民勤绿洲苦咸水空间分布及成因分析

苦咸水是半干旱、干旱区的重要水资源之一。2011年9-10月，采集民勤县红崖山水库以北灌区71个地下水水样，利用传统统计学方法和地理信息软件，对石羊河下游民勤绿洲苦咸水空间分布进行了研究。结果显示：民勤绿洲苦咸水（＞1 g•L^-1）面积共781.59 km2，其中微咸水（1～3g•L^-1）面积占27.6%，分布在泉山区和湖区南部部分地区，咸水（3～10 g•L^-1）和盐水区（10～50 g•L^-1）面积分别占55%和17.4%，集中分布在湖区内；苦咸水水化学类型随着矿化度的升高，由泉山区的微咸水逐渐向湖区的盐水变化；气候、地质和人类活动是形成苦咸水的主要原因。

Spatial Distribution of Brackish Groundwater and Its Formation Causes in the Minqin Oasis in Lower Reaches of the Shiyang River

Brackish groundwater is one of the important water resources in arid and semiarid areas. During the period from September to October 2011, 71 groundwater samples were collected in the irrigated area dowstream from the Hongyashan Reservoir in Minqin County, Gansu Province, and the traditional statistical methods and geographic information software were used to research the spatial distribution of brackish groundwater in the Minqin Oasis. The result showed that brackish groundwater (＞1 g•L-1) in the Minqin Oasis was distributed in an area of 781.59 km2, in which the proportion of areas with brackish groundwater (1-3 g•L-1) was 27.6%, and these areas were distributed in Quanshan District and some parts of south Lake District. The proportions of areas with salt water (3-10 g•L-1) and brine (10-50 g•L-1) accounted for 55% and 17.4% respectively, and these areas were mainly located in Lake District. With increasing groundwater salinity, the chemical type of brackish groundwater changed gradually from SO2-4-Cl--Mg2+-Ca2+ (brackish groundwater) in Quanshan District to SO2-4-Cl--Mg2+-Na+ (K+) (brine) in Lake District. Climatic and geological conditions and human activities were the main factors of forming brackish groundwater.