Abstract
The water cycle in the key agricultural and pastoral zones (KAPZs) is an important factor for maintaining the stability of the ecosystem. Groundwater collection and lateral seepage are indispensable parts of the water cycle, and it is difficult to monitor the groundwater situation in each area. The strength of the alternate circulation of groundwater is directly related to the utilization value and development prospects of groundwater; therefore, creating an effective method for the detection of groundwater burial depth has become an issue of increasing concern. In this paper, we attempt to create a method for the detection of groundwater burial depth that combines cokriging interpolation, spatial autocorrelation, geographically weighted regression, and other methods to construct a quantitative relationship between different land cover types and groundwater depth. By calculating the band index of the land cover type, the groundwater depthinformation of the unknown area can be obtained more accurately. Through collaborative kriging interpolation, normalized difference vegetation index (NDVI), precipitation, and hydrogeological conditions were used as covariates. The groundwater burial depth of Wengniute Banner in 2005, 2009, 2013, and 2017 was the response variable, and the groundwater burial depth in the study area was calculated. The groundwater burial depth data after the cokriging interpolation was used to transform the raster data into vector data in space using the improved hydrological response unit (HRU) model to make it more suitable for the actual groundwater confluence. Subsequently, 551 minimum response units (MHRUs) were obtained by division, and the spatial autocorrelation analysis was performed accordingly. The groundwater burial depth in the study area is spatially distinct from east to west, and the groundwater level shows a trend of being high in the west and low in the east, gradually increasing due to precipitation and rivers. The average change of groundwater depth in the time series is not significant, but it does gradually show a trend of accumulation. According to the aggregation characteristics of spatial autocorrelation analysis, a geographically weighted regression model of groundwater depth and NDVI, normalized difference drought index (NDDI), and net relatedness index (NRI) was established. The NDVI representing the forest land and the Adjusted R2 of the groundwater depth is 0.67. The NRI representing the cultivated land and the Adjusted R2 of the groundwater depth is 0.8675. The NDDI representing the bare land and the Adjusted R2 of the groundwater depth is 0.7875. It shows that the band index representing the ground type has a good fitting effect with the groundwater burial depth.
Highlights
The Earth critical zone (ECZ), proposed by the National Research Council of the United States in 2001 [1], is a complex combination of geology, geochemistry, biology, hydrology, landforms, and atmospheric processes
The excessive exploitation of groundwater in China has caused a dramatic drop in the groundwater level, which is a comprehensive reflection of hydrogeological elements, including the changes in groundwater recharge, runoff, excretion, as well as the environmental problems of groundwater and its severity
Interpolation analysis can present the buried depth of groundwater in space and simulate the buried depth of groundwater at a specific location; kriging interpolation has low accuracy when there are fewer original points and uneven distribution; the use of cokriging interpolation combines multiple factors that affect the depth of groundwater to improve the model to improve the accuracy of groundwater depth prediction
Summary
The Earth critical zone (ECZ), proposed by the National Research Council of the United States in 2001 [1], is a complex combination of geology, geochemistry, biology, hydrology, landforms, and atmospheric processes. Groundwater is the boundary between the soil layer and the rock layer in ECZ It is a buffer zone for underground soil and rock, and frequently interacts with energy on the ground [5]. The shallow groundwater level has dropped drastically, the original swamp wetlands have been drained, the original oasis has become a bare ground, and the landscape has been destroyed [15]. All of these issues have caused great damage to the buffer zone of the ECZ, which seriously affects the stability and self-healing ability of the ECZ [16,17]. The groundwater volume could quantitatively reflect its characteristics—the change of groundwater depth is the most direct manifestation of the amount of groundwater, and is the most important control indicator of groundwater management [18]
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