WHAF Lake Health Scores are available for a selected set of nearly 3,000 monitored lakes across Minnesota. Lake Health Scores are scaled 0 (least healthy) to 100 (best health) and are symbolized with a brown to blue color ramp for low to high health scores. These health scores are available interactively within the WHAF for Lakes application.
What does the lake health score mean?
The Lake Health Score is a starting point to investigate a lake's current health. Each score is a snapshot in time that 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.
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.
Creating a Lake Health Score
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The diagram shows of the hierarchy of inputs into each Lake Health Score. The arrows show how scoring metrics are combined to calculate a suite of index scores and the index scores are combined into three component scores. The component scores are then combined into a mean overall Lake Health Score. While Lake Health is scored for three different components, the underlying metrics for the hydrology component represent aspects of geomorphology and connectivity, maintaining the Health Assessment Framework use of five ecological components to evaluate system health.
For all Lake Score calculations:
- When an index or component score is not available (NA), the Health Score or the Component Score will be calculated based on the remaining available score values.
- Lake health scores are standardized across the state by comparing each lake to a healthy lake with similar physical characteristics.
Lake Health Score - Combined
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 for assessing system health (Water Quality, Biology, Hydrology, Geomorphology, and Connectivity).
How is the Combined Lake Health Score calcuated?
The Lake Health 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). 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.
Water Quality
The quality of the water within a lake basin has a critical impact on lake health. Excess nutrients can create explosive algae growth. Turbid water can reduce light penetration and stress fish communities. Other contaminants may accumulate in fish tissue or influence their hormonal balance. Improvements to lake health must address water quality challenges present in the lake system.
How is the Water Quality Score calculated?
The Water Quality Score compares the assessment of lake nutrients and water clarity across Minnesota. This component score is calculated as an average of two index scores:
- Phosphorus Score - percent deviation of lakes' summer mean total phosphorus from their aquatic recreation goal.
- Water Clarity Score - percent deviation of lakes' last 5-year average of estimated summer water clarity from their aquatic recreation goal
Biology
Thriving animal and aquatic plant communities provide functions that are essential for the overall health of a lake. Monitoring the composition of these communities can determine whether a lake supports the expected range of aquatic life. The status of aquatic communities can help indicate the overall impact and response to lakeshed conditions.
How is the Biology Score calculated?
The Biology Score compares the health of the fish and aquatic plant communities in lakes across Minnesota. This component score is calculated as an average of two index scores:
- Fish Community Quality Score - percent deviation from the lakes’ fish index of biological integrity score from their aquatic life threshold.
- Lake Plant Community Quality Score - percent deviation from the lakes’ plant floristic quality index score from their aquatic life threshold
Hydrology (Connectivity, Geomorphology)
When the supply of water is consistent with the geomorphology of the lakeshed, the lake receives an appropriate range of water, energy, nutrients, and sediment. The presence of intact, connected natural communities in the lakeshed help provide this consistency, as well as the resilience needed to handle disturbance and return to a healthy state.
How is the Hydrology Score calculated?
The Hydrology Score (which also includes facets of Geomorphology and Connectivity) compares conditions within a lakeshed and along the lakeshore that influence water movement, risks to water quality, and habitat conditions for aquatic species across lakes in Minnesota. This component score is calculated as an average of two index scores:
- Lake Watershed Health Index - the Lake Watershed Transport Capacity Class multiplied by Percent Disturbed Land Cover in lakeshed.
- Score the Shore - a natural resources survey to estimate the amount of natural habitat in three lakeshore zones: shoreland, shoreline, and aquatic.
How can you contribute to a healthy lake?
Individual and community stewardship is necessary for the long-term health of any lake. There are many resources available for individuals to get involved in efforts to support lake health.
- Learn more about why maintaining and restoring natural shorelines is beneficial.
- Apply best management practices on shoreland properties to support lake health.
- Participate in the Score your Shore survey for lakeshore property owners to self-assess lakeshore habitat and find suggestions for lakeshore friendly actions
- Join forces with your neighbors or lake association to make a bigger impact.