Research On Groundwater Contamination Risk In Zhangye Basin Of The Middle Reaches Of Heihe River

Zhangye Basin is located in the middle reaches of Heihe River. It is an important commodity grain, with a wide range of agricultural irrigation district. With the increasing development of industry and agriculture, groundwater contamination from human activities is gradually increased in Zhangye basin. Therefore, research on groundwater contamination risk in Zhangye Basin in the middle reaches of Heihe River is significant.Study areas including three counties, i.e. Ganzhou, Linze and Gaotai. There are total33sample points, which are all from shallow groundwater. By using descriptive statistical analysis, Pearson correlation analysis, respectively, to make analyses on the hydrochemical characteristics for the33points. In addition, using the ArcGIS software on the spatial interpolation of the eight-ions to study on the change of chemical characteristics of33points along groundwater flow direction.In this study, improve DRSATIC model from seven factors to five factors:Depth of water table, Net recharge, Aquifer media, Vadose Zone and Hydraulic Conductivity. By using the improved model to make groundwater vulnerability risk assessment. Then calculated the total weight of natural and human factors W’. By multiplying W’ and level R’associated to the corresponding factors in DRASTIC model to get groundwater vulnerability risk assessment result value R.Conclusions are as follows:1.The main anions in groundwater in Zhangye Basin are SO42-, HCO3-and cation is Na+.2.The variation coefficients of Na+、Cl-and SO42-are large, these three are the major variables resulting in groundwater salinization.3. Although the spatial variability of TDS is large in the study area, it is gradually increasing from Ganzhou to Gaotai. The concertration of Na+、K+、Mg2+、SO42-、Cl-is gradually increasing along the groundwater flow; the concentration of Ca2+changes very little; the concentration of HCO3-changes along the groundwater flow. 4. There is a strong correlation between SO42-and Na+, Mg2+and this phenomenon can prove that Ions mainly source from sulfate. There is a strong correlation between IDS and Na+, Mg2+, Cl-, SO42-and it can prove that TDS is mainly determined by the concentration of these four Ions in groundwater.5. The average value of nitrate nitrogen is3.9568mg/L. For example, the value in Shajing town, Xinhua town both of them exceeded nation standard. The value in Liaoquan town is close to exceeded value.6. The ordering relationship of groundwater vulnerability from big to small is:Linze> Ganzhou>Gaotai. This relationship mainly result from that there is a higher population density in Ganzhou than other two counties and higher fertilizer utilization in Linze. The average value of nitrate nitrogen in Shajing town well and Chang’an town well, Xinhua town are all exceeded nation standard; the value in Liaoquan town No.2water supply well is close to exceeded value; there is no exceeded value in Gaotai County. All the above can prove the ordering relationship.