76-10 Effectiveness of a Roadside Two-Stage Ditch for Nutrient Reduction in an Agricultural Watershed, Iowa, USA

Session: Contaminants Near Groundwater-Surface Water Interfaces

Presenting Author:

Authors:

Abstract:

Runoff associated with agricultural practices presents water quality problems in rivers and streams throughout Iowa. Conservation practices installed at the edges of fields have proven effective for nutrient and sediment reductions. Additional mitigation potential exists within drainage ditches that connect fields to streams, and the two-stage ditch design has been shown to be an effective BMP to reduce nutrient and sediment loading. The Iowa Geological Survey partnered with the Iowa Department of Transportation to design, construct and monitor a unique two-stage roadside ditch along the westbound lane of Highway 30 in Benton County. The ditch drains a 0.75 mi2 catchment and flows approximately 1500 feet before discharging into Prairie Creek. Upstream and downstream sediment turbidity and nutrient concentrations were measured during four (4) runoff events. Suspended sediment and nitrate concentrations variably decreased during storm runoff events, and generally improved as vegetation progressed in establishment.  Potential locations for installing similar two-stage roadside ditches across Iowa are being identified and utilized to estimate potential nutrient reduction benefits if adopted statewide. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9202

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