A modeling analysis of THM precursors for a eutrophic reservoir

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Mass balance modeling analyses were conducted for trihalomethane (THM) precursors in eutrophic Cannonsville Reservoir to resolve the contributions of allochthonous and autochthonous inputs to the reservoir's precursor pool, and to move toward a predictive tool that would support related managementactions. The analyses focus on the April-November interval of 1995, and are supported by detailed external loading (Stepczuk et al. 1998a) and reservoir water column (Stepczuk et al. 1998b) data for precursors. Net autochthonous production of precursors in the epilimnion, apparently driven by primary productivity, was a major source of precursors for the reservoir, representing about two-thirds of the cumulative mass input over the April-mid-summer interval. An undefined loss process(es) operated simultaneously during the study period. Major differences in behavior of the dissolved organic carbon (DOC) and THM precursor pools of the reservoir, depicted by the modeling analysis, are not supportive of the use of DOC as a surrogate estimator of precursor concentration. A preliminary mechanistic precursor model, developed by adding a primary production-based source term and a first order loss/decay term to a eutrophication model for the reservoir (Doerr et al. 1998), performed reasonably well in matching the precursor patterns observed for the lacustrine zone of the reservoir in 1995. An analysis conducted with this model indicates the need to resolve differences in the lability of allochthonous and autochthonous inputs within the model framework. © 1998 Taylor & Francis Group, LLC.

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Lake and Reservoir Management