Estimating the Likelihood of Harm to Lakes from Groundwater Withdrawals in the St. Johns River Water Management District for the Year 2025

摘要

A geographic information systems-based model was developed to predict the likelihood of harm to lakes in the St. Johns River Water Management District (SJRWMD) from future groundwater withdrawals. Six spatial data layers representing hydrogeological features that characterize or influence lakes, including the thickness of the confining unit, head difference between the surficial and Floridan aquifer water levels, soil permeability, wetland frequency, topographic curvature (regionally high or low elevations), and topographic deviation (local hills and valleys), were combined to produce a map of lake susceptibility to groundwater withdrawals. This map was then combined with GIS layers representing SJRWMD lakes and estimated drawdown of the surficial aquifer for the year 2025 to produce a final map showing likelihood of harm to lakes within SJRWMD. Parts of Seminole County, Orange County, southeastern Lake County, and central Volusia County contained a high concentration of lakes at risk of harm from groundwater withdrawals by the year 2025, reflecting the occurrence of lakes susceptible to drawdown and modeled declines of surficial aquifer water levels in these areas.