Lakes Rank Process

Flow Chart
Calculate an individual lake score
Calculate a watershed or subwatershed lakes rank

Flow Chart

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Calculate an individual lake score

The lakes evaluation as a component of the watershed ranking is based on the lakes´ sensitivity to phosphorus loading. A series of yes/no questions help determine the presence of water resource problems and /or threats and the probability of a positive response to nonpoint source controls.

Step 1: Is the lake classified based on phosphorus sensitivity as 1A or as an ORW in NR102?

If NO, it is not a 1A or ORW lake, go to step 2

If Yes, it is a 1A or ORW lake, ask: is the water quality in this lake "threatened"?

A "phosphorus-threatened lake" is one which is both:

1. expected to respond to either an incresae or decrease in phosphorus loading (defined as Class I of the phosphorus sensitivity classification) and
2. the watershed is either already developed or has a high potential for development in the future.

If the answer is YES, the lake´s water quality is "threatened" and it is ranked high.

If the answer is NO, the lake´s water quality is "not threatened" and it is ranked low.

Step 2: Is the lake classified as 1B or 2A?

If the answer is NO, go to step 3.

If the answer is YES, ask: does it have a documented water resource problem and/or threat related to nonpoint source pollution?

Examples of water resource problems due to increases in nutrient and sediment loading include: fish kills, poor water quality, toxic algae, beach closings, endangered resources or lake of species diversity in benthic organisms, phytoplankton, zooplankton, and aquatic plants.

Examples of NPS-related threats include habitat threatened by low dissolved oxygen levels or an increase in nutrient and/or sediment loadings.

If the answer is YES, document the problem and/or threat. Continue to the next question.

Does the lake have the potential for positive response to NPS control measures and/or will the water quality be protected by implementation of NPS control measures?

The potential for response and/or protection implies that the NPS controls will prevent further degradation of the water quality, therefore protecting and maintaining the resource value of the lake. The lake will not age as rapidly once the NPS control is in place, but at the same time this lake will not become a Class 1A or outstanding resource water. Potential response does not imply that all lakes will support two-storied fisheries or become swimming pools. Implementation of best management practices must maintain the water quality at its current level or improve it.

If the answer is NO, the lake receives a low rating (0 points). Provide statements supporting this position.

If the answer is YES, the lake receives a high rating (10 points). Provide statements supporting this position.

Step 3. Is the lake a high resource or high recreational use lake?

High resource lakes include valuable shallow lakes, large wetlands or bogs which provide habitat for waterfowl, wildlife, and/or fish.

If this is a high resource lake, the response to any of the following questions should be yes:

• Is the ecosystem unique to the region or district? Describe.
• Are there endangered species in the system? Identify.
• Is there an active fish management and/or wildlife management program?

If the lake is a high recreation lake, it must have adequate public access and the response to any of the following questions should be yes:

• Is this resource within a state or county park system?
• Do we have an investment in this resource? Examples include fish stocking programs and waterfowl production areas.
• Is the lake near a large population center?

If the answer is NO, the lake is not "valuable" as either a high resource or high recreational lake. It receives a low rating.

If the answer is YES, ask: does the lake have a documented water resource problem and/or threat related to NPS pollution?

Examples of water resources problems due to increases in nutrient and sediment laoding include: fish kills, poor water quality, toxic algae, beach closings, endangered resources or lake of species diversity in benthic organisms, phytoplankton, zooplankton, and aquatic plants.

Examples of NPS-related threats include habitat threatened by low dissolved oxygen levels or an increase in nutrient and/or sediment loadings.

If the answer is NO, the lake receives a low rating.

If the answer is YES, document the problem and/or threat and continue to next question.

Does the lake have the potential for positive response to NPS control measures and/or will the water quality be protected by implementation of NPS control measures? (See Step 2 above).

If the answer is NO, the lake receives a low rating. Provide statements supporting this decision.

If the answer is YES, the lake receives a medium rating. Provide statements supporting this decision.

If the answer is YES, and there is enough data to show the lake system can benefit from NPS controls through modeling, then the lake receives a high rating. Provide documentation of this decision. Download Worksheet for Lakes Ranking Score in Microsoft Word or PDF.

Calculate a Watershed Lake Rank

1. Follow steps for calculating individual lake scores in the previous section for all lakes in your watershed or subwatershed area. You will end up with numeric scores for each lake.
2. Calculate an overall watershed or subwatershed lake score, which will then translate into an overall lake ranking for that area. To do so, follow the directions below.
3. To receive a watershed lake rating, you must have data for at least 50 acres in the watershed or subwatershed to calculate a score. To determine the score, you calculate a weighted mean based on total lake acres. Each lake receives a rating. Lakes with no data or inadequate data receive zero points.

Example

A watershed with 3,900 acres of lake area of which 2,000 acres ranked high, 1,500 ranked medium and 300 acres ranked low and had 100 acres of inadequate data would be calculated as:
(2,000*10)+
(1,500*5)+
(300*0)+
(100*0)= 27,000 divided by 3,900 acres = 7 points.

Seven points are awarded for the lakes in this watershed. Go to Overall Watershed Ranking