Study On Soil Water-Salt Dynamic And Monitoring Network Optimization In Plain Reservoir Downstream Of Arid Area

In arid areas in western China, many plain reservoirs were constructed to meet the water needs. Surrounding soil salinization problems caused by plain reservoir leakage are very serious. In this paper, the author analyzes and studies four indicators of groundwater depth of typical soil section, mineralization degree of ground water, soil quality moisture content and total soluble salts of a large plain reservoir in northern Xinjiang to explore the dynamic characteristics and laws of soil water and salt in the downstream of the reservoir; uses clustering algorithm to optimize the design of the existing dynamic groundwater monitoring network of downstream of the reservoir, remove redundant, monitoring wells, and improve the existing monitoring well network.After the research, the author finds that:(1) The dam foundation seepage of plain reservoirs downstream will uplift the groundwater level in surrounding areas, and with increases in distance from the dam foundation,this effect wane.(2) Mineralization degree of groundwater shows the trend that the farther away from the dam foundation, the lower mineralization degree, indicating that foundation seepage will lower groundwater salinity near the downstream of the reservoir.(3) The soil quality moisture content of most 0.0-4.0m full section in the downstream of the reservoir is higher than that of 0.0-1.0m section, and the soil quality moisture content of deeper layer(lower than 1.0m) is generally higher than that of the shallower layer(0.0-1.0m), and this effect will gradually decrease with increase in the distance from dam foundation.(4) For most of the monitoring wells, the farther they are from the dam foundation, the smaller total soil soluble salt, and with the increase in the distance from the dam foundation, this effect gradually decreases.(5) In the downstream of the reservoir, the greater the groundwater depth is, the smaller soil quality moisture content, and the effect gradually decreases with the increase in the distance from the dam foundation.(6) When the mineralization degree of groundwater increases, the soil quality moisture content also increases, and vice versa. This is because the higher mineralization degree of groundwater, the harder it is for moisture to evaporate and dissipate, thus indirectly increasing the soil moisture rate.(7) When the groundwater depth increases, the total soil soluble salt correspondingly decreases. This phenomenon is more pronounced in deeper layers of the soil.(8) When the mineralization degree of groundwater increases, the total soil soluble salt also increases, and vice versa.In this paper, clustering module of SPSS software is used for systematical clustering optimization(twelve effective monitoring Wells) of the design of existing monitoring well network(Q-type clustering). After variance test of the optimization results and comparison of optimization schemes, 12 existing monitoring wells are ultimately determined to be divided into seven clusters in accordance with similar features, and given the similarities and differences in dynamic characteristics of soil water and salt of different monitoring wells, three monitoring wells with high similarity are excluded, and a total of nine monitoring wells, namely CJ1-1, CJ1-3, and CJ1-5 in section 1, CJ2-1, CJ2-2, CJ2-3, and CJ2-5 in section 2, and CJ3-1 and CJ3-2 in section 3 are retained to ensure the monitoring accuracy and reserve a complete vertical and horizontal monitoring wells network.