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Healthy Watersheds Protection

Examples of Water Quality Assessments for Watershed Health

Aquatic ecosystems are substantially affected by the quality of their water, but also by the chemical and physical characteristics of the air, surrounding watershed soils and sediment transported through the aquatic system. EPA and states have established water quality criteria for freshwater ecosystems that address important ecological parameters. Chemical and physical parameters include:

  • concentrations of organic and inorganic chemicals, such as nutrients, trace metals and dissolved organic matter;
  • additional chemical parameters indicative of habitat suitability, such as pH and dissolved oxygen; and
  • physical parameters, including water temperature and turbidity.

Many of these parameters are dynamic and related to natural watershed hydrology. For example, dissolved oxygen fluctuations in streams are related to watershed nutrient loading, biotic activity, stream flow and temperature.

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USGS National Water Quality Assessment Program (NAWQA)  NAWQA provides an understanding of water-quality conditions and how those conditions may vary locally, regionally and nationally; whether conditions are getting better or worse over time; and how natural features and human activities affect those conditions. In the early 1990s, NAWQA began to systematically collect chemical, biological and physical water quality data from 51 study basins across the nation. Sampling has included concentration measurements for approximately 3,000 chemical constituents at 4,700 surface water monitoring locations. These data and other information are periodically synthesized to report on regional and national water quality trends and produce topical reviews of priority water quality issues.

National Lakes Assessment (NLA)  Every five years, EPA, in collaboration with states and tribes, surveys the condition of lakes, ponds and reservoirs across the nation. Its probability-based sampling scheme is intended to collect data that provide a statistically valid representation of lake condition when analyzed on either a regional or national level. Water quality data collected include concentrations of nutrients, algal toxins, pathogens and fish tissue contaminants. Results are used to report on the condition of U.S. lakes at national and regional scales. Results of the 2007 assessment are summarized in the 2007 National Lakes Assessment Report and analysis of 2012 assessment data is underway.

National Rivers and Streams Assessment (NRSA)  U.S. EPA’s NRSA program uses a random sampling design to provide regional and national estimates of the condition of rivers and streams. Physical and chemical water quality, as well as biological integrity, are assessed periodically over time to better understand the condition of the nation’s waters. Results of the 2008-09 assessment are summarized in the 2008-2009 National Rivers and Streams Assessment Draft Report and sampling for the 2013-14 assessment is underway.

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Minnesota National Lakes Assessment Project As a product of U.S. EPA’s 2007 National Lake Assessment, the Minnesota Pollution Control Agency compiled a report summarizing the water chemistry of the state’s lakes. This assessment incorporates data collected from 50 surveyed lakes and 14 reference lakes to characterize the water clarity, ion chemistry, nutrient concentrations and trophic status of Minnesota’s lakes.

Implementation of a Stream/River Probabilistic Monitoring Network for the State of Oklahoma (PDF) This assessment describes the implementation of a probabilistic monitoring plan for Oklahoma’s streams and rivers. The Oklahoma Water Resources Board intends that this monitoring plan will fill data gaps that historically have not been covered in through the state’s Beneficial Use Monitoring Program and Small-Watershed Rotating Basin Monitoring Program.

Oregon Water Quality Index Oregon Department of Environmental Quality developed a water quality index that aggregates subindex scores for water quality parameters including bacteria, biochemical oxygen demand, dissolved oxygen, ammonia and nitrate nitrogen, total phosphorus, pH, temperature and total solids using an unweighted harmonic square mean formula. The index is particularly sensitive to whichever parameter is most severely impaired.

Ohio Statewide Biological and Water Quality Monitoring and Assessment The state collects water quality data and examines and counts fish and macroinvertebrates in streams and rivers throughout the state as part of its monitoring program.

Maine Volunteer Lake Monitoring Program  The program trains citizen volunteers to collect water quality samples, assess invasive species coverage in lakes and determine overall watershed health.

Vermont Lake Score Card Vermont’s Lake Score Card allows water resource managers and citizens to more easily assess lake condition by providing monitoring data on Google Earth map.

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