2006 Worthley Pond Water Quality Report
Lake & Watershed Resource Management Associates
P O Box 65; Turner, ME 207-336-2980
LWRMA @megalink.net
The Water quality of Worthley Pond was assessed through baseline monitoring and sampling of the pond on August 10, 2006. The sampling entailed water clarity readings, a dissolved oxygen and temperature profile from the surface to the bottom of the deepest point in the pond, total phosphorus samples taken near the surface and bottom of the pond, a chlorophyll-a sample to determine the concentration of algae in the water, a check of the natural background color, pH measurement, and a measurement (total alkalinity) of the ability of the pond to buffer (resist) changes in pH.
The indicators used to assess lake water quality are highly dynamic, in that most are in a state of constant change, due to a wide range of factors that include the influence of weather, natural daily (circadian) rhythms of the physical, chemical and biological elements of the lake ecosystem, and human influences that, over time, can alter water quality in a number of ways.
This “natural variability” of lake systems presents challenges to our ability to characterize water quality, and to identify changes, or trends, over time. For this reason, many years of data are generally required to be able to discuss the water quality of individual lakes with a degree of confidence. Fortunately, water quality data have been collected for Worthley Pond since 1980 (Maine DEP and Maine VLMP database). A large percentage of the basic information has been obtained by trained volunteers, with the remainder provided by lake water quality professionals, including Maine DEP and LWRMA biologists.
Worthley Pond was very clear on August 10, 2006, measuring 6.82 meters (22.2 feet). While only a single reading, this is considerably above the average for Maine lakes (approximately 5.5 meters). The historical average for Worthley Pond is 6.7 meters, and the average in 2005 was 6.6 meters. Water clarity is an indirect indication of the growth of algae in the water. User perception surveys in Maine have indicated that clear water is highly valued by the public.
Phosphorus is the nutrient that most influences the growth of algae in lakes and ponds. The concentration of total phosphorus (organic and inorganic forms) near the surface of Worthley Pond last August measured 5 parts per billion (ppb). This is a relatively low concentration that is consistent with the excellent water clarity of the pond. The historical phosphorus average for Worthley is 7 ppm, and the 2005 concentration measured 6 ppm. All of these readings are lower than the average for Maine lakes.
Chlorophyll-a (CHL) is a pigment that occurs in plant cells. Its measurement is a direct means of determining the concentration of algae in lake water. The 2006 concentration of CHL in Worthley Pond measured 3.6 ppb, compared to the historical average of 3.1 ppb, and the 2005 average of 4.3 ppb. Although the number of historical CHL samples from Worthley Pond is limited, there is some indication that the concentration of CHL has increased since sampling first started in 1980. This should be monitored closely in the future, since an increase in CHL levels in lake water may indicate not only an increase in algal growth, but possibly a decline in water quality.
The temperature and dissolved oxygen profiles taken on August 10 showed moderate oxygen loss in the deepest area of the pond. Readings below 7 meters depth showed progressive depression, then depletion of oxygen levels, similar to what has been documented in the past.
The loss of dissolved oxygen in late summer is associated with thermal stratification, in which cold, dense water in the deepest area of the lake loses oxygen because it is unable to mix with the warmer, well-oxygenated water near the surface. The degree to which oxygen is lost during the summer period may be an indication of the extent to which a body of water is “stressed”. Although Worthley Pond presently experiences above average water quality, based on water clarity and phosphorus and chlorophyll levels, the persistent late summer oxygen loss suggests that the pond is vulnerable to change.
A phosphorus sample taken near the bottom of the pond, where the dissolved oxygen concentration was very low, was nearly three times as high as the phosphorus level near the surface. This may indicat that the low level of oxygen is triggering the release of phosphorus from the bottom sediments. This sample was consistent with results obtained in previous years.
Natural color, pH and total alkalinity levels were within the normal historical range for Worthley Pond in 2006.
Overall, 2006 was a good year for Worthley Pond. With continued conservation efforts on the part of the watershed community, the future of this pond is hopeful. Compared to other lakes and ponds in the region, the water quality of Worthley is certainly above average.
Maine Lakes - Worth $aving?
Each year, $1.8 billion dollars are spent in Maine on lake related activities. Lakes in Maine support 52,000 jobs and provide drinking water for 400,000 people. In many towns, lakes are the greatest economic and natural resource.
But what if a lake gets polluted or turns green with scum? Fewer people come to boat, fish and support local businesses. Residents lose jobs. More money is spent on water treatment. Property values can drop 5% - 10%, lowering taxes collected by towns.
With so much value generated by our lakes, it’s important to do whatever we can to protect them. Test your own "lake protection IQ" with the following quiz:
1. What type of engine does your boat have?
Jet propulsion (PWC or jet ski)
Two stroke outboard
Four stroke outboard
2. How do you care for your septic system?
I have it pumped when the toilet backs up.
I have it pumped it out every three years even if it seems to be OK.
I don’t do anything. It has always worked.
3. What type of fertilizer do you use in your yard?
None
Four step weed and feed
Phosphorus-free once a year
4. Which best describes your yard?
Lawn and flower beds
Small lawn surrounded by natural vegetation or landscaping
Lawn down to the water, stream or drainage ditch
5. Even if you do not live on a lake, can what you do in your yard make a difference to a lake?
No
Yes
I don’t know
The Answers:
1. c. Four stroke high efficiency engines are the best for the environment. They discharge 1/3 less fuel than two stroke engines and PWC (jet skis). Paddling is even better!
2. b. Pump your tank every 3-5 years. Conserve water and do not dump harsh chemicals, paint, grease, or septic tank additives down drains or toilets. Old systems can contaminate ground water or leak into lakes.
3. a. or c. Conduct a soil test before you fertilize to determine how much, if any, your soil needs. Phosphorus-free fertilizer does not cause green scum in lakes. Watch out for "weed and feed" blends. They contain pesticides.
4. b. Trees, shrubs and ground cover protect lakes by filtering dirty stormwater. It is better not to rake these areas since the leaves, twigs and pine needles act as a natural mulch to absorb and filter stormwater. A smaller lawn means less mowing and less pollution for the environment.
5. b . Even if you do not live on a lake you do live in a watershed. Since 50% of Maine drains to a lake, what you do in your yard can make a difference!
Your lake protection knowledge:
4-5 correct - Excellent! If you are not already a lake association member call Maine COLA (toll free) 877-254-2511 to join.
2-3 correct - OK, but there’s lots more to learn. Visit the lakes web site at:
http://www.state.me.us/dep/blwq/lake.htm
0-1 correct - Not good. Hope this little quiz has provided you ideas about protecting your lake. For more information call Christine Smith at 287-7734.
