Water Resources of Catahoula Parish, Louisiana

Knowing how much water Catahoula Parish, Louisiana, has, how it is used and how good it is matters for managing its supply. This U.S. Geological Survey fact sheet, prepared with the Louisiana Department of Transportation and Development, draws on earlier reports and the USGS National Water Information System to give water managers, residents and others that picture.

How much water is used

In 2010 the parish withdrew 30.01 million gallons a day (Mgal/d): 22.63 from groundwater and 7.38 from surface water. Farming — aquaculture, general and rice irrigation, and livestock — took about 93 percent (28.05 Mgal/d); the rest went to public supply and rural homes. Records kept every five years since 1960 show withdrawals peaking in 2000, at 30.99 Mgal/d.

Groundwater and surface-water withdrawals in Catahoula Parish, 1960–2010. USGS.

Groundwater

The parish's main freshwater aquifers are the alluvial aquifers and the Catahoula aquifer. The Upland terrace and Jasper aquifers also hold fresh water but are too limited in extent to be major sources.

Fresh groundwater here means no more than 250 milligrams per litre (mg/L) of chloride. In the alluvial aquifers its base ranges from less than 100 feet below the National Geodetic Vertical Datum of 1929 (NGVD 29) in the north to more than 200 feet below in the south; in the Catahoula aquifer, from above NGVD 29 in the northwest to more than 700 feet below in the centre. Some intermediate sands in the east-central parish hold saltwater, and the far northwestern corner has little or no fresh groundwater, because the Vicksburg-Jackson confining unit comes to the surface there and the aquifers below contain saltwater.

Catahoula Parish: depth to the base of fresh groundwater, river subbasins, and the wells and river sites described here. USGS.

The alluvial aquifers

These are sand and gravel laid down by rivers. The Mississippi River alluvial aquifer, which includes the Red River and Ouachita River alluvial aquifers (some classifications treat these as separate but connected), is the parish's main aquifer. Its deposits are from less than 80 to more than 160 feet thick, and its base lies from less than about 25 feet below NGVD 29 in the north-centre to more than 200 feet below in the southeast.

It is recharged mainly by rain soaking in, and less by streams and rivers at high water; water leaves into streams and rivers, by evapotranspiration and through wells. In 1990, water levels ranged from less than 50 feet above NGVD 29 in the north to about 20 feet above in the south-centre, so groundwater generally flows south to southwest.

• Well Ct-87, in the south: levels have risen and fallen each year and dropped about 2 feet overall from autumn 1972 to autumn 2015.
• Well Ct-74, in the south, in the Red River alluvial aquifer: levels fell in the late 1970s and recovered in the early 1980s — the dip was caused by dewatering wells used in 1978–84 to build the Red River Lock and Dam No. 1.
• Well Ct-347, in the north: levels have usually varied by less than 5 feet a year and fell about 8 feet from 1990 to 2016.

In 2015 the state listed 467 active wells in the Mississippi River and Red River alluvial aquifers — 419 irrigation, 36 domestic, 10 public supply and 2 industrial — from 30 to 187 feet deep, yielding 3 to 4,300 gallons a minute. In 2010 they supplied about 20.71 Mgal/d: 11.86 for rice, 7.19 for general irrigation, 1.44 for aquaculture, 0.14 for public supply and 0.07 for rural homes.

The Catahoula aquifer

The Catahoula aquifer runs across central Louisiana and reaches the surface in a narrow band from the Texas line to northern Catahoula Parish. In the parish it holds fresh water from about Jonesville west to the parish line and north to near Sicily Island, and where it outcrops it dips south at about 50–70 feet per mile. It is made of white to light grey sands, very coarse to very fine, seldom widespread and interbedded with silts and clays, and is recharged by rain where it outcrops and by flow from neighbouring aquifers.

In 2013, water levels were about 100 feet above NGVD 29 in the northwest and less than 20 feet above in the centre, so water generally flows southeast; under Sicily Island they reached about 80 feet above. In the central and north-central parish, levels fell about 20 feet or more from 1980 to 2015, and at well Co-50, in neighbouring Concordia Parish, by more than 45 feet from 1970 to 2015.

In 2015 there were 58 active wells — 29 public supply, 24 domestic, 4 irrigation and 1 industrial — from 124 to 798 feet deep, yielding 5 to 608 gallons a minute. In 2010 the aquifer supplied 1.93 Mgal/d, mostly for public supply (1.72).

Groundwater quality

• Mississippi River and Red River alluvial aquifers: similar median pH (7.1 and 6.9), hardness (300 and 320 mg/L as calcium carbonate — very hard) and magnesium (28.5 and 28 mg/L). Iron exceeded the Environmental Protection Agency's secondary maximum contaminant level in 71 percent of Mississippi River alluvial samples and 95 percent of Red River alluvial samples.
• Catahoula aquifer: a higher median pH (7.4), and lower median hardness (8.5 mg/L), magnesium (0.5 mg/L), iron (205 micrograms per litre) and manganese (35 micrograms per litre) than the alluvial aquifers.

Surface water

The parish lies in three regional basins: the Boeuf–Tensas, along the northern and eastern borders north of Jonesville; the Lower Ouachita, in the northern interior; and the Lower Red, in roughly the southern half. Its lakes include Larto, Wallace, Tew and Mean Lakes. In 2010, 7.38 Mgal/d of surface water was taken from miscellaneous streams, 7.34 of it for general irrigation.

• The Boeuf River forms part of the north-central border and joins the Ouachita on the northwest side of Sicily Island; the Tensas River runs along the eastern border into the Black River.
• The Ouachita River enters from Caldwell Parish, gathers Bayou Louis, Gastis Creek and many small streams, and ends near Jonesville. At Columbia Lock and Dam near Riverton it averaged about 21,326 cubic feet per second in 1982–87.
• The Little River enters from LaSalle Parish and ends near Jonesville, where it joins the Ouachita and Tensas to form the Black River, which flows south along the eastern border into the Red River, the southern border. Upstream at Alexandria, the Red averaged 30,770 cubic feet per second in 1928–82.

Surface-water quality

Samples from the Ouachita River at Columbia (1974–93), the Red River at Lock and Dam No. 1 near Vick (1983–95) and the Black River at Jonesville (1958–72) had median hardness from soft to hard and median pH of 6.7 to 7.6. Chloride and sulfate generally stayed within the secondary limits. Median dissolved oxygen was 7.2 mg/L in the Ouachita and 8.1 mg/L in the Red; 5 mg/L is considered the minimum for a diverse community of warm-water life, including sport fish.

Sources

• U.S. Geological Survey, in cooperation with the Louisiana Department of Transportation and Development, Water Resources of Catahoula Parish, Louisiana, Fact Sheet 2016–3101, February 2017. https://doi.org/10.3133/fs20163101
• USGS Lower Mississippi-Gulf Water Science Center: http://la.water.usgs.gov