Simulation of Terrigenous Minerogenic Particle Populations in Time and Space in Cayuga Lake, New York, in Response to Runoff Events

Abstract

The important effects of minerogenic particles delivered from watersheds on optical and phosphorus metrics of lacustrine water quality have recently been quantified through measurements of the projected area of these particles per unit volume of water (PAVm), using an individual particle analysis technique. A mass balance type model for PAVm, partitioned according to the contributions of four size classes, is developed and tested for Cayuga Lake, New York, supported by long-term monitoring of PAVm in the lake and its primary tributaries. The model represents the source of PAVm of tributary inputs and three in-lake loss processes: (1) size-dependent settling, (2) enhancement of settling through aggregation, and (3) filter feeding by dreissenid mussels. The central roles of major runoff events and localized external loads of minerogenic sediment at one end of the lake in driving patterns of PAVm in time and space are successfully simulated, including (1) the higher PAVm levels in a shallow area (“shelf”) adjoining these inputs, relative to pelagic waters, following runoff events; and (2) the positive dependence of the shelf increases on the magnitude of the event. Analyses conducted with the model establish that settling, with aggregation enhancement, dominates the loss of PAVm from the water column of the shelf, while mussel filtration increases in relative importance in pelagic waters. The utility of PAVm predictions to quantify the effects of these particles on optical and phosphorus concentration metrics of water quality is established.