Modeling the effects of vegetation on stream temperature dynamics in a large, mixed land cover watershed in the Great Lakes region

Abstract

Stream temperature controls biological processes and affects the species composition of aquatic communities. Riparian vegetation plays an important role in influencing stream temperatures due to vegetation shading and by changing the riparian microclimate (wind speed, relative humidity, etc). This paper explores the effects of spatial heterogeneity in riparian vegetation on stream temperature using a process-based hydrologic model in a 5200 km2 mixed land-use watershed (Kalamazoo River, Michigan, USA). By explicitly incorporating interactions of thermal and water fluxes at the air-land surface and surface-subsurface interfaces, the model enables comprehensive representation of stream thermal dynamics. The riparian land-use effects on stream temperature are represented by coupling with a vegetation phenology module. The riparian land-use information is rescaled using different nested resolutions within a model grid cell to represent the land-use effects on stream temperature to show that a resolution of 90 m × 90 m best represents the land-use effects while simulating stream temperatures using 1 km × 1 km model grid cells. The simulation covers a 7-year period from 2003 to 2009, during which period the results are compared with multiple observations. Stream thermal budgets and responses of stream temperature to vegetation change scenarios including potential deforestation effects are reported.