The Impact Of Scale Irrigation To Groundwater

Since the mid-twentieth century, with the development of population and agriculture, irrigation area in Yanqi basin is increasing, and draw heavily on surface water for irrigation, pose a threat to the ecological security of irrigation. Around 2000, people began to realize the importance of the rational use of water resources, high efficiency water saving measures in agricultural irrigation popularized gradually. Irrigation water is changed from the previous single use surface water into joint use of surface water and groundwater, the proportion of well irrigation is increasingly high.Simultaneously, irrigation from single surface irrigation to combining single ground to ground irrigation and drip irrigation, the area of the basin irrigation farmland is gradually reduced. In 2012, “the opinions of the State Council on the implementation of the most stringent water management system “was introduced, the opinion is intended to be strictly controlled total water consumption, improved water use efficiency, and strictly controlled the total amount of sewage into the rivers and lakes to solve the water shortage, water pollution, deterioration of the aquatic environment and other issues. Under the controlled of this opinion, the amount of surface water intake in irrigated area began to fall away.For Yanqi, groundwater levels and groundwater resources is declining because of both new backgrounds. Choose Yanqi County Xia Wu Hao Qu Village as a typical experimental area, through field investigation, statistical analysis and real-time monitoring and other methods to understand the change of groundwater embedded depth, and then evaluate the status of water resources. Use Processing Modflow numerical simulation software to test the different surface water, study the influence of groundwater table in different rate of water-saving irrigation scheme, to meet "the most stringent water management system” and best scale of water-saving irrigation in ecological water depth. Through research and analysis, obtained the following conclusions:(1) With the increase of the exploitation of groundwater, groundwater level in test area continued to decline, up to 2013, the buried depth of groundwater in the study area was 2.5 ~ 3.5m.(2) By studying the relationship between groundwater levels and vegetation diversity, soil salinization and evaporation, and then comprehensive consider Bosten Lake ecological water level control, determine that the suitable test area for the depth interval should be 3 ~ 4.5m, and the buried depth of >4.5m constraints in the area of less than 15% of the total area as the reasonable scheme of groundwater simulation in depth.(3) Take 2013 as the status quo, based on PMWIN to establish numerical model of the groundwater, on four different surface water volumes, different water-saving irrigation rate scheme is simulated by use of this model to obtain the changes of balance and water level zone under different scenarios. The results show that under the scheme of the four conditions, namely, when the surface water quantity is 350×104m3, the groundwater exploitation is 131.68×104m3, maintain the existing 4800 acres of responsibility fields based on the same land, 30% non responsibility farmland should abandoning, water saving rate of 75% is the most suitable irrigation scale.