Phosphorus and nitrogen are nutrients that help plants grow. A lake can become eutrophic when it contains too much of these nutrients. Phosphorus in human or animal waste, or synthetic fertilizers, eventually may work its way into a lake either directly along the shoreline or through its tributaries. Parts of Lake Champlain, a 435 square-mile water body in New York, Vermont, and Quebec, Canada, are eutrophic, resulting in excessive growth of aquatic plants and seasonally unpleasant and potentially toxic algal blooms.

Reducing the amount of phosphorus entering Lake Champlain to curb eutrophication is a priority of Vermont, New York, and Quebec. Since 1990, State, Provincial, and Federal governments have established several phosphorus-reduction goals and agreements. Most recently, these agreements include a 2002 Missisquoi Bay Agreement between Vermont and Quebec to allocate phosphorus-reduction responsibility (The Gouvernement du Quebec and the Government of the State of Vermont, 2002), a 2002 Lake Champlain phosphorus Total Maximum Daily Load (TMDL) limit (Vermont DEC and New York State DEC, 2002), and the 2003 updated Opportunities for Action (Lake Champlain Steering Committee, 2003).

Progress toward achieving targeted phosphorus reductions is measured, in part, by tracking the implementation of best management practices (BMPs) and assigning a standardized load-reduction credit for each BMP. A BMP is a structure, plan, or educational effort that is designed for an area or site to achieve a specific result. A BMP can be anything from an engineered structure, such as a settling pond or constructed wetland; to a plan for crop rotation or nutrient management on farms; to an educational newsletter explaining water-quality implications of activities taking place in the watershed.

In 1999, the U.S. Geological Survey (USGS) began monitoring concentrations of nutrients and suspended sediment in two streams in order to determine how effective BMPs are in reducing transport of these pollutants to Lake Champlain. One stream, Englesby Brook, drains a developed watershed in Burlington and South Burlington, Vermont. In 2007, data collection at Englesby Brook entered the second year of the post-BMP monitoring phase, which followed 6 years of pre-BMP and construction-period data collection. The second stream, Little Otter Creek, drains an agricultural watershed in the vicinity of Ferrisburg, Vermont (see map). Data collection at Little Otter Creek ended in September 2005, after only a subset of several planned BMPs was constructed and there was little likelihood that additional BMPs were to be completed. The USGS assessed the first 6 years of water-quality data collected from the 2 streams in the report "Concentrations and loads of nutrients and suspended sediments in Englesby Brook and Little Otter Creek, Lake Champlain Basin, Vermont, 2000-2005".

• To access the effectiveness of urban BMPs in reducing total phosphorus and suspended-sediment loads in a small tributary to Lake Champlain .
• To estimate 6 years of phosphorus and suspended-sediment export from a dairy farm in Vermont including potential changes resulting from barnyard BMPs.
• To provide a demonstration study for urban BMP effectiveness.
  

Three water-quality monitoring stations were established for this project. A single monitoring location is on Englesby Brook in Burlington, Vermont, downstream of several urban BMPs. Two monitoring locations were on Little Otter Creek in Ferrisburg, Vermont, upstream and downstream of a dairy farm that was expected to implement several agricultural BMPs. The study compares total phosphorus and suspended-sediment loads before and after BMP implementation. The project design is described in more detail by following the links to Englesby Brook and Little Otter Creek.

Field methods for sample collection and processing follow the USGS National Field Manual (U.S. Geological Survey, variously dated). Water samples are collected through a combination of automated and manual techniques. Manual samples are collected monthly and during occasional storms. In September 1999 (Englesby Brook) and July 2001 (Little Otter Creek), automated stage-triggered samplers were installed to collect discrete samples during all stages of storm or snowmelt hydrographs. Temperature, specific conductance, dissolved oxygen, turbidity, and pH were monitored continuously at Englesby Brook from 1999 to 2002 and at Little Otter Creek from 2001 to 2002. Since 2002, field parameters and concentrations of total nitrogen have been measured monthly and for occasional storms. Sampling is done during ice-free conditions, typically from March through December.

Analyses for suspended-sediment concentrations (SSC) are done at the USGS Sediment Laboratory in Kentucky. Laboratory analyses for total phosphorus and total nitrogen are done at the Vermont Department of Environmental Conservation Laboratory. Sample holding times and laboratory techniques follow protocols established by the USGS Sediment Analysis Quality-Assurance Plan (Shreve and Downs, 2005) and the Department of Environmental Conservation Quality Laboratory Quality Assurance Plan (Department of Environmental Conservation Laboratory, 2006).

Monthly and annual loads are the aggregation of daily load data estimated using one of two USGS computer programs. Input data sets for both programs are sample concentrations and streamflow. The program GCLAS (Koltun and others, 2006), which graphically facilitates use of the mid-interval or integration method (Porterfield, 1972), is used to estimate daily loads for days with storms when there were sufficient samples to define the storm. The program LOADEST (Runkel and others, 2004), which formulates a regression equation to model loads over a user-specified interval, is used to estimate daily loads during base-flow conditions and when storms were insufficiently sampled.

Medalie, Laura, 2000, Monitoring the effectiveness of urban best management practices in improving water quality of Englesby Brook, Burlington, Vermont: U.S. Geological Survey Fact Sheet 114-00, 4 p.

Medalie, Laura, 2001, Characterizing nutrient loads prior to best management practices implementation in a small urban watershed, Burlington, Vermont, in Proceedings: 8th national nonpoint source monitoring workshop, EPA/905-R-01-008, p. 43-5.

Medalie, Laura, 2007, Concentrations and loads of nutrients and suspended sediments in Englesby Brook and Little Otter Creek, Lake Champlain Basin, Vermont, 2000-2005: U.S. Geological Survey Scientific Investigations Report 2007-5074, 50 p.

The Gouvernement du Quebec and the Government of the State of Vermont, 2002, Missisquoi Bay Phosphorus Reduction Agreement.

Department of Environmental Conservation Laboratory, 2006, Quality assurance plan: accessed November 13, 2006, at http://www.anr.state.vt.us/dec/lab/htm/QualityControl.htm.

Lake Champlain Steering Committee, 2003, Opportunities for action--An evolving plan for the future of the Lake Champlain Basin, Lake Champlain Basin Program.

Medalie, Laura, 2000, Monitoring the effectiveness of urban best management practices in improving water quality of Englesby Brook, Burlington, Vermont: U.S. Geological Survey Fact Sheet 114-00, 4 p.

Porterfield, George, 1972, Computation of fluvial-sediment discharge: U.S. Geological Survey Techniques of Water-Resources Investigations, book 3, chap. C3, 66 p.

Runkel, R.L., Crawford, C.G., and Cohn, T.A., 2004, Load Estimator (LOADEST): A FORTRAN Program for Estimating Constituent Loads in Streams and Rivers: U.S. Geological Survey Techniques and Methods Book 4, Chapter A5, 69 p.

Shreve, E.A. and Downs , A.C., 2005, Quality-Assurance Plan for the analysis of fluvial sediment by the U.S. Geological Survey Kentucky Water Science Center Sediment Laboratory:1230, 28 p.

U.S. Geological Survey, variously dated, National field manual for the collection of water-quality data: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chaps. A1-A9, available online at http://pubs.water.usgs.gov/twri9A.

Vermont Department of Environmental Conservation and New York State Department of Environmental Conservation, 2002, Lake Champlain Phosphorus TMDL, September 25, 2002, Waterbury, Vermont and Albany, New York.