Explore Watershed Lakes: Minnesota Department of Natural Resources

Lake Health

A healthy lake is one that is near its natural state. Water entering the lake has low levels of pollution. A healthy lake is protected by a natural shoreline and by investments in careful stewardship of the lake and its watershed (lakeshed).

About the Score

What is a healthy lake?

A healthy lake is one that is near its natural state. It has low levels of pollution and has a natural shoreline that protects the bank and filters runoff. It is surrounded by a landscape that delivers water and energy consistent with its self-sustaining plant and animal communities. A healthy lake can withstand changing conditions and seasonal fluctuations. Most importantly, it has a human community and society that values these resources and invests in the protection and restoration of the water, watershed, and interacting and dependent communities.

An unhealthy lake has received more disturbance than it can handle, forcing it to deviate from its natural state. The lake is out of balance with its water and nutrient input levels, impacting the health of fish and plant communities. A degraded lake is less resilient and may decline further under changing conditions.

Restoring a degraded lake back to a healthy condition is usually a lengthy, expensive, and complex challenge. In contrast, protecting a healthy lake and the surrounding land helps ensure that the ecological and economic benefits that it currently provides are likely to be sustained into the future.

How is lake health related to watershed health?

A lake's watershed (or lakeshed) is all land and surface water upstream of its outlet that contribute water to it. Lakes are influenced by the landscape characteristics and land uses within their respective lakeshed.

Lake health reflects the intensity of landscape alteration. Agriculture, forestry, transportation, industrial, and urban uses introduce contaminants that impact the health of our lakes.

Lake health is also affected by internal factors, such as lake area, depth, and diversity of nearshore habitat, and external factors, such as soils in the lakeshed, altered hydrology, lakeshed to lake size ratio, groundwater inflow, and the source and amount of surface water inflow.

It is the unique combination of these influences that determine the quality of the water and the aquatic community in a particular lake.

What do the lake health score and grade mean?

The Lake Health Score is a starting point to investigate a lake's current health. The letter grade helps compare lakes across Minnesota.

Lake Health Scores fall between a range of 0 to 100 and are graded as follows:

91 to 100 = A+
81 to 90 = A
71 to 80 = B+
61 to 70 = B
51 to 60 = C+
41 to 50 = C
31 to 40 = D+
21 to 30 = D
11 to 20 = F+
0 to 10 = F

Each score compiles several inputs and is designed to encourage investigation into what might be influencing the lake ecosystem.

Expectations for a shallow wetland lake are much different than a deep, cold northern lake. To provide context, Lake Health Scores are calculated based on the expectations for a lake of that type.

The Lake Health Score reflects both measured conditions in the lake and the level of risk from land use activities in the lakeshed.

The scores reflect inputs from each of the 5 Components that are used throughout the Watershed Health Assessment Framework (WHAF) for assessing system health (Water Quality, Biology, Hydrology, Geomorphology, and Connectivity). Learn more about the WHAF (opens in new tab).

No matter what score/grade a lake currently receives, all Minnesota lakes require stewardship actions to keep them as healthy as possible, improve lake health when there are challenges, and address existing and future emerging risks.

Lakes Included

There is currently information presented on 2,939 lakes. These lakes were included based on the presence of water chemistry (total phosphorus) and morphological data. The number of lakes included in this dataset will likely increase in the future.

How is the lake health score calculated?

The Lake Health Score uses existing measures that are regularly assessed and updated. The score represents a snapshot in time and is computed as the average of the three component scores including the Water Quality Score, the Biology Score, and the Hydrology Score (the Hydrology Score also includes facets of the Geomorphology and Connectivity components). When a component score is not available (NA), the Lake Health Score is calculated based on the remaining scored components.

Each of these component scores are themselves an average of multiple index scores which reflect different indicators of health. Lake Health Scores are on a 0 to 100 scale with scores of 100 representing the best overall health according to available inputs.

A table of scores, metrics used for scores, and other supporting data is included at the bottom of this page.

Component Input Status

Some of the inputs used to derive component scores are evaluated relative to a target value called a 'goal' or a 'threshold'.

Goals are used in deriving the index scores of Phosphorus and Water Clarity (inputs of the Water Quality Score). Fish Community Quality and Lake Plant Community Quality (inputs of the Biology Score) use established thresholds.

For each of these inputs, if a value is:

"Below (Goal or Threshold)", the condition for the lake has degraded to the point that it may not support one or more desired outcomes (e.g., water clarity quality, natural diversity of plants and animals).
"At or Above (Goal or Threshold)", the condition for the lake currently meets or exceeds the minimum criteria to support these desired outcomes.

Statuses indicating a lake is above a goal or threshold do not imply that criteria will necessarily continue to be met in the future and it is important to consider the lakes proximity to this goal or threshold.

Source Data

Watershed Health Assessment for Lakes Scores (opens in new tab).

The Lake Health Score is an average of the Water Quality, Biology, and Hydrology Lake Health Component Scores and is on a 0 to 100 scale.

Lake Health Score ():

Lake Health Grade:

Lake Health Score Major Watershed Mean ():

Lake Health Score Major Watershed Min/Max: /

Lake Health Component Scores

Water Quality Score:

Water Quality Score Major Watershed Mean: ; Min/Max: /

Biology Score:

Biology Score Major Watershed Mean: ; Min/Max: /

Hydrology Score:

Hydrology Score Major Watershed Mean: ; Min/Max: /

Component Input Status

Each component score is created by combining data inputs. Some of these data inputs have a target value labeled a 'goal' or 'threshold'. If an input value is:

"Below (Goal or Threshold)", the condition for the lake has degraded to the point that it may not support one or more desired outcomes (e.g., water clarity quality, natural diversity of plants and animals).
"At or Above (Goal or Threshold)", the condition for the lake currently meets or exceeds the minimum criteria to support these desired outcomes.

Water Quality

Phosphorus:

Water Clarity:

Biology

Fish Community Quality:

Lake Plant Community Quality:

Lake Basics

About Lake Basics

Why is this important?

Lake morphology (size, shape, and depth) determines many other lake characteristics.

For example, whether a lake is deep or shallow will change expectations for water temperature, fish and aquatic plant communities, nutrient levels, and water clarity.

What is included?

Lake Basics are included in a table below.

The littoral zone is the near shore area where sunlight penetrates all the way to the sediment and allows aquatic plants to grow. The DNR typically uses a depth of 15-ft as the extent of the littoral zone. The actual depth to which plant growth occurs will vary depending upon the clarity of the water.

A lake is a Managed Fisheries Lake if it is surveyed by DNR Fisheries.

DNR Lake Finder includes fishing regulations; location; water access sites; lake maps; lake reports on stocking, ice in/out and water quality; fish consumption; and aquatic plant surveys. Learn more about Lake Finder here.

The lakeshed acreage is the total area of land that drains to a lake.

Lake Basics

Lake Summary

Lake Metrics

Watershed Health Assessment Framework: Lakes
WHAF: Lakes

Lake Search

Lake Health

Lake Basics

Lake Basics

Lake Summary

Watershed Health Assessment Framework: LakesWHAF: Lakesmenumenu

Lake Search

Lake Health

Lake Basics

Lake Basics

Lake Summary

Watershed Health Assessment Framework: Lakes
WHAF: Lakes