Sweetest Water in the U.S.

The Mississippi Embayment (ME) extends 250,000 square kilometers across 9 states, with most coverage occurring in Tennessee, Mississippi, and Arkansas. It provides water for domestic, agricultural, and industrial use for western Tennessee and the surrounding states, and provides public water systems for upwards of 2.28 million people (TN Roadmap to Securing the Future of Our Water Resources, 2018).

The conservation and health of the aquifer is dependent on the recharge zone's ability to replenish the groundwater in the embayment. The recharge zone is greatly impacted by evapotranspiration, precipitation, land cover, and water use in the area. The zone is sensitive to changes in these factors, as the recharge zone is very narrow and lies outside of the alluvial plain, meaning that all of its recharge is done laterally through streams.

The Memphis Regional Megasite is an industrial campus that is located in the sensitive recharge zone of the Mississippi Embayment. The megasite will soon be home to the "Blue Oval City", a campus for Ford Motor Company to begin building electric trucks. This new Ford Plant is expected to be built on 4,100 acres, making it one of the largest manufacturing sites in the nation.

Based on identified areas of high precipitation totals, low evapotranspiration, high total water storage, and the least variable landcover changes, The North East corner of the embayment was identified as a thriving area within the Mississippi Embayment and in need of protection and conservation.

Note: Seasonality was considered when understanding high ET, as evapotranspiration is heavily dependent on temperature.  

The increasing trends of ESI show that plants in these areas are thriving. When the actual ET approaches the PET, ESI values increase and indicate that plants have access to water supply and are adequately evapotranspiring. 

ESI displays a relatively strong positive linear trend, meaning that plants here are thriving due to having accessible water.  

Overall, the annual mean precipitation is greater than the annual mean evapotranspiration inside the Mississippi Embayment in any given year. Excess precipitation in the form of runoff can directly recharge the aquifer in alluvial regions; outside of these areas, runoff can flow into stream systems and laterally recharge the aquifer.  

 A notably higher or lower water balance is apparent in some years during the time period. In 2010, water balance is high as precipitation is relatively large; while in 2011, water balance is low in response to a drought event.    

DEVELOP is part of NASA’s Capacity Building Program that addresses environmental and public policy issues by using NASA Earth observations in 10-week projects. DEVELOP projects apply the Earth observations to learn more about Agriculture, Disasters, Ecological Forecasting, Energy, Health & Air Quality, Transportation & Infrastructure, Urban Development,  Water Resources, and Environmental Justice Needs. 

Evapotranspiration: the sum of evaporation from the land surface plus transpiration from plants 

Potential Evapotranspiration: the amount of evaporation and transpiration that would occur if a sufficient water source were available 

Evaporative Stress Index: Actual ET / Potential ET; A measure of anomalies in ET that can indicate unusually high or low water usage rates  

Water Balance: Precipitation – Actual ET; A measure comparing inflows (precipitation) and outflows (evapotranspiration) in the water system

P> ET = water surplus  

P<ET = water deficiency  

Total Water Storage: the changes in total water storage in a land mass and can quantify ground water storage and runoff

GRACE: Gravity Recovery and Climate Experiment 

Terra MODIS: Moderate Resolution Imaging Spectroradiometer 

GPM IMERG: Integrated Multi-satellitE Retrievals for GPM 

NLCD: National Land Cover Database  

Condon, L. E., Atchley, A. L., & Maxwell, R. M. (2020). Evapotranspiration depletes groundwater under warming over the contiguous United States. Nature communications, 11(1), 1-8. 

Mohan, C., Western, A.W., Wei, Y., Saft, M. (2018). Predicting groundwater recharge for varying land cover and climate conditions – a global meta-study. Hydrology and Earth System Sciences, 22, 2689-2703, doi: 10..5194/hess-22-2689-2018 

 Scanlon, B. R., Rateb, A., Pool, D. R., Sanford, W., Save, H., Sun, A., Long, D., & Fuchs, B. (2021). Effects of climate and irrigation on Grace-based estimates of water storage changes in major US aquifers. Environmental Research Letters, 16, 094009.  https://doi.org/10.1088/1748-9326/ac16ff   

Simco, W. (2018). Recharge of the Memphis aquifer in an incised urban watershed. [Master’s thesis, University of Memphis].  Electronic Theses and Dissertations. 1830.   https://digitalcommons.memphis.edu/etd/1830  

Smith, S. (2019). Recharge of the Memphis aquifer in an incised urban watershed: implications of impervious surfaces and stream incision. [Master’s thesis, University of Memphis]. Electronic Theses and Dissertations. 1970.   https://digitalcommons.memphis.edu/etd/1970  

Sarah Houston, Protect Our Aquifer. (2022). Memphis Bridge [JPG]. Written Permission. 

University of Memphis, CAESAR. (2022).  Geology below the Mid-South: a cross-section that reveals the Memphis Aquifer [PNG]. Written Permission and retrieved from   https://caeser.memphis.edu/resources/formedia/  

 Tennessee Department of General Services (2021). Utilities overview of Ford Plant [PNG]. Public Domain. Retrieved from  https://static1.squarespace.com/static/MRM-AssessmentStudy-Final.pdf  

Sarah Houston, Protect Our Aquifer. (2022). Protect Our Aquifer Sign [JPG]. Written Permission. 

Sarah Houston, Protect Our Aquifer. (2022). Urban Canal near park and road [JPG]. Written Permission. 

Sarah Houston, Protect Our Aquifer. (2022). Canal in forest location [JPG]. Written Permission. 

Sarah Houston, Protect Our Aquifer. (2022). Dry field at Ford Plant [JPG]. Written Permission. 

NASA. (2013). GPM satellite [PNG]. Public Domain. Retrieved from   https://gpm.nasa.gov/scienceteam/resources/gpm-core-observatory-left-angle  

NASA. (2002). GRACE satellites [PNG].. Public Domain. Retrieved from  https://www.jpl.nasa.gov/images/pia04235-artists-concept-of-gravity-recovery-and-climate-experiment  

NASA. (1999). Terra MODIS [PNG]. Public Domain. Retrieved from  https://pace.oceansciences.org/gallery_more.htm?id=150  

The National Land Cover Database (2006). NLCD US map [JPEG]. Public Domain. Retrieved from  https://eros.usgs.gov/doi-remote-sensing-activities/2011/usgs/national-land-cover-database-nlcd-delivers-update  

NASA/Goddard Space Flight Center Conceptual Image Lab. (2012). Evaporation and Transpiration [GIF]. Public Domain. Retrieved from  https://svs.gsfc.nasa.gov/10926  

 USGS. (2022). Water cycle diagram [PNG]. Public Domain. Retrieved from  https://www.usgs.gov/media/images/evapotranspiration-sum-plant-transpiration-and-evaporation  

USGS. (2022). Transpiration draws water out of the ground [PNG]. Public Domain. Retrieved from  https://www.usgs.gov/media/images/transpiration-draws-water-out-ground  

USGS. (2022). Example land cover data [JPEG]. Public Domain. Retrieved from   https://www.usgs.gov/media/images/example-land-cover-data  

NASA. (2018). ECOSTRESS on the ISS [JPG]. Public Domain. Retrieved from  https://ecostress.jpl.nasa.gov/downloads/images/ecostress_on_ISS.jpg  

This material is based upon work supported by NASA through contract NNL16AA05C. 

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Aeronautics and Space Administration (NASA). 

NPR 2200.2C D.6.4.1: Trade names and trademarks are used in this report for identification only. Their usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration.