NAWQA Basic Fixed Sites

8 Basic Fixed Sites

• Sampled at least monthly for 2-3 years
• Range of physiographic settings
• Different land uses
• Discharges for computing loads
• Data presented for 10/98-9/99

Constituents sampled

• Major inorganic ions
• Nutrients -- Nitrogen and Phosphorus
• Organic Carbon
• Indicator bacteria -- Fecal coliform & E. coli
• Trace metals
• Pesticides
• Volatile Organic Compounds (VOCs)
• Chlorophyll a & b

Basic Fixed Sites

Tchefuncte R. nr Covington

• Pesticide concs. very low -- Atrazine varies from <0.001 ug/L to .488 ug/L
• No problem with trace metals
• Fecal-coliform indicator bacteria typically range from 200-400 cols/100 mL, indicating possible NPS/point-source problems

Dawson Creek at BR

• Fecal-coliform indicator bacteria very high--from 370 to >1,000,000 cols/100 mL. 5,000 is typical
• Ammonia relatively high, 0.13-1.8 mg/L (.83 ave)
• VOCs surprisingly low
• Low levels, but wide variety of pesticides (diazinon, chlorpyrifos, atrazine, metolachlor, prometon, simazine, tebuthiuron)

Bayou Grosse Tete at Rosedale

• Low but persistant ammonia concs., from <.02 to 0.39 mg/L, (0.15 mg/L ave.)
• DO problem: Readings below 3.0 mg/L 8 out of 16 samplings for 6/98-8/99
• Atrazine problem: 41 ug/L detected 4/09/99 (4.34 ave. conc 6/98-8/99). Metolachlor 16 ug/l also on 4/09/99 (37.7ug/L & 11.8 4/00)

Bayou Boeuf at Amelia

• Commercial/industrial site does not have problems with VOCs or solvents in the water
• Shows influence of Atchafalaya River
• Atrazine lower than previous years: peak conc. 1.40 ug/L (.755 ug/L 4/11/00)

Mermentau R. at Mermentau

• High & persistent turbidity, no flow or upstream flow, nutrients combine to depress dissolved oxygen
• Fecal-coliform indicator bacteria concs. low
• Molinate peaked at 5.27 ug/L 5/26/99. Metolachlor, Tebuthiuron commonly detected at low levels.

Bayou des Cannes nr. Eunice

• Consistently high turbidity
• Fairly high DOC (6.1-15 mg/L)
• Herbicides molinate (peaks at 5.25 ug/L 513/99) and tebuthiuron (peaks at 6.33ug/L 5/133/99) common in Mermentau Basin

Bayou Lacassine nr. Lake Arthur

• High turbidity
• Fecal-coliform indicator bacteria concs. low, fewer than 85 cols/100 mL
• DOC ranged from 7.1 to 24 mg/L
• Herbicides similar to Bayou des Cannes, but at lower concs (molinate 1.37 ug/L).

Whisky Chitto nr. Oberlin

• Consistently high DO, low nutrients
• Almost no pesticide detections --reference site
• Fecal-coliform indicator bacteria variable; can be as high as 525 cols/100 mL

Further Information

• Check out the USGS, La District Hydrowatch page
• Visit the Louisiana NAWQA web page: la.water.usgs.gov/nawqa
• All BFS data are in the La. District annual report