关中平原灌区地下水电导率时间变化特征分析

Analysis on Variation of Groundwater Electrical Conductivity over Time in Guanzhong Plain Irrigation District

不合理的灌溉方式使我国干旱半干旱地区土壤次生盐渍化问题加重,已成为该地区灌溉农业发展和生态环境质量的制约因素,研究地下水电导率的时间变化对指导灌区农业灌溉具有重要意义。基于对洛惠渠灌区51个观测井地下水电导率的长期监测结果,利用Spearman秩相关系数法和相对差分法分析了地下水电导率的时间稳定性特征。结果表明:洛惠渠灌区地下水主要是微含盐水和中含盐水,其电导率随时间呈现出一定的变化,电导率值越大,其值随时间的变化也相对越大。51个井点的地下水平均电导率在整个监测期间没有呈现增大的趋势,但地下水电导率呈中等变异,变异系数的范围为61%～72%。地下水电导率的Spearman相关系数变化范围为0.81到0.98(p<0.01),这表明监测井点地下水电导率时空格局的稳定性较强。2#井点是洛惠渠灌区地下水平均电导率的代表性位置点,基于2#井点的电导率预测值与研究区地下水平均电导率的实际值差异不大。因此,基于洛惠渠灌区地下水的电导率在时间上的稳定性,通过确定地下水电导率代表性位置及该点平均电导率可以快速有效地监测该区地下水平均电导率变化,从而为确定灌溉时间提供科学指导。

Soil salinization is the current constraint on agriculture development in the irrigation areas throughout the world.To study the temporal and spatial variation of groundwater electrical conductivity(EC)is of importance for guiding agricultural irrigation in irrigation districts.Based on the long term monitoring data of EC in the 51 observation wells in Luohuiqu Irrigation District,relative difference analysis and non-parametric Spearman′s rank correlation test were used to check the EC temporal stability.The results indicated that 21 wells were slightly saline and 30 wells were moderately saline.The bigger the EC was,the greater the EC changed during the entire measurement period.The mean groundwater EC of the 51 wells did not show the increasing trend in the entire measurement period,but demonstrated moderate spatial variability with coefficient of variation(CV)values ranging from 61%to 72%.The groundwater EC exhibited strong spatial and temporal stability patterns with Spearman correlation coefficients ranging from 0.81 to 0.98(p<0.01).The mean EC representative location in the study area was well 2#.It was little difference between the predictive groundwater EC values based well 2#and the actual mean groundwater EC values of the study area.In conclusion,the groundwater EC is strong temporal stability in Luohuiqu Irrigation District.It is feasible to obtain the mean groundwater EC of the study site through the mean groundwater EC representative location.The method is of great importance to monitor the mean groundwater EC and to determine the correct irrigation time.