Water Resources of Caldwell Parish, Louisiana

How much water Caldwell Parish, Louisiana, has, how it is used and how good it is — from a U.S. Geological Survey fact sheet prepared with the Louisiana Department of Transportation and Development, drawing on earlier reports and the USGS National Water Information System.

How the water is used

In 2010 the parish withdrew about 4.39 million gallons a day (Mgal/d): about 2.67 Mgal/d of surface water and 1.73 Mgal/d of groundwater.

By source: the Cockfield aquifer 1.09 Mgal/d, the Mississippi River alluvial aquifer 0.61 and the Sparta aquifer 0.02; streams 2.67. Counted every five years since 1960, withdrawals peaked in 1980.

Groundwater

Fresh groundwater — chloride of 250 milligrams per litre (mg/L) or less — is available everywhere except near the far southeastern corner; its base lies from less than 100 to 800 feet below the National Geodetic Vertical Datum of 1929 (NGVD 29). The main sources are the Mississippi River alluvial aquifer and the Cockfield aquifer; the Sparta aquifer is a minor one.

The aquifers are recharged by rain, leakage from neighbouring aquifers and, in season, streams; they lose water to evapotranspiration, streams, neighbouring aquifers and wells. In 2010 state records listed 208 active wells — 90 domestic, 78 irrigation, 33 public supply and 7 industrial.

Mississippi River alluvial aquifer

Present from about the Ouachita River to the eastern boundary, less than 25 to 75 feet thick, its uneven base about 0 to 40 feet or more below NGVD 29. It is generally fresh, with local small lenses of salt water. Rain recharges it, with some leakage up from the Cockfield; it drains into streams, and water flows generally toward Bayou Lafourche and the Boeuf River. In 1990 levels were generally 50 feet or more above NGVD 29 along the Ouachita in the north and less than 40 feet along the Boeuf in the southeast.

• 109 active wells (68 irrigation, 38 domestic, 2 public supply, 1 industrial), 27 to 130 feet deep (median 90), yielding 5 to 3,000 gallons per minute.
• Withdrawals in 2010: about 0.61 Mgal/d — 0.57 rice irrigation, 0.03 rural domestic, 0.02 livestock.
• Water is generally very hard; limited data show iron and manganese far above the EPA's secondary maximum contaminant levels (SMCLs).

Cockfield aquifer

Present throughout except the northeast corner, where it is thin or absent, beneath the Vicksburg-Jackson confining unit and above the Cook Mountain confining unit. It reaches the surface and takes in rain west of the Ouachita, except in the valleys of Castor Creek and its tributaries and in the south-centre where Vicksburg-Jackson clay covers it. It dips southeast: its base falls from about 0 feet below NGVD 29 in the northwest to nearly 1,000 feet in the southeast, and it thickens from under 200 feet to 600–800 feet. It is generally fresh, but holds salt water in the southeast corner and along the eastern edge.

Water flows generally east toward the Ouachita. In 1993 levels were more than 140 feet above NGVD 29 in the northwest and about 60 feet along the Ouachita valley. Well Ca-86A varies 2 to 6 feet or more a year but has stayed at about the same level since 2002.

• 75 active wells (39 domestic, 26 public supply, 6 industrial, 4 irrigation), 50 to 630 feet deep (median 335), yielding 10 to 400 gallons per minute.
• Withdrawals in 2010: about 1.09 Mgal/d — 1.05 public supply, 0.03 rural domestic, 0.01 livestock.
• Water is generally soft and within the SMCLs for colour, pH, chloride and dissolved solids, but iron often greatly exceeds its 300 micrograms-per-litre (µg/L) limit and manganese generally exceeds its 50 µg/L limit.

Sparta aquifer

Present everywhere but fresh only in the northwestern quarter, between the massive clays of the Cane River confining unit below and the Cook Mountain above. It dips southeast, its base from about 800 feet below NGVD 29 in the far northwest to nearly 2,000 feet in the far southeast; it is 600 to 800 feet thick, and 800 to 1,000 in the southeast corner.

Regional pumping has reshaped its flow: water now moves north toward a pumping centre in Ouachita Parish. In 2007 levels ranged from about 80 feet above NGVD 29 in the southwest to about 20 feet below in the northwest, and well Ca-86B fell about 8 feet between 2002 and 2013.

• 14 active wells (9 domestic, 5 public supply), 400 to 845 feet deep (median 525), yielding 2 to 140 gallons per minute.
• Withdrawals in 2010: about 0.02 Mgal/d, mainly public supply.
• Water is generally soft and within the SMCLs for iron and manganese, but colour and dissolved solids exceeded them in the wells sampled, and the median pH sits at the upper limit of 8.5 — the water tends to be alkaline.

Surface water

About 2.67 Mgal/d of surface water was withdrawn in 2010: about 1.32 for rice irrigation, 1.32 for general irrigation and 0.03 for livestock. Notable waters are the Ouachita River, Bayou Lafourche, the Boeuf River, Castor Creek and Beaucoup Creek.

• Ouachita River at Columbia (1974–93): soft, generally within the SMCLs for pH, chloride and sulfate; dissolved oxygen generally above 5 mg/L, the minimum for a varied community of warm-water life, sport fish included.
• Boeuf River near Fort Necessity (1975–91): median hardness moderately hard; generally within the SMCLs for pH, chloride, sulfate and iron; dissolved oxygen generally above 5 mg/L.

Sources

• Prakken, L.B., and White, V.E., 2014, Water resources of Caldwell Parish, Louisiana: U.S. Geological Survey Fact Sheet 2014–3044, prepared in cooperation with the Louisiana Department of Transportation and Development. https://pubs.usgs.gov/publication/fs20143044
• The tables and figures come from the fact sheet's PDF, which the web version lacks.
• Rewritten in hubnx's own words.