Surface-Water Quality in Agricultural Watersheds of the North Carolina Coastal Plain Associated with Concentrated Animal Feeding Operations

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The effects of concentrated animal feeding operations (CAFOs) on water quality were investigated at 54 agricultural stream sites throughout the North Carolina Coastal Plain during 2012 and 2013.

Three general watershed land-use types were examined during the study, including 18 background watersheds with no active CAFOs, 18 watersheds with one or more active swine CAFOs but no poultry CAFOs, and 18 watersheds with at least one active swine CAFO and one active dry-litter poultry CAFO.

The Animal Feeding Operations Unit within the North Carolina Department of Environment and Natural Resources Division of Water Resources (DWR) is responsible for permitting and regulating animal feeding operations throughout North Carolina. As of 2010, DWR permitted approximately 2,150 swine operations in the state, the majority (about 2,000) of which are located in the Coastal Plain Physiographic Province.

The lack of stream water-quality data associated with the many permitted swine concentrated animal feeding operations (CAFOs) in eastern North Carolina makes it difficult for DWR to:

  • Assess the extent to which effects of swine CAFOs on stream nutrient concentrations can be measured
  • Determine how well existing CAFO regulations protect the waters of the state
  • Recommend effective changes to regulations or procedures

Therefore, the DWR collaborated with the U.S. Geological Survey (USGS) to generate needed information to provide a scientific basis for water-resource managers and policy makers to evaluate existing, or establish new, regulations or procedures at permitted CAFOs for protecting and enhancing stream water quality in nutrient impaired waters in eastern North Carolina.

SUMMARY

Stream study site in Duplin County, NC - Surface-Water Quality and Swine CAFOs
Stream study site in Duplin County, NC (Public domain.)

Developing and implementing water-quality restoration plans for impaired watersheds in the North Carolina Coastal Plain requires an understanding of the potential influence that different agricultural nonpoint sources may have on nutrient transport to receiving streams. North Carolina is the second highest swine producing state in the Nation, and as such, there is significant interest in understanding the extent to which swine CAFOs may influence water-quality conditions, especially in eastern North Carolina.

Several studies conducted in eastern North Carolina have indicated that nutrients associated with swine CAFOs have influenced water-quality conditions in surface water and groundwater. These studies conducted to evaluate offsite nutrient transport from swine CAFOs to receiving streams have been limited in geographic extent, either focusing on individual farm sites or several farms within a small watershed. Additional data were needed from a larger number of sites over a broader geographic area to better understand how swine CAFOs influence stream water quality in eastern North Carolina.

OBJECTIVES

The primary study objectives were to:

  1. Assess water-quality differences among streams draining watersheds with and without land-applied CAFO waste manures,
  2. Examine the use of multiple chemical constituents for identifying effects of CAFOs on stream water quality, and
  3. Examine relations of environmental variables among watersheds with and without measurable CAFO manure effects.

SCOPE

Surface-water samples were collected at study sites during 6 bimonthly sampling periods from June 2012 to April 2013 and analyzed for water-quality parameters. Data were compiled for various watershed variables, including number and type of CAFOs in the watersheds, number of swine and total weight, permitted amount of nitrogen that can be applied at the swine CAFOs, drainage area, land cover, and soil drainage characteristics. Statistical analyses were conducted to examine relations between watershed variables and water-quality conditions at the stream study sites.

APPROACH

 

Surface-Water Quality and Swine CAFOs - Stream study site in Martin County, NC
Swine CAFOs - Stream study site in Martin County, NC(Public domain.)

The following tasks were performed to meet the project objectives:

  • Develop stream sampling network
  • Conduct water-quality sampling
  • Compile watershed characteristics
  • Data analysis

Task 1: Develop stream sampling network

A total of 54 stream sites were selected for the study to collect water-quality samples for laboratory analyses. The study sites are distributed throughout the North Carolina Coastal Plain and are located in the Roanoke, Chowan, Tar-Pamlico, Neuse, Cape Fear, and Lumber River basins.

The drainage areas of the stream study sites range from 1.2 to 17.5 square miles. The 54 study sites represent 3 types of agricultural watersheds (18 each), including background watersheds with no CAFOs, watersheds with swine CAFOs, and watersheds with both swine and poultry CAFOs.

Task 2: Conduct water-quality sampling

Discrete water-quality samples were collected bimonthly from June 2012 to April 2013 at all study sites. At each site, surface-water samples were collected where the stream intersects a road (bridge or culvert) and analyzed for the water-quality parameters summarized in table 1.

Constituents

Samples were analyzed primarily for nutrients and major ions.

Table 1. Water-quality constituents measured in surface-water samples:
Constituent group                           Analytes
————————​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​         ​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—​​​​​​​—

Field measurements                        Specific conductance, pH, temperature, dissolved oxygen
Nutrients                                        Ammonia + organic nitrogen, ammonia, nitrate + nitrite, total nitrogen, ortho-phosphate, total phosphorus
Major ions                                      Calcium, chloride, magnesium, potassium, sodium, sulfate

Task 3: Compile watershed characteristics

Geographic Information System (GIS) analyses were used to determine the types and extent of land cover (developed, agriculture, forest, wetlands, etc) and soil-drainage characteristics within the drainage area of each stream study site. The numbers and types of CAFOs were compiled for each watershed and incorporated in the GIS data sets.

Task 4: Data analysis

All data were compiled into a database for processing and analysis. The stream water-quality data and watershed variable data (tasks 2 and 3) were evaluated to determine if there were similarities or differences in water-quality conditions among the study sites based on such things as number and type of CAFOs in the watersheds, number of swine and total weight, permitted amount of nitrogen that can be applied at the swine CAFOs, drainage area, land cover, and soil drainage characteristics. Results of the data analyses were used to characterize potential impacts of swine CAFOs on receiving surface water.

 

During the study, samples were collected and analyzed from 54 Coastal Plain watersheds to determine whether swine CAFOs had a mesuarable effect on stream water quality.

 

DATA COLLECTION

All water-quality data collected during this project are available online in the USGS National Water Information System (NWIS).

  • Bi-monthly water-quality sampling at 54 locations
  • Sampling across watershed variables: number and types of CAFOs, land cover, soil drainage

 

Locations of background, swine, and swine and poultry study sites, streamgage sites, and precipitation sites in the North Caroli
(Public domain.)

 

All water-quality data collected during this project are available online in the USGS National Water Information System (NWIS) database.

  • Bi-monthly water-quality sampling at 54 locations
  • Sampling across watershed variables: number and types of CAFOs, land cover, soil drainage

USGS water-quality sampling stations

Background sites

Station name                                                                     USGS Station #   Field ID
—————————————————————————         ———————   ————

Blue Hole Swamp at SR 11/42 near Cahaba, NC                   0208102325     BK-01
Smithwick Cr near Bear Grass, NC                                           02081065     BK-02
Etheridge Swamp at SR 1326 near Oak City, NC                      02081040     BK-03
Conoho Creek at SR 1336 near Oak City, NC                       0208103875     BK-04
Conoho Creek Tributary at SR 1002 at Hassell, NC              0208105040     BK-05

Kirby's Creek Trib at SR 1356 near Pendleton, NC               0205309110     BK-06
Williamson Branch at SR 1128 near St Lewis, NC                     02083583     BK-07
Tyson Creek at SR 1245 at Kings Crossroads, NC                   02083889     BK-08
Hunting Run near Pactolus, NC                                               02084212     BK-09
Beaverdam Swamp at SR 1520 near Alligoods, NC              0208451810     BK-10

Whiteoak Swamp at SR 1514 near Holdens Crossroads, NC     02090770     BK-11
Moccasin Run near Patetown, NC                                         0209096970    BK-12
Langs Mill Run at SR 1242 near Fountain, NC                          02091623     BK-13
Middle Swamp near Marlboro, NC                                           02091712     BK-14
Big Creek at SR 1006 at Bethany Crossroads, NC                 0210682145     BK-15

Sevenmile Swamp at US HWY 13 at Rosin Hill, NC                0210591785     BK-16
White Oak Branch at SR 1209 near Ivanhoe, NC                    0210754615     BK-17
Horse Swamp at SR 2436 near Fairmont, NC                       0213453011      BK-18

———————————————————————————————————————————————————————————————————————————————

Swine-Poultry sites

Station name                                                                       USGS Station #         Field ID
--------------------------------------------           -------------       -------

Chicod Cr at SR 1565 near Grimesland, NC                              02084148           SP-01
White Oak Br at SR 1144 near Strickland Crossroads, NC         0208813655       SP-02
Thoroughfare Swamp near Dobbersville, NC                             02088285          SP-03
Falling Creek at SR 1102 near Dobbersville, NC                        0208831520       SP-04
Unnm Trib to Southwest Creek at SR 11 near Albrittons,NC      02089598           SP-05
Davis Creek at SR 1713 near Lisbon, NC                                  02105702            SP-06
Hammonds Creek at SR 1709 near Elizabethtown, NC             0210564590        SP-07
Big Swamp at SR 1441 near Clement, NC                                0210687150         SP-08
Cypress Creek at SR 1503 near Ammon, NC                           02107005             SP-09
Unnm Trib to Bearskin Swamp at SR 1240 at Concord, NC      02106011             SP-10
Six Runs Creek at SR 1742 near Giddensville, NC                   0210608620          SP-11
Bear Swamp at SR 1301 at Bowdens, NC                                0210778820          SP-12
Nahunga Creek at SR 1301 near Warsaw, NC                         0210782005           SP-13
Poley Branch at SR 1534 at Outlaws Bridge, NC                      0210760950           SP-14
Buck March Branch at SR 1753 near Hines Crossroads, NC     0210760860           SP-15
Stephens Swamp at SR 1807 at Quinns Store, NC                    0210798920          SP-16
Tenmile Swamp at SR 1207 near Cypress Creek, NC                0210858154           SP-17
Doctors Creek at SR 1129 near Shanghai, NC                         0210850250            SP-18

———————————————————————————————————————————————————————————————————————————————

Swine Only sites

Station name                                                                          USGS Station #          Field ID
--------------------------------------------           -------------       -------

Steptoe Run near Scotland Neck, NC                                          02081016             SW-01
Kitten Creek at SR 1251 near Sharp Point, NC                           02083686               SW-02
Unnm Trib to Otter Cr at SR 1615 nr Sharp Point, NC                0208368850          SW-03
Little March Run at SR 1714 at Parkstown, NC                           02089225              SW-04
Hornpipe Branch at SR 1130 near Deep Run, NC                       02089584               SW-05

Creeping Swamp near Calico, NC                                               02091960              SW-06
Whiteoak Swamp Trib at SR 1514 at Drivers Store, NC                02090793             SW-07
Sandy Run at US HWY 13/258 at Lizzie, NC                                02091725             SW-08
Hornet Swamp at SR 242 near Piney Green, NC                          0210596803         SW-09
Ward Swamp at SR 1711 near Monks Crossroads, NC                 0210592050         SW-10

Youngs Swamp at SR 1725 near Giddensville, NC                      0210770367          SW-11
Big Branch at SR 1301 at Bowdens, NC                                      0210778920          SW-12
King Branch at SR 1305 at Friendship, NC                                 0210782015          SW-13
Rattlesnake Branch at SR 1516 at Lennon's Crossroads, NC      0213449620          SW-14
Aaron Swamp at SR 2455 near McDonald, NC                           0213453155          SW-15

Little Whites Creek at SR 1700 near Bluefield, NC                      0210899420          SW-16
Horseshoe Swamp at SR 1713 near Lisbon, NC                          0210899878          SW-17
Butler Branch at US HWY 701 near Wootens Crossroads, NC      0210910290          SW-18

Report

The final report for the completed study was released on June 23, 2015 and is available online.