Water Resources of Tangipahoa 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 Tangipahoa Parish, which runs from the Mississippi line south to Lakes Maurepas and Pontchartrain, for water managers and residents.

Tangipahoa Parish, shaded by the depth to the base of fresh groundwater, with its river subbasins, the wells charted below and the stream-gaging sites. USGS.

Water use

In 2010 the parish withdrew about 20.1 million gallons a day (Mgal/d) — 19.90 from groundwater and 0.18 from streams — much the same total as in 1960.

Water withdrawals, 1960–2010. USGS.

Groundwater

Fresh water (no more than 250 mg/L chloride) comes from the Chicot equivalent, Evangeline equivalent and Jasper equivalent aquifer systems; its base generally lies from more than 2,000 to 3,500 feet below the National Geodetic Vertical Datum of 1929 (NGVD 29). The aquifers dip and thicken to the south. Rain falling from central Tangipahoa about 100 miles north into Mississippi is the main recharge, with some from neighbouring aquifers and, seasonally, rivers; water leaves to rivers, to deeper aquifers and through wells.

• Chicot equivalent — the Upland terrace aquifer lies at or near the surface in the northern half of the parish; the upper Ponchatoula, in the south, may be its buried continuation. The system is 100–400 feet thick, its base from about 125 feet above NGVD 29 in the north to 900 feet below in the south. In 2009 water levels ran from about 250 feet above NGVD 29 in the north to about NGVD 29 in the southern lowlands, flowing from hilltops toward valleys in the hilly north and south overall. Levels track rainfall; at well Ta-362 they fell about 5 feet from 1998 to 2012. Its water mostly serves rural homes (3.29 Mgal/d) and public supply (1.19).
• Evangeline equivalent — aquifers 50–500 feet thick, based from about 600 feet below NGVD 29 in the north to more than 2,700 feet in the south. In 2003 the Kentwood aquifer's level fell from about 225 feet above NGVD 29 in the north to 75 feet at Ponchatoula, flowing south. At well Ta-278, northeast of Hammond in the Covington aquifer, levels declined about 15 feet from 1991 to 2012. Most of its water goes to public supply (1.82 Mgal/d).
• Jasper equivalent — aquifers 100–250 feet thick, their top from about 700 feet below NGVD 29 near Kentwood to 2,700 feet in the south. The parish's main public supply (11.57 Mgal/d), plus industry (0.99). Pumping has lowered the Hammond and Amite aquifers since the 1950s: about 7 feet at well Ta-268 near Hammond and about 10 feet at Ta-260 at Roseland from 1991 to 2012.

Water levels in wells Ta-362 (Upland terrace, 43 feet deep), Ta-278 (Covington, 1,430 feet), Ta-260 (Amite, 2,013 feet) and Ta-268 (Hammond, 2,449 feet). USGS.

Groundwater quality

The three systems' water is similar: soft, generally within the EPA's secondary limits for dissolved solids and color, with median pH from 7.0 to 7.9 and temperature rising with depth (median 21.0 °C in the Chicot, 30.5 °C in the Jasper). Iron and manganese can locally far exceed the limits, and hydrogen sulfide may occur in the Evangeline and Jasper systems.

Surface water

Most of the parish drains to the Lake Maurepas basin, with small areas in the Lake Pontchartrain and Pearl basins; all end in Lake Maurepas, Lake Pontchartrain or the Gulf of Mexico.

• Tangipahoa River — flows in from Mississippi and reaches Lake Pontchartrain about 12 miles southeast of Ponchatoula; at Robert it averaged 1,148 cubic feet per second in 1938–2009, from about 646 square miles.
• Natalbany River — drains the Tickfaw subbasin in the parish, joining the Tickfaw about 1.5 miles above its mouth on Lake Maurepas; at Baptist it averaged 117 cubic feet per second in 1943–2009, from 79.5 square miles.
• Tchefuncte River — rises near the Washington Parish line and flows through St. Tammany Parish to Lake Pontchartrain; near Folsom it averaged 158 cubic feet per second in 1943–2009, from 103 square miles.
• Lake Maurepas (about 91 square miles, average depth about 7 feet) connects to Lake Pontchartrain, a shallow estuarine bay of the Gulf (about 621 square miles, 11 feet deep), through Pass Manchac. Little Silver Creek drains to the Bogue Chitto in Washington Parish.

In 2010, 0.18 Mgal/d was drawn from streams for livestock.

Surface-water quality

Quality varies widely. Streams in the Tangipahoa and Liberty Bayou–Tchefuncta subbasins are well connected to shallow aquifers, so groundwater shapes their chemistry; the Natalbany River and its tributaries are poorly connected. Salinity in both lakes swings with fresh river water and salt water from the Gulf, and salt water may push up the lower reaches of streams during droughts or storms. Samples from the Tangipahoa River at Robert (1968–99) and the Natalbany at Baptist (1943–69) were soft and within secondary limits for chloride and sulfate; the Tangipahoa's dissolved oxygen was generally above 5 mg/L, enough for a diverse warm-water fish community. Median pH was 6.5 in the Tangipahoa and 6.2 in the Natalbany, where turbidity may be more of a problem because the river cuts through many clay deposits.

Sources

• Vincent E. White and Lawrence B. Prakken, Water Resources of Tangipahoa Parish, Louisiana, USGS Fact Sheet 2016–3049, July 2016, prepared with the Louisiana Department of Transportation and Development. https://doi.org/10.3133/fs20163049
• USGS National Water Information System: http://waterdata.usgs.gov/nwis