As per our fall newsletter, the 2017 OLRA Lake Water Testing Project was conducted by Mr. Bev Clark. Mr. Clark submitted his final report to OLRA of 17 pages which you can download below.
It contained good news about our high lake water quality. 🙂 OLRA’s top priority is to help educate lake property owners and visitors to make sure we keep our lake water this way!
Brad Chittick, OLRA‘s Lake Steward, has written the summary report below:
OLRA 2017 Water Quality Report Summary
November 19, 2017
By: Brad Chittick, P.Eng.
Director of Lake Stewardship
Otter Lake Ratepayers’ Association
In May of 2017 your Otter Lake Ratepayers’ Association (OLRA) engaged a water quality expert, Mr. Bev Clark, to conduct an extensive study on the quality of our lakes’ water. Over the spring, summer and fall Mr. Clark conducted six monthly tests in seven locations (six bay locations on Big Otter and one mid-lake location on Little Otter) on the Otter Lakes. This is a summary of Mr. Clarks findings, conclusions and recommendations. The full report is available to members who request it and will be posted on the new OLRA website coming by February of 2018.
Overall results of these tests indicate that the water quality in the Otter Lakes is excellent and has not changed dramatically over the past 24 years. At each sampling location, multiple water quality parameters were tested; Water Clarity, Temperature, Total Phosphorus, Oxygen, Acidity (pH), and Conductivity. This was a thorough examination of lake water quality. Although there was some variation in sample results, none of the measured parameters exceeded any environmental limits.
Water Clarity ranged from a depth of 3 – 6 meters in the spring and averaged 3 – 3.5 meters in July and August. Clarity increased in late October to an average of 5 metres. This is typical of lake water as algae grows and depletes during the open water season.
Total Phosphorus is an important parameter to measure, as it can indicate the potential development of algae blooms. It is generally accepted that measurements of below 20 g/L in water will avoid the development of nuisance algae blooms. All the testing this year showed below this level with most of the results less than 10 g/L throughout the year. Typically, concentrations ranged from 4 – 7 g/L. These are similar to historical levels measured through the Lake Partnership Program.
Temperature and Oxygen levels were measured at the surface to look for significant swings in levels. In all cases there was little variation in temperature and oxygen levels, specific to each location. A more detailed test was conducted on August 30th to determine the oxygen levels at the lake bed of each location. Oxygen and temperature measurements were taken at one (1) metre increments up to one (1) metre off the bottom. This was to determine if the lower depths, at a stratification level, were experiencing ‘Anoxia’, low oxygen levels, which can allow phosphorus from sediments to enter the water and potentially increase phosphorus levels. In three cases Anoxia was discovered that impacted the phosphorus levels at the lake bottom, however in only one case did it influence the phosphorus levels at the higher, mixed, depths and in no case, did the phosphorus in the higher depths exceed 20 g/L.
Acidity or alkalinity is measured on a pH scale. A pH of 7 is considered neutral, and measurements below indicate acidity while measurements above indicate alkalinity. The measured pH in this year’s sampling generally ranged from 5.0 to 7.6 with an average of 6.4 in both Big and Little Otter Lakes.
Conductivity is the measurement of water’s ability to conduct an electric current. It is a useful measurement to determine the ‘mineralization’ or degree of dissolved solids of the water. The results for Otter Lake were very low, ranging between 20 and 25 S/cm. This low reading indicates very dilute water. This is typical for lakes on the Canadian Shield. The narrow range of the measurements from all the sampling sites indicate that the water flow into the lake comes from lakes with similar watershed characteristics. Although the measurements on Little Otter lake was about twice those in Big Otter it is still considered low and the range was also narrow. The higher results on Little Otter are likely due to the relative shallow depth of the lake or perhaps due to the inflow from Rankin Lake.
The conclusion of Mr. Clark’s report notes that the water quality of both Otter Lakes is excellent, with low phosphorus concentrations, low conductivity, and water clarity levels that are similar to previous years. Mr. Clark goes on to recommend that the OLRA and the residents of the Otter Lakes continue following best practices to reduce the movement of phosphorus into the lakes and continue a volunteer based testing program to monitor the quality of our Otter Lakes’ water.
As the Director of Lake Stewardship, I will be further reviewing Mr. Clark’s conclusions and recommendations with the intent to develop a 2018 program. The draft program will be reviewed by the Board of Directors in February and the recommended 2018 Water Quality program will be presented to the OLRA membership at the Annual General Meeting in May