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La Salle Parish: depth to the base of fresh groundwater, and USGS monitoring sites. USGS.
Water use at a glance
In 2010 the parish withdrew about 2.40 million gallons a day (Mgal/d): 2.29 from groundwater and 0.10 from surface water. Measured every five years since 1960, withdrawals were highest in 1960.
| Use | Groundwater | Surface water | Total (Mgal/d) |
|---|---|---|---|
| Public supply | 2.18 | 0.00 | 2.18 |
| Rural domestic | 0.06 | 0.00 | 0.06 |
| Livestock | 0.01 | 0.03 | 0.03 |
| General irrigation | 0.00 | 0.08 | 0.08 |
| Aquaculture | 0.06 | 0.00 | 0.06 |
| Total | 2.29 | 0.10 | 2.40 |
Water withdrawals, 1960–2010. USGS.
Groundwater
Fresh groundwater (chloride 250 mg/L or less) is found along the northern parish line and in the central and southern parish, down to as deep as about 800 feet below sea level (NGVD 29). The main sources are the Mississippi River alluvial, Upland terrace, Catahoula and Cockfield aquifers. Recharge comes from rain, leakage between aquifers and seasonal streamflow.
In 2014 the state listed 168 active wells in these aquifers: 107 domestic, 35 public supply, 20 industrial and 6 irrigation.
Generalized northwest-to-southeast section through the parish (modified from Fisk, 1938). USGS.
| Aquifer | Where | Active wells (2014) | Well depths | Yields (gal/min) | Pumped, 2010 (Mgal/d) |
|---|---|---|---|---|---|
| Mississippi River alluvial | near the surface from about 2 mi northwest of Catahoula Lake to the parish's southern tip; 150–200 ft of sand and gravel under silt and clay | 9 (5 domestic, 2 irrigation, 2 industrial) | 24–220 ft | 100–1,500 | <0.003 |
| Upland terrace | at the surface over much of the central parish; 30–50 ft thick in the north, 100–150 ft in the center | 82 (61 domestic, 17 public, 3 irrigation, 1 industrial) | 8–227 ft | 2–350 | 1.28 (1.25 public supply) |
| Catahoula | at or near the surface across the central parish, southwest to northeast; fresh to about 800 ft below sea level in the south; salty in the southwest corner | 38 (25 domestic, 9 public, 3 industrial, 1 irrigation) | 21–873 ft | 24–350 | 0.16 |
| Cockfield | fresh only in a 3–7 mi band along the northern line; 400–800 ft thick there; surfaces near Olla | 39 (16 domestic, 14 industrial, 9 public) | 25–1,665 ft | 3–335 | 0.86 (0.85 public supply) |
Notes by aquifer:
- Alluvial: unconfined or partly confined; water moves northeast toward a low near the east end of Catahoula Lake.
- Upland terrace: fed by rain and flowing toward stream valleys; salty near Catahoula Lake. Water is soft and generally within secondary limits for color, iron, manganese and dissolved solids.
- Catahoula: discharges mostly to nearby streams, with the rest moving south toward the Little River valley. Water levels changed little from 2002 to 2012.
- Cockfield: dips southeast from about 400 ft above sea level in the northwest to more than 2,000 ft below it in the southeast, under the Vicksburg–Jackson clays. Clay above and below has kept saltwater from being flushed out downdip. Water levels in well La-254A have been fairly steady since 2001. Water generally met limits for chloride, iron and manganese but exceeded them for color and dissolved solids.
Water levels in Catahoula aquifer wells La-124 and La-172 and Cockfield aquifer well La-254A. USGS.
Groundwater quality
Medians; values in mg/L unless noted:
| Aquifer | Color (PCU) | pH | Hardness | Chloride | Iron (µg/L) | Manganese (µg/L) | Dissolved solids |
|---|---|---|---|---|---|---|---|
| Upland terrace, 1939–84 (72 wells) | 0 | 6.4 | 15 | 9.8 | 90 | 25 | 74 |
| Catahoula, 1945–83 (44 wells) | 5 | 7.6 | 15 | 10 | 120 | 50 | 268 |
| Cockfield, 1939–85 (39 wells) | 100 | 8.4 | 8 | 35 | 110 | 30 | 622 |
Surface water
Only about 0.10 Mgal/d of surface water was used in 2010. The parish's waters include the Little River, Bayou Funny Louis, Chickasaw and Little Chickasaw Creeks, Hemphill Creek, Trout Creek, Saline Lake, Muddy Bayou, Big Saline Bayou, French Fork Little River and Catahoula Lake.
| Stream | Period | Average flow | Drainage area |
|---|---|---|---|
| Hemphill Creek at Nebo | 1978–95 | 63 cubic feet per second | 35 sq mi |
| Bayou Funny Louis near Trout | 1939–70 | 123 cubic feet per second | 92 sq mi |
| Little River near Rochelle | 1958–96, 1998–2011 | 2,182 cubic feet per second | 1,899 sq mi |
- Little River near Rochelle (1964–86 samples): generally soft, within limits for pH, chloride and sulfate, with dissolved oxygen generally above 5 mg/L — the minimum for a diverse warmwater fish community, including sport fish.
- Catahoula Lake, the largest natural inland freshwater lake in Louisiana at more than 46 square miles, lies on the Little River and is a key stopover and wintering area for hundreds of thousands of migratory waterfowl and shorebirds. It is managed for high water in winter and spring and drawdown in summer and fall, mainly for bird habitat. Samples from 1976–78 showed soft water, dissolved oxygen generally above 5 mg/L, and median manganese of 90 µg/L.
Sources
Based on Vincent E. White and Lawrence B. Prakken, "Water resources of La Salle Parish, Louisiana," U.S. Geological Survey Fact Sheet 2014–3089 (2015), prepared with the Louisiana Department of Transportation and Development; a work of the United States government in the public domain. The map, charts, section and tables are taken from the fact sheet's PDF. The text gives Catahoula Lake's median manganese as 90 mg/L; its table gives 90 µg/L, used here.
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