The Grass River Soil Water Assessment Tool: A model for predicting sources and sinks of sediment

Abstract

Soil Water Assessment Tool was implemented in the Grass River watershed, Michigan, to determine sources and sinks of sediments. The model was developed after watershed stakeholders such as the Tip of the Mitt watershed council and the Three Lakes Association, started receiving complaints from boaters who believed the Grass River was filling up with sediment at unprecedented rates. Small boat navigation was a concern. The model was developed from STATSGO soil data and 2006 era land cover extracted from Landsat Thematic Mapper imagery. Daily precipitation and temperature data from the Kalkaska climate station was used to force the model. Results from the uncalibrated model suggest that Finch Creek is the largest source of sediment in the Grass River, contributing some 401 tons/year over the period between Jan 1, 2006 and December 31, 2010. Cold Creek is the second largest source, contributing 166.8 tons/yr followed by Shanty Creek, contributing 50.0 tons/yr over the same period. Together the three tributaries contribute 363 cubic meters of sediment (equivalent to over 47 dump truck loads) every year to the Grass River. Several stream segments in Finch creek were found to be significant sinks of sediments. Sediments eroded mainly from areas underlain by the Emmet-Montcalm soil series. Urbanized areas in Shanty Creek appear to be significant sources of sediment, however much of this sediment is deposited before it reaches Grass River.