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LakeQuality
A

Sandhill Lake

Polk County, WisconsinOligotrophic

Sandhill Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Polk County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI value of 38 puts Sandhill Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Among the 77 graded lakes in Polk County, Sandhill Lake sits at rank 27, above the county median.

Sandhill Lake has no invasive species recorded in Wisconsin state databases as of 2023, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Sandhill Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.

Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2023-09-11. Grade methodology: LakeGrade methodology.

Swimming Safety

Excellent for swimming, crystal clear water with minimal algae

Water Quality Grade: A, Excellent

Crystal clear, you can see 27.1 ft down. Phosphorus level: 19.2 µg/L. Trophic State Index: 38.

MetricValueGrade
Water Clarity (Secchi Depth)27.1 ftA
Phosphorus19.2 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)38Oligotrophic

Low nutrients, clear water, excellent for swimming

Water Quality Trend: Declining

Based on 2 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Declining-1.25 m/yr2
Phosphorus Declining+2.2 µg/L/yr2
See year-by-year chart →

Location

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County Ranking

Ranked #27 of 77 lakes in Polk County

Nearby Lakes in Polk County

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2023-09-11

Monitoring stations: 2