Geostatistics-based spatial variation characteristics of groundwater levels in a wastewater irrigation area, northern China

Although wastewater reuse in agriculture can ease water scarcity, this practice also alters the variation of groundwater recharge and groundwater levels. This study employed a geostatistical method to systematically investigate the spatio-temporal variations and storage fluctuations of groundwater in a wastewater irrigation area in a southeastern suburb of Beijing. Specifically, we generated an optimal geostatistical model for measuring groundwater levels. Furthermore, we proposed that universal kriging is a suitable method for examining groundwater spatial variations, whereas a raster-based model can provide high accuracy for studying groundwater fluctuations; the nugget effect value of groundwater levels increases with increasing exploitation intensity. Our results indicated that groundwater levels increased overall in the early stages of wastewater irrigation development, followed by local increases in some pockets in the middle stages of development, large-scale increases in the late stages and an increasing variation of magnitude over time. The results also showed that groundwater level declined less on farmlands than that in urban areas, suggesting that wastewater irrigation facilitates groundwater conservation by reducing groundwater exploitation and enhancing groundwater recharge. Our results are conducive to developing an effective groundwater management plan and for improving the accuracy of groundwater resource assessments.