02-09-21 - Laserfiche WebLink

Home Browse Search

• Building a rain garden to catch runoff nutrients from Nusery Hill Lane; • Stocking the lake with 1,000 predator fish several years ago to drive down algae through the food chain; • Annual removal of excess weeds and debris (in order to remove nutrients). The graphs on the next page below show the annual average readings for years 2006 through 2019 of 1. Chlorophyll-A (Chl-A) & Total Phosphorus (TP) and 2. Secchi Depth. Chl-a (Chlorophyl A) average is an indicator of the algae level. It held at about 9 ug/L, equal to the previous year, which is: • Less than half the 20 ug/L MN standard maximum for non-impaired lakes; • Less than one-third the level of 40 ug/L we averaged in 2010. TP average increased slightly to about 35 ug/L which is • About 58% of the 60 ug/L MN standard maximum for non-impaired lakes; • And about 58% of the 60 ug/L level we averaged in 2009. Secchi depth average (clarity) increased slightly to 2.5 meters which is: • 2.5 times better than the 1.0 meter MN standard minimum for non-impaired lakes; • About 3 times better than the 0.8 meter level we measured in 2009. I continue to be pleasantly surprised by the stable positive results we get each year because there are many factors working to drive up nutrients and drive down clarity, including: runoff from the streets and watershed that adds nutrients and silt and makes the lake shallower; yearly increases in average temperatures that speed the growth of algae. Several Board members reported seeing heavy fishing in Karth Lake last season and asked whether we needed to consider restocking. Action: Gary will ask the DNR for their opinion.