Declining nitrogen (primarily nitrate) concentrations in the Upper Floridan aquifer within the Santa Fe River Basin, Florida (2014‐2024)

Since the 1950s, land use applications of nitrogen have resulted in increased nitrate (NO 3 + NO 2 as N) concentrations in waters of the Santa Fe River Basin. In 2008, the Florida Department of Environmental Protection declared the waters impaired. A restoration plan was enacted to lower concentrations to a threshold of 0.35 mg/L and monitor restoration progress. For springs and surface water, nitrate-loading data are used for tracking. For groundwater nitrate concentrations are used. To assist the Department, Alachua County Environmental Protection Department, AquiferWatch, and Florida LAKEWATCH are now monitoring groundwater. The latter entities use volunteers to sample. Assessment of historical data in the basin indicates that nitrate is the predominate nitrogen species. Trend analysis revealed that on a decadal scale, since 2014 in the lower basin, nitrogen (mostly nitrate) levels decreased. Reductions are tied to increase rainfall and groundwater dilution but not necessarily to modifications in land use. Once informed of these findings, the Department adjusted its monitoring strategies to better track NO 3 loading changes and correlate them with changes in nitrate concentrations in groundwater and potentially other indicators. The actions will improve its ability to track restoration progress. Finally, volunteers obtained reliable data at reduced monitoring costs.