New quality index for city lakes will provide better recreation information

On July 1, the city of Minneapolis implemented a procedure to more comprehensively measure things recreational lake users want to know. The scale is called the Lake Aesthetics and User Recreation Index (LAURI), replacing the previous Carlson's Trophic State Index (TSI).

TSI just rated ecology, LAURI also focuses on the lake's looks and potential plant infestation (think milfoil), as well as environmental quality and public health status.

Lakes will be rated as excellent, good or poor in each of the four categories.

For example, Lake Calhoun's rating, based on May-June 2005 data, is:

– Aesthetics: Excellent.

– Aquatic plants: Poor.

– Clarity: Excellent.

– Public health: Excellent.

(Ratings of other Southwest lakes were not available at press time.)

Aesthetic considerations include water color, odor and debris in the lakes. These are measured from the shore or a dock and are averaged over the year; higher numbers mean worse conditions.

While an abundance of aquatic plants is a sign of a healthy lake, they can also be a hindrance for lake users. Non-native plants, such as the Eurasian water milfoil and the curly-leaf pondweed, grow rapidly and get in the way of boating and swimming. A "poor" rating means there's a plant infestation.

Said Mayor R.T. Rybak, "The Parks and Watershed District have done their job measuring the water quality of the lakes. But I'm proud that we've kept our standards high and we're not satistifed with the conditions today. As someone who grew up swimming in these lakes and still swims in them, I want these measurements to help ensure the next generation is as lucky as we have been."

Environmental quality is judged by water clarity in feet, based on the lake's depth. Lake Calhoun, Cedar and Harriet are all classified as deep lakes by the Minnesota Pollution Control Agency. Loring and Isles are considered shallow lakes. Lakes with higher environmental quality numbers have better water clarity.

Swimmers are particularly interested in lakes' public health status; LAURI includes levels of E. coli taken at beaches. Low numbers of organisms mean swimmers have less chance of experiencing gastrointestinal illness.

The Minnesota Park and Recreation Board, Barr Engineering and Minneapolis Public Works created the new index design.

More information about LAURI reports can be found on the Minneapolis Park and Recreation Board Web site, www.minneapolisparks.org.