Ten Things You Might Not Know About Water Resources in Washington County


  1. There are LOTS of lakes. According to the Washington Conservation District, there are between 175 and 180 lakes in Washington County, though many of these could be classified as wetlands or basins. The Minnesota Department of Natural Resources (MN DNR) lists 252 lakes in Washington County.
  2. There are trout streams. There are eight trout streams in Washington County, six of which are included on the MN DNR “Designated Trout Stream” list. Brown’s Creek, which originates near Withrow and meets the St. Croix River just north of Stillwater, is stocked annually with yearling brown trout.
  3. The St. Croix River was one of the first eight rivers to be designated by the National Wild and Scenic Rivers Act in 1968. The act was created to “preserve certain rivers with outstanding natural, cultural, and recreational values in a free-flowing condition for the enjoyment of present and future generations.”
  4. Some lakes are healthy but others are in trouble. The Metropolitan Council uses lake monitoring data to create an annual report card for the Twin Cities area. Of the 71 lakes in Washington County included in this report card, ten received an “A” in 2012 and eight received an “F.” Forty-four lakes in Washington County are currently listed as impaired by the Minnesota Pollution Control Agency (MPCA) due to excess phosphorus (which causes algae blooms), unsafe levels of mercury in fish tissue, or chlorides from road salt.
  5. Some streams are in trouble too. Portions of Brown’s Creek, as well as Hardwood and Clearwater Creeks in Hugo, are unable to support aquatic life. In addition, several streams in the county, including Brown’s Creek, Perro Creek in Bayport, and Trout Brook and Kelle’s Creek in Afton are impaired for e. coli, which can pose a health risk for people wading or swimming in these streams.
  6. But…many lakes are getting better. Three lakes in Washington County have been “delisted” by the MPCA because they are now meeting water quality standards. These include Tanners Lake in Oakdale (listed in 2002 for excess nutrients, delisted in 2004; the lake still has a mercury impairment), Sunset Lake in Hugo (listed in 2002, delisted in 2008), and Lake McKusick in Stillwater (listed in 2006, delisted in 2012). Carver Lake and Battle Creek Lakes in Woodbury will be delisted for excess nutrients this year, though the MPCA now plans to list both for excess chloride.
  7. Groundwater provides 100% of the drinking water in Washington County.
  8. Washington County is divided into five distinct “geomorphic regions.” The St. Croix Moraine runs diagonally across the county and includes areas of rolling hills and ridges with many lakes. There are deep glacial sediment deposits over the bedrock in this region and most surface water either infiltrates into the ground or runs to closed depressions. The Glacial Lake Hugo Plain in the northwestern portion of the county is flatter, with more wetlands and shallow lakes. In south-central Washington County, the Lake Elmo – Cottage Grove Outwash Plain is gently rolling with shallow depressions and sandy outwash deposits. The Denmark Dissected Plain in southeastern Washington County was never covered by glaciers and now has streams, but very few lakes. Finally, the St. Croix and Mississippi River Terraces include flat areas formed by sediment deposited from glacial rivers, which were much wider than the rivers are today. (For a map, see the draft Washington County Groundwater Plan, pg. 88.)
  9. There are eight governmental watershed management organizations in Washington County. Each is governed by a board of local citizens; they establish rules and implement projects to prevent flooding and protect surface water resources.
  10. Surface and groundwater are connected. Many lakes and streams in the county, such as Square Lake and Valley Creek, are fed by groundwater resources. There are also recharge areas in Washington County where water from wetlands, lakes and basins soaks into the ground and recharges aquifers.