A Spatially Distributed Groundwater Metric for Describing Hydrologic Changes in a Regional Population of Wetlands North of Tampa Bay, Florida, from 1990 to 2015

A groundwater condition metric is presented and used to evaluate hydrologic changes in a regional population of wetlands in and around municipal well fields with large groundwater withdrawals. The approach compares a 26-year, monthly time series of groundwater potentiometric surfaces to light detection and ranging (LiDAR) land-surface elevations at 10,516 wetlands in a 1505-km(2) area. Elevation differences between the potentiometric surface and the wetland land surface provide flow direction (upward or downward) and a proxy for vertical hydraulic-head difference in Darcy's groundwater flow equation. The resulting metric quantifies the groundwater condition at a wetland through time as the potential for groundwater to discharge upward into a wetland or for water in a wetland to leak downward to recharge the underlying aquifer. The potential for wetland leakage across the regional wetland population decreased by 33% in the 13 years after cutbacks in groundwater withdrawals (2003 - 2015) compared to years before cutbacks (1990 - 2002). Inside well-field properties, wetland leakage potential decreased by 24%. In the wet season month of September, wetlands with the potential to receive groundwater discharge increased to 21.6% of the regional population after cutbacks compared to 13.3% before cutbacks. When mapped across regional drainage basins, discharging wetlands formed spatial connections, suggesting they play a critical role in generating streamflow.

Automated summary

A groundwater condition metric was used to evaluate hydrologic changes in regional wetlands, showing a decrease in wetland leakage potential after cutbacks in groundwater withdrawals. Wetlands with the potential to receive groundwater discharge increased in the wet season following the cutbacks, suggesting the importance of wetlands in generating streamflow across regional drainage basins.