Ranch Lake
Oconto County, WisconsinMesotrophic
Ranch Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Oconto County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.
The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. A maximum depth of 44 ft puts Ranch Lake in the middle of Wisconsin's depth distribution. Ranch Lake is small — 52 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Ranch Lake ranks 27 of 62 in Oconto County — solidly in the upper half of the local distribution.
Ranch Lake has at least one documented invasive species (Purple Loosestrife), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. Bass fishing is part of the appeal: the species list runs to 3, anchored by largemouth and/or smallmouth bass. Public access is available — the lake is on the Wisconsin DNR public-access list. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-08-06. Grade methodology: LakeGrade methodology.
Watch Ranch Lake water quality
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Good clarity, visible to about 12.5 ft. Phosphorus level: 14.4 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.5 ft | B |
| Phosphorus | 14.4 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 44 ft |
| Surface Area | 52 acres |
| Public Access | Yes |
Fish Species
Click a species to see every graded lake where it is documented.
→ Best fishing times for Ranch Lake (14-day solunar calendar)
→ Is it safe to eat fish from Ranch Lake? (mercury & PFAS guide)
→ Ranch Lake fishing regulations (limits, seasons, special rules)
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +1.407 m/yr | 6 |
| Phosphorus | ↑ Improving | -2.45 µg/L/yr | 3 |
Recreation & Access
Location
County Ranking
Ranked #27 of 62 lakes in Oconto County
Nearby Lakes in Oconto County
More Wisconsin Lake Rankings
State Parks Near Ranch Lake
Other Grade A Lakes in Wisconsin
Washington County · Clarity: 11.8 ft
Washington County · Clarity: 12.6 ft
Walworth County · Clarity: 11 ft
Waukesha County · Clarity: 11.3 ft
Walworth County · Clarity: 20.2 ft
Kenosha County · Clarity: 10 ft
Mesotrophic Lakes in Wisconsin
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1987. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Ranch Lake covering fish populations, stocking, water quality, and management. 4 reports on file.
- 2018First South Branch Oconto River trend survey, 2018Fisheries Survey · WI DNR · 2018 (PDF)
- 2017South Branch Oconto River information sheet 2017Fisheries Survey · WI DNR · 2017 (PDF)
- 2016First South Branch Oconto River fisheries information sheet 2016Fisheries Survey · WI DNR · 2016 (PDF)
- 2015South Branch Oconto River fisheries information sheet 2015Fisheries Survey · WI DNR · 2015 (PDF)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Fish and recreation data from Wisconsin DNR Lakes
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2025-08-06
Monitoring stations: 1
Where to stay near Ranch Lake
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