变化环境下灌区地下水动态演变趋势及驱动因素

以陕西省宝鸡峡灌区为研究区,从地下水系统与外部环境的关系出发,运用了线性趋势回归检验、Kendall秩次相关检验及Spearman秩次相关检验3种统计水文学方法,分析了近30 a(1981—2010年)灌区变化环境因素——降水量、蒸发量、地表水灌溉量及地下水开采量的变化趋势,结果表明:灌区降水量呈不显著下降趋势,平均年降水量倾斜率为-2.900 mm/a,而蒸发量呈波动上升趋势,平均年蒸发量倾斜率为3.270 mm/a,降水量和蒸发量两者具有互逆变化特征;灌区地表水灌溉水量呈显著下降趋势,而地下水开采量呈不显著下降趋势.基于GIS技术和地统计学方法,研究了灌区地下水位动态的时程演变趋势和空间分布特征,研究表明:1995—2005年,灌区西北部地区地下水位有明显下降趋势,10年间下降约7~8 m,中部乃至东南部也有小幅度的下降,下降不足1 m;2005年以后,灌区内仅在渭河北岸的武功、兴平南部及咸阳中南部有小幅度下降趋势.通过灰关联分析方法,识别了灌区地下水位动态变化的主要驱动因素,得知各影响因子的关联度都较大,均在0.5以上,且塬上灌区与塬下灌区地下水位动态变化的主要人类活动驱动因素分别为地表水灌溉和地下水开采.

Dynamic evolutionary tendency of groundwater in irrigation district in changing environment and its driving factors

The tendency of variation in environmental factors,namely precipitation,evaporation,amount of surface water irrigation and groundwater mining amount during 30 years(1981—2010) in Baojixia Irrigation District was analyzed by using three statistic methods and starting with the relationship between groundwater system and external environment. The results showed that precipitation declines but not significantly,its average decline slope is 2. 900 mm / a; evaporation rises in increasingly fluctuation manner,its average increase slope is 3. 270 mm / a,suggesting precipitation and evaporation have an opposite variation tendency. Amount of surface water irrigation shows a significant decrease,and groundwater mining amount decreases but not obviously. The temporal evolutionary tendency and spatial distribution features of groundwater were explored by means of the GIS technology and geostatistical methods too. It was presented that the groundwater level declines obviously from 1995 to 2005 in the north-west area in the irrigation district,eventually it has decreased about 7-8 m within 10years; even though the groundwater level also decreases in the central and south-east area in the district,the declination is less than 1m. Fortunately,after 2005,the groundwater levels exhibit a less decline tendency only in Wugong which is located in the north bank of Weihe river,in the south of Xingping,and in the central south of Xianyang,respectively. Finally,the main factors for deriving change in groundwater level in the irrigation district were identified by using grey relational analysis,showing that the grey relational degree for each environmental factor is all above 0. 5. Clearly,surface water irrigation and groundwater mining are the main factors of human activity related that derive change in the groundwater level in both highland and lowland areas in the irrigation district.