Transcript Hydrologic Cycle and Groundwater

Classroom presentations
to accompany
Understanding Earth, 3rd edition
prepared by
Peter Copeland and William Dupré
University of Houston
Chapter 12
The Hydrologic Cycle and Groundwater
Hydrologic Cycle and Groundwater
M. L. Sinibaldi/Stock Market
Groundwater
The study of groundwater and its effects is
called Hydrology.
Uses of Water:
Living
Drinking
Photosynthesizing
Respiring
Metabolizing
Engineering
Recreation
Cooling
Heating
Cleaning
Flushing
Irrigating
Swimming
Fishing
Sailing
Skating
Skiing
Distribution of
H2 O
on Earth
Fig. 12.1
Uses of Groundwater
Why is groundwater such a valuable resource?
1.Abundant - 70 times more in the subsurface
than in surface reservoirs.
2.Because groundwater moves so slowly it is
stored in the earth and remains available even
in dry periods.
3.In some regions groundwater flows from humid
environments to dry ones, making water
available.
Groundwater
• Water contained in spaces within soil,
bedrock, and regolith
• Less than 1% of all H2O on Earth
• 40 times more abundant than water
found in lakes and streams
Hydrologic Cycle
Fig. 12.2
Rain Shadow Deserts
Fig. 12.3
Average Annual Precipitation in the
U.S.
Fig. 12.4a
Average Annual Runoff in the
U.S.
Fig. 12.4b
Swamps as Reservoirs
Fig. 12.5
Groundwater terms
zone of aeration: portion of soil and rock
near the surface in which open spaces
are filled primarily with air (a.k.a vadose
zone)
saturated zone: zone in which pore spaces
are filled with water
water table: boundary between zone of
aeration and saturated zone
Geologic activity of groundwater
• Dissolution (most important in
carbonates and evaporites)
• Cementation
• Replacement
Springs
Locations
where a
perched
water table
intersects
the ground
Soils and rocks are not completely solid.
porosity: portion of volume of a material
that consists of open spaces
permeability: measure of the speed at
which fluid can travel through a porous
medium
Imagine two vertical pipes, one filled with
gravel, one with sand. Out of which one
will the water flow faster?
Porous Sandstone
Fig. 12.7a
Cemented Sandstone
Fig. 12.7b
Well-sorted Sandstone
Fig. 12.7c
Poorly-sorted Sandstone
Fig. 12.7d
Unfractured Shale
Fig. 12.7e
Fractured Shale
Fig. 12.7f
More groundwater terms
aquifer: body of rock that is sufficiently
water permeable to yield economically
significant quantities to wells and springs
aquitard: body of rock that retards but does
not prevent flow of water to or from an
adjacent aquifer
aquiclude: body of relatively impermeable
rock that is capable of absorbing water
slowly but does not transmit it rapidly
enough to supply a well or spring
Groundwater
Table
Fig. 12.8
Groundwater Movement in
Temperate Regions
Fig. 12.9
Wet Period
Fig. 12.10
Dry Period
Fig. 12.10
Confined Aquifer
Fig. 12.11
Perched Water Table
Fig. 12.12
Drawdown Due to Pumping
Fig. 12.13
Fissures and
Depressions
Caused by
Overpumping
James W. Borchers/USGS
Fig. 12.13
Saltwater Intrusion
Fig. 12.15
Rates of groundwater movement
• Slow to very slow (depending on
permeability)
• Generally within the range of 10 to
100 cm per day
Darcy’s Law
Q=
AK(h1– h2)
l
Q = discharge (m3/sec)
A = cross-sectional area (m2)
K = coefficient of permeability (m/sec)
h1 = beginning height (m)
h2 = ending height (m)
l = length of flow (m)
Darcy’s Law
Fig. 12.16
U.S. Groundwater Withdrawals
1950–1995
Fig. 12.17
Ogallala
Aquifer:
“Mining”
Groundwater
David Muench
Fig. 12.18
Sinkhole in Florida
Leif Skoogfors/Woodfin Camp.
Fig. 12.19
Major Features of Karst Topography
Fig. 12.20
Water Quality and
Groundwater Movement
Fig. 12.21
Groundwater Contamination
Fig. 12.22
Groundwater
Distribution
in a Typical
Section of
Continental
Crust
Fig. 12.23
Geyser
Peter Kresan
Fig. 12.24