Using a Mass Balance Model to Evaluate Groundwater Budget of Seawater‐Intruded Island Aquifers1

Jang, Cheng‐Shin, Chen‐Wuing Liu, Shih‐Kai Chen, and Wen‐Sheng Lin, 2011. Using a Mass Balance Model to Evaluate Groundwater Budget of Seawater‐Intruded Island Aquifers. Journal of the American Water Resources Association (JAWRA) 48(1): 61‐73. DOI: 10.1111/j.1752‐1688.2011.00593.x Abstract: The study developed a mass balance model to evaluate the groundwater budget of seawater‐intruded island aquifers using limited available data. The Penghu islands were selected as a study area. As sparse observed data were available in the islands, methods of combining water and chloride balances were used to determine the amounts of groundwater pumping, seawater intrusion, aquifer storages, and safe yields in the shallow and deep aquifers. The groundwater budget shows that seawater intrusion to freshwater aquifers was 1.38 × 10⁶ and 0.29 × 10⁶ m³/year in the shallow and deep aquifers, respectively, indicating that the seawater intrusion is severe in the both aquifers. The safe yield of the shallow aquifer was 14.56 × 10⁶ m³/year in 2005 which was four times higher than that of the deep aquifer (3.70 × 10⁶ m³/year). However, the annual pumping amounts in the shallow and deep aquifers were 4.77 × 10⁶ and 3.63 × 10⁶ m³/year, respectively. Although the safe yield of the shallow aquifer is enough for all water resources demands, only 55% of exploitation amount was extracted from the shallow aquifer due to its poor water quality. Groundwater exploitation in the deep aquifer should be significantly reduced and regulated by a dynamic management of pumping scheme because the annual pumping amounts are close to the safe yield and seawater intrusion occurs continually. Additionally, to alleviate further aquifer salination, at least half of the current annual groundwater abstraction should be reduced.     

Estimating Water Budgets and Vertical Leakages for Karst Lakes in North‐Central Florida (United States) Via Hydrological Modeling1

Lin, Zhulu, 2011. Estimating Water Budgets and Vertical Leakages for Karst Lakes in North‐Central Florida (United States) Via Hydrological Modeling. Journal of the American Water Resources Association (JAWRA) 1‐16. DOI: 10.1111/j.1752‐1688.2010.00513.x Abstract: Newnans, Lochloosa, and Orange Lakes are closely hydrologically connected karst lakes located in north‐central Florida, United States. The complex karst hydrology in this region poses a great challenge to the hydrological modeling that is essential to the development of Total Maximum Daily Loads for these lakes. We used a Hydrological Simulation Program – Fortran model coupled with the parallel Parameter ESTimation model calibration and uncertainty analysis software to estimate effectively the hydrological interactions between the lakes and the underlying upper Floridan aquifer and the water budgets for these three lakes. The net results of the lake‐groundwater interactions in Newnans and Orange Lakes are that both lakes recharge the underlying upper Floridan aquifer, with the recharge rate of the latter one magnitude greater than that of the former. However, for Lochloosa Lake, the net lake‐groundwater interaction is that the lake gains water from groundwater in a significant amount, approximately 40% of its total terrestrial water input. The annual average vertical leakages estimated for Newnans, Lochloosa, and Orange Lakes are 6.0 × 10⁶, ?8.9 × 10⁶, and 44.4 × 10⁶ m³, respectively. The average vertical hydraulic conductance (K_v/b) of the units between a lake bottom and the underlying upper Floridan aquifer in this region are also estimated to be from 1.26 × 10^?4 to 1.01 × 10^?3 day^?1.     

Enhanced water resource base for sustainable integrated water resource management

The article states the case for greatly enhanced reliance on desalination in the provision of freshwater. It argues that the concept of integrated water resource management (IWRM), should be expanded to routinely include desalination, and that sea water and brackish water should be listed among available sources of freshwater. In recent years, the price per m3 of freshwater obtained from desalination has steadily declined, and is now within competitive range of conventional sources, especially as extracting water from surface sources (rivers, lakes) is becoming increasingly expensive as well as ecologically harmful, and groundwater in many locations is saline or depleted. With the expectation that by 2020, five billion people will reside in megacities, today's conventional water resources are likely to become insufficient. As many of these megacities are located near ocean coasts, sea water seems a logical solution.     

Large-scale impact of CO2 storage in deep saline aquifers: A sensitivity study on pressure response in stratified systems

Large volumes of CO₂ captured from carbon emitters (such as coal-fired power plants) may be stored in deep saline aquifers as a means of mitigating climate change. Storing these additional fluids may cause pressure changes and displacement of native brines, affecting subsurface volumes that can be significantly larger than the CO₂ plume itself. This study aimed at determining the three-dimensional region of influence during/after injection of CO₂ and evaluating the possible implications for shallow groundwater resources, with particular focus on the effects of interlayer communication through low-permeability seals. To address these issues quantitatively, we conducted numerical simulations that provide a basic understanding of the large-scale flow and pressure conditions in response to industrial-scale CO₂ injection into a laterally open saline aquifer. The model domain included an idealized multilayered groundwater system, with a sequence of aquifers and aquitards (sealing units) extending from the deep saline storage formation to the uppermost freshwater aquifer. Both the local CO₂-brine flow around the single injection site and the single-phase water flow (with salinity changes) in the region away from the CO₂ plume were simulated. Our simulation results indicate considerable pressure buildup in the storage formation more than 100 km away from the injection zone, whereas the lateral distance migration of brine is rather small. In the vertical direction, the pressure perturbation from CO₂ storage may reach shallow groundwater resources only if the deep storage formation communicates with the shallow aquifers through sealing units of relatively high permeabilities (higher than 10^?18 m²). Vertical brine migration through a sequence of layers into shallow groundwater bodies is extremely unlikely. Overall, large-scale pressure changes appear to be of more concern to groundwater resources than changes in water quality caused by the migration of displaced saline water.     

Performance investigation of a new solar desalination unit based on sequential flat plate and parabolic dish collector

A new system composed of a sequential flat plate and parabolic dish solar collector was applied to enhance the solar desalination productivity. Heated saline water was desalinated using the evaporation/condensation principle and an effort was made to achieve higher distillate production compared to previous studies. Desalination efficiency values were calculated between 23% and 57%. Maximum desalinated water productions were obtained as 1,038 mL/m².h in autumn and 1,402 mL/m².h in summer. The cost of solar desalination system was found as economically feasible with 3 years’ payback period and the produced water cost of 0.014 $/L. Physicochemical analyses revealed that as a result of the desalination process, salinity level decreased from 35.6‰ to 0.0–0.1‰, chloride concentration decreased from 21,407 mg/L to 10 mg/L, and electrical conductivity decreased from 53.1 mS/cm to 0.11 mS/cm.     

Regional Blue and Green Water Balances and Use by Selected Crops in the U.S.

The availability of freshwater is a prerequisite for municipal development and agricultural production, especially in the arid and semiarid portions of the western United States (U.S.). Agriculture is the leading user of water in the U.S. Agricultural water use can be partitioned into green (derived from rainfall) and blue water (irrigation). Blue water can be further subdivided by source. In this research, we develop a hydrologic balance by 8‐Digit Hydrologic Unit Code using a combination of Soil and Water Assessment Tool simulations and available human water use estimates. These data are used to partition agricultural groundwater usage by sustainability and surface water usage by local source or importation. These predictions coupled with reported agricultural yield data are used to predict the virtual water contained in each ton of corn, wheat, sorghum, and soybeans produced and its source. We estimate that these four crops consume 480 km³ of green water annually and 23 km³ of blue water, 12 km³ of which is from groundwater withdrawal. Regional trends in blue water use from groundwater depletion highlight heavy usage in the High Plains, and small pockets throughout the western U.S. This information is presented to inform water resources debate by estimating the cost of agricultural production in terms of water regionally. This research illustrates the variable water content of the crops we consume and export, and the source of that water.     

A Retrospective Look at the Water Resource Management Policies in Nassau County,Long Island,New York1

Abstract: The residents of Nassau County Long Island, New York receive all of their potable drinking water from the Upper Glacial, Jameco/Magothy (Magothy), North Shore, and Lloyd aquifers. As the population of Nassau County grew from 1930 to 1970, the demand on the ground‐water resources also grew. However, no one was looking at the potential impact of withdrawing up to 180 mgd (7.9 m³/s) by over 50 independent water purveyors. Some coastal community wells on the north and south shores of Nassau County were being impacted by saltwater intrusion. The New York State Legislature formed a commission to look into the water resources in 1972. The commission projected extensive population growth and a corresponding increase in pumping resulting in a projected 93.5 to 123 mgd (4.1 to 5.5 m³/s) deficit by 2000. In 1986, the New York Legislature passed legislation to strengthen the well permit program and also establish a moratorium on new withdrawals from the Lloyd aquifer to protect the coastal community’s only remaining supply of drinking water. Over 30 years has passed since the New York Legislature made these population and pumping projections and it is time to take a look at the accuracy of the projections that led to the moratorium. United States Census data shows that the population of Nassau County did not increase but decreased from 1970 to 2000. Records show that pumping in Nassau County was relatively stable fluctuating between 170 and 200 mgd (7.5 to 8.8 m³/s) from 1970 to 2004, well below the projection of 242 to 321 mgd (10.6 to 14.1 m³/s). Therefore, the population and water demand never grew to projected values and the projected threat to the coastal communities has diminished. With a stable population and water demand, its time to take a fresh look at proactive ground‐water resource management in Nassau County. One example of proactive ground‐water management that is being considered in New Jersey where conditions are similar uses a ground‐water flow model to balance ground water withdrawals, an interconnection model to match supply with demand using available interconnections, and a hydraulic model to balance flow in water mains. New Jersey also conducted an interconnection study to look into how systems with excess capacity could be used to balance withdrawals in stressed aquifer areas with withdrawals in unstressed areas. Using these proactive ground‐water management tools, ground‐water extraction could be balanced across Nassau County to mitigate potential impacts from saltwater intrusion and provide most water purveyors with a redundant supply that could be used during water emergencies.     

A Comparison of Three Federal Datasets for Thermoelectric Water Withdrawals in the United States for 2010

Historically, thermoelectric water withdrawal has been estimated by the Energy Information Administration (EIA) and the U.S. Geological Survey's (USGS) water‐use compilations. Recently, the USGS developed models for estimating withdrawal at thermoelectric plants to provide estimates independent from plant operator‐reported withdrawal data. This article compares three federal datasets of thermoelectric withdrawals for the United States in 2010: one based on the USGS water‐use compilation, another based on EIA data, and the third based on USGS model‐estimated data. The withdrawal data varied widely. Many plants had three different withdrawal values, and for approximately 54% of the plants the largest withdrawal value was twice the smallest, or larger. The causes of discrepancies among withdrawal estimates included definitional differences, definitional noise, and various nondefinitional causes. The uncertainty in national totals can be characterized by the range among the three datasets, from 5,640 m³/s (129 billion gallons per day [bgd]) to 6,954 m³/s (158 bgd), or by the aggregate difference between the smallest and largest values at each plant, from 4,014 m³/s (92 bgd) to 8,590 m³/s (196 bgd). When used to assess the accuracy of reported values, the USGS model estimates identify plants that need to be reviewed.     

Seawater Intrusion and Sustainable Yield of Basal Aquifers1

Liu, Clark C.K. and John J. Dai, 2012. Seawater Intrusion and Sustainable Yield of Basal Aquifers. Journal of the American Water Resources Association (JAWRA) 48(5): 861‐870. DOI: 10.1111/j.1752‐1688.2012.00659.x Abstract: Basal aquifers, in which freshwater floats on top of saltwater, are the major freshwater supply for the Hawaiian Islands, as well as many other coastal regions around the world. Under unexploited or natural conditions, freshwater and the underlying seawater are separated by a relatively sharp interface located below mean sea level at a depth of about 40 times the hydraulic head. With forced draft, the hydraulic head of a basal aquifer would decline and the sharp interface would move up. It is a serious problem of seawater intrusion as huge amounts of freshwater storage is replaced by saltwater. Also, with forced draft, the sharp interface is replaced by a transition zone in which the salinity increases downward from freshwater to saltwater. As pumping continues, the transition zone expands. The desirable source‐water salinity in Hawaii is about 2% of the seawater salinity. Therefore, the transition zone expansion is another serious problem of seawater intrusion. In this study, a robust analytical groundwater flow and salinity transport model (RAM2) was developed. RAM2 has a simple mathematical structure and its model parameters can be determined satisfactorily with the available field monitoring data. The usefulness of RAM2 as a viable management tool for coastal ground water management is demonstrated by applying it to determine the sustainable yield of the Pearl Harbor aquifer, a principal water supply source in Hawaii.     

Impacts of Bakken Shale Oil Development on Regional Water Uses and Supply

The Bakken shale play in western North Dakota is one of the largest unconventional oilfields in the United States, but published research about impacts on the region's water resources is rare. In this study, besides examining North Dakota water management policies and activities, we also analyzed three datasets: the Bakken horizontal well completion data (2008‐2014), North Dakota permitted water consumption data (2000‐2014), and groundwater level and streamflow observations in western North Dakota (2000‐2014). We found from 2008 to 2014, the annual total industrial water uses for Bakken shale oil development ranged between 0.5 and 10% of statewide total consumptive water use. The percentage increases were between 3.0 and 40% within the Bakken oil production region. The increased population of temporary oilfield service workers contributed additional domestic water use, which was equivalent to ~15% of annual industrial water use for the shale oil development in the Bakken. Despite being in a semiarid region, the impact of Bakken development on regional water supply was limited because the water in the Bakken was adaptively managed and the region received on average over 20% more precipitation than normal during 2008‐2014. Of the 15 glaciofluvial aquifers under study, 12 have seen water levels increasing or unchanged and the water levels for the remaining 3 aquifers have decreased.     

Transboundary Groundwater Policy: Developing Approaches in the Western and Southwestern United States1

Hathaway, Deborah L., 2011. Transboundary Groundwater Policy: Developing Approaches in the Western and Southwestern United States. Journal of the American Water Resources Association (JAWRA) 47(1):103‐113. DOI: 10.1111/j.1752‐1688.2010.00494.x Abstract: The western and southwestern United States include dozens of groundwater basins that cross political boundaries. Common among these shared groundwater basins is an overlay of differing legal structures and water development priorities, typically, with insufficient water supply for competing human uses, and often, a degraded ecosystem. Resolution of conflicts over ambiguously regulated groundwater has clarified transboundary groundwater policy in some interstate basins, while transboundary groundwater policy in international basins is less evolved. This paper identifies and contrasts approaches to transboundary groundwater policy, drawing from recent conflicts and cooperative efforts, including those associated with the interstate compacts on the Arkansas and Pecos Rivers; the Hueco and Lower Rio Grande Basins shared by New Mexico, Texas, and Mexico; and the Mexicali Basin in California and Mexico. Some efforts seek to fit groundwater policy into existing surface water allocation procedures; some strive for a better fit – incorporating scientific understanding of key differences between groundwater and surface water into policy frameworks. In some cases, neither policy nor precedent exists. The collective experience of these and other cases sets the stage for improved management of transboundary groundwater; as such, challenges and successes of these approaches, and those contemplated in several hypothetical model agreements, are examined.     

A preliminary cost and engineering estimate for desalinating produced formation water associated with carbon dioxide capture and storage

The risk associated with storage of carbon dioxide in the subsurface can be reduced by removal of a comparable volume of existing brines (e.g. Buscheck et al., 2011). In order to avoid high costs for disposal, the brines should be processed into useful forms such as fresh and low-hardness water. We have carried out a cost analysis of treatment of typical subsurface saline waters found in sedimentary basins, compared with conventional seawater desalination. We have also accounted for some cost savings by utilization of potential well-head pressures at brine production wells, which may be present in some fields due to CO₂ injection, to drive desalination using reverse osmosis. Predicted desalination costs for brines having salinities equal to seawater are about half the cost of conventional seawater desalination when we assume the energy can be obtained from excess pressure at the well head. These costs range from 32 to 40¢ per m³ permeate produced. Without well-head energy recovery, the costs are from 60 to 80¢ per m³ permeate. These costs do not include the cost of any brine production or brine reinjection wells, or pipelines to the well field, or other site-dependent factors.     

Impacts of Urbanization and Intensification of Agriculture on Transboundary Aquifers: A Case Study

The objectives were to (1) delineate the complex set of rules governing the fate and transfer of water rights as agricultural land is urbanized in Texas and New Mexico in the United States and Chihuahua in Mexico and (2) estimate the change in water use as a result of such urbanization. Important additional determinants of water use in the region include intensification of agriculture and the hydroschizophrenic policy framework. We conducted interviews with key informants to identify the possible outcomes for changes in water rights as land is urbanized. We constructed decision trees for each of the three jurisdictions, Chihuahua, Texas, and New Mexico, that identified the possible outcomes from urbanization. For each of the possible outcomes in the decision tree, we estimated a range of potential water use outcomes and the most likely water use outcome on a per unit of land area basis. Results show that urbanization of agricultural land has almost no impact on the aggregate demand for or use of surface water. However, the impacts of urbanization on groundwater use vary considerably over the region from Texas to New Mexico to Chihuahua. In New Mexico and Chihuahua where groundwater rights can be leased or sold to other users, the likely impact is a net increase in groundwater use as land is urbanized, ranging from 0 to 3,000 m³/ha in New Mexico and averaging 3,000 m³/ha or more in Chihuahua. In Texas, there is a net benefit in groundwater savings, but those savings are subject to being offset by increased groundwater pumping to meet the needs of expanding pecan production. The net result is continued groundwater depletion, threatening the life of the transboundary aquifers, the Hueco Bolson and the Mesilla Bolson, in the Middle Rio Grande basin (defined as the part of the basin between Elephant Butte Reservoir in New Mexico to the confluence of the river with the Rio Conchos from Mexico).     

BRACKISH GROUNDWATER DESALINATION: A COMMUNITY'S SOLUTION TO WATER SUPPLY AND AQUIFER PROTECTION1

The City of Cape May, New Jersey, draws its primary water supply from the Cohansey Aquifer, a unit serving residential, community, and industrial users throughout the Coastal Plain. By the year 2000, projected population growth will impose a peak water demand beyond available supplies. In addition, regional over-pumping threatens the Cohansey with saltwater intrusion, placing the city wells at risk by 1998. In the early-to mid 1990s, three broad categories of water-supply alternatives were evaluated by regional, state, and federal agencies — additional pumping from the Cohansey, conjunctive use of the Cohansey with other aquifers, and desalination of brackish groundwater. An approach was adopted in 1996 which derives up to 2 MGD from desalination of brackish groundwater, with the remaining peak demand satisfied by short-term pumpage from existing wells in the Cohansey. The first of two wells has been completed, yielding 1.4 MGD of brackish groundwater. Similar performance from the second well will exceed the design goal. When the initial system comes on line during the summer of 1998, New Jersey will have its first public water supply derived from desalinated groundwater. The use of desalinated groundwater balances competing demands for water resources in the southern Cape Region of New Jersey, allowing continued economic growth while reducing human impacts on a threatened aquifer.     

Modeled Sources,Transport, and Accumulation of Dissolved Solids in Water Resources of the Southwestern United States1

Anning, David W., 2011. Modeled Sources, Transport, and Accumulation of Dissolved Solids in Water Resources of the Southwestern United States. Journal of the American Water Resources Association (JAWRA) 47(5):1087‐1109. DOI: 10.1111/j.1752‐1688.2011.00579.x Abstract: Information on important source areas for dissolved solids in streams of the southwestern United States, the relative share of deliveries of dissolved solids to streams from natural and human sources, and the potential for salt accumulation in soil or groundwater was developed using a SPAtially Referenced Regressions On Watershed attributes model. Predicted area‐normalized reach‐catchment delivery rates of dissolved solids to streams ranged from <10 (kg/year)/km² for catchments with little or no natural or human‐related solute sources in them to 563,000 (kg/year)/km² for catchments that were almost entirely cultivated land. For the region as a whole, geologic units contributed 44% of the dissolved‐solids deliveries to streams and the remaining 56% of the deliveries came from the release of solutes through irrigation of cultivated and pasture lands, which comprise only 2.5% of the land area. Dissolved‐solids accumulation is manifested as precipitated salts in the soil or underlying sediments, and (or) dissolved salts in soil‐pore or sediment‐pore water, or groundwater, and therefore represents a potential for aquifer contamination. Accumulation rates were <10,000 (kg/year)/km² for many hydrologic accounting units (large river basins), but were more than 40,000 (kg/year)/km² for the Middle Gila, Lower Gila‐Agua Fria, Lower Gila, Lower Bear, Great Salt Lake accounting units, and 247,000 (kg/year)/km² for the Salton Sea accounting unit.     

Impacts of Residential Development on Humid Subtropical Freshwater Resources: Southwest Florida Experience1

Abstract: The population of Collier and Lee Counties in southwestern Florida has increased 11‐fold from 1960 to 2004 with a concomitant increase in freshwater demand. Water levels and salinity within the water table aquifer over the past two to three decades have generally been stable, with more monitoring wells showing statistically significant temporal increases in water level than decreases. Residential development has had a neutral impact on the water table aquifer because the total annual evapotranspiration of residential communities is comparable to that of native vegetation and less than that of most agricultural land uses. Public water supply systems and private wells also result in net recharge to the water table aquifer with water produced from deeper aquifers. Confined freshwater aquifers have overall trends of decreasing water levels. However, with the exception of the mid‐Hawthorn aquifer, water levels in most areas recover to near background levels each summer wet season. Freshwater resources in humid subtropical areas, such as southwestern Florida, are relatively robust because of the great aquifer recharge potential from the excess of rainfall over ET during the wet season. Proper management can result in sustainable water resources.     

SUBSURFACE RETURN FLOW AND GROUND WATER RECHARGE OF TERRACE FIELDS IN NORTHERN TAIWAN1

ABSTRACT: This study estimates subsurface return flow and effective ground water recharge in terraced fields in northern Taiwan. Specifically, a three dimensional model, FEMWATER, was applied to simulate percolation and lateral seepage in the terraced fields under various conditions. In the terraced paddy fields, percolation mainly moves vertically downward in the central area, while lateral seepage is mainly focused around the bund. Although the simulated lateral seepage rate through the bund exceeded the percolation rate in the central area of the paddy field, annual subsurface return flow at Pei‐Chi and Shin‐Men was 0.17 × 10⁶ m³ and 0.37 × 10⁶ m³, representing only 0.17 percent and 0.21 percent of the total irrigation water required for rice growth at Pei‐Chi and Shin‐Men, respectively. For upland fields, the effective ground water recharge rate during the second crop period (July to November) exceeded that during the first crop period (January to May) because of the wet season in the second crop period. Terraced paddy fields have the most efficient ground water recharge, with 21.2 to 23.4 percent of irrigation water recharging to ground water, whereas upland fields with a plow layer have the least efficient ground water recharge, with only 4.8 to 6.6 percent of irrigation water recharging to ground water. The simulation results clearly revealed that a substantial amount of irrigation water recharges to ground water in the terraced paddy, while only a small amount of subsurface return flow seeps from the upstream to the downstream terraced paddy. The amounts of subsurface flow and ground water recharge determined in the study are useful for the irrigation water planning and management and provide a scientific basis to reevaluate water resources management in the terrace region under irrigated rice.     

Pre‐Development Groundwater Conditions Surrounding Memphis,Tennessee: Controversy and Unexpected Outcomes

Reliance on groundwater resources by differing governing bodies can create transboundary disputes raising questions of ownership and apportionment as the resource becomes strained through overuse or threatened by contamination. Transboundary disputes exist at varying scales, from conflicts between countries to smaller disputes between intrastate jurisdictions. In 2005 within the United States, the State of Mississippi filed a lawsuit against its political neighbor and their utility, the City of Memphis and Memphis Light, Gas, and Water, for groundwater deemed owned by the State of Mississippi to be wrongfully diverted across the state line and into Tennessee by the defendants. The basis of the lawsuit was potentiometric maps of groundwater levels for the Memphis aquifer that showed under suggested pre‐development conditions no flow occurring across the Mississippi‐Tennessee state line, but subsequent historic potentiometric maps show a cone of depression under the City of Memphis with a clear northwesterly gradient from Mississippi into Tennessee. The suggested pre‐development conditions were derived from limited groundwater level observations between 41 and 74 years post‐development. A new pre‐development map is constructed using historic records that range 0‐17 years post‐development that shows the natural flow is northwesterly from Mississippi into Tennessee and transboundary groundwater quantities have actually decreased since pre‐development conditions.     

Reasonable Use?: The Challenges of Transboundary Groundwater Regulation in the Eastern United States

Regulating groundwater in the Eastern United States (U.S.), particularly transboundary aquifers between states, is a challenge given the patchwork quilt of common law, statutory frameworks, and agency rules. Such regulation is made more challenging by the need for better quantification of pumping and use. These dynamics are exemplified through several case studies, including the first ever U.S. Supreme Court case related to groundwater withdrawals (set in the Eastern U.S.). As dynamics such as expanded irrigation, population increases, and ecological considerations influence groundwater use across the Eastern U.S., water use will continue to be an important driver for economic activity and interaction within and between states. To effectively regulate transboundary aquifers, governance solutions must incorporate current science into decision making and be implemented at local, state, regional, and federal scales.