Study Results
Key findings
Here is a summary of our key findings from the Lake Scugog Environmental Management Plan:
- Every year, 9.1- 9.6 tonnes of phosphorus enter Lake Scugog.
- Estimates show that we need to reduce phosphorus entering the lake by 3-3.4 tonnes per year to improve water quality and maintain the lake's ecosystem.
- More than two-thirds of the phosphorus that enters the lake remains and accumulates within the lake.
- The nutrients taken up and produced by aquatic plants accumulate on the bottom of the lake and feed new plants.
- It takes only 1 tonne of phosphorus to promote the growth of 500 tonnes of aquatic plants.
- Aging of the lake (build up of sediments and increase of aquatic plants) can be accelerated by human inputs of nutrients.
- Average phosphorus concentrations in most rivers and streams are typically two times higher than the Provincial Water Quality Objective (PWQO) of 30 µg/L.
- Nutrient ‘hotspots’ include Cawker’s Creek, the Nonquon River, Blackstock Creek, and Layton River.
- phosphorus is a limiting agent. A reduction in this nutrient can have the greatest impact on aquatic plants.
Phosphorus levels in Lake Scugog Tributaries
Our monitoring shows that water quality is heavily affected in most Lake Scugog tributaries. We observed the highest levels in Cawker’s Creek, the Nonquon River, Blackstock Creek and Layton River. Fingerboard Creek had the lowest levels of phosphorus. The highest phosphorus concentrations are usually observed during the spring snow melt.
PWQO stands for Provincial Water Quality Objective. The PWQO for phosphorus is 30 ug/L in river water.
Phosphorus levels in Lake Scugog
During our 2007 and 2008 monitoring seasons, phosphorus concentrations have been lower than the Provincial Water Quality Objective of 20 ug/L. We observed the lowest levels at View Lake, Caesarea and Starr's Beach. The highest levels were at Port Perry, the mouth of the Nonquon River and Gilson's Point.
Phosphorus Sources
Through our studies, we have identified the main sources of phosphorus and their contributions to the lake.
Phosphorous targets
By identifying the main sources of phosphorus and how much each contributes to the lake, we have been able to find areas where reductions can be made. These areas include urban runoff, agriculture, septic systems, and rural road runoff. For atmospheric deposition (i.e. precipitation) and natural sources, it is very difficult to reduce nutrient loading.
SOURCE |
WATERSHED AREA |
PHOSPHORUS LOAD |
TARGET – MAX LOAD |
Urban runoff |
3.56% |
1,713 kg (18.2%) |
700 kg |
Agriculture |
53% |
2,213 kg (23.5%) |
1,100 kg |
Septic systems |
0.76% |
911 kg (9.7%) |
350 kg |
Rural road runoff |
1.56% |
600 kg (6.4%) |
300 kg |
Port Perry Sewage Treatment Plant |
1.2% |
170 kg (1.8 %) |
150 kg |
Atmosphere |
na |
1,784 kg (19.0%) |
1,600 kg |
Natural Sources |
na |
2,017 kg (21.4%) |
2,017 kg |