Knowing how much water Evangeline Parish, in south-central Louisiana, has, how it is used and how good it is helps water managers and residents look after it. This fact sheet, by the Bureau of Indian Affairs and the U.S. Geological Survey with the Louisiana Department of Transportation and Development, sums it up.
How the water is used
In 2014 the parish withdrew about 282.66 million gallons a day (Mgal/d): 122.05 from groundwater and 160.61 from surface water.
| Use (2014) | Groundwater | Surface water | Total (Mgal/d) |
|---|---|---|---|
| Power generation | 0.16 | 146.17 | 146.33 — about 52% |
| Rice irrigation | 77.46 | 8.61 | 86.06 |
| Aquaculture | 29.21 | 5.16 | 34.37 |
| General irrigation | 5.57 | 0.62 | 6.19 |
| Livestock | 0.18 | 0.06 | 0.24 |
| Public supply | 5.85 | 0.00 | 5.85 |
| Industry | 3.27 | 0.00 | 3.27 |
| Rural domestic | 0.34 | 0.00 | 0.34 |
Agriculture — aquaculture, irrigation and livestock — took 45 percent (126.86 Mgal/d). Figures are rounded, so they may not add up exactly.
Water withdrawals, 1960–2014, measured every five years to 2010 and again in 2014; they peaked in 1980.
| Source (2014) | Mgal/d |
|---|---|
| Bayou Cocodrie | 148.94 |
| Chicot aquifer system | 112.18 |
| Evangeline aquifer | 9.87 |
| Bayou des Cannes | 1.63 |
| Bayou Marron | 1.63 |
| Millers Lake | 1.50 |
| Bayou Choupique | 1.25 |
| Other surface water | 5.66 |
The aquifers
Evangeline Parish. Shading shows the altitude of the base of fresh groundwater; A–A′ is the section below. From the fact sheet.
The main freshwater aquifers are the Chicot aquifer system and the Evangeline aquifer. The deeper Jasper aquifer system holds fresh water in the northwest, but nothing is reported drawn from it. Fresh groundwater — 250 milligrams per litre (mg/L) of chloride or less — mostly ends in the Evangeline aquifer, from less than 300 to more than 2,000 feet below sea level (NGVD 29); in the far south it ends in the Chicot system.
An idealised north-to-south section through the parish; individual sand and clay layers are not shown.
Chicot aquifer system
- Makeup: in this parish, a massive, undivided sand — thick beds of coarse sand with gravel — whose top is usually less than 50 to more than 100 feet below the land surface, and whose base runs from about NGVD 29 to more than 400 feet below it, dipping south. It is at or near the surface in the north, and is recharged by rain where it crops out or streams cut into it.
- Water levels: in January 2003, from more than 60 feet above NGVD 29 in the north to more than 60 feet below near Mamou. At well Ev-229, in the middle of the parish, levels varied yearly and fell more than 30 feet from 1948 to 2018; at Ev-500, near Turkey Creek, they barely varied and fell less than 5 feet from 1953 to 2018.
- Wells (2017): 895 active — 545 irrigation, 302 domestic, 24 public supply, 20 industrial, 4 power generation; 14 to 500 feet deep; yields 2 to 4,600 gallons a minute.
- Use (2014): about 112.18 Mgal/d — 74.36 rice irrigation, 29.21 aquaculture, 5.35 general irrigation, 2.20 industry, 0.45 public supply, 0.27 rural domestic, 0.18 livestock, 0.16 power generation.
Evangeline aquifer
- Recharge: when Chicot water levels are high enough for water to flow down into it, the Evangeline is recharged in Rapides and Avoyelles parishes and northern Evangeline Parish.
- Shape: its upper part dips south at about 20 feet a mile, its lower part at about 60. Its top runs from about NGVD 29 in the north to about 500 feet below near the southern border; its base from more than 500 to more than 3,000 feet below. The clay Castor Creek confining unit separates it from the Jasper system.
- Water levels: in 2004, from more than 40 feet above NGVD 29 in the northwest corner to more than 60 feet below near Mamou. At Ev-691, north of Lake Chicot, they varied less than about 2 feet a year and fell about 15 feet from 1967 to 2018; at Ev-474, in the southwest corner, they varied less than about 5 feet a year and fell about 25 feet from 1991 to 2010.
- Wells (2017): 114 active — 53 domestic, 37 public supply, 15 industrial, 9 irrigation; 190 to 1,804 feet deep; yields 6 to 2,700 gallons a minute.
- Use (2014): about 9.87 Mgal/d — 5.40 public supply, 3.10 rice irrigation, 1.08 industry, 0.22 general irrigation, 0.07 rural domestic.
Water levels in wells Ev-500 and Ev-229 (Chicot) and Ev-691 and Ev-474 (Evangeline), relative to NGVD 29.
Groundwater quality
The state's long-term monitoring sampled 131 Chicot wells (1940–2015) and 78 Evangeline wells (1948–2015), compared with the EPA's secondary maximum contaminant levels (SMCLs) — guidelines for taste, colour, staining and similar effects.
| Chicot | Evangeline | SMCL | |
|---|---|---|---|
| Median hardness | 130 mg/L — hard | 18 mg/L — soft | — |
| Median pH | 7.2 | 7.9 | 6.5–8.5 |
| Median iron | 1,250 µg/L | 200 µg/L | 300 µg/L |
| Samples within the iron limit | 29% | 62% | |
| Median manganese | 200 µg/L | 40 µg/L | 50 µg/L |
| Samples within the manganese limit | 27% | 70% | |
| Median dissolved solids | 298 mg/L | 403 mg/L | 500 mg/L |
Chloride and sulfate were within the SMCLs in at least 95 percent of samples from both; iron and manganese exceeded them in more than 70 percent of Chicot samples; median pH and dissolved solids were within the limits in both.
Surface water
Two subbasins drain the parish: the Mermentau Headwaters (HUC 08080201) in the centre and southwest, draining south and southwest, and the Bayou Teche (HUC 08080102) in the north and east, draining east and south.
Mermentau Headwaters. The main streams are Bayou Nezpique — formed where its East and West forks meet in the west-centre, with tributaries including Castor Creek, Boggy Bayou and Caney Creek — and Bayou des Cannes, formed east of Mamou where Coulee de Manuel meets Bayou Joe Marcel.
| Gauge (water years) | Mean flow (ft³/s) | Monthly means |
|---|---|---|
| Bayou Nezpique near Basile (1939–2014) — may be affected by irrigation pumping | 816 | 1,555 in February to 362 in August |
| Bayou des Cannes near Eunice (1939–2017) — may be affected by a diversion | 275 | 460 in January to 155 in October |
| Bayou Cocodrie near Clearwater (1923–2017) | 412 | 664 in February to 198 in October |
In 2014, rice farms and fish farms drew water from Bayou des Cannes (1.63 Mgal/d), Millers Lake (1.50), Bayou Choupique (1.25) and Bayou Marron (1.63).
Bayou Teche. Its main stream, Bayou Cocodrie, starts near the northwest corner, flows through Cocodrie Lake, then turns south and leaves the parish near Lake Chicot. In 2014, 148.94 Mgal/d was drawn from it — 146.17 for power generation, 1.72 for rice and 1.05 for aquaculture.
- Cocodrie Lake, on the northern border, covers about 6,000 acres, averages 5–6 feet deep and is thick with cypress and tupelo. It was created in 1959, mainly for irrigation and power generation, secondarily for recreation.
- Lake Chicot, created in 1942 for recreation and surrounded by Chicot State Park, covers about 1,600 acres, with about 32 miles of shoreline and an average depth of about 7 feet.
Surface-water quality
Samples came from Bayou Nezpique near Basile (1943–98), Bayou des Cannes near Eunice (1967–2001) and Bayou Cocodrie near Clearwater (1944–79). Chloride, sulfate and dissolved solids were within the SMCLs in at least 98 percent of samples at all three.
| Bayou Nezpique | Bayou des Cannes | Bayou Cocodrie | |
|---|---|---|---|
| Median hardness | 28 mg/L — soft | 72 mg/L — moderately hard | 13 mg/L — soft |
| Median dissolved oxygen | one reading: 4 mg/L (July 20, 1998) | 5.6 mg/L | 5.9 mg/L |
| Median pH | 6.5 | 7.5 | 7.1 |
| Median colour | 100 PCU | 115 PCU | 80 PCU |
Five mg/L of dissolved oxygen is generally considered the minimum for a diverse community of freshwater warm-water life, including sport fish.
Sources
- Murphy, C.J. (Bureau of Indian Affairs), and White, V.E. (U.S. Geological Survey), 2020, Water resources of Evangeline Parish, Louisiana: U.S. Geological Survey Fact Sheet 2020–3020, prepared in cooperation with the Louisiana Department of Transportation and Development. https://pubs.usgs.gov/publication/fs20203020
- The tables, figures and captions come from the fact sheet's PDF, which the web version lacks.
- Rewritten in hubnx's own words.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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