Potentiometric Surface in the Sparta-Memphis Aquifer of the Mississippi Embayment, Spring 2007

Schrader, T.P.

doi:10.3133/sim3014

Cited by 10 publications

(26 citation statements)

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“…17). An embayment-wide potentiometric surface for the middle Claiborne aquifer was constructed representing the spring of 2007 (Schrader, 2007). The potentiometric surface was constructed using water-level measurements from 309 wells in Arkansas, 7 wells in Kentucky, 116 wells in Louisiana, 150 wells in Mississippi, 6 wells in Missouri, and 160 wells in Tennessee.…”

Section: Simulated and Observed Potentiometric Surfacesmentioning

confidence: 99%

The Mississippi Embayment Regional Aquifer Study (MERAS): Documentation of a groundwater-flow model constructed to assess water availability in the Mississippi embayment

Clark¹,

Hart²

2009

Scientific Investigations Report

136

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The Mississippi Embayment Regional Aquifer Study (MERAS) was conducted with support from the Groundwater Resources Program of the U.S. Geological Survey Office of Groundwater. This report documents the construction and calibration of a finite-difference groundwater model for use as a tool to quantify groundwater availability within the Mississippi embayment. To approximate the differential equation, the MERAS model was constructed with the U.S. Geological Survey's modular three-dimensional finite-difference code, MODFLOW-2005; the preconditioned conjugate gradient solver within MODFLOW-2005 was used for the numerical solution technique. The model area boundary is approximately 78,000 square miles and includes eight States with approximately 6,900 miles of simulated streams, 70,000 well locations, and 10 primary hydrogeologic units. The finitedifference grid consists of 414 rows, 397 columns, and 13 layers. Each model cell is 1 square mile with varying thickness by cell and by layer. The simulation period extends from January 1, 1870, to April 1, 2007, for a total of 137 years and 69 stress periods. The first stress period is simulated as steady state to represent predevelopment conditions. Areal recharge is applied throughout the MERAS model area using the MODFLOW-2005 Recharge Package. Irrigation, municipal, and industrial wells are simulated using the Multi-Node Well Package. There are 43 streams simulated by the MERAS model. Each stream or river in the model area was simulated using the Streamflow-Routing Package. The perimeter of the model area and the base of the flow system are represented as no-flow boundaries. The downgradient limit of each model layer is a no-flow boundary, which approximates the extent of water with less than 10,000 milligrams per liter of dissolved solids. The MERAS model was calibrated by making manual changes to parameter values and examining residuals for hydraulic heads and streamflow. Additional calibration was achieved through alternate use of UCODE-2005 and PEST. Simulated heads were compared to 55,786 hydraulic-head measurements from 3,245 wells in the MERAS model area. Values of root mean square error between simulated and observed hydraulic heads of all observations ranged from 8.33 feet in 1919 to 47.65 feet in 1951, though only six root mean square error values are greater than 40 feet for the entire simulation period. Simulated streamflow generally is lower than measured streamflow for streams with streamflow less than 1,000 cubic feet per second, and greater than measured streamflow for streams with streamflow more than 1,000 cubic feet per second. Simulated streamflow is underpredicted for 18 observations and overpredicted for 10 observations in the model. These differences in streamflow illustrate the large uncertainty in model inputs such as predevelopment recharge, overland flow, pumpage (from stream and aquifer), precipitation, and observation weights. The groundwater-flow budget indicates changes in flow into (inflows) and out of (outflows) the model area during the...

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Section: Simulated and Observed Potentiometric Surfacesmentioning

confidence: 99%

The Mississippi Embayment Regional Aquifer Study (MERAS): Documentation of a groundwater-flow model constructed to assess water availability in the Mississippi embayment

Clark¹,

Hart²

2009

Scientific Investigations Report

136

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“…A comparison of groundwater volumes crossing the Tennessee‐Mississippi state line, specifically along the Shelby County‐Desoto and Marshall County boundary, is made using our proposed pre‐development conditions and more recent conditions as mapped by Schrader (). To estimate the volumes of flow crossing between Mississippi and Tennessee specifically along the Shelby County border, Darcy's law was employed using a range of saturated thickness of 209‐284 m (Gomberg et al ., ), a range of hydraulic conductivity of 13‐18.6 m/day for the Memphis Sand (TN) or Sparta Sand (MS) (Waldron et al ., ), and calculated hydraulic gradients that vary in magnitude depending upon location along the Shelby County southern border.…”

Section: Approach and Methodsmentioning

confidence: 99%

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

Waldron

Larsen

2014

J American Water Resour Assoc

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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.

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“…Regional groundwater withdrawals have greatly affected the direction of groundwater flow in the Sparta aquifer. In Caldwell Parish, the direction of groundwater flow in the Sparta aquifer is northward toward a pumping center in Ouachita Parish (Schrader, 2008). The water level in well Ca-86B ( fig.…”

Section: Sparta Aquifermentioning

confidence: 97%

“…The altitude of the base of freshwater within the Sparta aquifer in northwestern Caldwell Parish is shown in figure 1. In 2007, water levels in the Sparta aquifer in Caldwell Parish ranged from about 80 ft above NGVD 29 in the southwestern corner of the parish to about 20 ft below NGVD 29 in the northwestern corner (Schrader, 2008). Regional groundwater withdrawals have greatly affected the direction of groundwater flow in the Sparta aquifer.…”

Section: Sparta Aquifermentioning

confidence: 99%

Water resources of Caldwell Parish, Louisiana

Prakken¹,

White²

2014

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Potentiometric Surface in the Sparta-Memphis Aquifer of the Mississippi Embayment, Spring 2007

Cited by 10 publications

References 0 publications

The Mississippi Embayment Regional Aquifer Study (MERAS): Documentation of a groundwater-flow model constructed to assess water availability in the Mississippi embayment

The Mississippi Embayment Regional Aquifer Study (MERAS): Documentation of a groundwater-flow model constructed to assess water availability in the Mississippi embayment

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

Water resources of Caldwell Parish, Louisiana

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