- Lake Forest Association (LFA) - Caretakers of Eastwood Lake in Chapel Hill, NC.
Our first, “pre-season” 2016 water samples were taken Monday , April 4, 2016 between 9:10am and 9:30am
#1 Dock 25 cfu
#2 Cedar Fork Creek 28 cfu
#3 Booker Creek 34 cfu
Caution level is individual reading above 400 cfu, or average above 200 cfu.
Lake water temp ranged from 17C/63F to 17.5C/64F, still too cool for swimming without a wetsuit. The SECCI clarity reading was 26 inches, about the same as it was at the end of last summer. The rain gauge had 3.1 inches of water in it.
The CFU readings are well within the safe limits. The lake will warm quickly near the shore when we have mild evening temperatures and sunny warm days. Sometimes the lake can become “swimmable” after one or two warm days with mild overnight temperatures.
I took off-season temperature and clarity readings. The water temperature was 58F and the SECCI turbidity was 21 inches in mid-February, and it was 61F, and 25 inches on March 21. We track the overall temperature, clarity, and rainfall with our water tests in order to have an idea about what may have changed if our results come back different from the normal values.
I put the new rain gauge out on March 29, so the 3 inches had fallen since then. The lake level is up. The water going over the spillway is at the highest level, and there is some pooling at the bulkhead where the storm creek drains into the lake near the boat racks.
Eastwood Lake has two main surface tributaries: Cedar Fork Creek and Booker Creek. Our swim area and the two docks near the park are about at the confluence of those creeks. The lake was created by the CCC in the 1930s. The dam was improved in about 1984. There are also several underground springs that feed the lake. They are located mostly to the left of a line from the docks to the gazebo on the far shore. If we show higher readings upstream in summer when the tributaries run slow, this indicates that the springs are diluting anything coming in from surface water.
We test the water between the docks, which is both the deepest part of the lake (about 14 feet), and near the downstream outflow to Booker Creek at the dam. We also test near the two inlets so we can determine, in the case of any elevated readings, the source of that elevation. There are a couple of sewer lines below the lake, so an elevated downstream test without any upstream contamination would indicate that we need to check for leaks.
The Coliform bacteria we test for is the same test the state runs at state park beaches and ocean beaches. It is an “indicator organism” meaning its presence or absence is associated with the presence or absence of other water contamination that is more difficult to measure and analyze. By itself, the coliform bacteria is not particularly hazardous to health. It does not “live” or “multiply” in water, so its presence in any concentration is always decreasing. It lives in the guts of all warm-blooded animals, including humans. It is present, to some degree, in all open water, including our municipal reservoirs. Water treatment for drinking water and swimming pools eliminates it. When the concentrations get high, it can cause skin irritation or diarrhea. If it is absent altogether, the water may be contaminated with something toxic.
The clarity of the water is the product of a combination of biological activity and silt/sediment. Very clear water, as found in mountain lakes or spring or glacier fed lakes, where the water is filtered through rocks is not a natural occurrence in this region. Some turbidity is normal and healthy. A lot of turbidity can be the product of silt from erosion, or the result of an overgrowth of algae from too much “nutrient” in the water.
Some silt is normal. As we have some major construction projects at the edge of our four-square mile watershed, we are always concerned about both the disturbance of the soil on the ground and the affect that having more built and paved area in the watershed will have on how much silt gets to our lake. I will discuss this in future water test reports.
Too much fertilizer of the wrong type, incorrectly applied to lawns and gardens near the shore, can trigger an algae bloom. The results of that are usually more unpleasant (stains on bathing suits, thick debris in the water) than dangerous, but it can get out of hand and become a serious problem. Check previous water test reports for information about “lake-margin” fertilizer formulation and application guidelines.
I don’t get to the lake frequently enough to keep an accurate record of how much rain we actually get there. If anyone who gets to the lake more regularly would like to empty the rain gauge and make a note of when and how much water was in it, we might be able to have a better idea of how much rain we are actually getting. It is very localized. I live about 1.5 miles away, in the watershed. Often the readings at my home and at the lake vary significantly
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