Abstract
Knowledge of groundwater recharge (GR) is important for the effective management of water resources under semi-arid continental climates. Unfortunately, studies and data in Mongolia are limited due to the constraints in funding and lack of research infrastructures. Currently, the wide accessibility of freely available global-scale digital datasets of physical and chemical soil properties, weather data, vegetation characteristics, and depths to the water table offers new tools and basic information that can support low-cost physically based and process-oriented models. Estimates of GR over 41 study sites in Mongolia were obtained using HYDRUS-1D in a 2-m-thick soil profile with root depths of either 0.30 or 0.97 m by exploiting the daily precipitation and biome-specific potential evapotranspiration values. The GR simulated by HYDRUS-1D arrives at the water table and becomes the actual GR with a lag time that has been calculated using a simplified form of the Richards equation and a traveling wave model. The mean annual precipitation ranges from 57 to 316 mm year−1, and on average about 95% of it is lost by mean annual actual evapotranspiration. In the steppe region, the vegetation cover induces higher-than-normal actual transpiration losses and consequently lower GR. The mean annual GR rates span between 0.3 and 12.0 mm year−1, while travel times range between 4 and 558 years. Model prediction uncertainty was quantified by comparing actual evapotranspiration and GR with available maps and by a sensitivity assessment of lag time to the soil moisture in the deep vadose zone. The partial least squares regression (PLSR) was used to evaluate the impact of available environmental properties in explaining the 47.1 and 59.1% variability of the spatially averaged mean annual GR and travel time, respectively. The most relevant contributors are clay content, aridity index, and leaf area index for GR, and depth to the water table and silt content for the lag time. In data-poor, arid, and semi-arid regions such as Mongolia, where the mean annual GR rates are low and poorly correlated to precipitation, the ever-increasing availability of world databases and remote sensing products offers promise in estimating GR.
Highlights
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)
Higher groundwater recharge (GR) rates due to focused recharge are reported in river catchments, where runoff generated by snowpack in mountainous areas serves as the water source for GR in topographic depressions with extensive surface water– groundwater exchange
The three sites are characterized by contrasting climate and vegetation cover with maximum (Sukhbaatar), average (Arvaikheer), and minimum (Saikhanovoo) Aridity Index (AI) and annual-average leaf area index (LAI) values in Mongolia (Table 1)
Summary
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). 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). These approaches have not been used yet in Mongolia, to our knowledge. Results are largely based on the hydrograph separation method and provide the only material relevant to groundwater recharge assessment According to this map, 76% of the country has groundwater renewable resources of
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
