[[Links to detailed annual Lake Steward reports are at the bottom of this page.]
Kahshe Lake is being monitored for long term changes in water quality under two main initiatives as outlined below. Because of its smaller size, the water quality program for Bass Lake is limited to the more comprehensive Lake System Health Program.
This program is operated by The District Municipality of Muskoka (DMM), with support from the Muskoka Watershed Council (MWC), the MECP and several other participating agencies. For Kahshe and Bass Lakes, the DMM program consists of the following activities which are conducted every other year for Kahshe and lately, every year for Bass Lake:
This program is operated by the Ontario Ministry of Environment, Conservation and Parks (MECP) through the Dorset Environmental Science Centre (DESC). Under this program, water sampling and measurement of water clarity is conducted by the Kahshe Lake Steward every year.
The program consists of the following activities:
Water clarity measurements - Clarity of the water is measured every two weeks during the ice-free period at three locations (Deep Bay, Kluey’s Bay and Grant Bay, using a Secchi disc, and these findings are forwarded to the MECP for compilation and comparison with other lakes in Ontario.
Water quality testing - Water is sampled from the same three mid-lake locations in May each year and sent to the MECP for analysis of total phosphorous, an indicator of the potential for algal blooms and nutrient enrichment and for calcium.
A detailed report on the findings of these two water quality sampling programs for both lakes has been provided in the Lake Steward reports from 2012 through 2019 and in related Executive Summaries which are posted via links below. However, due to COVID-19, no sampling or analysis was carried out in 2020, and as such there was no Lake Steward Report. Sampling under the above two programs was conducted in 2021 and the data have now been included in a 2021 Lake Steward Report.
Based on the findings from over 35 years of water quality sampling and analysis carried out every other year by DMM and every year for a more limited set of parameters by the MECP with the assistance of the Kahshe Lake Steward, the following conclusions regarding the water quality and biological health of Kahshe and Bass Lakes have been drawn:
In the 2019 and 2021Lake Steward report (posted below), it was noted that several lakes in the Muskoka area have experienced harmful blue-green algal blooms in 2018 and 2019. Although no blue-green algal blooms had been detected at the time the 2019 Lake Steward report was published (May 2020), a late season blue-green bloom was confirmed by the MECP in the Oak Road area on November 11, 2020 and information on its investigation and findings can be found via this link: Current Algal Bloom Status for Kahshe and Bass Lake-R2 Dec2020-Fin.
Unfortunately, another HAB was identified in early October 2021 and the related health alert applied to the entire lake and was lifted on November 10, 2021. Although it no longer can be discussed in terms of a ‘likelihood’, it is still important to understand how the total phosphorus levels in Kahshe and Bass Lakes compare with levels in lakes where blue-green algal blooms have been documented. The chart above confirms that harmful blue-green algal blooms have developed in several of the impacted lakes that had total phosphorus levels well below those in Kahshe and especially Bass Lakes. Based on these findings, the presence of a blue-green algal bloom in November 2020 and October 2021 should not come as a surprise and this development underscores the importance of renewed efforts to drive our nutrient levels even lower than they currently are, as our climate is changing, and creating conditions that favour algal growth and bloom development.
As a result of the trend towards increasing numbers of harmful algal blooms in Muskoka, the DMM has now updated the Muskoka Official Plan to identify all lakes now considered ‘Vulnerable’ due to: a) the documented presence of an algal bloom, b) increasing concentrations of total phosphorus, or c) levels of total phosphorus in excess of 20 parts per billion. All ‘vulnerable’ lakes will undergo a ‘Causation Study’ to determine the factors that are causing the algal bloom development. The Causation Study for Bass Lake was initiated by the consulting firm retained by the DMM in 2021 and the findings will be published in late 2022. A DMM-funded Causation Study will be conducted on Kahshe Lake as well, but the timing has not yet been determined.A more detailed outline of the DMM’s Vulnerable Lake status program can be found HERE.
Given the impact these algal blooms have on the recreational enjoyment and property values of the lake, the KLRA agreed to fund a Near-Shore Water Sampling Program that was designed by the Conservation Committee and implemented in 2021. A full description of the Near-Shore project can be found HERE . A full report, as well as an Executive Summary, on the findings of this program can be found by clicking the links.
Based on the analysis of a large number of chemical and physical parameters by both the DMM and the MECP, it is apparent the waters of Kahshe and Bass Lakes are in a stable and reasonably good condition. However, as the Near-Shore Water Sampling Project has now shown, the quality of Kahshe Lake water which has been based on spring sampling from mid-lake sites is not providing a realistic assessment of water quality in the near-shore environment where algal blooms have been documented. The near-shore findings have clearly demonstrated that algal-promoting nutrient levels increase as the season progresses and appear to be related to accelerated leaching of phosphorus and nitrogen compounds sourced from septic systems and managed lawns located close to the shore. Although more evidence is warranted, the appearance of late season algal blooms appears to be related to precipitation events associated with our changing climate. The Near-Shore project findings have been examined by the Conservation Committee to determine if there are additional follow-up actions shoreline property owners can take to mitigate the impacts on near-shore waters. These follow-up actions can be found here. The findings will also inform the design and conduct of the DMM-funded Causation Study that will proceed when funds are available.
Based on the above water quality findings, we need to remain vigilant in our sampling efforts and overall lake stewardship, as climate changes, including more intense rainfall events, appear to be increasing the migration of algal friendly nutrients from our shorelines to the near-shore water. This has been underscored by the confirmed presence of blue-green algal blooms in the Oak Road area of Kahshe Lake on November 11, 2020 and in several locations in October 2021.
In summary, we can and must improve water quality and reduce the potential for future harmful algal blooms by the actions identified in the "How Can We Help" document referenced above. These actions have been further condensed below:
Ron Pearson, M.Sc.
Kahshe and Bass Lake Steward
Detailed Lake Steward reports are available below (PDF)
2019 Kahshe Lake Steward Report-Final (4804 KB)
2018 Executive Summary (736 KB)2018 Full Report (4613 KB)
2017 Executive Summary (463 KB)
2017 Full Report (4915 KB)
2016 Executive Summary (404 KB)
2016 Full Report (5031 KB)
2015 Executive Summary (1101 KB)
2015 Full Report (5252 KB)
2014 Lake Steward Report (4030 KB)
2013 Lake Steward Report (15594 KB)
2012 Lake Steward Report (4807 KB)