RESUMO
Climate change imposing additional stressors on groundwater resources globally, thereby predicting groundwater recharge (GR) changes is crucial to sustainably managing water resources, especially in the arid endorheic basins. Groundwater in the Endorheic Basins of Northwest China (NWEB) is potentially impacting regional socio-economic output and ecosystem stability due to the imbalance between supply and extraction exacerbated by climate change. Hence, recognizing the impacts of climate change on past and future GR is imperative for groundwater supply and sustainable groundwater management in the NWEB. Here, the impact of historical (1971-2020) and projected (2021-2100) climate changes on GR across the entire NWEB and three distinctive landscape regions (i.e., mountainous, oasis, and desert) were assessed. A coupled distributed hydrologic model (CWatM-HBV model), which integrates the Community Water Model (CWatM) and the HBV model, was run with three shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, and SSP3-7.0) forcing from 10 general circulation models (GCMs) to simulate and analyze the interannual and seasonal variations of GR, along with their driving factors. Over the past 50 years, both precipitation and runoff have undergone significant increases, and leading to a dramatic rise in GR (0.09 mm yr-1). The future annual growth rate of GR is projected to range from 0.01 to 0.09 mm yr-1 from SSP1-2.6 to SSP3-7.0 across the entire NWEB, with the majority of the increase expected during the spring and summer seasons, driven by enhanced precipitation. GR from the mountainous region is the primary source (accounting for approximately 56-59 %) throughout the NWEB with the greatest increase anticipated. Precipitation and runoff have significant influences on GR in mountainous areas, and the impact of precipitation on GR is expected to increase over time. Changes in GR in oasis and desert areas are mainly limited by precipitation variation and increase in the SSP2-4.5 and SSP3-7.0 scenario. Additionally, the processes of glacial retreat and permafrost degradation will complicate the GR dynamics although the process is largely interfered with by anthropogenic environmental changes, especially in oasis-desert systems. The average annual recharge in the NWEB was 8.9 mm in the historical period and 13.6 ± 4.1 mm in the future. Despite an increase in GR due to climate change, groundwater storage is likely to continue to decline due to complex water demands in the NWEB. This study highlights the significance of future precipitation changes for GR and contributes to the understanding of the influence of climate change on groundwater systems and advances the sustainable management of water resources.
RESUMO
Recent global groundwater overpumping is threatening ecosystem stability and food security, particularly in arid basins. A solid investigation regarding the drivers of groundwater depletion is vital for groundwater restoration, hitherto, yet it remains largely unquantified. Here, a framework to quantify the contribution of natural forcing (NF) and anthropogenic perturbations (AP) to groundwater storage anomalies (GWSA) variability by separating the GWSA estimated by the Gravity Recovery and Climate Experiment (GRACE) satellite into natural- and human-induced GWSA was proposed in the northwest endorheic basin (NWEB) of China. Further, a multiple linear regression model was established for GWSA change prediction. Our results showed that, during the period 2003-2020, the GWSA depleted at a rate of 0.25 cm yr-1 in the entire NWEB. In addition, GWSA was found to decrease significantly (exceeding 1 cm yr-1) in the west of NWEB where there are heavily irrigated areas, and has become one of the regions with the most serious groundwater depletion in China. Whereas a significantly increasing trend (greater than 0.5 cm yr-1) was observed in the Qaidam basin and south part of the Tarim River basin, becoming a groundwater enrichment reservoir in NWEB. The negative contribution of AP to groundwater depletion has increased from 3% to 95% in the last decade, as determined by separating the effects of NF and AP on GWSA. The rapid expansion of the cropland area and the increase in water use due to population growth are investigated to be the main reasons for GWSA depletion, particularly in the North Tianshan Rivers, Turpan-Hami, and Tarim River basins. Therefore, we conclude that AP are dominating and accelerating groundwater depletion in the NWEB. The increase of GWSA in the Qaidam basin has been attributed to the increase in solid water melt and regional precipitation. The western route project of China's south-north water diversion and water-saving irrigation are important ways to solve the problem of groundwater depletion in NWEB. Our results emphasize that a more feasible framework capable of reliably identifying the driving factors of groundwater storage change is a necessary tool for promoting the sustainable management of groundwater resources under both NF and AP in arid endorheic basins.
