Abstract
The Bakhtegan catchment, an important agricultural region in south-western Iran, has suffered groundwater depletion in recent years. As groundwater is considered the main source of fresh water in the catchment, especially for agriculture, monitoring groundwater responses to irrigation is important. Gravity Recovery and Climate Experiment (GRACE) satellite data can help determine water mass changes in catchments and assess water volume changes. In this study, we compared GRACE-derived water mass data against groundwater volume variations measured in situ. We also assessed the efficiency of GRACE-derived data in catchments smaller than the 200,000 km2 recommended area when using GRACE. For the study period (January 2002 through December 2011), the GRACE data showed a 7.6 mm annual decline in groundwater level, with a total volume loss of 2.6 km3 during the period. The in situ monthly measurements of groundwater level showed an average depletion of 10 m in catchment aquifers during the study period. This depletion rate was supported by the recorded decrease in precipitation volume, especially in the post-drought period after 2007. These results demonstrate that GRACE can be useful tool for monitoring groundwater depletion in arid catchments.
Highlights
Increasing demand for water supply in arid and semi-arid zones has increased groundwater use, leading to wide-scale depletion [1]
The Gravity Recovery and Climate Experiment (GRACE)-derived data showed that total water mass storage (GWMI ) in the region decreased by 76 mm from April 2002 to December 2011 (Figure 4A)
The results showed that groundwater level decrease in different aquifers of the Bakhtegan catchment ranged between 5 and 30 m during the study period, with an overall average decrease of 10 m for the catchment (Figure 7)
Summary
Increasing demand for water supply in arid and semi-arid zones has increased groundwater use, leading to wide-scale depletion [1]. Semi-arid zones represent 30% of global terrestrial surface area and water scarcity in these regions is a severe problem, as a result of rapid population growth and expansion of irrigated agriculture [2]. In arid and semi-arid areas, where surface water resources are scarce and unreliable, groundwater is considered the only plausible fresh water source, owing to its quantitative and spatial availability [3]. Many of the groundwater resources developed in arid and semi-arid zones are non-renewable fossil water [4]. Sustainable management of aquifers in arid and semi-arid zones requires accurate estimates of recharge rate and groundwater resources, data that are often lacking in developing countries. If groundwater abstraction exceeds groundwater recharge for extensive areas and long time, overexploitation or persistent groundwater depletion can occur [5]
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