^ Section 319
WJ NO PIINI SOURCE PROGRAM SUCCESS STORY
PRO^
Federal and State Agencies Rally Together to Reduce Total Dissolved
Solids Concentrations in Bayou Nezpique
Water ho dv Improved Sediment and nutrient runoff from agricultural fields degraded
r"	water quality in Louisiana's Bayou Nezpique River. As a result,
Louisiana added total dissolved solids (TDS) as a cause of impairment for Bayou Nezpique
River on its 2008 Clean Water Act (CWA) section 303(d) list of impaired waters. Beginning in
2009, agricultural best management practices (BMPs) were installed in the Bayou Nezpique
subsegment. These efforts decreased the sediment and nutrient loads entering the bayou,
and resulted in the delisting of TDS as a cause of impairment in the Bayou Nezpique
subsegment in 2010.
Problem
Bayou Nezpique, which is 65 miles long and has a
drainage area of 611 square miles, empties into the
Merrnentau River in southwestern Louisiana The
bayou is in the prairie region of the state, where
rice and crawfish farms have been a dominant
part of the landscape for many generations. Bayou
Nezpique flows through the parishes of Evangeline,
Acadia, Allen, and Jefferson Davis. The segment
is long and narrow with a variety of land uses,
including evergreen and deciduous forest lands
(53 percent), developed lands (6.5 percent), and
agricultural lands. Primary agricultural cropland
includes rice (19 percent) and pasture or hay (17 per-
cent); other agricultural crops grown in the water-
shed include sweet potatoes, soybeans, sorghum,
and sugar cane (Figure 1). Because of its relatively
low relief, especially in the prairie and marsh areas,
the region is characterized by poor drainage and
annual backwater flooding of agricultural lands.
Agriculture is approximately 23 percent of the
watershed and contributes a substantial portion of
the nonpoint source load. The primary agricultural
crop in the watershed is rice, alternated with either
soybeans or crawfish. The rice fields are flooded
in the fall for crawfish; in early spring, the farmers
release the water and let the fields dry to allow
soybeans to be planted.
Runoff from fields after recent tillage, fertilizer
	a if;	„„„„„„	Figure 1. Bayou Nezpique is a re atively flat watershed in the
applications, and other field operations can con-	a.. ,y, f,M
/.. . . . , ,. . . I,. , |	prairie region of southwestern Louisiana I he predominant land
tain higher levels of sediments and pollutants. In	. ... , .	. . r
. , , . . ..	,	,	uses in the watershed include forest and agriculture,
particular, planting activities during the wet weather
N
Bayou Nezpique
Subsegment 050301
Land Use
Legend
Land Use
Evergreen Forest
Deciduous Forest

Rice

Pasture or hay

Developed low density

Soybeans

Water

Developed open space

Developed medium density

Sweet Potatoes
1 ¦
Forest
—
Sorghum
Developed high density

Sugarcane

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Figure 2. A farmer implements irrigation land
leveling, which reshapes the land to a chosen grade
and will permit uniform and efficient application of
surface irrigation water without causing significant
erosion.
season of late winter and early spring produce large
volumes of very turbid water. The most significant
source of TDS and sediment in this watershed is
suspended solids in wet weather runoff.
Louisiana's standards for TDS require that 25
percent of yearly samples not exceed 260 parts
per million (ppm). Monitoring data collected in
2003 showed that three samples out of twelve
(25 percent) exceeded 260 ppm TDS, resulting in a
violation of the TDS standard. On the basis of these
data, the Louisiana Department of Environmental
Quality (LDEQ) listed Bayou Nezpique as impaired
for TDS on the state's 2008 integrated report, with
agriculture identified as the source of impairment.
A total maximum daily load was not developed for
TDS.
Project Highlights
LDEQ worked along with the Louisiana Department
of Agriculture and Forestry Office of Soil and Water
Conservation (LDAF-OSWC) to implement agri-
cultural practices in all but one of the 10 HUC-12
(12-digit hydrologic unit code) watersheds within the
Bayou Nezpique subsegment. BMPs were imple-
mented from 2009 untii 2013 and included nutrient
management (9,701 acres), conservation cover
(297 acres), prescribed grazing (950 acres), crop
rotation (9,810 acres), irrigation land leveling (5,240)
(Figure 2), and riparian forest buffer (30 acres).
Bayou Nezpique, TDS, site 651
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
2003
2007
2010
2011
Figure 3. lotal dissolved solids (TDS) data, 2003-2011.
Results
Monitoring data collected in 2011 showed that only
one of twelve (8 percent) of samples exceeded
the maximum allowable TDS concentration of
260 mg/L (Figure 3), which meets the TDS standard.
Therefore, in 2010 Louisiana delisted TDS as a
cause of impairment for the Bayou Nezpique.
Partners and Funding
The partners responsible for making this project a
success include the U.S. Environmental Protection
Agency, LDEQ, U.S. Department of Agriculture's
Natural Resource Conservation Service (NRCS),
and LDAF-OSWC. Soil and water conservation
district (SWCD) funding for cost-share was provided
by LDAF-OSWC through a cooperative conserva-
tion partnership initiative, funded through NRCS,
which provided special funds for projects in the
Bayou Nezpique area LDAF also provided technical
assistance through the SWCDs in the area. LDEQ
works with the LDAF-OSWC to implement the agri-
cultural portion of the Louisiana's Nonpoint Source
Management Plan.
From 2009-2013, partners used $1,057,150 of
CWA section 319 funds to sponsor cost sharing,
monitoring and education projects. Within the
Bayou Nezpique watershed, LDAF-OSWC and the
Evangeline SWCD implemented BMPs using CWA
section 319 Water Quality Protection Project grant
funds awarded in 2008 (for the Evangeline Soil
and Water Conservation Protection Project and
the Calcasieu and Mermentau River Basin Coastal
Prairie Cooperative Project).


VPR0^°
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-15-001C
January 2015
For additional information contact:
Karen Vidrine
Louisiana Department of Environmental Quality
225-219-1208
Karen.Vidrine@la.gov

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