WATER QUALITY REPORT FROM DIRECTOR IAN MACKENZIE

Nutrients (nitrogen and phosphorus) originate from sources such as erosion, poor sewage treatment, fertilizer, detergents, or natural sources, and enter the lake in runoff. Nitrogen can also reach the lake from atmospheric deposition. 

Nutrients and light allow the growth of microscopic algae, which supports the food web, including small fish that are eaten by trout. When algae die they sink to the bottom of the lake where they decay (are broken down by bacteria). The decay process uses oxygen, which leads to low levels of dissolved oxygen in the bottom of the lake in summer and fall. 

If nutrient concentrations are too high, excessive growth of algae can occur, leading to the layer of low dissolved oxygen taking up more of the lower levels of the lake. Solar radiation and arm air warm the surface of the lake, while the deeper waters stay cool throughout the summer. If solar radiation levels and air temperatures are too high, more of the surface waters of the lake may become too warm for lake trout. 

Note that bass are more tolerant than trout of warm water temperatures and lower dissolved oxygen levels.

Various water testing has been done over the years. The current program has been influenced by what we know to be important to swimming, clarity & fish, and within the constraints of our budget (lab testing is expensive). Currently we do two types of tests:

Chemistry and Bacteria We monitor 21 locations around the lake. Up until 2019 we did these test every three years. In order to better monitor trends which may be changing quickly, the LWCA membership approved annual testing beginning in 2019. Measurements of Nitrogen, Phosphorus, E-Coli and total Coliforms are taken.

Deep water sampling Water is samples in order to measure the temperature and dissolved oxygen (DO). We’ve been monitoring two deep water locations. We take a measurement of temperature and DO every metre. The LWCA expanded the number of deep water test locations to 5 in the summer of 2018 which has provided interesting comparison data. 

Deep water test data has been compiled since 1989. Dissolved oxygen trends are relatively stable across data taken from 1989 to June 2020. You can take a look a this data by opening the files below. 

a) an overview of samples taken over time:  "Temp-DO Water Quality Testing Data 2014 to June 2020

b) a closer look at two sets of data: "Temp-Dissolved Oxygen sample comparing Feb 2014 with Feb 2019"

Chemistry test results show a generally worsening water quality trend, particularly in the 4 south end sampling locations. Nitrogen levels are well above the target range at all test locations while Phosphorus levels are within the target range at all locations. E-Coli only appears in any significant level in the south end locations. Total Coliforms are generally above the target level at all locations, and significantly higher at south end location where creeks flow into the lake. It should be noted that we have not yet taken a reading higher than the upper ‘safe for swimming’ limit established by Ontario for e-coli or total coliform levels. A full analysis of chemistry tests over the years can be is available in the file below: "Water quality analysis LWCA 2019". 

Implications 

Lake Weslemkoon is classified as a highly sensitive lake trout lake. Tests show dissolved oxygen remains above the survival minimum of 6 mg/litre, but below their preferred range of 9.6-11.7 mg/l. It’s important to keep our lake trout, and important to keep our ‘highly sensitive lake trout lake’ classification, as the level of further human development on the lake is constrained by having this classification. 

Nitrogen and Phosphorus levels influence growth of aquatic plants and algae.   The levels are significantly higher at the south end of the lake due to the higher level of development both on the shore and upstream of the creeks flowing into the lake. 

What we can do to Influence

• Have a septic system & be sure it’s working properly (see Septic report for how to get inspected)
• Minimize water use – where possible take laundry home and avoid use of dishwasher
• Choose soaps that are environmentally safe (e.g., contain no Phosphates) and don’t wash directly in the lake
• Don’t use fertilizers and pesticides
• Reduce erosion effects - maintain trees, shrubs & ground cover in the Riparian Zone by the lake