Post on 19-Jan-2016
transcript
Groundwater Continued
Consolidated
Unconsolidated
Confined
Unconfined
Aquifers
Basic Aquifer Classification
Unconsolidated or Consolidated
Consolidated: sandstone, limestone, granite
Can be low-yield or high-yield
Granite, sandstone Limestone, sand/gravel
Unconsolidated: granular sand or gravel
Consolidated Aquifer
Unconsolidated Aquifer
Low ConductivityGeologic or Soil material
Water
Highpermeability
Unconfined Aquifer
Conductivity: the ease with which water moves through material
Confined Aquifer
An inclined, water-bearing formation located below an impermeable layer of clay, rock, or shale.
High pressure
Flow
Confined and Unconfined
High pressure
Flowaquitard
Florida’s Aquifers
1. Florida has both confined and unconfined aquifers2. Florida exists on a raised platform3. The Florida platform was dominated by carbonate deposition from the Jurassic (-200 my) to the Miocene (-25 my).4. During the Miocene, clayey sediments blanketed the platform.5. These sediments form a confining unit for Florida’s main aquifer6. The major aquifer is a consolidated, carbonate confined aquifer.7. Unconfined aquifers exist above the clay confining unit.
Florida’s Aquifers
Suwannee Current
Georgia Channel
sediments
Jurassic To
Miocene
Miocene
Recent Deposits
25 to 5 Mya
200 Mya to 25 Mya
Basics
CaCO3
Clay
Sands
Sinkholes and springs are a product of the geology of Florida
Solution cavities exist in the limestone
Water in cavities is under pressure
Sinkholes: collapse of material into cavities
Springs: water bursts through thin confining units
Springs
Springs form best when the overlying clay layer is thin.
Springs
First magnitude: 100 ft3/s
Florida: 27 of 78 nationally
Confining unit less than 100 feet thick or is absent
(64.6 million gallons per day)Thin or absent
30 – 200 ft sandy
30 – 200 ft clayey
> 200 ft thick
Hawthorne Thickness
Ginnie
Poe Spring
Little Devil
http://www.underwaterflorida.homestead.com/springs.html
Manatee
Florida’s Dominant Aquifer Systems
Florida is the largest groundwater user east of the Mississippi
Floridan Aquifer
Biscayne Aquifer
Intermediate aquifer
Unconfined
Confined
Sea Levels
Temporary reestablishment of carbonate deposition
The Floridan Aquifer
The Floridan Aquifer
100,000 square miles• southern Alabama• southeastern Georgia• southern South Carolina• all of Florida
Confined
Miocene clay deposits (Hawthorne) are the confining unit
3 billion gallons per dayof freshwater withdrawn
Agriculture – 39%Domestic use – 47%Industry – 8.5%Misc.- 5.5%
Withdrawals
A thick sequence of carbonate rocks (limestone and dolomite)
The thickest and most productive formations of the system are the Avon Park Formation and the Ocala Limestone of Eocene age (37-58 million years ago)
CaCO3 + MgCO3
Water-Bearing Units
600
1200
2400
3000
ThicknessIn feet
1800
Floridan Aquifer
Biscayne Aquifer
Intermediate aquifer
surficial
The Intermediate Aquifer System
The Intermediate Aquifer System
•Between the surficial aquifer system and the Floridan aquifer system
•Used where the underlying Floridan aquifer system is deeply buried and/or contains brackish or saltwater.
•Clay confining units are above the Floridan and below the surficial aquifer.
•Artesian, but yields less water than the Floridan
•Sand, limestone, shell beds
•298 million gallons per day
Intermediate Aquifer
confined
Sand, shell, limestone
The Intermediate Aquifer System
Polk Co.
Collier Co.
flow
Polk: 120 ft
Main source ofwater supply for Charlotte, Lee, and Sarasota counties.
Floridan Aquifer:
Intermediate Aquifer:
Comparison
Withdrawal = 3 billion gal/day
Withdrawal = 298 million gal/day
Intermediate aquifer is used where the Floridan is inadequate
Surficial aquifers: The Biscayne
Surficial aquifers
Water stored above an impermeablelayer and unconfined at the surface
low conductivity
high conductivity
water
Surficial aquifers
Soils or Geologic Materials
Biscayne Aquifer
4,000 square miles
DadeBrowardPalm Beach
highly permeable sand, limestone,sandstone, shells, marl
low-permeability sandy silt
786 million gallons/day
70 % for public supply
Biscayne Aquifer
Marls: carbonate-rich muds containing clays and calciteOolitic limestone: spheroidal carbonate grains with a mineral cortex
Plio-pliestocence
EoceneMiocene
240 ft
Thickness
Water in the Biscayne
Recharge
Flow
Recharge and Flow
Pesticides, fertilizers, landfills, septic systems, injection wells
Injection well
Salt water
pumping Salinization
Coastal Canals
Inland Canals
Flood Control
pollu
tant
s
Floridan Aquifer:
Intermediate Aquifer:
Biscayne Aquifer
Three Major Florida Aquifers
Withdrawal = 3 billion gal/day
Withdrawal = 298 million gal/day
Withdrawal = 786 million gallons/day
Total = 4.084 billion gallons/day
Floridan Aquifer
Biscayne Aquifer
Intermediate aquifer
Unconfined
ConfinedConfined