Summary of Cayuga Lake and its watersheds 1927 to 2008

Summary of Cayuga Lake and its watersheds 1927 to 2008 Bouldin, David The data base consisted of Cayuga Lake data from 1927, 1968-1974 and 2000 to 2008 and water shed data from 1972 through 2008 – overall on the order of more than 2000 samples. An excel spreadsheet was developed to analyze this data as a calcium-carbonate-phosphate system and interactions with biomass and chemical precipitation. First, as is well known, the Lake is a huge reservoir containing an amount of water equal to 10 years of runoff. This means consequences of changes in watersheds occur gradually but once changed are difficult to reverse. Second, calcium carbonate chemistry of the lake has not changed 1927 to 2008. ALL (1927 to 2008) of the calcium carbonate parameters fit nicely on one cluster of points around one line. The stream water deviates slightly from the lake data but clearly belongs to the same “family”. Third, for the stream data, concentrations of phosphate, nitrate and sediment increases as flow increases and the relation between flow and concentrations has not changed 1972-2008. Fourth, the most reactive phosphate fraction in lake samples (1968-1974 plus 1999-2008) fits within a framework defined by slightly soluble calcium phosphates. As pH increases, the solubility decreases. This provides a feed back mechanism which reduces the impact of inputs of phosphate; photosynthesis reduces the total inorganic carbon in solution and increases pH which in turn decreases solubility and slows photosynthesis. Stream samples do not conform to this framework. Fifth, the concentration of most soluble phosphate fractions of stream water, mixed with inputs from waste water treatment and lake source cooling, decreased by a factor of more than 2 as measured by sampling within 100 m from stream input and to about the concentration of bulk lake in samples at 1000 m from inlet. This is hypothesized due to some unknown combination of dispersion, biological immobilization and precipitation. Clearly, the changes within 1000 m from the inputs transformed the water into something very nearly like bulk lake water. Don’t mess with the inlet until we understand these transformations. Sixth, for future monitoring of streams, the Impact of flow and seasonal effects must include samples from all flow regimes and seasons or else misleading / useless data will be collected. Seventh, there are many discrepancies between observations and expectations based on solubility of mineral forms of calcium carbonates and calcium phosphates. But these relationships are not happenstance – so what is the basic chemistry? In 1972 a project was initiated to study the impact of human activity on water quality in NY with partial funding from the Rockefeller Foundation. Over the next 5 years a multidisciplinary group studied social, economic, and environmental aspects of human activities in central NY and summarized their findings in a book which influenced and influences applied research and extension. I was very fortunate to be part of that work and subsequently I have continued to study water quality in central NY periodically to 2008. During the initial work, Dr R.T. Oglesby introduced us to the limnology of lakes (Cayuga Lake in particular) and I have continued to work on understanding interactions between Cayuga Lake and its watersheds. See also the report "Lake and Phosphorus Inputs: A Focus on Management": http://hdl.handle.net/1813/30560