**10. The southeast lowlands groundwater province in Missouri**

The Southeast Lowlands Groundwater Province in Missouri (SLGP) spans 10,142 km<sup>2</sup> and contains 15.2% of the State of Missouri's groundwater, estimated at 287 billion m3 . The Cretaceous age McNairy aquifer crops out (at or near the surface) on the flanks of Crowley's Ridge and the Benton Hills [18]. In Stoddard County and Butler County, the McNairy formation primarily underlies alluvial materials, whereas in Dunklin County and Pemiscot County the McNairy formation is reached by wells having a depth of 600 m. In Dunklin County and Pemiscot County where wells are in thick and clean sands, the water yields range from 570 to 2800 L min−<sup>1</sup> . Overlying the McNairy formation, the Clayton Owl Creek and Porter's Creek clay formations constitute confining layers. Water from the McNairy formation in the northern regions along Crowley's Ridge are classified as iron rich, calcium-magnesium carbonate type waters, whereas waters from the McNairy formation in the southern portion of southeastern Missouri are sodium chloride type waters.

The Wilcox Group is composed largely of Tertiary-age sands, some regions having minor inclusions of lignite and clay. The Wilcox aquifer is commonly separated into the upper and lower Wilcox aquifers because of sand grain size distribution patterns. The Wilcox aquifer overlies the Porter's Creek clay and is largely absent in northern Stoddard County and attains thicknesses greater than 427 m in Pemiscot County and Dunkin County. Water yields from the Wilcox in Stoddard Co. are approximately 2900 L min−<sup>1</sup> and in Pemiscot County are approximately 6400 L min−<sup>1</sup> . The water composition is calcium-magnesium carbonate or calcium carbonate [18]. The Claibourn aquifer lies on the Wilcox aquifer. The Claibourn aquifer is separated in the upper, middle, and lower Claibourn aquifers, with the upper and middle Claibourn aquifers separated by a layer of thin, clayey materials that act as a confining unit (aquitard).

The Mississippi River Valley Aquifer (the Southeast Lowlands Alluvial Aquifer) consists of unconsolidated clay, silt, sand, and gravelly textured alluvium. Groundwater usage of the Mississippi River Valley Aquifer constitutes approximately 92% of the groundwater withdrawal in southeastern Missouri. These alluvial materials were largely deposited by the ancestral Mississippi and Ohio River systems, coupled some prominent deposits by the Black, St. Francois, and Little River systems. Alluvial thickness is variable, with typical thicknesses west of Crowley's Ridge ranging from 15 to 45 m, whereas the alluvial thicknesses in Mississippi, Pemiscot, and Dunklin Counties average 76 m. These unconfined aquifers are baseflow recharged annually from the Mississippi River, other prominent rivers and land drainage ditches. Water yield ranges from 3800 to 11,360 L min−<sup>1</sup> ; however, although water level fluctuations do occur between wet and dry seasons, no long-term depletions have been observed [18].

**12. Soils and soilscapes**

time for soil profile horizonation.

**Figure 3.** The Cooter-Hayti-Portageville Association.

In the study area, presentative soil orders (US Soil Taxonomy) include: Alfisols, Entisols, Histosols, Inceptisols, Mollisols, and Vertisols. Landforms include: alluvial fans, splays, flood plains and backswamp deposits, ox-bows and meander channels, Holocene and Pleistocene terraces of coarse to fine-silty textures, and modern to old natural levees and constructed levees. A great portion of the landscape has been recently land-graded for furrow and flood irrigation. For example, the Cooter-Hayti-Portageville Soil Association rests on Holocene sediment having a transitional texture from sandy alluvium to silty-loamy alluvium to clayey alluvium (**Figure 3**). The poorly drained Portageville clay series (Vertic Endoaquolls: Ap/A–Bg–Cg) exhibits soil organic matter accumulation and soil profile depletion of Fe attributed to anaerobic conditions, whereas the Cooter (Fluvaquentic Hapludolls: Ap/A-2C1-2C2) is a bisequal soil (clayey over sandy) featuring few subsurface redoximorphic features because of the quartz parent material. The fine-silty, poorly drained, non-acid Hayti series (Mollic Fluvaquents: Ap-C) developed in recent silty alluvium lacks soil profile development because of the lack of

A Large-Scale Wetland Conversion Project in Southeastern Missouri: Sustainability of Water and Soil

http://dx.doi.org/10.5772/intechopen.81254

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The Memphis-Loring-Calhoun-Foley Association rests in the Advance Lowlands (also called the Western Morehouse Lowlands) with the fine-silty, deep, strongly acid, well-drained
