Note: This plan has not been adopted by City Council; it is for informational purpose only.
Located just minutes from downtown, Lake Mitchell is a man-made reservoir that was built in 1928 to serve as a drinking water supply and recreation center for the City of Mitchell and surrounding area. While used and enjoyed by generations of families over the years, a steady decline in water quality has also occurred over time. A water quality assessment study was completed in 1997 and has since resulted in implementation of a project designed to reduce both the sediment and nutrients which enter the lake. While no longer Mitchell’s source for drinking water, Lake Mitchell continues to provide area residents and visitors with a variety of outdoor recreational opportunities.
What Is a Watershed?
A watershed can be described as a geographic area of land that drains water to a common or shared point such as a lake, river, or stream. Wherever you live, you are in a watershed, and the activities that occur within a watershed can and do impact, both positively and negatively, downstream conditions. While lakes naturally age over a long period of time, the process can be accelerated significantly as a result of human activities (called cultural eutrophication). Eutrophic lakes are rich in nutrients and usually become highly productive for plant growth. Eutrophic lakes can become green with algae or choked with aquatic plants. The main nutrient that drives eutrophication in most surface waters is phosphorus.
Firesteel/Lake Mitchell Watershed Project
The Firesteel/Lake Mitchell Watershed Project is designed to reduce the nutrient load entering Lake Mitchell from Firesteel Creek by installing Best Management Practices (BMPs) throughout the watershed. The goal was to reduce the phosphorus concentration by 50% by 2015 from its pre-assessment study levels in order to decrease lake productivity and ease the intensity and duration of the lake's annual algae blooms. Information dissemination and educational outreach has also played an important role in the continuing effort to reach this goal. Efforts continue as the city pursues avenues for limiting phosphorus-laden run-off from both upstream of and surrounding Lake Mitchell.
Best Management Practices (BMPs)
BMPs are methods that have been determined to be the most effective and practical means of preventing or reducing the movement of sediment, nutrients, or other pollutants from the land to surface or ground water. While most BMPs are targeted towards rural resource concerns, urban residents also share a responsibility to do their part towards improving and protecting the water quality of Lake Mitchell. Some of the BMPs that have been applied within the Firesteel Creek Watershed Project include the following:
1) Riparian Areas
Riparian areas can be thought of as land situated along the bank of a stream or other body of water where vegetation is strongly influenced by the presence of water. These zones are typically the most environmentally sensitive areas of a watershed and are an essential part of a healthy stream.
Loss of riparian vegetation by either crop production or overgrazing can cause stream bank erosion, decrease water infiltration, and increase the amount of runoff and nutrients entering the water. By buffering these riparian zones, we can improve water quality by trapping sediment, filtering nutrients such as nitrogen and phosphorus before they reach the surface water, and providing valuable habitat and corridors for fish and wildlife.
2) Feedlot Improvements & Nutrient Management Planning
Runoff from animal feeding operations can contain extremely large loads of nutrients and if not properly collected, they can degrade surface water quality. A Comprehensive Nutrient Management Plan (CNMP) is an overall conservation system that addresses all aspects of an animal feeding operation, from manure and wastewater handling and storage, to proper land application and record keeping.
3) Urban Lawns & Landscapes
An often overlooked but equally important source of phosphorus can come from modern-day urban landscapes. Storm water runoff will pick up nutrients from lawn fertilizers, grass clippings, and pet waste just as easily as it can from pastures and fields. Here are a few tips for urban residents to help protect your lake:
- Soil test your lawn every 3 - 5 years. If soils are high in phosphorus, use a low- or phosphate-free fertilizer. Soil testing information and fertilizer recommendations are available at your local extension office. The majority of soils in our region already contain all the phosphorus an established lawn will need, so adding more is rarely ever needed.
- Before making fertilizer applications, check the weather forecast. Make applications when a heavy rain isn't likely to wash the fertilizer directly into a lake or storm sewer.
- Keep fertilizers on the lawn and off paved surfaces. Use a broom to sweep up excess fertilizer on paved surfaces and reapply to lawn.
- Control soil erosion around homes. Bare soil is easily washed away with rain, carrying phosphorus with it. Keep soil covered with vegetation or mulch.
- Keep grass clippings and leaves out of the lake. Leaves and grass can be major sources of phosphorus to lakes as they break down.
- Consider leaving a "buffer zone" - strip of unmanaged grasses or natural vegetation - to grow along the shoreline. This unfertilized vegetation will remove and retain some of the nutrients that would otherwise enter the lake.
- Pick up pet waste properly. Pet waste contains harmful bacteria as well as nutrients.