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West Final Report09

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					Matanuska -Susitna Borough Volunteer Lake Monitoring Program

West Lake Data Summary
2009

Morvro Lake - June 2009

West Lake is located just north of Big Lake and west of Horseshoe Lake. It has been monitored by the Matanuska-Susitna Borough Volunteer Lake Monitoring program for four years. This data is the result of the efforts of volunteers and staff of the Matanuska-Susitna Borough Volunteer Lake Monitoring Program, which has the goal of monitoring our lakes to obtain baseline data and to evaluate trends over time. Details of the monitoring program can be found in the Borough Lake Monitoring Manual, Standard Operating Procedures 2008 document available online or by request. Current information can be found on the Matanuska-Susitna Borough Planning Division’s website at: http://www.matsugov.us/Planning/PlanningDivision.cfm

West Lake 2009

MSB Volunteer Lake Monitoring Program

page 1

pH Our lakes usually fall within a range of 6.5-8.5. State standards for pH for “recreation with contact” state that waters should not be below a pH of 6.5 and not above a pH of 8.5. For growth and propagation of fish, shellfish, and other aquatic life and wildlife, the pH should stay between 6.5 and 8.5 and not vary more than 0.5 pH units from the natural conditions. Conductivity (Specific Conductance) Conductivity is a measure of the water’s ability to conduct an electric current. Conductivity is usually stable over the sampling season but will be affected by precipitation, erosion events or disturbance of the substrate. Generally, as Dissolved Oxygen concentrations decrease at the lower level of deep lakes, the Specific Conductance increases. Lakes in the Matanuska-Susitna Borough Lake Monitoring Program have specific conductance measurements that usually range from 0.01-0.25 mS/cm. A thermocline is a layer of water that separates an abrupt change in water temperature. Lakes that show a thermocline in their profile often have higher conductivity readings near the bottom where water has near zero oxygen levels. A steady increase over time in a single lake may indicate the addition of pollutants. Secchi Depth Secchi depth is an indicator of the clarity of the water. In Matanuska-Susitna area lakes, this reading is usually a good indicator of algae levels when lakes are not clouded with sediment of large levels of tannins.

West Lake 2009

MSB Volunteer Lake Monitoring Program

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West Lake Temperature & Dissolved Oxygen
Water Temperature We find that in shallower lakes, mixing occurs readily and the temperatures are generally uniform from bottom to top. Deeper lakes may become stratified when surface waters warm in the spring creating density layers that impede mixing. Mixing may sometimes occur only in the top layer, keeping oxygen from reaching the lower layers. This may cause or contribute to low oxygen levels in the lower reaches of the lake. Dissolved Oxygen (DO) Oxygen is important for almost all living things, including aquatic life. Oxygen dissolves in the water from the atmosphere and is added through photosynthesis by plants and Temperature and Dissolved Oxygen Profile algae. Carpenter Lake West Lake -- May 2009 Oxygen is used by living Temperature (C) organisms in respiration and is used in the 3.00 5.00 7.00 9.00 11.00 13.00 15.00 17.00 19.00 0.0 process of decomposition.
1.0 2.0

3.0 4.0 5.0 0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

Dissolved Oxygen (mg/L)

Alaska State Standards indicate that waters for recreation should not fall below 4 mg/L. In waters with resident or anadromous fish, DO levels of 7 mg/L or above meet with state standards. The oxygen profile will change with the seasons as temperatures change , changing density and allowing for mixing or “turnover.”

Depth (m)

Temperature oC

Dissolved Oxygen

Temperature and Dissolved Oxygen Profile West Lake -- August 2009
3.00 5.00 7.00 Temperature (C) 9.00 11.00 13.00 15.00 17.00 19.00

Temperature and Dissolved Oxygen Profile West Lake -- October 2009
3.00 5.00 7.00

Temperature (C) 9.00 11.00 13.00

15.00

17.00

19.00

0.0

0.0

1.0 2.0

1.0 2.0
Depth (m)

Depth (m)

3.0
4.0

3.0
4.0

5.0 0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

5.0 0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

Dissolved Oxygen (mg/L) Temperature oC Dissolved Oxygen mg/L

Dissolved Oxygen (mg/L) Temperature oC Dissolved Oxygen mg/L

West Lake 2009

MSB Volunteer Lake Monitoring Program

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Chlorophyll a Chlorophyll a is measured as an indicator of algae growth in a lake, and can be used to determine productivity and trophic status. In lakes where a relatively higher amount of the productivity is found in the form of aquatic plant growth, determining productivity by chlorophyll a may not be a good indicator of productivity and trophic status. Chlorophyll a levels can also help determine whether the clarity of the water is diminished by algae or other sources. There is no state standard for chlorophyll a.
Wolverine Lake Algal Bloom - June 2009

West Lake ● Chlorophyll a 2005-2009
2.5

2.0
Oligotrophic

µg/L

1.5

1.0

0.5

0.0 2005 2006 2007 2008 2009

West Lake 2009

MSB Volunteer Lake Monitoring Program

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Total Phosphorus Phosphorus is the most important nutrient for plant productivity in our area’s surface waters because it is usually the nutrient that is limiting. Phosphorus enters the lake naturally or from human sources such as fertilizer and increased runoff. Once in the lake, it cycles through living things and may end up in the sediment where it can once again become available to plants and algae. As with chlorophyll a, there are no Alaska State Water Standards for phosphorus, but it is generally accepted that phosphorus is normally found at concentrations of less than 10 µg/L in higher quality surface waters. A general guideline of 20-25 µg/L was suggested by the Alaska Department of Environmental Conservation as a level above which human inputs may be a concern for Alaska lakes.

West Lake 2009

MSB Volunteer Lake Monitoring Program

page 5

West Lake 2009 & 2008 Data Summary - Profile Measurements
Depth Temperature (m) (oC) Date Site Depth (m) Phosphorus (µg/L) Chlorophyll a (µg/L) Date Site Depth (m) Phosphorus (µg/L) Chlorophyll a (µg/L) Date Site Depth (m) Phosphorus (µg/L) Chlorophyll a (µg/L) 10/1/2009 5.5 10 1.4 8/3/2009 5.2 15 1.3 5/26/2009 5.0 9 0.9 0.0 1.0
2.0 3.0 4.0 8.45 8.16 8.09 8.00 7.95 18.76 18.65 18.54 17.89 17.43 15.92 15.96 15.89 15.45 13.86

Conductivity (mS/cm)
0.049 0.049 0.049 0.049 0.049 0.048 0.048 0.048 0.048 0.047 0.044 0.044 0.044 0.044 0.044

Dissolved Secchi pH stanOxygen Depth dard units (mg/L) mean (m)
12.38 11.53 11.25 11.11 10.95 8.92 8.86 8.92 8.94 8.91 9.68 9.54 9.65 9.79 9.65 7.84 7.66 7.53 7.39 7.27 7.69 7.59 7.48 7.39 7.31 7.30 7.23 7.27 7.29 7.26

4.78

0.0 1.0
2.0 3.0 4.0

3.18

0.0 1.0
2.0 3.0 4.0

4.28

Depth Temperature (m) (oC) Date Site Depth (m) Phosphorus (µg/L) Chlorophyll a (µg/L) Date Site Depth (m) Phosphorus (µg/L) Chlorophyll a (µg/L) 9/24/2008 5.0 10 0.8 7/15/2008 3.5 21 2.0 0.0 1.0 2.0 3.0 4.0 0.0 1.0 2.0 3.0 12.92 12.92 12.91 12.91 12.90 18.04 18.04 17.92 18.07

Conductivity (mS/cm) 0.043 0.044 0.044 0.044 0.044 0.045 0.046 0.046 0.045

Dissolved Secchi pH stanOxygen Depth dard units (mg/L) mean (m) 8.96 9.47 9.47 8.90 8.10 9.08 9.01 8.60 8.83 6.80 7.60 7.50 7.36 7.10 7.71 7.50 7.41 7.29 3.75

3.30

West Lake 2009

MSB Volunteer Lake Monitoring Program

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Trophic Status Changes The trophic status of lakes naturally changes over time due to inputs of nutrients from natural sources such as precipitation, natural runoff and salmon migration. This progression usually takes many years. The addition of nutrients from human sources such as septic systems, fertilizers and erosion may accelerate the change in trophic status. This more rapid change is termed “cultural eutrophication.” If severe, eutrophication can result in aquatic plant problems, algal blooms, fish kills and unpleasant smells. There have been few studies on the trophic status of Alaska’s lakes. One study by Alaska Department of Fish and Game (ADFG) defined trophic guidelines for lakes in the Matanuska-Susitna Borough. We used the guidelines outlined below in Table 1 for the graphs in this data summary. However, it is important to note when using these guidelines, that there is not currently enough information on trophic status for the Matanuska-Susitna Borough to accurately determine trophic status based on these numbers alone. Over time our monitoring program will be used to refine these general categories. Table 1 values represent averages over a season.

Table 1 Trophic Guidelines for Alaska Lakes (ADFG) Monitoring Parameter
(based on mean) Chlorophyll a (µg/L) <3 3-7 >7 Oligotrophic Mesotrophic Eutrophic

Total Phosphorus (µg/L)

<10

10-20

>20

Secchi Depth (m)

>4

2.5-4

<2.5

In addition to the quantitative data included in this report, MSB lake monitoring volunteers act as stewards of the lakes and note observations on aquatic plants, wildlife, lake levels and times of ice formation and breakup. Over time, this valuable data will help us detect changes and gain a better understanding of our lakes.

West Lake 2009

MSB Volunteer Lake Monitoring Program

page 7

West Lake 2009

MSB Volunteer Lake Monitoring Program

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