塔里木河下游地下水化学特征对输水响应的阶段性研究

通过对塔里木河下游英苏断面地下水化学特征在生态输水作用下变化的观测资料研究发现,地下水化学特征对间歇性输水的响应表现出阶段性的特点:在受输水影响的初期地下水中矿化度和主要离子含量呈现上升变化,随着输水的进行,矿化度和主要离子的含量逐步下降,最后又表现出上升态势.根据地下水盐变化特点可将地下水化学对输水的响应划分为3个阶段:初期阶段(盐分横向累积阶段)、中期阶段(淡化压盐阶段)和后期阶段(蒸发溶盐阶段);输水间歇地下水化学特征的变化与地下水化学对输水响应表现出的阶段性特征相一致的特点.在“盐随水来,盐随水去”规律作用下,地下水化学特征的阶段性变化受土壤盐分含量、与河道距离、输水水质、水量的影响,其中土壤盐分、输送水的水质与地下水位的抬升是主导因素,而距河道远近与水量的多寡则是导致与河道不同距离处阶段性变化时间差异的重要原因.从水盐运移规律的角度考虑,河道输水方式比面上输水方式更利于生态恢复.

Three Stages of the Groundwater Chemical Properties Reacting on the Intermittent Water Deliveries in Lower Tarim River,China

Based on the monitored data of groundwater chemical properties and groundwater depth influenced by five intermittent water deliveries in the lower reaches of the Tarim River,the regulation of groundwater chemistry varying was analysed,the variations in groundwater chemical properties unfolded a clear threestages changing character under the influence of water deliveries: the initial stage-concentrations of major ions and total dissolved solids(TDS) increasing; the intermediate stage-the concentrations decreasing;the late stage-the chemical properties increasing once more.The variation of groundwater chemistry resulted from many factors,such as the salinities in soil profile,the quality of transported water,the distance from watercourse,the amount and the season of the delivery.However,"salts coming with the water flow,and leaving with it" is the main reason that led to the increase and decrease of chemical properties at first stage and second stage,and with the uprising water level,more and more salinities in soil profile dissolved into ground water and the severe evaporation resulted the concentrations of major ions and TDS increase at late stage.Furthermore,the variations of groundwater chemistry at the intermission of water deliveries have close relationship to the three stages.It should be pointed out that the mode of water transport in surface scope is infeasible due to the climate characteristics of the lower reaches of the Tarim River.