Assessing coliform ratios in depressional wetlands as potential indicators of hydrologic connectivity

Depressional wetlands occur in dense clusters on the Dougherty Plain, a physiographic province of Georgia dominated by agricultural land use. These wetlands represent a major potential storage of surface water in southwest Georgia. Hydrologically, these systems are primarily driven by precipitation and evapotranspiration, but a substantial subset are connected to episodic storm flows. The water quality of wetlands connected to episodic flows (recurrence interval <2 years) differ from those that are more isolated from flows (recurrence interval >2 years). However, the extent and / or source water of wetland connectivity is unknown. It may be possible to determine these wetland characteristics through water quality methods. In ecological water quality studies, Esherichia coli and total coliform ratios can indicate wildlife presence or the influence of agricultural stormwater / anthropogenic contamination depending on landscape context. The objectives of this study are to: 1) analyze coliform ratios from an episodic flow event for potentially identifying source waters; 2) analyze coliform ratios in a subset of depressional wetlands with regard to episodic flow connectivity; and 3) determine additional water quality variables that may be associated with coliform ratios in depressional wetlands. Water quality data were collected from seven sites along an episodic flow path during an episodic flow event (February-March 2014). Data were also collected through monthly monitoring of 31 depressional wetlands on the Dougherty Plain (March 2014 March 2015). A suite of biological (coliforms), chemical (nutrients, dissolved carbon), and physical (conductivity, turbidity, dissolved solids) water quality parameters were measured. Preliminary analysis indicates that greater ratios of E. coli to total coliforms were observed in wetlands connected to episodic flows and in depressional wetlands isolated from flows. Results are directly applicable to determining depressional wetland source waters as well as source water signals in episodic flows.