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U.S. Department of the InteriorU.S. Geological Survey
Scientific Investigations Map 3426Sheet 1 of 2
laf19-0909_fig.01
ARKANSASMISSOURI
ARKANSASLOUISIANA
KENTUCKY
TENNESSEE
ILLINOIS
TENNESSEE
MISSISSIPPI
LOUISIANAMISSISSIPPI
KENTUCKY
ILLINOIS
MISSO
URI
Little Rock
Pine Bluff
Alexandria
Monroe
Houma
New Orleans
Helena-West Helena
Jonesboro
Clarksdale
Cleveland
Greenville
Greenwood
Jackson
Natchez
Vicksburg
Yazoo City
Cape Girardeau
Poplar Bluff
Memphis
Baton RougeBaton Rouge
LafayetteLafayette
0 30 60 MILES15 45
0 30 60 KILOMETERS15 45
Base modified from U.S. Geological Survey,digital data 1:100,000 scaleAlbers Equal Area projection;World Geodetic System of 1984
EXPLANATION
Mississippi Alluvial Plain extent
Bottom altitude, in feet. Datum is North American Vertical Datum of 1988
−429.06 to −400−399.99 to −300−299.99 to −200−199.99 to −100−99.99 to −50−49.99 to 00.01 to 5050.01 to 100100.01 to 200200.01 to 300300.01 to 367
88°30'90°0'91°30'
37°30'
36°0'
34°30'
33°0'
31°30'
30°0'
Figure 1. The Mississippi Alluvial Plain extent (Painter and Westerman, 2018) and geostatistical estimation of the bottom altitude of the Mississippi River Valley alluvial aquifer.
laf19-0909_fig 02
0 30 60 MILES15 45
0 30 60 KILOMETERS15 45
Base modified from U.S. Geological Survey,digital data 1:100,000 scaleAlbers Equal Area projection;World Geodetic System of 1984
Mississippi Alluvial Plain extent
Data source
Saucier (1994)
Wilson and Hosman (1987)
Hoffman (2017)
Missouri Department of Natural Resources (2007)
Csontos (2007)
EXPLANATION
88°30'90°0'91°30'
37°30'
36°0'
34°30'
33°0'
31°30'
30°0'
Figure 2. Locations of boreholes located in the Mississippi Alluvial Plain that contain lithologic and geophysical data used to define the bottom altitude and thickness of the Mississippi River Valley alluvial aquifer.
laf19-0909_fig03
0 30 60 MILES15 45
0 30 60 KILOMETERS15 45
Base modified from U.S. Geological Survey,digital data 1:100,000 scaleAlbers Equal Area projection;World Geodetic System of 1984
EXPLANATION
Mississippi Alluvial Plain extent
Thickness, in feet
28.6 to 8080.1 to 120120.1 to 160160.1 to 200200.1 to 240240.1 to 280280.1 to 320320.1 to 360360.1 to 400400.1 to 434.3
88°30'90°0'91°30'
37°30'
36°0'
34°30'
33°0'
31°30'
30°0'
Figure 3. The Mississippi Alluvial Plain extent (Painter and Westerman, 2018) and geostatistical estimation of the thickness of the Mississippi River Valley alluvial aquifer.
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Suggested citation: Torak, L.J., and Painter, J.A., 2019, Geostatistical estimation of the bottom altitude and thickness of the Mississippi River Valley alluvial aquifer: U.S. Geological Survey Scientific Investigations Map 3426, 2 sheets, https://doi.org/10.3133/sim3426.
ISSN 2329-132X (online)https://doi.org/10.3133/sim3426
Geostatistical Estimation of the Bottom Altitude and Thickness of the Mississippi River Valley Alluvial Aquifer
By
L.J. Torak and J.A. Painter
2019
The Mississippi River Valley alluvial aquifer (MRVA) caps a shallow system of aquifers and confining units in the Mississippi Alluvial Plain (MAP) that extends across 45,000 square miles of the midwestern and southern United States from Illinois to Louisiana (fig. 1). Irrigation water from the MRVA is required to sustain extensive crop production, which has resulted in groundwater-level declines since the late 1920s equal to nearly half of its thickness and in reduced baseflow of
streams. Increased groundwater withdrawal for irrigation is expected to continue and threatens complete and irreversible aquifer dewatering (depletion) (Clark and others, 2013; Reba and others, 2017). The exact amount of dewatering in the MRVA is uncertain because its vertical extent is poorly defined and the effects of groundwater withdrawal on the aquifer are not well understood. To provide stakeholders and managers with information and tools that promote understanding of
the hydrogeologic framework of the MAP extent (Painter and Westerman, 2018) and its role in water-resource management, the U.S. Geological Survey (USGS) Water Availability and Use Science Program (WAUSP) has funded a 5-year effort to assess groundwater availability and project future sustainability of water resources. Part of this study involves mapping the bottom altitude and thickness of the aquifer by using compilations of hydrogeologic data and applications of
geostatistical analytics. Results of this mapping effort, presented here, are intended to enhance characterization of the shallow hydrogeologic framework and direct future airborne, ground-based, and waterborne geophysical surveys. Data used in support of the findings presented in this report are available as a USGS data release (Torak and Painter, 2019).
Bottom altitudes of the MRVA were compiled from interpretations of subsurface lithologic and geophysical logs (log picks) at about 10,000 boreholes located throughout the MAP extent that were available from previous investigations (fig. 2). Log picks were corrected to the National Elevation Dataset (NED) 10-meter digital elevation
model (DEM; https://nationalmap.gov/elevation.html). Log picks that required a DEM correction of less than 20 feet were used for the geostatistical estimation of the MRVA bottom altitude, after additional filtering removed duplicate log picks, yielding a bottom-altitude dataset of 9,392 data points.
Introduction Data Compilation, Processing, and Filtering Prior to Estimation