Stevens Hydra Probe Soil Sensors Deployed in Florida Swamp for Restoration Study
By Keith Bellingham
Note: The full published research article is available for free through October 7, 2010 on the American Society of Agronomy website.
Coastal wetlands provide a large number of critical functions that can benefit the surrounding ecosystems but the neighboring human population centers. The healthy wetlands of the southeastern US help distribute billions of dollars into the local economy from commercial fishing, recreation, and tourism. Coastal flood plains and wetlands help prevent the flooding and destruction of coastal communities by storm surges, acting as a natural buffer to protect communities near the coast.
Despite their many benefits, there are many natural and manmade factors that threaten coastal wetlands. Federal and state laws now require the protection of these areas through better land use and water resources management practices. However, it’s not always clear which policy or management practice will be the most effective while weighing in other economic considerations.
The bald cypress (Taxodium distichum) is one of the dominant tree species of southeastern coastal floodplains. Bald cypress can flourish in wetlands, but is also very sensitive to certain environmental factors. The soil needs to stay moist for seeds to germinate and seedlings to thrive. If the soil gets too dry or stays overly saturated for too long, the ecosystem cannot sustain itself. The bald cypress is also sensitive to salt, and the intrusion of saline coastal waters can kill seedlings and even mature (>1000 year-old) trees.
Changes in hydrology and saltwater intrusion that threaten many coastal habitats are in part caused by manmade factors such as reduction in stream flow from dam diversions; municipal withdrawals from coastal fresh water aquifers, and changes in land drainage patterns. Excessive municipal water withdrawals can also pull saline seawater into the groundwater. Once in the groundwater or soil water (also known as porewater), salts threaten plants that thrive on fresh water like the bald cypress.
A four-year study was recently completed that characterized and modeled the hydrology of Florida’s Loxahatchee River floodplain. Conducted by Dr. David Kaplan and Dr. Rafael Muñoz-Carpena of the University of Florida’s Department of Agriculture and Biological Engineering, the study characterized and modeled the hydrology of Florida’s Loxahatchee River floodplain. Soil moisture and porewater salinity data were collected with Stevens Hydra Probe soil sensors at 24 locations. Meteorological data, groundwater levels and river flows were also monitored in the study.
To study how salt water intrusion was affecting the ecosystem, two study areas (transects) were selected, one upstream transect that contains freshwater, and a downstream transect that is transitionally-tidal, with changing salt water content during daily tide changes.
Several stations were installed along each transect, with each station containing three Stevens Hydra Probe soil sensors installed in vertical columns, to measure water content and salt water intrusion into the groundwater. The soil data provided by the Stevens Hydra Probes was recorded to a data logger at each station and downloaded by the research team every three to four weeks.
With this data, useful relationships between river channel flows, soil moisture and porewater salinity were developed to better predict the effects of proposed restoration and management scenarios.
The study found that the proposed wetland restoration plan, which includes maintaining adequate channel flows and limitations on groundwater withdrawals for agricultural and municipal uses, will provide adequate soil moisture and maintain porewater salinity below identified thresholds for bald cypress health, protecting the wetlands from further harm and helping to keep this natural resource healthy for future generations.
This work was recently published in the Journal of Environmental Quality titled, "Linking River, Floodplain, and Vadose Zone Hydrology to Improve Restoration of a Coastal River Affected by Saltwater Intrusion", and features the extensive data sets collected with the Hydra Probe soil moisture sensor. The article is available as a free download until October 7, 2010 on the American Society of Agronomy website (click on “Full Text” or “Full Text (PDF)” in the left-hand column to view the article). You can also read highlights from the study at the American Society of Agronomy's Newswise Site.
For more information about The Stevens Hydra Probe Soil Sensor, please visit the Hydra Probe product information page.