Ground Water Availability and Resource Protection - PowerPoint PPT Presentation

1 / 17
About This Presentation
Title:

Ground Water Availability and Resource Protection

Description:

Limited resource - recharge occurs in a 'Spine Area' ... threats - to the water table from land use activities and to the confined ... – PowerPoint PPT presentation

Number of Views:79
Avg rating:3.0/5.0
Slides: 18
Provided by: clifto8
Category:

less

Transcript and Presenter's Notes

Title: Ground Water Availability and Resource Protection


1
Ground Water AvailabilityandResource Protection
  • June 2007

2
General Water Supply Issues
  • Sole Source Aquifer - no significant fresh water
    streams or rivers
  • Limited resource - recharge occurs in a Spine
    Area
  • Fresh ground water is restricted to depths less
    than 350 feet
  • Multiple contamination threats - to the water
    table from land use activities and to the
    confined aquifers from over pumping
  • Most likely cause for a loss of fresh ground
    water is salt water intrusion due to over pumping

3
What is an Aquifer
  • Any coarse grained material (sand, gravel) that
    can supply sufficient water for a beneficial use
  • A confined aquifer is one that is under pressure
    (the water surface is higher than the physical
    top of the aquifer)
  • An unconfined or water table aquifer is the
    closest to the surface and is not under pressure

What is a Confining Unit
  • Any fine grained material (silt, clay) that can
    significantly restrict vertical movement of
    groundwater such that the underlying groundwater
    is under pressure.

4
Schematic Cross-Section of Freshwater Lens
WEST
Water Table Surface
Confining Unit
Freshwater Aquifer
Saltwater Aquifer
Estimated Recharge to Water Table Aquifer 625
MGD approx Estimated Recharge to
Yorktown-Eastover Aquifer 8 MGD approx
5
Water Budget for the Water Table Aquifer
Total Estimated Recharge to Water Table Aquifer
625 MGD
6
Permitted Groundwater Withdrawals
7
Total Water Budget in the Confined Aquifer
Public/Industrial pumping domestic pumping Is
equal to Water Leaking through upper confining
unit water released from storage
8
Groundwater Level Trends Near Perdue
9
Recharge to Yorktown-Eastover is Limited
  • USGS collected water samples collected from wells
    and age dated them
  • Much of the water table aquifer was less than
    50-years old.
  • In contrast, average age for water samples from
    the upper Yorktown-Eastover exceeds 1,000 years

10
Rate of Flow Through Upper Confining Unit
11
Schematic Cross-Section of Freshwater/Saltwater
Interface
12
Increasing Chloride Trends Over TimeTown of
Chincoteague Well
13
Cape Charles Chloride Levels Near Production
Wells
14
Chloride Increase With DepthUpshur Neck Seaside
Example
Fresh Ground Water
Brackish Ground Water
15
Available Water Evaluations
  • Previous Used Tools
  • Empirical Observations
  • Analytical models / calculations
  • Numeric Models USGS SHARP Model EPA FEMWATER
    models
  • Current Tool
  • USGS Eastern Shore Model (SEAWAT)

16
USGS SEAWAT Model
  • Beta Version
  • Major Enhancements
  • Increased resolution
  • minimum horizontal size 1,000x1,000 Feet from
    original 1-mile
  • Vertical layers increased from original 4 to 46.
  • Functional Water Table
  • Increased lateral extent into Maryland
  • Ability to simulate gradational increase in
    saltwater
  • Calibrated from 1920 through 2003 at 20
    observation points

17
Three Dimensional Grid
Write a Comment
User Comments (0)
About PowerShow.com