Phosphorus Monitoring Initiatives
Phosphorus concentrations are measured on 64 lakes to assess the levels and trends. Elevated phosphorus levels can lead to algae growth and impact the quality of lake water.
Human sources of phosphorus include:
- sewage discharge,
- septic system seepage and
- lawn fertilizer run-off.
Results of our phosphorus monitoring initiatives can be found in our annual reports. This helps to determine the focus of future sampling programs.
Spring is the best time to sample for phosphorus as it is the only time of the year when a water sample taken from the surface will give an accurate phosphorus reading of the entire water column.
- If spring phosphorus levels in a lake are greater than 20 micrograms per litre (ug/L), the lake is considered eutrophic. Eutrophic lakes are generally classified as warm, poorly-oxygenated lakes with low water clarity and abundant aquatic plant growth.
- Oligotrophic lakes are lakes with less than 10 micrograms of phosphorus per litre (ug/l). These lakes are generally deep, very clear, cold water lakes with little aquatic plant growth.
- Mesotrophic lakes fall between eutrophic and oligotrophic lake classifications.
More detailed summer lake sampling is conducted on approximately 15 priority lakes based on lakefront development pressures and historically high phosphorus levels.
Summer sampling helps determine if the phosphorus is:
- flushed out of the lake
- remains in the lake and/or
- is replaced by urban run-off sources
Summer sampling can also help determine if internal loading is occurring within a lake. Internal loading is the process of phosphorus release from bottom sediments into lake water during times of low oxygen.