- Lake Forest Association (LFA) - Caretakers of Eastwood Lake in Chapel Hill, NC.
Our Memorial Day, 2016, water samples were taken Thursday, May 26, 2016 between 11 am and 11:30 am This is our second water test this year.
#1 Dock 1 cfu
#2 Cedar Fork Creek less than 1 cfu
#3 Booker Creek 1 cfu
Caution level is individual reading above 400 cfu, or average above 200 cfu.
Lake water temperature was 26C/79F at all sites. The SECCI clarity reading was 42 inches, unusually clear and free of debris for this time of year. The rain gauge had a trace of water in it; I suspect someone has emptied it and not reported the result. I had about 2 inches in my yard, about a mile (as a crow flies) from the lake gauge.
The CFU readings are the best we have ever had in recent memory! We should never become complacent about this, but it is reassuring to know these readings are possible. I was surprised by the Cedar Fork Creek inlet reading, the bay was absolutely full of geese and ducks, all scolding me for being there.
I adjusted my sampling location for site #1 because the near dock has drifted about 25-30 yards to the left (as viewed from the beach) from its normal location. That location is the deepest point in the lake, about 14 feet. That location is 20-25 yards beyond the safety line that is parallel to the shore on the far side of the swimming area, and roughly centered on that line. That location represents the confluence point in the lake of the two main tributary streams.
We have not had a previously –normal June algae-bloom and die-off for the last couple of years, and we may not have one again this year.
Our next thing to watch for is silt entering the lake. This is a normal process in this part of the US, which occurs without human intervention. If we did not manage it, most of our lake would become a meadow is about 15-20 years. We have two forebays, one in the lake on the Cedar Fork creek inlet side, and one upstream on the Booker Creek inlet. This forebay is behind the wetland (swamp) at the southwestern end of the lake, near the N. Lakeshore bridge between Kensington and Rock Creek. Forebays slow the water coming into the lake, providing an opportunity for mud and silt to settle out, following the same principle used in wastewater filtration. When we have prolonged hard rain and see light muddy colored plumes of water in the lake, this is silt that has made it past the forebay.
Our watershed is 4 square miles, mostly to the North and West of the lake. The intersection of Weaver Dairy Road and Martin Luther King Jr. Blvd is near the northwest corner of it. Development in the watershed disturbs the soil and makes more of the surface “impervious” through paving and building. This keeps water from soaking in, so rainwater runs faster, carrying more silt and sand. Builders are supposed to put up barriers to this erosion during construction. Most builders are pretty good at doing what they are supposed to do to stop erosion. It doesn’t always work. If we stay vigilant, we can catch problems quickly.