary salinization and restoring downstream ecological environment, efficient water-saving technology begins to be vigorously promoted in agricultural irrigation. Hejing county in 2009 begins to promote efficient water-saving irrigation, until 2013, Hejing county completes the area having reached 26.97×103hm2. With the further promotion of efficient water-saving technology, increasing exploitation of groundwater and declining groundwater level, seriously affects the local ecological environment.Based on the status quo, combined with existing studies and using GMS, GIS, PMWIN and other data analysis tools, the spatial structure of the aquifer and characteristics of groundwater recharge and discharge, spatial and temporal variability law of groundwater level are analyzed, then the relationship between groundwater level change and water-saving irrigation are known clearly. Lastly, it uses of numerical simulation software to predict groundwater study and proposes viable agricultural water schemes. The main results of this study are as follows:(1) In the groundwater recharge items, the proportion of the river leakage, the canal system leakage, and the field infiltration are larger, which account for 68% in 2005. Canal leakage in 2013 compared to 2005 decreases 48.1%, while the field also diminishing infiltration. In the groundwater discharge items, wells exploitation increase rapidly, in 2013 compared to 2005 increased by 4.72 times.(2) Through the geostatistical analysis of depth to water data, interannual variability of nugget coefficient tended to increase, indicate the extent of spatial correlation of the groundwater level is weakening. The range decreasing year by year, shows that the influence of human factors on the groundwater level is growing. The direction of the major range is in agreement with the river flow, which indicates that there is a definite correlation between the groundwater depth and the river recharge. The trend of interannual variability of groundwater level, shows shallow buried depth(<6m) region has shrunk year by year. Meanwhile, the region of deep depth began to expand.(3) the relationship between groundwater level change and water-saving irrigation, shows the conventional irrigation farmland area added 1×103hm2, groundwater level on average drop of 0.17 m, the efficient water-saving irrigation area added 1×103hm2, groundwater level drop of 0.46 m on average.(4) Using numerical simulation software for the simulation of groundwater, it runs to 2030 according to the current exploitation of groundwater, the water level dropped more serious. This mining model is not sustainable. Combined with "three red lines" issued water use index, the paper makes different plans and forecast. Taking into account of the control of the groundwater level in the study area and the feasibility of the implementation of the project, it considers that efficient water-saving irrigation ratio should be controlled in 81%, irrigation water use efficiency and the proportion of surface water in efficient water-saving irrigation should be improved. This is to ease the region declining groundwater, soil and water relationship resolve tensions in the region, to achieve a more efficient way of sustainable development of irrigated agriculture.