Title

Geochemical determinations of groundwater flow in Everglades National Park

Date of Award

2001

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Peter K. Swart, Committee Chair

Abstract

Both natural and anthropogenic tracers were used to provide estimates of groundwater flow within Everglades National Park (ENP). Groundwater was collected from both the freshwater and brackish portions of the Surficial Aquifer System (SAS) and from the underlying Hawthorn Group. Groundwater and surface water were collected on an approximately monthly basis from January 1997 to September 1999 for the following parameters: stable isotopes of oxygen and hydrogen, major cations and anions, specific conductance, salinity, temperature, and pH. In addition, groundwater was sampled once a year for three years for tritium, helium isotopes and CFCs in order to date the groundwater. Precipitation was collected in four locations for stable isotopes of oxygen and hydrogen.Groundwaters within the upper 28 m of the SAS had 3H/ 3He ages of less than 42 years and were recharged locally by either the overlying surface water or rainfall. Deeper groundwater within the SAS (>28m) was older than 42 years and recharged by rainfall upgradient of the northern boundary of ENP. There was little connection of water flow between Shark Slough and Taylor Slough suggesting that the two watersheds be managed separately. Horizontal groundwater flow rates in Taylor Slough estimated using 3H/3He ages varied from 386 to 500 m yr-1 and were similar to Darcian flow. Poor correlation between CFCs and 3H/3He ages suggested that CFCs were degraded in the Everglades environment. A linear increase in Delta 4He with depth suggested that radiogenic 4He produced in the underlying Hawthorn Group was dispersed into the SAS. Higher Delta 4He values in brackish groundwaters compared to fresh waters from similar depths indicated that 4He was advected upward in the seawater mixing zone.Seawater intrudes at horizontal distances from the coastline from 6 to 28 km at shallow depths (<28m), and further inland at depths from 28 to 68 m in the SAS. In Taylor Slough, fresh groundwater discharges to the surface water landward of the seawater intrusion zone. Brackish groundwater associated with the seawater intrusion also discharges to the overlying surface water of the Everglades.

Keywords

Hydrology; Environmental Sciences; Geochemistry

Link to Full Text

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