Water Resources of St. Helena Parish, Louisiana

This U.S. Geological Survey summary, prepared with the Louisiana Department of Transportation and Development, sets out what is known about the supply, use and quality of water in St. Helena Parish, on Louisiana's border with Mississippi, for water managers and residents.

St. Helena Parish, shaded by the depth to the base of fresh groundwater, with its river subbasins, the wells charted below (SH-56, SH-116) and the stream gages on the Amite and Tickfaw Rivers. USGS.

Water use

In 2010 the parish withdrew about 1.06 million gallons a day (Mgal/d): 1.05 from groundwater and 0.01 from surface water.

Withdrawals, recorded every 5 years since 1960, peaked in 1960, fell below 1.00 Mgal/d in 1965 and 1975, and have stayed between 1.00 and 1.50 Mgal/d since 1980.

Water withdrawals, 1960–2010. USGS.

Groundwater

Fresh groundwater (no more than 250 mg/L chloride) comes from, shallowest first, the Chicot equivalent, Evangeline equivalent and Jasper equivalent aquifer systems and the Catahoula aquifer; deeper aquifers hold saltwater. The base of fresh water lies more than 2,000 feet below the National Geodetic Vertical Datum of 1929 (NGVD 29) in the northwest and less than 3,000 feet along the southern boundary. The aquifers are recharged mainly by rain falling over an area stretching from the parish about 100 miles north into Mississippi, with some help from streams; they lose water to neighbouring aquifers, streams and wells, and all dip south to southwest toward the Gulf.

• Upland terrace aquifer — the only aquifer of the Chicot system here: a broad, patchy, near-surface aquifer under the whole parish, extending into East Feliciana and Tangipahoa Parishes and Mississippi. It surfaces along ridges and valleys, dips 10–30 feet per mile, and is mostly medium to coarse sand, over 300 feet thick in places; near the southern line it matches the Baton Rouge area's "400-foot" and "600-foot" sands. Close to the surface, it takes in rain and passes some down to deeper aquifers. In 2009 its water level ranged from about 75 feet above NGVD 29 in the south to more than 250 feet in the northeast, following the land surface, with flow southward and toward the Amite and Tickfaw Rivers. It supplied rural homes (0.53 Mgal/d), livestock and some public supply.
• Evangeline equivalent system — the "800-foot" to "1,700-foot" sands, fine to coarse sand separated by clays that sometimes merge; its base lies from about 450 feet below NGVD 29 in the north to about 1,200 feet in the south. In 2003 levels in the "1,500-" and "1,700-foot" sands ranged from about 215 feet above NGVD 29 in the northeast to 35 feet below in the southwest, flowing toward pumping centres in East Baton Rouge Parish.
• Jasper equivalent system — the "2,000-," "2,400-" and "2,800-foot" sands, based roughly 1,800 to 2,000 feet below NGVD 29. In 2006 levels in the "2,800-foot" sand ranged from about 80 feet above NGVD 29 in the northeast to 20 feet above in the southwest. It supplies most public water (0.32 Mgal/d) and some industry.
• Catahoula aquifer — fresh at about 2,000 to 2,450 feet below NGVD 29 in the central parish and 1,900 to 2,350 in the northwest, with saltwater in its deepest sands.

Water levels in well SH-56 (Upland terrace aquifer, 160 feet deep), which varies less than 3 feet a year, and SH-116 ("2,800-foot" sand, 1,634 feet deep), which varies up to 5 feet a year and declined from 2002 to 2011. USGS.

Groundwater quality

Samples from 15 Upland terrace wells (1940–2001) and 12 Jasper wells (1954–84) were generally soft and within the EPA's secondary limits for chloride and dissolved solids. But the shallow Upland terrace water is acidic — median pH 5.2, with no sample inside the 6.5–8.5 range — while Jasper water is alkaline (median 8.6, 42% of samples in range), and iron and manganese can be locally very high in the Jasper system. Limited data suggest Evangeline water falls between the two.

Surface water

The parish lies in the Lake Maurepas basin, divided into three subbasins; streams flow generally south, fed by rain and groundwater from the parish and from Mississippi. In 2010, 0.01 Mgal/d was drawn from small streams for livestock.

• Amite (western third): the Amite River, along most of the western border, with the East Fork Amite River, Sandy Run and Darling, Buck, Black and Channey Creeks. Near Darlington it averaged about 906 cubic feet per second in 1951–2014 from about 580 square miles; its highest and lowest yearly averages were 1,924 (1982–83) and 328 (1999–2000).
• Tickfaw (centre): the Tickfaw River, from Mississippi through the parish into Livingston Parish south of Montpelier, with Twelvemile Creek, Joseph Branch and East and West Hog Branches; the Natalbany and Little Natalbany Rivers also start here. Near Liverpool it averaged about 111 cubic feet per second in 1956–2014 from 89.7 square miles; highest and lowest yearly averages were 208 (2012–13) and 52 (2005–6).
• Tangipahoa (a small northeastern corner): drained by Beaver Creek to the Tangipahoa River.

River samples — the Amite near Darlington in 1961–76 and the Tickfaw near Liverpool in 1961–98 — were generally soft and within secondary limits for chloride, sulfate and iron, and dissolved oxygen was generally above 5 mg/L, the minimum for a diverse community of warm-water fish. Median pH was 6.6 in the Amite and 6.3 in the Tickfaw.

The sheet says the rivers did not exceed the secondary limit for pH, but its own table puts the Tickfaw's median pH (6.3) below the 6.5–8.5 range, with only 45% of Tickfaw samples and 75% of Amite samples inside it.

Sources

• Vincent E. White and Lawrence B. Prakken, Water Resources of St. Helena Parish, Louisiana, USGS Fact Sheet 2016–3047, July 2016, prepared with the Louisiana Department of Transportation and Development. https://doi.org/10.3133/fs20163047
• USGS National Water Information System: http://waterdata.usgs.gov/nwis