Abstract
Investigating spatiotemporal dynamics and varying relationships between water table depth (WTD) and land use changes is critical for efficient groundwater management and land use planning in arid zones. The primary objective of the present study is to combine satellite and field measured data to quantitatively analyze variations in WTD and its relationship with land use change in the Ogan–Kucha River Oasis in the northwest arid zones of China, and reveal the spatial heterogeneity and variations in the abovementioned relationship at spatiotemporal scales. The spatiotemporal variations in WTD and land use change at different time intervals (1997–2007, 2007–2017, and 1997–2017) were analyzed based on geostatistical analysis methods and grid cell approaches. The relationships between land use types and changes in WTD were assessed using correlation and ordinary least square analyses. The relationships between spatiotemporal variations in WTD and land use change were explored using local level geographically weighted regression. The results indicated that influences of human activity on the variation of WTD have gradually increased, and that WTD has declined rapidly in most parts of the study area. The spatial distribution of WTD exhibited significant spatiotemporal heterogeneity, and WTD was lower in the inner parts of the oasis and shallower in the oasis-desert ecotone. The WTD decline rates in the irrigation area were much higher than those in the oasis-desert ecotone. The cultivated land area has expanded markedly, whereas the shrub covered area has shrunk rapidly. Changes in WTD were positively correlated with changes in cultivated land area, and the expansion center of cultivated land has gradually moved from upstream of the alluvial fan to downstream of the alluvial fan and to the oasis-desert ecotone. The relationships between changes in cultivated land and WTD in the ecotone were more prominent than those in the inner parts of the oasis. Therefore, agricultural land expansion and planning in the study area should be integrated based on spatiotemporal changes in the groundwater depth to maintain the stability of groundwater systems and sustainable groundwater exploitation.
Highlights
Groundwater is one of the most valuable and vulnerable freshwater resources [1], which plays a critical role in irrigated agriculture and global food security [2]
water table depth (WTD) and Land use land cover (LULC) changes, the results demonstrated that compared with traditional linear regression models, geographically weighted regression (GWR) could consider information neglected by ordinary least square (OLS) models and enhance the predictive ability of the model [35]
The results show that the nugget and sill values considerably increased from 1997 to 2017, indicating that as the spatial heterogeneity caused by stochastic factors of WTD are gradually reinforced and as the degree of spatial heterogeneity increases, the difference in WTD between oasis and desert areas increases
Summary
Groundwater is one of the most valuable and vulnerable freshwater resources [1], which plays a critical role in irrigated agriculture and global food security [2]. Groundwater serves as the primary source of drinking water in both rural and urban areas, providing fresh water storage for domestic, agricultural, and industrial demands, while meeting basic human needs and maintaining the ecological balance and aquatic ecosystems [3,4,5]. Water 2019, 11, 673 have naturally existing desert oasis with limited surface water storage, groundwater becomes the major lifeline, supplying freshwater for rivers, wetlands and vegetation [6,7]. Most arid regions have focused on achieving rapid economic growth, which has resulted in an ever- increasing food demand and overexploited groundwater resources, with less importance on maintaining a balance between the supply and demand for groundwater resources. Groundwater discharge rates have exceeded the natural recharge rates, whereas withdrawal intensities have reached the highest levels, resulting in successive depletion of water table depth (WTD) and deterioration of water quality [8,9,10,11]
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