UGA
Georgia Water Resources 
From Space to Subsurface: A Story of Groundwater in Southwest Georgia

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>> Wenjing: The use of groundwater can be dated back to 5000 BC. Long-term heavy pumping has resulted in significant water level declines. The growing population also increase pressure on groundwater supply. In the meantime, the increasing sinkhole formation in Southwest Georgia posts serious threat to groundwater quality. In face of the problem related to the subsurface, what we can learn from space? This term, Georgia water resources team used NASA observations to evaluate groundwater in southwest Georgia from two perspectives: quantity and quality.

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>> Jason: Recent innovations in remote sensing allow scientists to measure terrestrial water storage from the detection of changes in the Earth's gravity field. These changes are measured by NASA's GRACE satellite. Using data gathered from GRACE and land surface models, we measured the changes in groundwater storage from 2002 to 2009 by calculating the difference of soil moisture and snow water from total water storage. Using data gathered from GRACE and land surface models we measured the changes in groundwater storage from 2002-2009. First we subtract the soil moisture and the snow water from the GRACE data, and we get the resulting map of groundwater storage variation. Analysis of the GRACE data has shown an overall decline of groundwater storage in the Floridan Aquifer from 2002-2009. A decrease of about 12 centimeters of groundwater storage has occurred in this time period. Depletion of groundwater can cause water shortages and an increased risk of sinkhole development.

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>> Mingshu: To address the water quality part of our project, we utilized NASA's EO satellite remote sensing and model-assimilated data, in conjunction with USGS GIS layers of Dougherty County, Georgia. We then developed a DRASTICS model by modifying US EPA's water quality risk assessment model DRASTIC and incorporating regional sinkhole density maps from previous terms of DEVELOP Program. We produced water contamination risk maps in 2002 and 2009, respectively. We also found both the overall trend and spatial variation of water contamination risk has increased from 2002 to 2009 in the study area.

>> Linli: Due to the dramatic increases of groundwater contamination risk in the western part of Dougherty County, we recommend a detailed monitoring in this area. For the east Dougherty County, clusters of area with high water contamination risk were identified for both of the two years. These high-risk areas were dominated by agricultural land  close to urban areas. Therefore, further examination, long-term monitoring, and rigid control are suggested for the use of pesticides and wastewater discharge in this area particularly.

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