扬水灌区封闭型水文地质单元的地下水盐动态研究

西北内陆干旱区的扬水灌区灌溉排水属外引内排方式,灌区内的水盐运移主要受控于灌溉水入渗,属于典型的入渗-蒸发型水盐运移。对扬水灌区封闭型水文地质单元15 a监测资料的分析表明,监测区的地下水运移具有径流滞缓、水盐积累的特点。灌溉水入渗带和溶质迁移带的地下水矿化度受入渗溶滤影响呈振荡变化型,汇水聚盐带的盐沼化面积由1993年的25.83 km2增加为2008年的30.88 km2,地下水矿化度和土壤含盐量均呈逐年上升趋势,地下水矿化度最高达172.15 g/L,水化学类型为Cl-—SO42-—(K++Na+)—Ca2+型。

Water and Salt Movement in Closed Hydro-geological Units of Pumping-irrigation Area

In the arid area of Northwest China,external drainage and internal pumping is the principal approach of irrigating and drainage in the pumping-irrigation area,in which the water-salt transport is mainly influenced by infiltration of irrigation water,identified as typical infiltration-evaporative type of water-salt transport.According to the analysis on the 15 years monitoring data of closed hydro-geological units of pumping-irrigationc area,the migration of groundwater in monitoring area showed the characteristic of stagnated run-off,as well as that of water and salt accumulation.Mineralization of groundwater in infiltration zone of irrigation water and transportation zone of solute in groundwater present a oscillating type of change,affected by the infiltration leaching.The area of salt marsh in watershed poly salt zone has increased to 30.88 km2 in year 2008 from 25.83 km2 in year 1993.Besides,the groundwater and soil salinity is rising year by year,with the mineralization of groundwater up to 172.15 g/L,and the water chemistry type is Cl-—SO2-4—(K++Na+)—Ca2+.