Overview

Lake Onalaska is a shallow headwater backwater of the Mississippi River that covers over eight thousand acres. The lake was last monitored in 2010, but its general condition remains unknown.

Date  2011

Author   Aquatic Biologist

General Condition

This 7,700 acre lake is bounded by Lock and Dam 7 on the south, Wisconsin on the east, the Black River delta to the north, and barrier islands which define the navigation channel of the Mississippi River on the west. The lake receives flow from both the Mississippi and Black Rivers. Halfway Creek also discharges to the northeastern part of the lake. The U.S. Corp of Engineers restricted the Mississippi River inflow to the lake to help maintain the navigation channel. Lake Onalaska management issues are dealt with by the Mississippi-Lower St. Croix Team within the WDNR and several federal agencies.

The northeastern shoreline of Lake Onalaska contains many homes. The nearshore area of the lake was historically dredged to move logs easily from the mouth of the Black River to the City of La Crosse. Dredging has not occurred in this portion of the lake for over 20 years. This Brice Prairie channel has become more shallow over the years and surface water flows have changed due to sedimentation patterns. Excessive algae blooms occur in this channel during the summer months (Endris). A winter survey of the Brice Prairie channel in February 1997 revealed elevated levels of nitrate plus nitrite nitrogen. This channel is influenced by groundwater inflows which result in relatively warm water conditions in this channel during the winter months. The source of these nutrients may be originating from several sources including the Onalaska landfill, septic systems and manure and fertilizer applications on nearby agricultural fields (Sullivan). The Town of Onalaska, Onalaska Lake District, and major industries in the Brice Prairie area should re-examine sewering all or portions of the Brice Prairie. Lakeside residents would like to see some improvement to the water quality conditions in this channel.

One aquatic plant which is vital to the canvasback duck is Vallisneria sp., also known as wild celery. Lake Onalaska at one time contained vast quantities of this plant species and was an important migration stop for the canvasback. As the worldwide population of canvasbacks shrank drastically, the Mississippi River flyway contained the last stable population. When the decline of the wild celery populations occurred after a number of drought years (1987-89), many were concerned about the demise of the canvasbacks. A systemwide reduction of plant species occurred at the same time. It is theorized that low flows during the drought years reduced the nitrogen available to submergent aquatic plants via lower concentrations and competition with algae for nitrogen and light. Several years of low flow with reduced available nutrients stressed plants enough to cause their decline. Subsequent normal flow years produced higher suspended sediment concentrations than expected, which reduced light penetration. For the submergent aquatic plants to rebound and thrive, proper amount of nutrients, light penetration, flow, and other factors must exist. The aquatic plant community of Lake Onalaska and the Upper Mississippi River has shown improvements in the extent of the submergent aquatic plant community since the drought years between 1987-89. Fluctuation of plant populations occur from year to year, but three consecutive drought years resulted in more severe conditions and a longer recovery time for the aquatic plants (Sullivan, 1999).

Three islands were constructed in Lake Onalaska in 1989 to reduce wave re-suspension of fine sediments, provide predator free nesting and loafing sites for waterfowl, and aid in the re-establishment of aquatic vegetation beds. Each crescent shaped island is approximately 3.5 acres in size and provides areas of diverse lake habitat that didn't previously exist within the shallow lake. Signs of increasing use by nesting waterfowl have been noted on the relatively predator free islands. An increase of aquatic vegetation has been documented throughout the lake. The protected areas downstream of the islands may be experiencing an accelerated rate of re-vegetation (Janvrin). Other areas of the river are also seeing an improvement in aquatic vegetation.

Date  2000

Author   Aquatic Biologist

Condition

Wisconsin has over 84,000 miles of streams, 15,000 lakes and milllions of acres of wetlands. Assessing the condition of this vast amount of water is challenging. The state's water monitoring program uses a media-based, cross-program approach to analyze water condition. An updated monitoring strategy (2015-2020) is now available. Compliance with Clean Water Act fishable, swimmable standards are located in the Executive Summary of Water Condition in 2018. See also the 'monitoring and projects' tab.

Reports

Management Goals

Wisconsin's Water Quality Standards provide qualitative and quantitative goals for waters that are protective of Fishable, Swimmable conditions [Learn more]. Waters that do not meet water quality standards are considered impaired and restoration actions are planned and carried out until the water is once again fishable and swimmable

Management goals can include creation or implementation of a Total Maximum Daily Load analysis, a Nine Key Element Plan, or other restoration work, education and outreach and more. If specific recommendations exist for this water, they will be displayed below online.

Monitoring

Monitoring the condition of a river, stream, or lake includes gathering physical, chemical, biological, and habitat data. Comprehensive studies often gather all these parameters in great detail, while lighter assessment events will involve sampling physical, chemical and biological data such as macroinvertebrates. Aquatic macroinvertebrates and fish communities integrate watershed or catchment condition, providing great insight into overall ecosystem health. Chemical and habitat parameters tell researchers more about human induced problems including contaminated runoff, point source dischargers, or habitat issues that foster or limit the potential of aquatic communities to thrive in a given area. Wisconsin's Water Monitoring Strategy was recenty updated.

Grants and Management Projects

Monitoring Projects

Watershed Characteristics

Lake Onalaska is located in the Lower La Crosse River watershed which is 145.46 mi². Land use in the watershed is primarily forest (42.30%), agricultural (14.80%) and a mix of urban (10.30%) and other uses (32.50%). This watershed has 295.20 stream miles, 1,187.12 lake acres and 5,641.64 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Medium for runoff impacts on streams, Not Ranked for runoff impacts on lakes and Low for runoff impacts on groundwater and therefore has an overall rank of Low. This value can be used in ranking the watershed or individual waterbodies for grant funding under state and county programs.This water is ranked High Lake for individual Lakes based on runoff problems and the likelihood of success from project implementation.