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Utilizing Stable Isotopes ( 2 H & 18 O) to Identify Water Types of the Floridan Aquifer System in Southwest Florida. 20 th Salt Water Intrusion Meeting June 24 , 2008. Authors: Ed Rectenwald, PG MWH Americas Michael Bennett, PG Boyle Engineering. Presentation Overview. Background
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Utilizing Stable Isotopes (2H & 18O) to Identify Water Types of the Floridan Aquifer System in Southwest Florida 20th Salt Water Intrusion Meeting June 24 , 2008 Authors: Ed Rectenwald, PG MWH Americas Michael Bennett, PG Boyle Engineering
Presentation Overview • Background • Hydrogeology • Geochemistry • Inorganics • Stable Isotopes • Summary • Conclusions Overview Background Hydrogeology Geochemistry Summary Conclusions
Why Stable Isotopes? • Identify different water bodies in the aquifer system • Better understand groundwater circulation patterns • Identify possible recharge and discharge areas Overview Background Hydrogeology Geochemistry Summary Conclusions
Investigated Wells • Five FAS test wells (TW) owned by the SFWMD • GLF-5 • LAB-TW • IWSD-TW • I-75 TW • BICY-TW • Seven FAS monitor wells owned and operated by various Water Reclamation Facilities (WRF) • Zemel Road Landfill • Burnt Store WRF • North Fort Myers WRF • Fort Myers Beach WRF • North Collier Regional WRF • South Collier Regional WRF • Marco Island WRF Overview Background Hydrogeology Geochemistry Summary Conclusions
Quantity of Wells Sampled Per Hydrogeologic Unit • Upper Floridan Aquifer – Nine wells • Middle Confining Unit – Thirteen wells • Lower Floridan Aquifer – Five wells Overview Background Hydrogeology Geochemistry Summary Conclusions
Study Area Overview Background Hydrogeology Geochemistry Summary Conclusions
SouthwestFloridaHydrogeology Overview Background Hydrogeology Geochemistry Summary Conclusions
HydrogeologyGeneralized Cross-Section Overview Background Hydrogeology Geochemistry Summary Conclusions
Chlorides and TDS in the FAS Overview Background Hydrogeology Geochemistry Summary Conclusions
Piper Tri-Linear Diagram Applying Frazee’s Geochemical Pattern Analysis Overview Background Hydrogeology Geochemistry Summary Conclusions
Stable Isotopes in the FAS Overview Background Hydrogeology Geochemistry Summary Conclusions
Relationship Between 2H and 18O Overview Background Hydrogeology Geochemistry Summary Conclusions
Spatial Distribution of Isotopes in the UFA -2.08 -10.46 -0.85 -4.54 -1.43 -6.24 -1.60 -7.71 Overview Background Hydrogeology Geochemistry Summary Conclusions -1.46 -8.79 -1.69 -7.77 Legend 18O/2H -1.14 -1.53 -1.19 -5.53 -1.26 -6.60 -0.08 -5.17
Spatial Distribution of Isotopes in the MCU -1.92 -5.36 -0.42 0.97 0.43 2.05 -1.11 -11.35 -1.14 -8.06 Overview Background Hydrogeology Geochemistry Summary Conclusions 0.48 0.18 -1.59 -7.90 0.40 9.00 Legend 18O/2H 0.55 5.33 0.47 0.53 -0.35 0.28
Spatial Distribution of Isotopes in the LFA -0.41 -1.67 Overview Background Hydrogeology Geochemistry Summary Conclusions 0.47 0.02 0.12 3.76 0.65 1.16 Legend 18O/2H 0.73 0.06
Summary • Stable Isotopic Analysis • UFA • Meteoric in origin • Different climate and/or meteoric water at time of recharge • Evaporation minimal at time of recharge • MCU • Mixture of meteoric and seawater • Concentrations are location dependent • Hydraulic connection between UFA and LFA • LFA • Seawater in origin • Recharged after the “Last Glacial Period” (~15,000 years) Overview Background Hydrogeology Geochemistry Summary Conclusions
Conclusions • Need to improve our understanding of the FAS • Additional geochemical analyses • Radiocarbon • Noble Gases • Modeling the effects of sea level change • Potentiometric head data of the FAS • Additional inland monitor/test wells Overview Background Hydrogeology Geochemistry Summary Conclusions