Tracing recent climate and environmental impacts on groundwater storage using GRACE

Groundwater resources assessments in Chao Phraya basin, Thailand, and Western Australia, Australia, have been made by using satellite GRACE (Gravity Recovery and Climate Experiment) and in situ hydrological, meteorological and hydrogeological data. Changes in land water storage analyzed by satellite GRACE (CNS/GRGS ver.2) showed the decreasing trend at Chao Praya basin during 2002 and 2008, though groundwater potentials in confined aquifers recovered due to regulation of groundwater pumping after severe land subsidence. The decreasing trend using a JLG model with increasing precipitation data during the period relatively agreed well with GRACE data in Chao Phraya basin. On the other hand, the changes in land water storage analyzed by satellite GRACE (GRGS ver.2) showed the decreasing trends at both northern and southern parts of Western Australia during 2002 to 2008, even though the values of precipitation minus evaporation remain the same. This is attributed to the depletion of groundwater storage which is confirmed by in situ data with the decrease in groundwater level. Hydrogeology in northern WA and southern WA is very different in terms of recharge rate and the character (such as storage). The degree of depletion of groundwater storage depends on the hydrogeology, which have higher recharge rate with higher depletion in northern WA and lower recharge rate with lower depletion in southern WA. The satellite GRACE (Gravity Recovery and Climate Experiment) is useful tool for basin and continental scale groundwater assessments.