“We think of our land and water and human resources not as static and sterile possessions but as life giving assets to be directed by wise provisions for future days.”¹

Citizens living around the Mississippi River have long assumed there would always be ample water to sustain their populations.² But this assumption is rapidly changing as states confront the reality of climate change, drought, and increased water demands from their growing populations.³ Current conflicts in the American West demonstrate the difficulties that arise when states try to protect a rapidly depleting water supply.⁴ Having failed to reach a solution to solve a problem that has been apparent for decades, these western states now face the daunting task of rationing limited water sources among themselves and among their growing populations.⁵ Unlike other regions in the nation in which states realized belatedly the consequences of their failure to reach a compromise, the Mid-South still has a narrow time frame to protect the Middle Claiborne Aquifer from a similar fate.

Due to the well-documented strain on the United States’ water supply, experts forecast that the coming decades will be marked by interstate water conflicts.⁶ Despite previous assumptions, the Mid-South will not be immune from these types of conflicts. Indeed, interstate water litigation in the region has already begun. Although similar lawsuits around the country previously focused on surface water, such as rivers and lakes,7 the United States Supreme Court in Mississippi v. Tennessee for the first time extended its jurisprudence to groundwater.⁸ After more than a decade of litigation between Mississippi and Tennessee over their shared groundwater resource, the Middle Claiborne Aquifer, the Court held that the Aquifer’s waters were subject to the remedy known as “equitable apportionment.”⁹  

Equitable apportionment is the sole federal common law doctrine that the Supreme Court employs to settle conflicts when states have not worked together to regulate a shared water resource.¹⁰ If the state bringing suit can prove that its access to the water source has been substantially impaired by a competing user, the Court apportions allotments of the contested water resource among the states.¹¹ Despite holding that the Aquifer was subject to equitable apportionment, the Mississippi Court did not apply the doctrine.¹² Instead, the Court dismissed the case because Mississippi had expressly disavowed an equitable apportionment decree.¹³ 

The dismissal left the Aquifer judicially undisturbed, which is for the best. The remedy of equitable apportionment is largely disfavored by states, scholars, and the Court itself.¹⁴ Instead, an interstate compact — a congressionally approved contract between two or more states¹⁵ — is the preferred means for states to prevent future litigation while securing the sustainable usage of a shared water supply. Although existing interstate compacts are exclusive to groundwater, there is no reason to restrict its application groundwater.¹⁶ The typical use of a compact is to create a regional level of regulation to resolve a problem that is interstate but does not merit, or for which states do not want, federal or judicial intervention.¹⁷ These compacts provide an opportunity for states to overcome federal overreach on “local” matters, ensuring an adaptive and collaborative means for regional water regulation.¹⁸  

This article raises awareness about the vulnerable groundwater resource shared by multiple states in the Mid-South, the Middle Claiborne Aquifer. By showing that an interstate compact is the Mid-South’s most appropriate long-term solution to protect the Aquifer, this article also provides a framework for all interstate groundwater sources across the United States.¹⁹

I.    THE MID-SOUTH & THE MIDDLE CLAIBORNE AQUIFER

The warming climate, severe drought, turbulent weather, and increased water demands have adversely impacted the nation’s water supply.²⁰ This has led experts to predict that the Mid-South—a region that has long been recognized for its fertile soil and agricultural promise²¹ —holds the potential to become the dominant farming region in the United States.²² The future of the Mid-South as an agricultural hub depends, in large part, on the continued supply of water for irrigation. This water supply is provided almost exclusively by the Middle Claiborne Aquifer.²³

The Middle Claiborne Aquifer is located within the larger Mississippi Embayment Aquifer System that stretches from Missouri towards the Gulf of Mexico.²⁴ The Middle Claiborne Aquifer’s waters are located hundreds of feet beneath the surface eight states — Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee—covering over 70,000 square miles.²⁵ However, Arkansas, Louisiana, Mississippi and Tennessee encompass the bulk of its territory.²⁶ Due to groundwater pumping, the United States Geological Survey (USGS) has found that water levels declines are more dramatic in the Middle Claiborne Aquifer than the overlying Mississippi Embayment Aquifer.²⁷ Consequently, the Aquifer has become the second fastest depleted groundwater system in the country.²⁸ For example, the USGS has noted that the most significant declines are in southern Arkansas and northern Louisiana.²⁹ There, increased pumping from the Aquifer has resulted in dramatically decreased water levels.³⁰

The states drawing water from the Middle Claiborne Aquifer are aware of these declines.³¹ A nationwide 2017 survey recorded states’ concerns over groundwater governance.³² Arkansas noted concerns over the Middle Claiborne Aquifer’s depletion in both eastern and southern portions of the state.³³ Arkansas also forecasted that an interstate compact and water right litigation will require more attention in the coming decade.³⁴ Mississippi’s primary Aquifer concerns were long-term quality, quantity, and contamination.³⁵ Overdrawing from portions of the Aquifer can lead to irreversible damage, reducing its water-yielding capacity and ability to recharge.³⁶ Currently, withdrawals exceed recharge in parts of the Middle Claiborne Aquifer located in eastern Arkansas, northern Mississippi, and western Tennessee.³⁷ And long-term pumping along the border of Arkansas and Louisiana has created extensive regional water-level declines.³⁸   

The survey also revealed that contamination was another top concern for the Aquifer’s users.³⁹ Due to the use of the Aquifer’s waters for public drinking supply, contamination has the potential to pose a profound public health risk.⁴⁰ Breaches — where the clay layer protecting an aquifer is weakened during well pumping, causing contaminates to pull down pollution into drinking water supply—are a known issue within certain areas of the Middle Claiborne Aquifer.⁴¹ Aquifer contamination in Louisiana can impact Arkansas, just as contamination in Mississippi can impact Tennessee. The impact is thus not merely a local matter, but a shared concern of all Aquifer users.⁴²

Each state pumps water from the Aquifer for different purposes. The three main purposes are irrigation, public supply, and industry.⁴³ Tennessee uses the Aquifer primarily for public supply, including drinking water.⁴⁴ The City of Memphis, for example, pumps close to 120 million gallons of water from the Aquifer each day through 160 wells located around the city.⁴⁵ The majority of Arkansas’s Aquifer use of is for rice and soybean crop irrigation, with some use for public drinking.⁴⁶ Louisiana’s use is mixed, extending to public supply, livestock treatment, general irrigation, and industry purposes.⁴⁷ Mississippi uses the Aquifer primarily for crop irrigation and aquaculture.⁴⁸ And so, the Aquifer is the “single hydrogeological unit”⁴⁹ that, while unseen, plays a major role in the region’s health and economy.     

II.    HOW AN INTERSTATE COMPACT CAN SECURE WATER FOR THE MID-SOUTH’S FUTURE

Often legal solutions are implemented only to react to problems. When problems are too far gone to remedy, the law applies band aids over bullet wounds. But the problems facing the Middle Claiborne Aquifer have not reached this level — yet. Protecting the Middle Claiborne Aquifer through an interstate compact obviates this all-too common and unfortunate situation.

Because the Mid-South is one of the most important agricultural regions in the United States, the entire nation depends on farming production of the Mid-South.⁵⁰ And because of the water scarcity problems other agricultural regions are facing, the Mid-South’s role in crop production will only become more important. The Mid-South’s ability to farm is inextricably linked to its water supply, which is the Middle Claiborne Aquifer. This regional and national dependence on the Aquifer requires interstate regulation. Unfortunately, the groundwater system is poorly understood and shows sign of decline.⁵¹ The economic and environmental costs that result from declining water availability are apparent, yet the region isn’t working together to form a cooperative solution.⁵² The solution is not unattainable; the solution is an interstate compact.

The reasons for the states who share the Middle Claiborne Aquifer to enter into a compact are as follows: (1) to ensure sustainability; (2) to prevent contamination; and (3) to create a uniform regulatory body, comprised of stakeholders from participating states, to sufficiently protect the Aquifer. The primary concern for the Aquifer is sustainability—the development and use of its waters for an indefinite time without causing harmful environmental, economic, or social consequences.⁵³

Regulating groundwater allocation and pollution protects all parties using the Aquifer by mitigating the harmful effects of groundwater depletion through cooperative environmental and economic sustainability.⁵⁴ Over-pumping or contaminating the Aquifer can result in significant harms to each state, which manifests itself through litigation, water scarcity, and increased financial burdens.⁵⁵ Additionally, the lack of shared and standardized data among states results in a patchwork of policies that undermines the ability of experts to react and regulate the resource.⁵⁶ These issues can be categorized as problems for individual states to solve themselves. Due to groundwater’s inherent interstate nature, however, interstate cooperation is required. States are aware of the concerns, and now is the time to act.

Although the Aquifer’s withdrawal rates are greater than its recharge rates, the compact should not arise solely from a scarcity mindset. Instead, the basis should be one of cooperative engagement and study.  Indeed, groundwater governance, like all areas of water governance, is receiving global attention.⁵⁷ Gone are the days when it was acceptable to use a precious resource without understanding or regulating its sustainability and protection.⁵⁸ The conversation surrounding the sustainability of the Aquifer has been ongoing for at least a century,⁵⁹ and continues to this day.⁶⁰ It is time to turn this conversation into action.

Pumping has caused changes in groundwater movement from Mississippi and Arkansas into Tennessee.⁶¹ However, studies suggest that this may not be permanent.⁶² The urban growth occurring in northwestern Mississippi will likely result in the Aquifer’s waters reversing course and moving from Tennessee to Mississippi in the future.⁶³ The demand for the Aquifer will only increase,⁶⁴ demonstrating a need for all users of the Aquifer to work together to manage, understand, and protect their shared water supply. Armed with this foresight, an interstate compact has the potential to achieve this needed regional regulation.

To properly ensure sustainability and prevent contamination of the Aquifer, an interstate compact is needed to create a uniform regulatory body that can achieve these goals. Although states traditionally refrain from sharing resources, horizontal federalism principles encourage collaboration. After the Court declared the Middle Claiborne Aquifer an interstate groundwater body, each state is aware that the groundwater they rely on is not solely theirs — it is a common waterbody that demands collaboration. Currently, there is no such collaboration. The USGS recognizes this and notes, “Technical specialists working in various Federal and State agencies and universities have worked individually and in partnership over many years to address aspects of particular water issues in the [Aquifer], but no single agency or group has had the resources to support a broad-based and comprehensive scientific effort.”⁶⁵ An interstate compact would pool federal and state resources to provide a focused and comprehensive approach to ensuring the sustainability of the Aquifer.

This current status quo of patchwork policies independently regulating the Aquifer is not an effective, or efficient, means to promote the Aquifer’s needed sustainability and prevent future conflict. For example, Mississippi laws governing groundwater operate under a prior appropriation system⁶⁶ while Arkansas emphasizes a reasonable use theory⁶⁷ and Tennessee regulates groundwater through a riparian system.⁶⁸ Louisiana can be broadly categorized as a riparian state, but Louisiana Civil Code provides for limited groundwater law.⁶⁹ Similarly, Missouri, which lies over the upper portions of the Aquifer, has no formal doctrine and relies on state case law to dictate intrastate water disputes.⁷⁰ The result is a network of irreconcilable management programs, although they impact an interconnected body of underground water. For all these reasons, an interstate compact that creates a cohesive system of legal processes and rules led by a regional regulatory body ensures the Aquifer’s sustainability and longevity. And by entering a compact, the Mid-South can avoid future conflict and an undesired equitable apportionment decree.

III.    THE MIDDLE CLAIBORNE AQUIFER INTERSTATE COMPACT

The most effective way for the Mid-South to protects its precious groundwater resource is through an interstate compact. The process of drafting a compact would ensure a collaborative effort among the states sharing the Aquifer. Best practices for regulating the Middle Claiborne Aquifer should be developed with the perspectives and guidance of regional scientists, legal experts, and state decision-makers.⁷¹ To begin this needed discussion and provide a framework for the compact, this section provides key recommendations while leaving specific compact language to be decided upon during the actual drafting process.⁷²

Although portions of the Middle Claiborne Aquifer are being depleted, the compact should focus exclusively on water allocation. Instead, like other eastern compacts, it should emphasize cooperative study and water-quality protection.⁷³ First, the compact should be rooted in provisions of shared research and cohesive groundwater management. Such efforts are currently being completed individually by states in uncollaborative echo chambers. Each state currently has its own governing body; thus, the eight states that overlie the Aquifer perform redundant responsibilities for research and planning. This inefficiency could be eliminated by concerted research through one regional governing body, created by compact. And if the federal government participates, each state could benefit from additional federal funding.⁷⁴ Continual and region-wide assessments of water availability in the Middle Claiborne Aquifer are critically important for making well-informed conservation decisions regarding water allocation and protection. Further, this effort can establish best practices for groundwater use in the region and predict changes to the regional water cycle on a rolling basis.⁷⁵ Foresight and preparation are the hallmarks of sustainability for the region’s dependence on the Aquifer.

Second, a water quality protection program is critical to ensure the Aquifer’s long-term quality. Breaches and contaminants already threaten various portions of the Aquifer. A compact ensures that each user of the Aquifer is aware of and takes part in efforts to ensure water quality protection. For example, if a project from one state poses the threat of contaminating the Aquifer, each state should have the ability to review and ensure regional conformity and consensus.⁷⁶ The creation of a governing body that includes stakeholders from each participating state to ensure water quality protection increases administrative efficiency by replacing these overlapping state authorities with a single guiding entity.

Third, the compact must contain dispute resolution mechanisms. Interstate compacts have previously resulted in conflict and litigation, and provisions to encourage litigation alternatives and dispute resolutions are critical to long-term success.⁷⁷ Similarly, a sunset limitation on compact duration should be included. By including a sunset provision, states can use determined periods of review to assess the compact’s effectiveness and impact. Just as compacts in the past have required updates, so too may changed circumstances in the Aquifer convince signatory states that the pact should be modified. 

IV.    CONCLUSION

All growing regions face a similar issue: how to effectively manage nonrenewable, complex, and misunderstood natural resources across state boundaries. Mississippi v. Tennessee put all eight states withdrawing from the Middle Claiborne Aquifer on notice that the region’s groundwater supply is such a resource. Further, the Court has made clear that interstate groundwater resources are now subject to equitable apportionment. The current status quo of state-by-state management of the Aquifer is unsustainable and inefficient. An interstate compact is by far the most effective to support long-term water security for the region.

For users of this resource in an era of drought, climate change, and increased water demand, it is critical to work together to understand and regulate the Aquifer. If states choose to do nothing and wait for future conflicts to arise, the Mid-South will have missed its unique and timely opportunity to preserve its most previous resource. The Aquifer is not yet depleted. And through an interstate compact, the states can ensure that it never will be.

---

PHILL RUSTON is a third-year law student at the University of Memphis Cecil C. Humphreys School of Law. After graduation, he will clerk for Justice Holly M. Kirby of the Tennessee Supreme Court during the 2024–2025 term, and Judge Thomas L. Parker of the United States District Court for the Western District of Tennessee during the 2025–2026 term.

---

1. President Franklin D. Roosevelt, Message to Congress on the Use of Our Natural Resources (Jan. 24, 1935).   
2. In large part, this assumption is based on the region’s wet climate and historical lack of understanding of groundwater.  See TN H20, Tennessee’s Roadmap to Securing the Future of Our Water Resources 1, 4 (2018), https://www.tn.gov/content/dam/tn/environment/water/tn-h2o/documents/plan-&-appendices/wr-tnh2o_plan app_institutional-and-legal-framework-chapter.pdf (discussing eastern water right laws being grounded in the assumption that there would always be enough water for all users).  
3. E.g., Jacey Fortin, Shrunken Mississippi River Snarls Barge Traffic and Imperils Drinking Supplies, N.Y. TIMES (Oct. 6, 2022), https://www.nytimes.com/2022/10/06/us/mississippi-river-low-water-barges.html?searchResultPosition=1 (discussing the Mississippi River drought); Zach Rosenthal, The Northeast is in the Middle of an Intense Drought, WASH. POST (Aug. 16, 2022, 1:27 PM), https://www.washingtonpost.com/climate-environment/2022/08/16/northeast-drought-dry-rivers/ (discussing the Northeastern United States drought); Jane M. Daily, A Watershed Agreement: Fixing the Wild West of Water Usage, 5 LSU J. ENERGY L. & RES. 341, 341–42 (2017) (discussing global drought).
4. The conflict along the Colorado River is a premier example of states being aware of, but not working together, to protect their limited water supply.  See, e.g., Christopher Flavelle, As the Colorado River Shrinks, Washington Prepares to Spread the Pain, N.Y. TIMES (Jan. 31, 2023), https://www.nytimes.com/2023/01/27/climate/colorado-river-biden-cuts.html.
5. Using the Colorado River conflict again, each state was aware of the river’s depleting water supply for decades.  Despite having multiple opportunities to renegotiate an interstate compact that allocated the river’s waters, the states chose not to act.  See Robert W. Adler, Revisiting the Colorado River Compact: Time for A Change?, 28 J. LAND, RES., & ENVTL. L. 19, 22 (2008) (arguing that the Colorado River Compact must be updated to account for “significant changes in the population, economy, culture, and environment of the Colorado River Basin”).
6. E.g., Daily, supra note 3, at 341–42 (“With the upcoming challenges to secure water quickly approaching, water wars may be looming.  Similar to how oil security and sustainability sharply defined the twentieth century, countries with water wealth will visibly shape the twenty-first century.”) (internal citations omitted); Ellen M. Gilmer, Water Wars at the Supreme Court: ‘It’s Only Getting Worse’, Bloomberg Law (Sept. 17, 2020, 12:16 PM), https://www.bloomberglaw.com/bloomberglawnews/environment-and-energy/XASOS1ES000000?bna_news_filter=environment-and-energy#jcite (predicting upcoming “water wars”).
7. See Wyoming v. Colorado, 259 U.S. 419 (1922); Nebraska v. Wyoming, 325 U.S. 589 (1945); South Carolina v. North Carolina, 558 U.S. 256 (2010); Florida v. Georgia, 138 S. Ct. 2502 (2018); Texas v. New Mexico, 141 S. Ct. 509 (2020) (interstate compact litigation).
8. Mississippi v. Tennessee, 142 S. Ct. 31, 39 (2021).
9. Id. at 40. 
10. Darian B. Taylor, Equitable Apportionment Among States as Applied to Water Resources, 73 A.L.R. Fed. 3d § 7 (2022).
11. Mississippi, 142 S. Ct. at 39.
12. Id. at 41.
13. Id. (“Mississippi’s initial pleadings in this case disavowed equitable apportionment entirely . . . The State instead sought relief under principles of tort law.”); see discussion infra Section II.C. (discussing dismissal).
14. E.g., Noah D. Hall, Toward A New Horizontal Federalism: Interstate Water Management in the Great Lakes Region, 77 U. COLO. L. REV. 405, 410 (2006).
15. U.S. CONST. art. 1, § 10, cl. 3
16. Noah D. Hall & Benjamin L. Cavataro, Interstate Groundwater Law in the Snake Valley:  Equitable Apportionment and A New Model for Transboundary Aquifer Management, 2013 UTAH L. REV. 1553, 1571 (2013).
17. Rex A. Mann, Note, A Horizontal Federalism Solution to the Management of Interstate Aquifers: Considering an Interstate Compact for the High Plains Aquifer, 88 TEX. L. REV. 391, 403 (2009).
18. See Interstate Water Resource Management Agreements and Organizations, INTERSTATE COUNCIL ON WATER POL’Y 1, 1 (Dec. 2020), https://icwp.org/wp-content/uploads/2020/12/Primer_ICWP-Interstate-Water-Agreements_FINAL_12_18_2020.pdf [hereinafter Agreements]; Noah D. Hall, Interstate Water Compacts and Climate Change Adaptation, 5 ENVT'L & ENERGY L. & POL'Y J. 237, 240 (2010).
19. Almost all groundwater resources are interstate.  Principal Aquifers of the United States, USGS (March 8, 2021), https://www.usgs.gov/mission-areas/water-resources/science/principal-aquifers-united-states [hereinafter Principal]; Sharon B. Megdal & Jacob D. Petersen-Perlman, Decentralized Groundwater Governance and Water Nexus Implications in the United States, 59 JURIMETRICS J. 99, 100, 103 (2018).
20. Tapan B. Pathak, Mahesh L. Maskey, Jeffery A. Dahlberg, Faith Kearns, Khaled M. Bali, & Daniele Zaccaria, Climate Change Trends and Impacts on California Agriculture: A Detailed Review, 8(3) AGRONOMY 25 (2018), https://doi.org/10.3390/agronomy8030025; California Crops Under Climate Change, USDA CALIFORNIA CLIMATE HUB, available at https://www.climatehubs.usda.gov/hubs/california/california-crops-under-climate-change# (last visited Dec. 20, 2022).
21. C. W. Watson, Soil, An Agricultural Empire, in THE MID SOUTH AND ITS BUILDERS 51, 51 (C.P.J. Mooney ed., 1920, https://hdl.handle.net/2027/yale.39002030689260.
22. Julia Kurnik, The Next California: Investigating Potential in the Mid-Mississippi Delta River Region, THE MARKETS INSTITUTE AT WWF 1 (Feb. 28, 2020), https://files.worldwildlife.org/wwfcmsprod/files/Publication/file/34t96wfe6b_The_Next_California_Phase_1_ReporR_02_27_20.pdf (proposing that the Mid-South is poised to increase agricultural demand to counteract California’s decreased production).
23. The Middle Claiborne Aquifer has a variety of regional names, including:  “Sparta Aquifer,” “Memphis Aquifer,” and “Memphis Sand Aquifer.”  Brief for the United States as Amicus Curiae in Support of Overruling Mississippi’s Exceptions to the Report of the Special Master at *3, Mississippi v. Tennessee, 142 S. Ct. 31 (2021) (No. 143), 2021 WL 4729967.
24. See Report of the Special Master at *16 Diagram 2, Mississippi v. Tennessee, 142 S. Ct. 31 (2021) (No. 143), 2020 WL 11629023 (diagram of the Middle Claiborne Aquifer).
25. Mississippi v. Tennessee, 142 S. Ct. 31, 36 (2021); Alec Sweet, Comment, Addressing Interstate Ground Water Ownership: Mississippi v. Tennessee, 17 DUKE J. CONST. L. & PUB. POL'Y SIDEBAR 215, 218 (2022).
26. Mississippi, 142 S. Ct. at 36.
27. What is the Affect?, USGS: MERAS GROUNDWATER AVAILABILITY STUDY 1, https://www2.usgs.gov/water/lowermississippigulf/lmgweb/meras/whatisaffect.html (last visited Nov. 5, 2022 12:09 PM).  For more studies on the Aquifer’s water levels see Water Levels and Water Quality in the Sparta-Memphis Aquifer (Middle Claiborne Aquifer in Arkansas, Spring-Summer 2009, USGS, https://pubs.usgs.gov/sir/2013/5100/pdf/sir2013-5100.pdf (last visited Nov. 5, 2022 12:12 PM) [hereinafter Water Levels]; The Sparta Aquifer: A Sustainable Water Resource?, USGS 1, 1 fig.1, https://pubs.usgs.gov/fs/fs-111-02/fs-111-02.pdf (last visited Nov. 5, 2022 12:15 PM) [hereinafter Sparta].
28. Alec Sweet, Comment, Addressing Interstate Ground Water Ownership: Mississippi v. Tennessee, 17 DUKE J. CONST. L. & PUB. POL'Y SIDEBAR 215, 218 (2022).
29. What is the Affect?, supra note 27.
30. Id.
31. The 2017 survey cited infra outlines the states’ awareness of the Aquifer’s decline.  For another example, see Sparta, supra note 123, at 3 (“As early as the 1940’s, substantial declines in water levels were documented in Union and Jefferson Counties in Arkansas.  Substantial declines in Arkansas County have been documented only recently because of increased agricultural use from the Sparta Aquifer.”) (emphasis added).
32. Megdal & Vimont, supra note 5, at 1.
33. Arkansas listed depletion of the Sparta and Alluvial aquifers as one of the state’s primary concerns.  Arkansas was also concerned about its inability to complete surface-water delivery projects before the aquifers would be depleted.  Id. at 57–59.
34. Id. at 70–71.  Mississippi cited increased pumping and water quality monitoring as areas that will require more attention in the next decade.  Id. at 69–70.  Tennessee cited litigation and water rights.  Id.  Because Mississippi v. Tennessee had yet to be resolved at the time of the survey, Tennessee’s response may be different now.
35. Id. at 57–58, 60.  Louisiana’s primary concern was groundwater quality.  Id. at 57.  Tennessee cited internal communication and staffing as their primary concerns.  Id. at 58–59.  Missouri did not respond to the survey.
36. Sparta, supra note 123, at 3.
37. Sharon B. Megdal & Ethan Vimont, State-Level Groundwater Governance and Management in the U.S.: Summary of Survey Results of Groundwater Quality Strategies and Practices 1, 5 tbl.1 (2018), https://perma.cc/PR6B-R9P5
38. Sparta, supra note 27, at 2.
39. E.g., Megdal & Vimont, supra note 37, at 70–71.
40. WILLIAM GOLDFARB, WATER LAW 42 (Lewis Publishers 2d ed. 1988)
41. See Rodrigo Villalpando-Vizcaino, Brian Waldron, Daniel Larsen, & Scott Schoefernacker, Development of Numerical Multi-Layered Groundwater Model to Simulate Inter-Aquifer Water Exchange in Shelby County, Tennessee, 13(18) WATER 1, 2, fig.1 (2021), https://doi.org/10.3390/w13182583 (discussing aquifer recharge).
42. Although it is unknown how individual breaches impact the Aquifer as a whole, it is well documented that such breaches have the potential to impact long-term water quality.  This “unknown” is another reason why states should work together to protect the Aquifer.  See id.
43. Water Levels, supra note 27, at 3 (“Irrigation used about 61.0 Mgal/d (35.9 percent), public supply used about 58.9 Mgal/d (34.6 percent), and industrial used about 48.0 Mgal/d (28.2 percent).”).
44. Memphis is the largest city on the Mississippi River that derives its public drinking water solely from groundwater.  CAESER University of Memphis, Memphis Aquifer Research: Recharging the Groundwater Supply, YOUTUBE (Nov. 27, 2019), https://www.youtube.com/watch?v=AV70-0_QMc8 (Dr. Brian Waldron at 0:12).
45. Mississippi v. Tennessee, 142 S. Ct. 31, 37 (2021).
46. Catherine Janasie & Rachel Buddrus, Mississippi River Valley Alluvial Aquifer and Sparta Aquifer Comparison Report for the States of Mississippi, Arkansas, Louisiana, Tennessee, and Missouri, SEA GRANT LAW CENTER 1, 3 (2018).  
47. Water Resources of Claiborne Parish, Louisiana, USGS, https://pubs.usgs.gov/fs/2013/3029/FS2013-3029_Claiborne.pdf, (last visited Nov. 5, 2022 12:29 PM).
48. Janasie & Buddrus, supra note 46, at 3.
49. Mississippi, 142 S. Ct. at 38.
50. See TN H20, supra note 2, at 59.
51. Mississippi Alluvial Plain (MAP) Regional Water Availability Study, USGS, https://www2.usgs.gov/water/lowermississippigulf/map/index.html (last visited Dec. 21, 2022) [hereinafter MAP].
52. For example, the USGS has further stated that, “Lack of regionally consistent monitoring efforts, focused groundwater modeling on the alluvial aquifer, and sub-regional hydrogeologic characterization have resulted in a limited capability to quantify the conjunctive use of groundwater and surface water in the region.”  National Water Census: Regional Groundwater Availability Studies, USGS (Feb. 28, 2019), https://www.usgs.gov/mission-areas/water-resources/science/national-water-census-regional-groundwater-availability#MAP.
53. Sparta, supra note 27, at 3.
54. See Emily Brophy, Feature, The Importance of Regulating Transboundary Groundwater Aquifers, 10 SUSTAINABLE DEV. L. & POL'Y 19, 19 (2009).
55. See J.R. Bartolino & W.L. Cunningham, Groundwater Depletion Across the Nation, USGS 1 (Nov. 2003), https://pubs.usgs.gov/fs/fs-103-03/JBartolinoFS(2.13.04).pdf.
56. Cf., Megdal & Petersen-Perlman, supra note 19, at 100, 102 (noting the lack of federal policy or direction regarding “best practices” for groundwater leads to differing approaches to regulations among states who share groundwater).
57. See GROUNDWATER GOVERNANCE, https://groundwaterportal.net/project/groundwater-governance-gwg (last visited Dec. 20, 2022).
58. See, Clean Water Act, 33 U.S.C. §§ 1251–1414 (2018); see also 33 U.S.C. § 1251(a)(6) (“[I]t is the national policy that a major research and demonstration effort be made to develop technology necessary to eliminate the discharge of pollutants into the navigable waters, waters of the contiguous zone, and the oceans.”).
59. Cf., J.N. Chester & D.E. Davis, The Water Supply of Memphis, Tennessee, 8(4) AMERICAN WATER WORKS ASSOCIATION 377, 379 (July 1921) (“One of the critical questions in this study has to do with the decision as to whether or not it will be safe to further exploit this artesian supply.”).
60. Sparta, supra note 27, at 3.
61. Report of the Special Master at *21, Mississippi v. Tennessee, 142 S. Ct. 31 (2021) (No. 143), 2020 WL 11629023.
62. Brian Waldron & Daniel Larsen, Pre-Development Groundwater Conditions Surrounding Memphis, Tennessee: Controversy and Unexpected Outcomes, Paper No. JAWRA-13-0018-P JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 1, 2 (2014).
63. Id. at 3, 19.
64. Id. at 19.
65. Map, supra note 27.
66. MISS. CODE. ANN. § 51-3-5(3) (West 2022) (“Any person using groundwater prior to April 1, 1985 for a beneficial use shall be entitled to continue such use . . . .”).
67. ARK. CODE ANN. § 15-22-215 (West 2022).
68. TENN. CODE ANN. § 68-221-702 (West 2022).  
69. LA. STAT. ANN. § 9:1104 (2022).
70. Bollinger v. Henry, 375 S.W.2d 161 (Mo. 1964); Higday v. Nickolaus, 469 S.W.2d 859, 869 n.15 (Mo. App. 1971) (quoting Bollinger v. Henry, 375 S.W.2d 161, 166 (Mo. 1964); Frequently Asked Missouri Water Resources Questions – PUB1350, MISSOURI DEPARTMENT OF NATURAL RESOURCES, https://dnr.mo.gov/document-search/frequently-asked-missouri-water-resources-questions-pub1350/pub1350 (last visited Dec. 20, 2022) (“There are no state laws, regulations or policies that specify the quantity of water that any diverter may use.”).  
71. Noah D. Hall, Political Externalities, Federalism, and A Proposal for an Interstate Environmental Impact Assessment Policy, 32 HARV. ENVTL. L. REV. 49, 84 (2008).
72. For more detailed compact language, see Jerome C. Muys, George William Sherk, & Marilyn C. O’Leary, Utton Transboundary Resources Center Model Interstate Water Compact, 47 NAT. RESOURCES J. 17, 23 (2007).  
73. See Hall & Cavataro, supra note 16, at 1553 for an in-depth analysis of how research and water-quality can be imbedded in a compact applied to groundwater.
74. Marlissa S. Briggett, Comment, State Supremacy in the Federal Realm: The Interstate Compact, 18 B.C. ENVTL. AFF. L. REV. 751, 736 (1991).
75. The Great Lakes Compact requires the signatory states to work in conjunction to develop strategies that strengthen the scientific basis for sound water management decision making.  Great Lakes–St. Lawrence River Basin Compact, Pub. L. No. 110–342, 122 Stat 3739 (2008).
76. Marilyn C. O’Leary & George William Sherk, Reinventing the Interstate Water Compact:  A New Model, 52 ROCKY MTN. ROCK. MIN. L. INST, 21-1 § 2(b) (2006).  
77. See Emma Easley, Note, Improving Interstate Water Compacts One ADR Provision at A Time, 37 OHIO ST. J. ON DIS. RES. 369, 375–77 (2022) (arguing for dispute resolution mechanisms within interstate compacts).