Subsurface permeability is a key parameter that controls the contribution of the subsurface flow to stream flows in watershed models. Directly measuring permeability at the spatial extent and resolution required by watershed models is difficult and expensive. Researchers therefore commonly estimate permeability through inverse modeling. The wide availability of stream surface flow data compared to groundwater monitoring data provides a new data source for integrated surface and subsurface hydrologic models to infer soil and geologic properties.