Measuring Wetland Recovery
More than 60 percent of Tampa Bay Water’s drinking water supply comes from groundwater wells located in and around Tampa Bay area wetlands. Wetlands are saturated lands filled with marshes, swamps, gators and birds, and their health is essential to our region’s water supply. Wetlands are particularly vulnerable to human activity and changes in land use, and therefore are carefully monitored and protected by federal, state and local laws.
This is the second of a three-part series for American Wetlands Month. American Wetlands Month is sponsored by the Environmental Protection Agency.
As with any water supply source, Tampa Bay Water carefully monitors the environment in and around regional wellfields and wetlands. Tampa Bay Water uses monitoring wells to assess the health and recovery of once-damaged wetlands by gauging water levels in both the Floridan aquifer and the shallower surficial aquifer as well as the wetlands themselves.
Ecosystems in wetlands are complex and extremely sensitive to changes in rainfall and temperature. As temperatures increase and rainfall decreases during times of drought, water levels in wetlands drop or even disappear, and the plants and trees can become severely stressed. Tampa Bay Water and the District have implemented several long-term monitoring programs to measure changes in water levels and wetland habitat. Groundwater production is managed and shifted in response to these changes, and other environmental factors such as changing weather patterns.
In accordance with its water use permits, Tampa Bay Water must meet minimum wetland water level requirements established by the District. Healthy wetland water levels should be above the minimum level at least half the time, and below it half the time. In 2002, before the first alternative water supply was introduced into the regional water supply system, data showed that only 24 percent of select wetlands met this standard of health. By 2012, the same wetlands were measured and the amount significantly increased to 62 percent of wetlands meeting this standard of health.
As a sign of recovery, water levels in lakes and wetlands are once again responding appropriately to rainfall trends – water levels are high at the end of the summer rainy season and lower at the end of the spring dry season.
Tampa Bay Water uses plant growth as a bio-indicator when measuring wetland recovery. Plant and tree types are assigned to specific zones, and if certain plant types are not growing in the proper zone it may indicate that water levels aren’t getting high enough. For example, upland trees like pine trees should not be growing next to cypress trees in the middle of a wetland.
Monitoring efforts generate data that is used to establish water level fluctuations within ranges appropriate for each wetland considering its surrounding landscape. By tracking environmental data, Tampa Bay Water is able to assess current conditions and predict regional trends. This knowledge enables Tampa Bay Water to evaluate the success of our environmental recovery efforts.
Since wetland recovery measures were implemented, Tampa Bay Water has documented wide-spread improvements in wetland health due to reduced groundwater production and normal to above-normal rainfall. On average, Floridan aquifer levels have increased an average of 10.4 feet near Tampa Bay Water’s wellfields since the first alternative water supplies were introduced into the regional system in 2002. Lakes and wetlands on and in the vicinity of those wellfields have also seen a dramatic increase in water levels.