Wetlands ecosystems have high levels of biodiversity and are necessary for flood protection and nutrient cycling. Although they are sensitive to changes in precipitation, surface run-off, and groundwater release, the flooding, or inundation, of wetlands is important for maintaining the health of the ecosystem. As wetlands flood, the soil is able to store carbon and nitrogen and can increase the diversity of amphibians. Land development, climate variation, and groundwater extraction may impact the extent and timing of wetland flooding.
CEID’s Andrew Kramer and a research team conducted a comparative study to identify sources of variation of wetland inundation for 152 freshwater wetlands in west-central Florida during the 2005-2009 and 2010-2018 time periods. These time periods are distinctly separated due to the implementation of water conservation policies in 2009, which reduced groundwater extraction activity in this region. The team specifically focused on the effects of nearby land development, precipitation, groundwater extraction, topographic basin features, and vegetation classification on wetland flooding.
Around the world, groundwater is extracted to supplement water demand during periods of drought, which negatively affects ecosystems that are dependent on this water source. Groundwater extraction can lower water tables, and deplete aquifers, which can lead to droughts. Climate change can also exacerbate drought conditions in wetlands by decreasing water input via decreased precipitation.
For the 2005-2009 time period, results showed lower water levels and shorter hydroperiods (the portion of the year when the wetland has ponded water) in the wetlands, which correlated with low amounts of rainfall and high levels of groundwater extraction. After the passing of the water conservation policies, years 2010-2018 saw the median hydroperiods increased by 37% and the median wetland water depth increased by 1.35 meters. These changes were associated with lower rates of groundwater extraction. During this second time period, precipitation levels increased inundation, likely due to greater amounts of groundwater being available to be stored in wetland basins. Inundation varied significantly between wetlands even after a variety of explanatory variables were accounted for, and the individual differences between the ecology and typical levels of water flow for specific wetlands are likely influential on inundation.
These findings display the success of the 2009 water conservation policies in limiting the impact of groundwater extraction on wetland flooding. Future water conservation policies should consider that wetland flooding is more likely to be impacted by groundwater extraction during periods of low rainfall levels.
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By: Brenna Daly