The Ohio EPA’s recent assessment of the East Fork of the Lower Miami River (EFLMR) identified segments of the main stem and major tributaries as impaired due to nutrient enrichment, sediment runoff and poor habitat. In addition, estimates from the U.S. EPA-ORD watershed modeling indicate row-crops contribute approximately 70% of the nitrogen and phosphorus flushing into East Fork streams in the upper watershed above Harsha Lake. Excess nutrients fuel Harmful Algal Blooms (HABs) which have been increasing in frequency and intensity in William H. Harsha Lake since 2008.
Harsha Lake is a drinking water source for +100,000 residents and serves as a $1.6 million regional hub for outdoor recreation. HABs have led to increased water treatment costs, public health advisories, beach closures, and event cancellations.
The Williamsburg Off-Channel Wetland utilizes an existing 3-acre reservoir located in the Village of Williamsburg. The reservoir was formerly connected to a low-head dam on the EFLMR; the dam was removed, and the reservoir was drained in 2018.The former reservoir is adjacent to the East Fork of the Little Miami River. Hydrologic and hydraulic modeling served as the basis for the floodplain wetland complex design. The preliminary project scope entails improving the connectivity of the river and floodplain by creating a gravity-connected inflow and outflow channel that will be cut through the existing berm in two locations. As originally planned, this improved connectivity would provide important spawning and nursery habitat for fish and other aquatic life.
Water quality monitoring is a significant component of this project. A key outcome of this work will be an assessment of the nutrient removal efficiency of the constructed wetland. Clermont OEQ works regularly with regional partners to manage a robust water quality sampling program for the EFLMR watershed, including an agricultural wetland demonstration project funded through a Conservation Innovation Grant (CIG) (2012). The wetland was designed as a linear submerged vegetative bed with the capacity to treat sediment and nutrient runoff from 80 acres of surrounding row-crop fields. Clermont OEQ’s water quality analysis of the CIG project site has shown an approximate 30% removal efficiency for sediment and nutrient removal. Due to the proximity of the Williamsburg project site to the EFLMR and opportunities to improve storage capacity with additional excavation, project partners estimate a 40-50% reduction in the nutrient and sediment loading entering the system.
Human Interest/Community Benefit:
Water quality improvement for the potable water supply for >100,000 southwest Ohio residents and an improved aquatic recreation experience for a high-use reservoir.
Project Timeline:
Project completion is scheduled for 9/30/22
Partners:
USFWS Fish Passage Program
U.S. EPA
Clermont Office of Environmental Quality
Clermont Soil and Water Conservation District
Ohio DNR H2Ohio
Village of Williamsburg
Buckeye United Fly Fishers
Bethel Boy Scouts
Duke Energy Foundation