Effects of Discharge of Spent Cooling Water from an Oligotrophic Lake to a Polluted Eutrophic Lake

Abstract

Water quality and related management issues for a proposed lake source cooling (LSC) facility discharge of water from oligotrophic Lake Ontario to polluted eutrophic Onondaga Lake, NY, are considered in the context of ongoing rehabilitation programs for domestic waste and industrial contamination at Onondaga Lake. The analysis is supported by monitoring data for the lakes, a nearby LSC facility, a domestic wastewater treatment discharge (Metro), and local meteorological conditions. Model simulations are presented to address effects of a LSC discharge on thermal stratification, hypolimnetic dissolved oxygen, and epilimnetic total phosphorus, critical features for cold water fish and eutrophication. Eight LSC discharge scenarios, representing a range of flows, entry depths within the lake, and mixture with Metro effluent, are identified and evaluated. The high salinity of Onondaga Lake would prevent retention of the LSC discharge within the hypolimnion and associated benefits with respect to oxygen resources. Further, a hypolimnetic discharge would increase the upward transport of undesirable constituents mobilized from the sediments. In contrast, water quality and habitat benefits for two metalimnetic LSC discharge scenarios were predicted that would either ameliorate the lake’s cultural eutrophication problem or could serve to provide a modest refugium for certain cold water fish.