Research On Groundwater Dynamic In Karamay Agricultural Area

The Karamay Agricultural Area of Xinjiang is located in the southeast of Karamay, and the irrigation water was transferred from the Irtysh river, with the deeper development of the agricultural area, the groundwater depth kept rising and phreatic water was evaporated, at last lots of salinity accumulated on the surface and caused serious soil salinization extensively; At present the whole agricultural area was in different level of salinization, and most of the groundwater samples belong to brackish water and saline water with high TDS, it has been a serious problem with water-soil safety of the area. For this reason, careful management of water quantity and quality and implementation of salinity management stragies are considered necessary in order reduce the risk of further salt accumulation and damage to farming and local ecosystems, along with the purpose of sustainable development of agricultural economy.This paper based on the Karamay agricultural area, analysis of water level variation and water budget, along with the hydrochemical and the spatial heterogeneity of soil-water salt in the shallow groundwater were carried out in order to assess the dynamic change of the groundwater. The main contents and results are as follows:(1) The study area is characterized by low precipition, high evapotranspiration, low soil fertility and the vulnerable ecological environment after the careful analysis of initial information, there is no flow of surface water through the area in recent year and the groundwater is characterized with high total dissolved solids and serious soil salinization before the area has been exploitation and utilization. The soil of the study area is characterized with low hydraulic conductivity, this lead to slow lateral flow after the infiltration of irrigation water, at last the groundwater level of the whole area rised since the irrigation water vertical infiltration into the superficial layer ultimately.(2) It has found a significant rise in the groundwater level according to the analysis of several monitoring wells data since the exploitation and utilization. The mean rise in the groundwater table since 2000 was 6.93 m, and the area of water level more than 6m reduced and the area of less than 4m increased obviously according to the contours of water depth. Amplitude distribution of shallow groundwater table change during the main growing period and the water level change of monitoring wells also shows that the groundwater depth rise significantly because of infiltration of irrigation water. The analysis of water budget shows that the groundwater storage keeps in a net increase for a long time, and the annual net increment of water storage close to 11 million cubic meters. The analysis of aquifer water budget shows that infiltration of irrigation water occupied 93.8% of the total recharge of the groundwater in the study area, and evapotranspiration occupied 95% of the total discharge of the groundwater, the water storage was finally demonstrated determined by the infiltration of irrigation and evapotranspiration.(3) The analysis of hydrochemical shows that more than 90% of the shallow groundwater is belong to brackish water and saline water with TDS over 1g/l in 2010. It is shows that the area of high TDS occupied most in the agricultural area according to the contours of TDS and pH in 2008, 2009, 2013 and 2014, and groundwater quality was in the form of alkalescence mainly. At the same time, analysis of the Piper p lot of major ions concentration, the sodium adsorption rate(SAR) and the molar ratios of major ions indicates that the quality of groundwater has degradation entirely, and can’t be used in agriculture, industry, and domestic due to the high TDS.(4) The spatial variability of soil- water salinity was analysed by the combined method with traditional statistics and geostatistics, the distribution of the soil salinity and ion of water samples indicate a spatial heterogeneity intensively. The nugget effect indicates that most of the properties have a strong spatial autocorrelation except the ammonium nitrogen and rapid available phosphorus. The semi- variogram and simulative model made by the software GS+ shows that different water-soil property has a high spatial variability. The statistics result of major ions shows that the variable coefficient of different ions belongs to medium variation and high variation, the study area showed a high spatial heterogeneity affected by external factors.