Water monitoring results
Sacandaga Lake: Summary of CSLAP data
One of the more crucial missions of LPSA is the monitoring of our lakes for water quality and invasive species. To assist us in the former, we have enrolled in DEC’s CSLAP* (Citizen’s Statewide Lake Assessment Program) program starting in 1987. Association members are trained to measure water clarity on the lake, and collect and process water samples for later analysis by a state certified analytic lab. So far we’ve had three, five-year sample periods—1987-91, 1997-2001 and 2009-13—so we have good information over nearly three decades to look at how the lake is doing over the long run.
In general, Sacandaga Lake is classified by the DEC as “AA –suitable as a water supply, public bathing beach, general recreation and aquatic life support.” This is the second highest lake classification, and only a few lakes in the state, like Lake George, are ranked higher at “AA Special.” So we are fortunate that our lake has such good water quality, and it is LPSA’s primary goal to keep it that way.
The major characteristic of a lake that both contributes to our aesthetic enjoyment as well as indicates the biological “health” of the lake is its water clarity. We measure this by lowering an eight-inch diameter, black and white disc into the lake on a calibrated line to a depth where it disappears from view. The disc is called a Secchi disc and we call this disappearance depth the “Secchi depth.” The deeper the Secchi depth, the clearer the water. Secchi depth is determined by a combination of suspended solids (such as soil particles), the tea-colored molecules from tributary wetlands (measured as “color”), and algae. The good news from our 26-year CSLAP data set is that the water clarity in Sacandaga has not changed much at about 4-5 meters (13-17 feet). Whereasmany other NY lakes have seen deteriorating water clarity over this period, Sacandaga has not.
Many of the chemical tests supported by CSLAP are focused on factors contributing to water clarity. Both phosphorus and nitrogen will encourage algal growth, so both are measured at every sample date. In Sacandaga, phosphorus (P) is most important to algal growth, so we want to keep the lake’s P levels low. Over the 26 year sampling period, P levels have remained nearly constant, with the possibility of a slight upwards trend in the last five-year sample. Nitrogen levels have actually decreased over the 26 years, mainly due to the Clean Air Act that reduced the release of airborne nitrogen compounds. Chlorophyll levels, which indicate the size of the algal populations, have also slightly decreased over the 26 years, a small surprise since P levels stayed mainly constant over this period. However, the tea color of the water increased in the last five-year sample, perhaps due to the severity of some of the storms that flooded the lake. In summary, the chemical parameters most closely related to water clarity have stayed relatively constant over the sampling period, with some (nitrogen and chlorophyll) actually improving, whereas others (P and “color”) showing mild upward trends. The increasing P levels in the last five-year sample will be followed by us in subsequent years to see if the trend is real, and if so, we’ll try to determine its source.
Other chemical tests supported by CSLAP include acidity as measured by pH, which has remained fairly constant in the range of pH 7.5 to 6.5—roughly in the neutral range, Calcium levels remained constant and low at about 4 parts per million, which means that there is at least some bedrock in our watershed that contributes to the buffering of the acidity of the lake (helping to reduce the effects of acid rain). Another conclusion we can draw from these low calcium levels is that Sacandaga Lake is not now subject to infestations by zebra mussels, since they require about 15 parts per million calcium to build their shells. There is always the possibility that they may evolve to survive in our low calcium levels sometime in the future, but so far, so good.
Many lakes in NY have seen blooms of toxic blue-green (B/G) algae due to high nutrient levels, so in recent years CSLAP has been routinely measuring B/G levels as well as the toxins they produce. All lakes have some B/G algae as part of their natural algal populations, and Sacandaga is no exception. However B/G levels were quite low, and no toxins were detected.
The summer of 2013 ended our most recent 5-year sampling sequence for Sacandaga, and CSLAP has allowed us to start a sampling Lake Pleasant in 2014. We hope that we will be able to alternate sampling periods between the two lakes in the future. We have only the one year’s data for LP, and there were no surprises since LP is very similar to Sacandaga. We will continue to sample LP for a few more years so we can determine if there are any water quality trends that we need to study further.
* The CSLAP program is subsidized by the state. Each year the program supports the sampling of 80-90 lakes throughout the state with eight sample dates per summer resulting in about 15+ individual chemical analyses for each sample date. Analyses are run in state-certified analytical labs. We paid $460 for this service last year, and if we had get the same analyses done on our own from a lab without CSLAP support, it would cost between $2000 and $3000.
LPSA News JAN 27th
New Directory planned for Spring