Enhancing and Protecting Water Quality

brown trout in the water

The quality of the water in our watershed is vital to the 9 million New York State residents who depend on it for consumption, and to the people living in the watershed who enjoy and depend on healthy streams. Water quality benefits the local economy through revenues generated by fishing, whitewater, and other stream-based recreational activities. Water quality is vital for the plants and animals that share our watershed, and is part of the natural beauty of this place.

While overall water quality in the Ashokan Watershed is good, the major water quality concern affecting drinking water is turbidity. Secondary water quality issues are nutrient enrichment, invasive species, habitat alteration, and the potential loss of cold water as a result of climate change. There may be impacts from pollutants that originate in streamside areas, such as fuel oil tanks, septic systems, and runoff from roads.

Turbidity is the cloudiness or haziness of water resulting from sediment suspended in the water column. In the Ashokan watershed, suspended sediments are mostly clay and silt particles that enter the stream through eroding stream channels and hillslopes. Turbidity is what causes our watershed’s streams to run a reddish-brown or “chocolate” color after heavy rainstorms. The clay particles can harbor viruses and bacteria making it more difficult to effectively treat the water for drinking use. If turbidity levels are elevated for long periods of time, it may adversely affect local wildlife such as fish. Localized deposition of the silt particles can clog the spaces between rocks in streambeds and reduce habitat for aquatic insects.

Stream Corridor Assessments

AWSMP addresses water quality issues by performing stream corridor assessment to diagnose stream conditions and identify erosion hazards and water quality impairments. Stream assessments support the development of stream management plans and provide the data necessary to complete stream restoration and stabilization projects.

Geologic sources of turbidity exposed by eroding stream banks are mapped and catalogued in computer databases. This information is used to understand the distribution and nature of turbidity sources. The results of data analysis are used to prioritize further assessment or recommend treatment options. AWSMP sponsors research by the U.S. Geological Survey (USGS) to monitor turbidity and suspended sediment loading in several of the major streams of the watershed. We are also working with the NYS Geological Survey to map the glacial geology of the watershed.

A major source of turbidity in today’s streams is the legacy of sediment left behind during the Ice Age. Sediment deposits are subsequently disturbed by eroding and unstable stream channels and hillslopes. While erosion and deposition are natural processes operating over large timescales, human development within stream corridors can exacerbate erosion and introduce contaminants to the system. The application of best management practices in settled areas can help to mitigate these effects.

Restoration and Stabilization Projects

After sites with chronic sources of turbidity are identified through assessments, different levels of management intervention are evaluated. The options for stream management range from doing nothing (where instability is causing no problems), to allowing natural processes to resolve the problem, to assisted self-recovery and full restoration. In some reaches, minor levels of management intervention can resolve an issue, such as riparian plantings, slight bank grading, or the construction of isolated structures. Where full restoration of steam function and capacity is required, management may include extensive reshaping of the channel’s form. Engineering survey, design and construction work are required for this level of intervention.

Restoration and stabilization projects are designed to reduce the long-term, chronic introduction of fine sediment sources to the stream. AWSMP provides professional services and funding for the design and implementation of these projects, working in cooperation with landowners and municipalities. For more information on completed and ongoing restoration and stabilization projects, see the Projects & Funding section.