2006 Greater Everglades Ecosystem Restoration Conference

Standard Characterization of Canal Water Penetration into the Interior Marsh of the A.R.M. Loxahatchee National Wildlife Refuge

Donatto Surratt, Mike Waldon and Matthew Harwell

A.R.M. Loxahatchee National Wildlife Refuge, Boynton Beach, FL, USA

June 5-9, 2006 Lake Buena Vista, Florida To assess the influence of water management operations on canal water intrusion into the marsh interior of the A.R.M. Loxahatchee National Wildlife Refuge, we examined structure operations (flows and stages along canals and at structures) along with spatial patterns of conductivity along a series of transects from canals to marsh interior as part of the Refuge’s Enhanced Water Quality Monitoring and Modeling Program (http://www.sofia.usgs.gov/lox_monitor_model). Two spatial approaches characterizing canal water intrusion were examined at different time periods, including under hurricane and non-hurricane conditions in August 2004 and 2005. In the soft-water rainfall driven interior marsh, conductivity acts as a fairly conservative tracer, allowing us to characterize the magnitude of canal water penetration into the interior.
The first approach examined the gradient of conductivity for a series of marsh sites at varying distance from canals as snapshots in time. The second approach combines spatial trends and time series data to generate conductivity isopleths. These isopleths allow us to track penetration of particular water fronts and assess their relationship to structure operations.
In one example, comparison of hurricane and non-hurricane periods with respect to canal water intrusion into the marsh, demonstrates that operational structures supplying and removing water to and from marsh perimeter canals had a strong influence on canal water penetration into the interior marsh. Net inflow of water into the canals was 2 orders of magnitude greater in August 2004 than in August 2005 and August 2004 canal stage increase was ~2 times greater than August 2005 stage increase. Conductivity values greater than 500 uS cm-1 were observed further than 2 km into the marsh interior in August 2004, while conductivity at 0.5 km were less than 300 uS cm-1 in August 2005.
In the context of this study, these observations suggest that canal water intrusion into the marsh interior is related to both canal and marsh stage differences and net inflow of water into the marsh perimeter canals. These and similar finding will be discussed in further detail.

Contact Information: Donatto Surratt, A.R.M. Loxahatchee NWR, 10216 Lee Road, Boynton Beach, FL, 33437 USA, Phone: 561-735-6003, Fax: 561-735-6008, Email: donatto_surratt@fws.gov