IGS RESEARCH SUPPORTS WATER QUALITY IN IOWA
Erosion and Sediment Delivery in Southern Iowa Watersheds: Implications for Conservation Planning by Matthew Streeter
SEDIMENT DELIVERY (% OF FIELD EROSION)
SEDIMENT ERODING FROM AGRICULTURAL croplands is a major contributor to waterquality impairment in midwestern streams. Reducing soil export from agricultural watersheds is a key component of the Iowa Nutrient Reduction Strategy. Over the last few decades, improvements in land management and installation of best management practices (BMPs) have reduced field-scale soil erosion, but water-quality benefits of BMPs have been poorly quantified. Reducing the amount of soil erosion occurring from field to field is not the same as reducing the amount of sediment exported from a watershed, so sediment delivery ratios (SDRs) are used to estimate the fraction of gross soil erosion exported from a watershed for a given period of time. In 2020, IGS Soil Scientist Matthew Streeter and State Geologist Keith Schilling published new research in the Journal of Soil and Water Conservation that studied five eastern Iowa watersheds ranging in size from 8–1,487 km2. Their objective was to develop a new SDR curve for the Southern Iowa Drift Plain landform region in southeast Iowa that accounts for the effects of currently implemented BMPs, as well as current climatic conditions. The watersheds of interest included the HUC 12 Rapid Creek Watershed in Johnson County and two of its headwater subbasins,
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