Phosphorus in Southern Cayuga Lake and Its Tributary Streams

A Public Information ForumFebruary 27, 6-8 PM, Tompkins County Library

Purpose1. Present facts about phosphorus

2. Inform the public about phosphorus monitoring programs

3. Promote dialogue and collective problem-solving

Framing the Phosphorus Issue

• Phosphorus is the limiting nutrient in Cayuga Lake. Excessive phosphorus increases the risk of aquatic weeds, algae blooms and fish kills.

• Upper concentration considered “safe” is 20 ug/L (TP)• Three potential sources of excess phosphorus are:

– Tributary streams– Sewage treatment plants– Lake Source CoolingIf concentrations are higher on average than Cayuga

Lake, then a source is a potential net contributor of phosphorus.

Types of Phosphorus

Two general types of phosphorus in nature1. Dissolved phosphorus2. Particulate phosphorus

a. In algae and other organismsb. Attached to sediment

Two main types of phosphorus tests in the laboratory1. Soluble reactive phosphorus (SRP)2. Total phosphorus (TP)

Dissolved phosphorus in nature = SRP in the laboratoryParticulate phosphorus in nature = (TP – SRP)

Average Phosphorus Concentrations in Cayuga Lake, Salmon Creek Cluster, 2006-7

Regional stream conditions: Base flowShallow lake water Deep lake water

SRP 6.2 ug/L SRP 7.2 ug/LTP 16.0 ug/L TP 8.8 ug/L

Regional stream conditions: Elevated flowShallow lake water Deep lake water

SRP 5.7 ug/L SRP 8.0 ug/LTP 32.8 ug/L TP 16.6 ug/L

Average Phosphorus Concentrations in Cayuga Lake, South End Cluster, 2007

Regional Stream Conditions: Base Flow

Sampling site SRP (ug/L) TP (ug/L)

Control site 3.1 21.8

LSC outfall 3.6 20.1

CHWWTP outfall 5.2 18.3

IAWWTP outfall 5.8 28.6

Average Phosphorus Concentrations Entering Cayuga Lake from Tributary Streams

Base Flow AveragesStream SRP (ug/L) TP (ug/L)Fall Creek 17 28Six Mile Creek 10 15Salmon Creek 7 9

Averages of Base Flow and StormwaterFall Creek 21 117Six Mile Creek 12 124Salmon Creek 22 32

Conclusions

1. Total phosphorus is more concentrated in shallow water than in deep water in Cayuga Lake, 11.6 ug/L compared to 7.6 ug/L near Frontenac Point.

2. Total phosphorus averaged 22.2 ug/L in shallow water at the far south end of Cayuga Lake, twice as high as the mid-lake value.

3. Fall, Six Mile and Salmon Creek are net contributors of sediment-attached phosphorus to Cayuga Lake.

4. Fall and Salmon Creek are net contributors of dissolved phosphorus to Cayuga Lake.