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Water: Nonpoint Source Success Stories

North Dakota: Lake Lamoure

Implementing Best Management Practices and Targeting Technical Assistance Restores Lake


Waterbody Improved

  Agricultural activities contributed excess nutrients and sediment to North Dakota's Lake LaMoure, resulting in a hypereutrophic (high nutrient concentrations and poor water clarity) state. As a result, North Dakota added the lake to its 2002 Clean Water Act (CWA) section 303(d) list of impaired waters as threatened for its recreation and aquatic life designated uses. Implementing agricultural best management practices (BMPs) reduced the amount of nonpoint source pollution entering the lake. As a result, lake clarity has increased and chlorophyll a levels have decreased, allowing Lake LaMoure to return to a mesotrophic (lower nutrient concentrations and greater water clarity) state. On the basis of those data, North Dakota removed Lake LaMoure from the CWA section 303(d) list in 2010.



Bob Flath
LaMoure County Soil
  Conservation District

Greg Sandness
North Dakota
  Department of Health

Eric Steinhaus
U.S. Environmental
  Protection Agency Region 8

This map shows the location of and depth information for Lake LaMoure. Larger view of map (PDF)
(1 pg, 471K, About PDF)

Figure 1. Lake LaMoure is in southeast North Dakota.



Lake LaMoure is a 409-acre reservoir on Cottonwood Creek in  southeastern North Dakota. The lake provides recreational opportunities such as  swimming, boating and fishing (Figure 1). Agriculture (crop and livestock  production) is the primary land use in the lake's 160,000-acre watershed.

  In the 1990s, local residents became concerned as frequent  algae blooms plagued the lake in mid- to late-summer, and the fish community  became increasingly dominated by less desirable fish such as carp and  bullheads. In response, in 1995 the LaMoure County Soil Conservation District  (SCD) began evaluating the relationship between land management and degrading  water quality in the Lake LaMoure/Cottonwood Creek watershed. The SCD measured  water quality and quantity and inventoried the land use practices in the  watershed. The 1995 assessment revealed that Lake LaMoure received  approximately 72,712 pounds (lbs) of nitrogen and 11,987 lbs of  phosphorus—roughly equal to a fertilization rate of 147 lbs/acre nitrogen and  24 lbs/acre phosphorus. Models also indicated that the lake generated an  additional internal loading amount equal to a fertilization rate of 13.8  lbs/acre nitrogen and 11.4 lbs/acre phosphorus.

  The SCD's assessment identified that recreational use  impairments in Lake LaMoure were primarily caused by nonpoint source pollutants  from agricultural lands, including nutrients (nitrogen and phosphorus) and  suspended sediments. Potential nonpoint pollutant sources included excessively  tilled croplands, overgrazed rangeland and livestock winter feeding areas. The  assessment also identified the lake's carp population as possibly contributing  to resuspension of sediments and nutrients through rooting and foraging  activities on the lake bottom.

  The SCD's assessment determined that in–lake   phosphorus concentrations needed to be reduced to a mean annual concentration  of 0.19 milligrams per liter (mg/L) to change the lake's trophic state from  hypereutrophic to mesotrophic. Trophic State Index (TSI) values are calculated  according to seasonal means of total phosphorus, chlorophyll a (the  photosynthetic pigment that causes the green color in algae and plants), and  Secchi disc transparency (indicating water clarity). TSI values are often  grouped into trophic state classifications: oligotrophy, or low productivity  (values of 0–40); mesotrophy, or moderate productivity (values of 40–50); and  eutrophy, or high productivity (values of 50 or more). TSI values can assess  changes in a lake's productivity over time and compare the productivity of  lakes in the same region.

Project Highlights

The SCD developed a watershed project implementation plan  that identified beneficial use improvement and nonpoint source  pollutant–reduction goals, specific activities for accomplishing the goals and  a method for evaluating progress. The SCD began targeting conservation planning  assistance along with voluntary implementation of BMPs in 1997.

  With help from the SCD and other federal, state and local  partners, landowners applied BMPs to 56,950 acres, including implementing  conservation tillage (22,010 acres) and no-till (1,816 acres), converting  cropland to hayland (1,149 acres), establishing riparian easements (41 acres),  stabilizing streambanks (1,915 linear feet), and installing exclusion fencing  (2,610 linear feet). In addition, landowners adopted prescribed grazing  management on 319 acres, strategies for better managing livestock waste  nutrients (on 17,472 acres), and improved crop residue management (on 2,246  acres). The SCD worked with landowners to implement 10 manure management  systems and install fencing to exclude livestock from riparian areas. After the  watershed project had ended, one additional system was installed with funding  from Natural Resources Conservation Service's Environmental Quality Incentive  Program.    


Implementing BMPs reduced water pollution and improved the lake's water quality. Analysis of chlorophyll a data and Secchi disk  transparency yields TSI scores that show that Lake LaMoure has improved from a  hypereutrophic to a mesotrophic state (Figure 2). When analyzed for trends using  a Seasonal Kendall Test, the chlorophyll a data showed a significant decline  (slope of -0.810, p < 0.1). The Secchi disk transparency readings  showed a significant increase (slope of 0.124, p < 0.05). Water  quality improved, and recreation and aquatic life designated uses have been  restored. On the basis of those data, North Dakota removed Lake LaMoure from  the state's CWA section 303(d) list of impaired waters in 2010.

Partners and Funding

The LaMoure County SCD led the watershed assessment and  development of the Lake LaMoure/Cottonwood Creek Watershed Project. The SCD  hired staff to work with watershed landowners to develop contracts and deliver  technical assistance for implementing BMPs. SCD project staff worked closely  with federal, state and local partners, including the North Dakota Wetlands  Trust (renamed the Natural Resources Trust), Natural Resources Conservation  Service, U.S. Fish and Wildlife Service, U.S. Environmental Protection Agency,  and the Nonpoint Source BMP Team—a CWA section 319-funded engineering program  through the Sheyenne James Resource Conservation and Development program.

  In addition, the North Dakota Department of Health provided  oversight for project management, developed the quality assurance project plan,  conducted training for proper water quality sample collection, and helped to  develop and implement outreach and education activities. The North Dakota Game  and Fish Department provided financial assistance for establishing riparian  easements and restoration practices. Partners have encouraged and maintained  public involvement by holding workshops, distributing newsletters and offering  presentations to community groups.

  The project received $1,753,668 in CWA section 319 funding  that was matched by $1,169,112 in local funds (cash and in-kind services) from  landowners.

This chart shows that TSI scores for Lake LaMoure improved between 1994 and 2008.

Figure 2. TSI scores for Lake LaMoure from 1994 through 2008.

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