Fish and Aquatic Life
All of the stream in Waukesha County.
Author Aquatic Biologist
Mason creek originates in section 6 of Merton Township at the confluence of its east and west branches. These branches begin in Erin Township (Washington County) and are extensively ditched for agricultural drainage. The east branch is about one mile long, the west branch about two miles. The mainstem is 5.2 miles, has a relatively shallow gradient (6-7 feet per mile) and empties directly into North Lake. Historically, Mason Creek supported a brook trout fishery. Brook trout are found in Mason Creek today but their distribution fluctuates.
The west branch of Mason Creek experiences low dissolved oxygen concentrations (below 6 ppm; saturation 54-67 %), turbid water, siltation of substrate, and temperatures up to 75 degrees Fahrenheit. In the east branch, water temperature and dissolved oxygen concentrations are considered excellent for trout. A gravel substrate is present and could be suitable for trout reproduction.
The mainstem near the confluence of the east and west branches has good water quality for brook trout. Fish collections have included over 50 brook trout; forage fish on the other hand are dominated by pollution-tolerant species. In 2000, a four-mile stretch of the east branch and main stem of Mason Creek was classified as a Class I trout stream.
Upstream of County Trunk Highway CW, dissolved oxygen concentration, flows and cover are excellent for trout, but high temperatures (74 F) and silted substrate may be limiting trout populations. A recent fish collection showed only 12 brook trout, a forage fish population dominated by types of pollution tolerant fish, and one intolerant species (pearl dace).
Between 1973 and 1983, WDNR water resources managers extensively monitored the lower mainstem of Mason Creek at Shore Drive (just below County Trunk Hwy. CW); and at Krebster Road and County Trunk EC (above North Lake). Though dissolved oxygen concentrations ranged from 7.0 to 10 ppm, water temperatures were considered marginal for supporting trout. Phosphorus concentration ranged from 0.02 to 0.99 ppm. Gravel substrate was found at the three stations, but significant siltation was also noted.
Fish collections were conducted in the lower mainstem of Mason Creek in 1975, 1981 and 1983. In 1975, fish were collected at County Trunk Hwy. EC representing 14 species. Pollution-intolerant forage species dominated the fish community. The slender madtom, an state endangered catfish, was also found at this site. During 1981, the entire lower section of the mainstem was surveyed. No brook trout were found, but juvenile smallmouth and largemouth bass, hornyhead chub, rainbow darters and central stonerollers existed. In 1983, collections at County Trunk Highway EC found 13 forage species, with nine pollution-tolerant species.
Bacteriological sampling conducted at the County EC bridge showed counts for a type of bacteria (MFFC) ranging from <10 per 100 ml to 11,000 per 100 ml. About 40 percent of the samples exceeded 400 MFFC per 100 ml, the state water quality standard.
Author Aquatic Biologist
The 2018 assessments of Mason Creek (miles 0-4.11) showed continued impairment by temperature; new temperature sample data exceeded the 2018 WisCALM listing criteria for the Fish and Aquatic Life use. Based on the most updated information, no change in the existing impaired waters listing was needed.
Author Ashley Beranek
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.
Citizen-Based Stream Monitoring
Collect chemical, physical, and/or biological water quality data to assess the current overall stream health. The data can inform management decisions and may be used to identify impaired waters for biennial lists.
Monitor Water Quality or Sediment
2013 TP: "May Meet". AU: 11498. Station 10038441. Miles 0 - 4.11. Potential TP delisting in 2020.
Monitor Water Quality or Sediment
Category 4A. Confirmed with new temperature data. 2018 TP Results: May Meet. Station: 10038441. AU: 11498.
Monitor Targeted Area
Mason Creek Planning Program The North Lake Management District will acquire data on Mason Creek channel width, depth, sinuosity and length, habitat descriptors, biological and chemical water quality and input into DNR\2019s stream and lake monitoring program. The project deliverables include the following: 1) A copy of the completed plan which will identify strategic land and water resource management actions, specific interventions, such as streambank stabilization, buffer implementation and wetland restoration. 2) Results of an informational hearing.
The purpose of the project is to monitor and evaluate portions of Mason Creek and its tributaries in Waukesha and Washington Counties. Mason Creek is currently 303d listed for pollutants including total phosphorus and sediment/total suspended solids, with impairments including low DO, degraded habitat and elevated Temperatures and yet it is still listed as a Class I Trout stream. It is also part of the Rock River TMDL area.
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 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
|WBIC||Official Waterbody Name||Station ID||Station Name||Earliest Fieldwork Date||Latest Fieldwork Date||View Station||View Data|
Mason Creek is located in the Oconomowoc River watershed which is 130.86 mi². Land use in the watershed is primarily agricultural (24.90%), forest (19.70%) and a mix of wetland (16.90%) and other uses (38.40%). This watershed has 136.99 stream miles, 2,858.66 lake acres and 11,105.19 wetland acres.
Nonpoint Source Characteristics
This watershed is ranked Not Available for runoff impacts on streams, Not Available for runoff impacts on lakes and High for runoff impacts on groundwater and therefore has an overall rank of High. This value can be used in ranking the watershed or individual waterbodies for grant funding under state and county programs.However, all waters are affected by diffuse pollutant sources regardless of initial water quality. Applications for specific runoff projects under state or county grant programs may be pursued. For more information, go to surface water program grants.