Groundwater Quality Evolution And Prediction Of Yaoba Oasis In Alashan

Yaoba oasis is located in arid area, whose imbalance between supply and demand of water resources is very conspicuous, and groundwater is its main water sources. So,the study on evolution disciplinarian and prediction of groundwater quality makes effect to know the water quality variety tendency of groundwater in Yaoba oasis. The results of the research provided scientific base for reasonable exploration and utilization of groundwater resources in Yaoba oasis, which is significant to guarantee the environment continuous development in the area.The paper collects the geological informations and the hydrology geological informations, gathers and analyses the groundwater quality specimens in Yaoba Oasis. Combined with the analysis results of historical groundwater quality, this paper applies the theoretics and methods of hydrogeology, hydrogeochemistry and geographic information system software ArcGIS geological statistics module - Geostatistical Analyst to make researches on the evolution disciplinarian of groundwater quality in Yaoba oasis. The disciplinarians are as follows: The spatial distribution of groundwater chemical type assumes belt-shaped distribution obviously from the recharge area (approaching the Helan Mountain) to the discharge area (in the south-west of the oasis); The degree of mineralization in Yaoba oasis gradually increases from north-east to south-west, and the area with high degree of mineralization enlarged year by year; In different water-exploitation time, the spatial distribution of groundwater chemical type and the degree of mineralization varied each other, but it has a common regulation: in the exploitation time, groundwater chemical type is closed to the background value, and the degree of mineralization is rifeness low; in the non-exploitation time, groundwater chemical type get worse than before, which Cl^- and SO₄^2- are concentrated, and the degree of mineralization is rifeness higher; Groundwater excessive exploitation has changed the original recharge and discharge relationship of Yaoba oasis, which results in the salt water of the Taosu lake pouring into the oasis, which makes the groundwater chemical field evolves toward salinization and alkalination, and groundwater quality tends to deterioration in time. Based on these, the original causes of groundwater quality deterioration are analyzed. The causes are affected by many kinds of factors, but the salt water with high degree of mineralization of the Taosu lake pouring into the oasist caused by groundwater excessive exploitation is the main reason.Based on the gray system prediction theory, the groundwater water quality prediction model with error amendatory is established, on these basis, the paper develops gray systematic procedure forecast.m with the aid of MATLAB, and applies this procedure to predict the main ingredient of the groundwater water quality in 2010,2015 and 2020. The results of the prediction reflect that the water quality variety tendency of groundwater is deteriorating unceasingly keeping the exploring methods and quantity unchanged in Yaoba oasis.Finally, the paper puts forward the groundwater water quality protection measures. The groundwater managements of this area should control and reduce the exploring quantity; take the salt-truncation, salt-reducing and salt-drainage as the control measure; take the recharge as the engineering measure and take the water-using management as the managing measure, to solve the problem of Yaoba oasis comprehensively.