Lake Aesthetic and User Recreation Index (LAURI)

The lakes are scored for water color, odor, debris, and physical condition based on an assessments done from shore, dock, or boat, Table 1-1. Higher numbers indicate better aesthetics. Originally, individual color, odor, and debris scores were averaged over the season. The scoring was refined in 2017 to use the lowest of the three scores, rather than an average of the three, to better represent the impact of trash on lake aesthetics. The scoring was refined again in 2023 to include the physical condition of the water to better represent how algae impacts aesthetics. Aesthetics can be difficult to evaluate because they are qualitative and subjective from one person to the next.

Table 1-1.  Scoring for the aesthetic portion of LAURI.

Color	Score
Clear	10
Light brown or green	8
Bright green	5
Milky white	4
Brown, reddish, or purple	2
Gray or black	0

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Odor	Score
None/Natural	10
Musty – faint	8
Musty – strong	6
Sewage, fishy, or garbage – faint	5
Sewage, fishy, or garbage – strong	2
Anaerobic or septic	0

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Debris	Score
None	10
Natural	9
Foam	8
Piles of milfoil (>3)	7
Fixed trash (>3)	4
Floating trash (>3)	3
Dead fish (>5)	2
Green scum	2
Oil film	1
Sewage solids	0

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Physical Condition	Score
Crystal Clear	10
Some algae	9
Definite algae	6
High algae	4
Severe bloom	2

Water clarity, a simple and cost effective tool, measures how suspended particles and algae impact a lake’s quality. The average Secchi transparency reading from all the data collected during the growing season, May-September, is used to calculate the water clarity score. The lakes are scored differently based on whether they are considered shallow or deep by criteria developed by the Minnesota Pollution Control Agency (MPCA). Bde Maka Ska, Cedar, Harriet, and Wirth are considered deep lakes. Loring, Isles, Hiawatha, Nokomis, and Powderhorn are considered shallow lakes. A shallow lake is defined as 80% littoral (< 15 feet deep). Higher scores indicate clearer water.  LAURI scoring is shown below in Table 1-2.

Table 1-2.  Scoring for the water clarity portion of LAURI.

Secchi Depth (m)	Deep Lake Score	Shallow Lake Score
0-0.5	1	2
0.6-1	2	4
1.1-1.5	3	6
1.6-2.0	4	8
2.1-2.5	5	10
2.6-3.0	6	10
3.1-3.5	7	10
3.6-4.0	8	10
4.1-4.5	9	10
>4.6	10	10

Existing beach monitoring program data were used to determine whether a lake meets guidelines for swimming. E. coli, the indicator recommended by the Environmental Protection Agency (EPA), was measured at every public beach in the park system. Beaches are located on Bde Maka Ska, Cedar, Harriet, Hiawatha, Nokomis, and Wirth Lakes. The scoring used the season long geometric mean from the beach monitoring program for each lake, see Table 1-3. At lakes with more than one beach, beaches were averaged to create one score. This metric was chosen because EPA and Minnesota guidelines state that beaches should not exceed a geometric mean of 126 organisms per 100 mL during a 30-day time period. Lower numbers of organisms indicate less risk of illnesses for lake users. The scoring for the public health index was refined in 2019 to address the possibility of an outbreak that may not show up in the regular monitoring data.

Table 1-3.  Scoring for the public health portion of LAURI. The geometric mean of E. coli concentrations for the year is used to determine the score. If more than one beach is present at a lake, the average of the geometric means is used.

E. coli bacteria MPN/100 mL	Score
<2 (Not Detected)	10
2- 10	9
11-20	8
21-35	7
36-50	6
51-65	5
66-80	4
81-100	3
101-125	2
>126	1

 

 

 

 

 

 

 

 

 

 

*The value used is the running geometric mean for the year, averaged for all the beaches on a lake.

LAURI habitat scoring uses the most recent plant survey information available. Macrophyte surveys used in the assessment are conducted by MPRB staff and scoring is based on presence of aquatic plants (macrophytes), density of plants, and amount of coverage, see Table 1-4. The more species, density, and coverage of aquatic plants observed, the higher the habitat quality index was scored. Fish surveys were conducted by MNDNR and more points are awarded for a higher number of fish species. The score from the aquatic plant and fish surveys are averaged for the LAURI.

Table 1-4. Scoring for the habitat portion of LAURI.

# Macrophyte Species	Score
0	0
1-2	3
2-4	6
5-6	8
>6	10

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Density	Score
Low	0
Low-Medium	3
Medium	6
Medium-High	8
High	10

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Coverage > 15 ft	Score
0 – 25%	2
25 – 50%	4
50 – 75%	7
75 – 100%	10

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# Fish species	Score
≤6	2
7-8	4
9-11	6
12-14	8
≥15	10

The lakes are also scored for the quantity of recreational access points to the water. The recreational score considers the number of fishing docks or stones, beaches, boat launches, inter-lake connections, canoe racks, boat rentals, picnic areas, boardwalks, and concessions at a lake, see Table 1-5. While aquatic plants are a necessary part of a healthy lake ecosystem, they can also interfere with recreational uses of the lake; therefore, lakes also receive points for receiving aquatic plant management.

Table 1-5.  Scoring for the recreational access portion of LAURI.

Total number of recreational opportunities + aquatic plant management	Score
0	1
1	2
2	3
3	4
4	5
5	6
6	7
7-8	8
9-10	9
>10	10