One way that freshwater scientists categorize lakes is according to their "trophic status", which refers to the concentration of nutrients in the water. The greater the nutrient level, the more plants are able to grow and photosynthesize sunlight energy.
Lakes with less that 10 µg/L TP are considered oligotrophic. These are dilute, unproductive lakes that rarely experience nuisance algal blooms.
Lakes with TP between 10 and 20 µg/L are termed mesotrophic and are in the middle with respect to trophic status. These lakes show a broad range of characteristics and can be clear and unproductive at the bottom end of the scale or susceptible to moderate algal blooms at her concentrations.
Lakes over 20 µg/L are classed as eutrophic and may exhibit persistent, nuisance algal blooms.
Another way water quality is evaluated is Secchi depth, or the clarity of the water. This indicates the depth to which light can penetrate the lake. Light penetration can be affected by dissolved organic carbon (DOC), biological activity, and plant and algal growth, as well as non-biological factors such as sediment. Water clarity readings are used to track changes in the lake that might not be noticed by monitoring phosphorus alone.
The Koshlong Lake Association partners with Federation of Ontario Cottagers Association (FOCA) and the Ministry of the Environment (now MOECC) on a voluntary, province-wide water-quality monitoring effort now known as the Lake Partner Program. With data collected from over 500 inland lakes since1996, the LPP is the largest and longest-standing program of its kind in North America.
Volunteers collect water samples in May. These are delivered to the Dorset Environmental Science Centre for analysis, and made available online to the public. In addition, volunteers are asked to make a minimum of 6 (monthly) water clarity observations using a Secchi disk. Together, this information enables early detection of changes in the nutrient status and/or the water clarity of the lake due to the impacts of shoreline development, climate change and other stresses. Learn more in this Overview, or read FOCA's Full Report on the program.
Our team of volunteers collects samples annually and measures Secchi depth throughout the summer season at the following six sites on the lake.
Historic results for Koshlong can be viewed online from the ON Ministry of Environment, Conservation and Parks. Koshlong has typically fared well as an oligotrophic lake, but you can see from the samples below, taken in Dysart Bay, that clarity has declined over time, and that phosphorous levels have fluctuated, indicating that our activities do have a noticeable impact on water quality.
As noted in our Threats to Lake Health page, septic leaching is the leading source of pollution on inland lakes. In our region, maintaining septic systems is essential because our soil and bedrock conditions are not always optimum for treatment.
In Ontario, responsibility for residential septic systems falls to the municipalities, which in our case are Highlands East (most cottages) and Dysart et al.
In the spring of 2017, Highlands East Council implemented a septic system maintenance inspection program at their cost. The objective of the program is “to aid in keeping our lakes, rivers, streams and groundwater pollution free. Septic systems on waterfront properties are priority but all systems in the Municipality will be inspected.” Dysart et al also implemented a more extensive reinspection program in 2017 with a slower implementation timeline. In 2021, this program was updated making it mandatory to utilize a third-party inspection company (WSP Environmental) to conduct the inspections at the cottage owner’s expense.
The results of the Highlands East survey showed that Koshlong Lake had results in line with the total average from all lakes inspected:
174 low risk
The remaining unresolved properties on Koshlong continue to be contacted by the municipality with some already working toward compliance. We recommend that owners of at-risk septic systems contact the Highlands East Building Department (705- 447-0051) and resolve their septic issues as soon as possible in order to avoid fines and prevent ongoing or future damage to the water quality of our lake.
Thanks to KLA member Rob Horsburgh for his photograph of Wallace Island used as the background photo throughout this site