Hydrology and water quality of isolated wetlands: Stormflow changes along two episodic flowpaths

Abstract

The Dougherty Plain in southwest Georgia is a flat, karstic, depressional-landscape dominated by irrigated and dry-land agriculture devoted to row-crops and pasture with interspersed wetlands and forests. Stormwater runoff rarely discharges into perennial rivers and streams, except during large storms that induce hydrologic connectivity between fields, wetlands, and streams (event return period is less than one per year).We report the hydrologic and water-quality effects of a 173-mm rainfall event that generated three weeks (Feb 15 to Mar 9, 2014) of continuous flows through and between three normally isolated wetlands. A suite of water-quality parameters (physical, nutrients, and pathogen indicators) was monitored daily from offsite (agricultural) and onsite (forested) sources at two sites along one flowpath and five sites along a second at the Joseph W Jones Ecologic Research Center at Ichauway.Decreasing sediment, nutrient, and pathogen concentrations were observed as water moved across the forested landscapes with embedded wetlands. Two physical parameters (specific conductance and turbidity) were strongly-to-moderately correlated (r > 0.8, 0.5, respectively) with laboratory-measured parameters (e.g., nutrients, suspended solids, pathogens), which suggest their utility for routine stormwater monitoring and prioritizing sample collection for laboratory analyses at this site. Keywords: Longleaf-pine, Isolated wetlands, Stormflow, Agricultural runoff, Water quality, Dougherty plain, Nutrients, Pathogens