Groundwater Diffuse Recharge and its Response to Climate Changes in Semi-Arid Northwestern China

Abstract

Understanding the processes and rates of groundwater recharge in arid and semi-arid areas is crucial for utilizing and managing groundwater resources sustainably. We obtained three chloride profiles of the unsaturated-zone in the desert/loess transition zone of northwestern China and reconstructed the groundwater recharge variations over the last 11, 21, and 37 years, respectively, using the generalized chloride mass balance (GCMB) method. The average recharge rates were 43.7, 43.5, and 45.1 mm yr -1 , respectively, which are similar to those evaluated by the chloride mass balance (CMB) or GCMB methods in other semi-arid regions. The results indicate that the annual recharge rates were not in complete linear proportion to the corresponding annual precipitations, although both exhibited descending tendencies on the whole. Comparisons between the daily precipitation aggregate at different intensity and recharge rates reveal that the occurrence of relatively heavy daily precipitation per year may contribute to such nonlinearity between annual precipitation and recharge. The possible influences of vegetation cover alterations following precipitation change cannot be excluded as well. The approximately negative correlation between the average annual recharge and temperature suggests that changes in temperature have had significant influences on recharge.

Analysis of Groundwater Recharge in Mongolian Drylands Using Composite Vadose Zone Modeling

“…We observed weak sensitivity of the mean annual precipitation-recharge relationship in Mongolia, which is supported by some studies in similar regions (Deng et al, 2015;Huang et al, 2017). Soil moisture profiles across the vadose zone under permanent dry conditions simulated in HYDRUS-1D induce weak sensitivity of mean annual GR p to precipitation supply.…”

“…Groundwater is a vital ecosystem service in arid and semi-arid regions where the surface water resources are generally scarce and highly unreliable, especially under the increasing number of projected drought events induced by climate change (Deng et al, 2015). Therefore, sustainable management of water resources relies on the accurate assessment of low annual groundwater recharge (GR) rates that nevertheless are significant in a vast territory such as Mongolia.…”

“…Direct measurements of GR like lysimeters are unfeasible because they involve costly, timeconsuming, and labor-intensive efforts (Lerner et al, 1990;Jyrkama et al, 2002;Scanlon et al, 2002). More affordable field approaches based on chloride mass balance are commonly used to estimate GR in regions with similar environmental characteristics, e.g., Inner Mongolia, China (Gates et al, 2008;Yin et al, 2011;Deng et al, 2015;Huang et al, 2017). However, these approaches have not been used yet in Mongolia, to our knowledge.…”

Optimal Ridge–Furrow Ratio for Maximum Drought Resilience of Sunflower in Semi-Arid Region of China

“…The rising air temperature and more frequent and intense precipitation extremes have been observed and predicted under climate change projections in the northwestern semi-arid region of China [5][6][7]. This region has become warmer and drier with less groundwater resources [8][9][10], and the increasing variation of precipitation has led to fluctuating grain productions [11]. The projected changes of climate conditions increase the risks in rain-fed agricultural production [12].…”