Modeling Water, Sediment and Organic Carbon Discharges in the Hudson-Mohawk Basin: Coupling to Terrestrial Sources

Abstract

A previous modeling study (Howarth et al. 1991) showed the potential of a simple watershed hydrology model, the Generalized Watershed Loading Function model (GWLF, Haith and Shoemaker 1987) for estimating annual loads of sediment and organic carbon to the Hudson River from various land uses in the upper portion of the basin. We examined the quality and accuracy of model outputs after making two major modifications. First, we used a geographic information system (GIS) and several environmental databases to improve model estimates of several parameters. Second, we evaluated alternative methods for incorporating weather data.We examined seasonal variation of model output as well as annual averages. Annual fluxes increased over those of Howarth et al. (1991) by 10% for sediment and 20% for TOC for the Hudson-Mohawk basin, resulting in closer agreement with measurement-based estimates. The estimated fluxes exhibited a strong seasonal component, with greates sediment load occurring during a few sping events. Finally, model estimates of fluxes associated with forested and agricultural scenarios, characteristic of earlier periods of the region’s history, predicted a doubling of sediment and TOC loading in an agriculturally dominated Hudson basin but a reduction of sediment by 90% and of TOC by 60% in a completely forested basin.