Modeling Cl concentration in Cayuga Lake, U.S.A.

Abstract

The annual average concentration of Cl in Cayuga Lake, NY, has decreased from a value of approximately 102 mg L−1 in 1970, when the discharge of NaCl fines from an adjoining rock salt mine was discontinued, to a concentration of approximately 46 mg L−1 in 1988. A complete-mixed model for Cl concentration accurately simulated this decrease in concentration, establishing that the decrease was the result of an abrupt reduction in loading. The time course of the decrease strongly supports the position that the high Cl concentrations that prevailed in the lake in the late 1960's were largely a result of the discharge from the mining facility, and not due to the input of enriched groundwater as previously hypothesized. The predicted steady-state Cl concentration associated with the complete flushing of the mining facility input, expected in about the year 2000, is approximately 32 mg L−1. Further, the model analysis supports previous speculation that the major source of material loading to the lake, the Seneca River, ‘short-circuits’ to the outlet; i.e., this tributary should not be included in material budgets for the lake.