2nd UF Water Institute Symposium Abstract

Submitter's Name Rosanne Prager
Session Name Poster Session: Hydrologic, Biogeochemical and Ecological Processes 1
Category Hydrologic, biogeochemical and ecological processes
Poster Number 237
Author(s) Rosanne Prager,  CH2M HILL
  Steven Eakin,  CH2M HILL
  Managed Hydration Demonstrates Avoidance of Wetland Impacts by Groundwater Alteration
  Groundwater withdrawal can potentially result in impacts to surface wetlands by lowering the water table of the surficial aquifer. Active hydration by metered application of groundwater, and passive hydration by construction of a control weir in an outfall ditch are two possible strategies to maintain viable wetland hydrologic characteristics and avoid adverse drawdown affects on wetland resources. A five-year demonstration project was conducted by the St. Johns River Water Management District in northeast Florida in coordination with land owners and four regional water supply utilities to investigate the effectiveness of these two augmentation strategies. Completed in September 2008, the study yielded conclusions useful to the adaptive management and avoidance of impacts by well field operations. Wetlands managed by active hydration showed improved hydrologic conditions within the first year. Passive hydration did not compensate for deficits in rainfall-driven water inputs and was a less reliable strategy. Surface water elevations were controlled by outlet weir elevation but overall success was dependent on rainfall. Implementing control weirs in conjunction with active hydration could provide greater management flexibility and a faster hydrologic response. Amphibian communities, a sensitive indicator of wetland hydroperiod in contrast to plant communities, responded quickly to increased surface water availability from rainfall, hydration, or both; without adverse affects. A minimal amount of ecological data was needed to develop the wetland target hydrograph and an optimal augmentation schedule (quantity and timing). The target hydrograph can provide a useful metric for maintaining an ecological condition that avoids unacceptable harm. A comparison of active hydration unit costs (i.e., water delivery system, monitoring equipment, and data reporting) to unit costs of purchasing mitigation bank credits indicated that active augmentation can be cost-effective.