Lake Sarah - Excess Nutrients: TMDL Project

Lake Sarah

Algae on Lake Sarah - Photo credit: Mr. Dvorak

Lake Sarah is a 552-acre lake located approximately 18 miles west of Minneapolis in west central Hennepin County. The lake has a maximum depth of 60 feet, mean depth of 18.2 feet, and is used extensively for fishing, boating and aesthetic viewing. The majority of the lake’s west end is within Lake Sarah Regional Park, operated by Three Rivers Park District. Lake Sarah receives runoff from a 4,608-acre predominantly agricultural watershed which contains portions of five municipalities — Greenfield, Independence, Corcoran, Loretto, and Medina. Portions of the watershed are undergoing rapid urbanization, although the majority of the new residential lots are large.

Lake Sarah receives excess nutrient loading from the watershed and from internal recycling mechanisms. The internal loading factor is especially critical in Lake Sarah because an abundant curly-leaf pondweed population provides a phosphorus pulse to the lake when it undergoes senescence in late June each year. As a result of the excessive phosphorus loading, the lake experiences nuisance algae blooms in the summer, severely restricting recreational use.

In 2006, Lake Sarah was placed on the Minnesota Pollution Control Agency’s 303(d) list of impaired waters because of excess nutrients (phosphorus). Inclusion on the 303(d) list requires completion of a Total Maximum Daily Load (TMDL) study to determine the magnitude of the impairment, identify pollutant sources, and allocate pollutant loading among the permitted and non-permitted sources in the lake’s drainage basin.

Map and location

Lake Sarah is located near the cities of Independence and Greenfield in the western Twin Cities Metro Area, Hennepin County, within the North Fork Crow River watershed in the southern portion of the Upper Mississippi River Basin.

PDF icon Upper Mississippi River Basin - Twin Cities Metropolitan Area - map

TMDL report and implementation plan

Other documents

Meetings and events

The Lake Sarah Stakeholders Committee, a group of citizens concerned about the water quality of the lake, has been meeting since 2005. Meeting information, including agendas, minutes, presentations and electronic handouts can be found in PDF document below. This document is bookmarked for ease in searching for specific meeting details. 


Contact MPCA about this project