What Is It With Sylvan Lake’s Tributaries?

Tributaries collect snow melt and precipitation from areas of the watershed. That water discharges into Sylvan Lake in streams that flow in channels that are shown in this topographical map of the basin. The main tributary catchments are labelled A to H on this map:

Sylvan Lake Tributary Map

Figure 1. The most important tributaries are Golf Course Creek (H) and Northwest Creek (D) as they collect and drain most of the surface water flow that reaches the lake.

The goals of SLWSS water quality projects in 2006, 2007 and 2014 have been to determine the quantity of nitrogen and phosphorus plant nutrients that are transferred from the land into the lake. High nutrient concentrations increase the threat of blue-green algae (cyanobacteria) blooms in the lake.

Here are some of the facts that we have found:

1. Total Phosphorus (TP) concentrations  that are measured in the lab in units of milligrams per litre (mg/L) have always been above the important TP guideline for Sylvan Lake of 0.035 mg/L. The red line in Figure 2 is that Alberta Surface Water Quality Guideline (see the ASWQG label). The red squares show data collected in our first tributary sampling campaigns in 2006 and 2007 from all the streams. All tributaries that we tested carried high phosphorus concentrations into the lake.

All TP Data vs Date

Figure 2: Phosphorus concentrations in early-year runoff in 2006 and 2007 were above 0.035 mg/L

2. We also found that Total Nitrogen (TKN) levels were generally higher than the recommended TKN level of 1.0 mg/L. Results shown in Figure 3 are compared with TKN concentrations in the lake water. Data (the green points) collected by our SLWSS projects and by the Marina Bay Homeowners Association (MBHA) confirm that tributaries can also enrich the lake in nutrient nitrogen.

Sylvan Lake water quality data (see the yellow points) were reported by the Alberta Lake Management Society’s LakeWatch program between 2005 and 2010.

TN in SL 2006-08

 

 Figure 3. Nitrogen nutrients carried by tributaries enter Sylvan Lake in concentrations above the water quality guideline level of 1.0 mg/L.

Total Phosphorus concentrations in Sylvan Lake have been relatively stable over about three decades according to Alberta records although some analyses have been close to the ASWQ TP Guideline.

TP in SL 1983-2010

 Figure 4. Alberta water quality Total Phosphorus data for Sylvan Lake.

Sylvan Lake acts like a bathtub. Dissolved and suspended material carried by the watershed’s tributaries ends up in the lake. A small fraction leaves with the lake overflow but most remains in the water or lake sediments.

That is why everyone who values Sylvan Lake should prevent contaminants from entering stormwater or groundwater that might eventually discharge into the lake.

Watch the SLWSS News for more information on Sylvan Lake’s water quality.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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