Water Quality

The Metrics

Typical metrics followed are water temp, pH, chlorophyll, phosphate, nitrate, and water clarity. If bacterial or toxin contamination are concerns they can be measured as well. Three times per year the Chenequa foresters measure phosphorus, chlorophyll, dissolved oxygen, and Secchi disk depths. These are measured in the exact same spot off of the island. Below is the graph which shows Pine Lake metrics over time. Pine Lake is an oligotrophic lake and most site site indices reflect that, while phosphorus is at levels nearer to mesotrophic lakes. Downstream metrics would be lake weed surveys, fish and amphibian counts.

The Caveats

A static measurement three times per year does not reflect the microenvironment in your bay, at your shoreline, around your pier etc. We have under certain conditions had major algae blooms including blue green algae whose cyanotoxins are harmful to humans and can be fatal to pets. Major algae blooms may be seen after many days of still, hot weather, especially in wind protected bays. More commonly, each spring we see blooms of filamentous algae, a cold water algae that opportunistically consumes free nutrients before aquatic vegetation is present and able to consume them. This algae does not contain the same cyanotoxins as blue-green algae, and typically dissipates once the water warms up and aquatic vegetation gets established. If you would like to monitor your own shoreline, you can do that through the DNR’s Citizen Monitoring Lake Network, and share your data. See link below for more information.

The Threats

The greatest threats to water quality is the increase in developed shorelines with lack of natural vegetative cover which leads to excess runoff and nutrient loading of the lake with fertilizers. Phosphorus and nitrogen from lawns or agricultural runoff, legacy phosphorous kicked up in lake bottom sediment, increasing water temps, fewer black ice days, and invasive aquatic species such as Eurasian milfoil further reduce water quality. Zebra mussels have been present in Pine Lake since 2005. While they improve water clarity via filtration, these mussels are removing many zooplankton critically required as a food source by native species. This means clarity in and of itself needs to be interpreted carefully. Chloride levels are rising in freshwater lakes from road salt and water softener salt. Re-suspension of lake sediment by propellers, shoreline work, or dredging releases stored and previously inaccessible phosphorus fueling algae growth and inviting Eurasian Milfoil which is opportunistic. All of the above lead to excess algae growth, a change in the native weed population, and changes in subsequent fish and amphibian populations.

The Solutions

Planting and maintaining a native plant buffer for 35 feet from shore filters and traps excess nutrients. The presence of tree canopy within your buffer and upland slows and disperses water speed to soil so infiltration occurs instead of runoff. The presence of rip rap, while effective at minimizing soil erosion does little to decrease the movement of phosphorus and nitrogen into the lake. Vegetated rip rap, planted either above or into the stone system with native species will be more effective. Phosphorus in lawn fertilizers has been outlawed since 2007 in Chenequa, 2010 in WI. Minimize sediment dispersal with lakeshore projects using floating silt water curtains to help decrease phosphorus kick up in your lakeshore water and drift to your neighbors. Rain gardens and storm water drain systems also promote infiltration as opposed to surface runoff, mitigating the water volume reaching the lake. Permeable paving like gravel, permeable pavers, and pervious concrete lead to less surface runoff than hardscape. Many of us live on steeply sloped lots and need to be creative with slowing and absorbing storm water as it heads downhill to shore. Native plantings of trees, shrubs and perennials between house and shore will help.