Modeling the Fate and Transport of Plunging Inflows to Onondaga Lake

Abstract

The transport and fate of two plunging tributaries, Onondaga and Ninemile Creeks, in Onondaga Lake, New York, are quantified based on application of hydrodynamic/transport models. Short-term transport is simulated with a three-dimensional Estuary Lake and Coastal Ocean Model (ELCOM), while the longer term fate is represented by a previously validated one-dimensional model (UFILS4). The validation of ELCOM for the vertical distribution of tributary inflow into the lake's water column is demonstrated for four dye tracer experiments. The models are applied for three years to represent the dynamics of transport and fate for the two tributaries, with ELCOM predictions serving as input for UFILS4. The models together quantify the distribution of these inflows between the upper mixed layer (UML) and stratified depths, and the subsequent transport from stratified depths to the UML by vertical mixing. Substantial short-term variations are predicted for both tributaries in response to variability in hydrology and weather. Increased inflow to the UML is predicted for high runoff periods. The fraction of Ninemile Creek's inflow directly entering the UML is predicted to be 50% greater than for Onondaga Creek due to Ninemile's lower negative buoyancy. The plunging phenomenon has important water quality implications, by reducing the effective loading to the UML, particularly for constituents with large rates of loss/transformation relative to the rate of vertical transport from stratified depths.(KEY TERMS: environmental impacts; lakes; plunging inflows; transport and fate; models.)

Evaluation of Offshore Wastewater Outfall and Diffuser for Onondaga Lake, NY

“…Bacteria mediated losses are likely operative, though not presently quantified. Secondly, the contemporary tributary contributions to the summertime TDP L to the upper waters (Figure 2) are overestimated because these do not accommodate the effects of plunging that prevails to varying extents for important tributaries [35][36][37].…”

Resolution and Analysis of Spatial Variations and Patterns in an Urban Lake with Rapid Profiling Instrumentation

“…Matthews et al ., , unpublished data), respectively, was consistent with the differences in negative buoyancy of these inputs (Figure ). These efficiencies are subject to substantial short‐term variations in response to the dynamics of ambient mixing and runoff (Owens et al ., ). Moreover, the same ordering for the entry depth from plunging was predicted (e.g., Metro the shallowest).…”

“…The plunging of the tributaries and Metro diminishes the impacts of the external loads delivered by these inflows relative to upper mixed layer entries for issues of the upper lake waters, such as primary production (trophic state) (Effler et al ., , ) and acceptable FC levels for contact recreation (Canale et al ., ). The plunging phenomenon likely occurs more widely than is presently recognized (Owens et al ., ). Where the phenomenon is not recognized, the expected or model projected benefits for a lake from systematic loading reductions in negatively buoyant inflows will be overstated.…”

“…Matthews et al ., , unpublished data) to metalimnetic depths over the summer. The order of these predicted average efficiencies in reaching these depths, 75, 50, and 25% for Onondaga Creek, Ninemile Creek (Owens et al ., ), and Metro (for the predominant case of SC not being elevated from construction dewatering) (D.A. Matthews et al ., , unpublished data), respectively, was consistent with the differences in negative buoyancy of these inputs (Figure ).…”

“…Moreover, this system represents an appropriate site to further develop and test robust hydrodynamic models that can simulate these features of transport, and ultimately serve as the physical framework(s) for water quality models for this lake and other systems influenced importantly by these buoyancy effects. These signatures have been invaluable in supporting progress in related hydrodynamic modeling initiatives (Owens et al ., , ).…”