ENV 101 Ch11 lecture ppt_a

11-1
Environmental
Geology
James Reichard
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11-2
Chapter 11
Water Resources
Tim McCabe, USDA Natural Resources Conservation Service

11-3
Hydrologic Cycle
Jump to long description

11-4
Water

11-5
Precipitation
Mean Annual Precipitation (1981-2010)
Source: Copyright © 2015, PRISM Climate Group, Oregon State University
http://prism.oregonstate.edu
© 2009, PRISM Climate Group, Oregon State University, http://www.prismclimate.org Map created September 2009

11-6
Use of Fresh Water (1)
Consumptive
• City or municipal
• Electricity generation
• personal
Non-consumptive
• irrigation
Off stream

11-7
Use of Fresh Water (2)

11-8
Traditional Sources of Groundwater
Surface water
• Rivers and streams
• Lakes and reservoirs
Groundwater
• Quantity
• Ease of withdrawal
• Porosity
• Permeability
• quality
Aral Sea
a: USGS EROS Data Center and NASA; (b-c): NASA’S Earth Observatory

11-9
Groundwater (1)

11-10
Hydraulic conductivity

11-11
Groundwater (2)

11-12
Movement of Groundwater (1)
• Hydraulic head
• Hydraulic gradient
Alfonso Rivera, Geological Survey of Canada

11-13
Movement of Groundwater (2)

11-14
Groundwater Recharge

11-15
More Groundwater Sources
Springs
• Mineral
• Warm water/hot water
Water wells and drawdown cones
• Cone of depression

11-16
Springs
a: © The McGraw-Hill Companies. Inc./John A. Karachewski, photographer; (b-c): © Jim Reichard

11-17
Cone of depression

11-18
Modern water well
© Jim Reichard

11-19
Impacts of Groundwater
Withdrawals
• Dry wells
• Salinization
• Land subsidence
• Increased well costs
• Saltwater intrusion
• Reduced spring and stream flow
© Richard T. Nowitz/Corbis

11-20
Massive cone of depression
(left): Bush, P.W., and R. H. Johnson (1988), U.S. Geological Survey, Professional Paper 1403-C.; (middle right): Krause, R. E., and R. B. Randolph (1989), U. S. Geological Survey Professional Paper
1403-D

11-21
Salt water intrusion

11-22
Ogallala Aquifer

11-23
Subsidence
b: © Alan V. Morgan, Earth and Environmental Sciences, Universities of Waterloo

11-24
Selecting a Water-Supply Source
• Groundwater
• River
• Reservoir

11-25
Alternative Sources (1)
Desalinization
• Distillation
• Reverse osmosis
Reclaimed/recycled
• Municipal wastewater recycling
• Industrial and domestic recycling
© IDE Technologies

11-26
Alternative Sources (2)
Aquifer storage and recovery
Rain water harvesting
© Rainwater Services, LLC
Conservation
• Domestic and commercial users
• Agriculture
• Municipal supply systems

11-27
Irrigation systems
a: © Don Tremain/Getty Images; b: © Clark Dunbar/Corbis
Jeff Vanuga, Natural Resources Conservation Service, US Dept of Agriculture

11-28
Xeriscaping
A Phoenix, Arizona
B Las Vegas, Nevada
a: © Desert Crest, LLC; b: USDA

Appendix of Image Long
Descriptions

Hydrologic Cycle Long Description
The hydrologic cycle describes the cyclic movement of water through the Earth system. The cycle is driven
by solar energy that causes water to evaporate from the oceans and land surface and allows for plant
transpiration. Evaporation of seawater produces large quantities of freshwater, which is vital for humans and
the terrestrial biosphere. Humans’ primary sources of freshwater are streams, lakes, and groundwater
systems. Note that groundwater is found in fractured igneous and metamorphic rocks, but the vast majority
occurs in porous sedimentary material.
Jump back to slide containing original image

Water Long Description
Breakdown of the water in Earth’s hydrosphere.

Precipitation Long Description
Average annual precipitation varies widely across the United States, resulting in significant differences in the
availability of freshwater supplies.

Use of Fresh Water (1) Long Description
Total water withdrawals in the United States between 1950 and 2010.

Use of Fresh Water (2) Long Description
Breakdown of the rate of personal water usage inside the average U.S. household.

Traditional Sources of Groundwater Long Description
Satellite images showing how the Aral Sea was lost over time due to the off-stream use of water from the
rivers flowing into the lake. Note that the 1977 image is false color, in which vegetation is shown in red and
water appears black. The other two images are in natural color—the lakes appear green due to differences
in suspended sediment.

Groundwater (1) Long Description
Porosity determines the volume of groundwater that can be held in subsurface materials. Sedimentary
materials composed of clay, sand, or gravel sized particles normally have high porosity, whereas crystalline
rocks have little porosity and usually contain water only in fractures. Water moving through certain types of
limestone can create high porosity by dissolving the rock to form passageways and caverns.

Hydraulic conductivity Long Description
Graph showing the range of hydraulic conductivity for various geologic materials. Each tick mark on the
horizontal scale represents a tenfold change in conductivity. Some materials have a wide range of hydraulic
conductivity, and thus can be regarded as an aquifer in some instances and an aquitard in others.

Groundwater (2) Long Description
An unconfined aquifer is open to the surface environment and has a water table that marks the top of the
saturated zone. A confined aquifer has an overlying aquitard that limits the vertical movement of water,
causing the aquifer to become pressurized. When a well penetrates an aquitard, water rises to the
potentiometric surface, which represents the amount of pressure within the confined aquifer.

Movement of Groundwater (1) Long Description
Illustration showing how hydraulic head and hydraulic gradient in an unconfined aquifer are
determined by measuring the depth of the water in two wells. Note that groundwater flow is
always in the direction of the hydraulic gradient.
A free-flowing artesian well occurs when the potentiometric surface of a confined aquifer is higher
than the land surface, allowing pressurized water to rise above the surface.

Movement of Groundwater(2) Long Description
Water travels between different aquifers by the process of leakage. Downward leakage occurs when the
water table is higher than the potentiometric surface of a confined aquifer. When the potentiometric surface
is higher, leakage is upward.

Groundwater Recharge Long Description
Groundwater recharge occurs when soil moisture builds to the point where water begins to drain
due to gravity. Recharge is less common during hot summer months since most of the water
entering the soil zone is quickly returned to the atmosphere by evaporation and transpiration.
Graph showing how the groundwater level in a semiconfined aquifer in Georgia rises and falls
with the seasons. Between 2000 and 2001 the system was in balance as recharge replaced most
of the water lost due to discharge. Drought conditions in 2002 disrupted the system’s natural
equilibrium, causing the groundwater level to fall. Groundwater levels will return to their normal
maximum provided there is a wet year or series of years with enough recharge to make up for
the water deficit in
the system.

SpringsLong Description
Springs occur where groundwater discharges at the surface in a localized area. The geology of the site
determines the depth of the groundwater source, which in turn influences the spring’s salinity, temperature,
and consistency of flow. The spring in (A) forms when water becomes trapped in the unsaturated zone,
then flows laterally until discharging along a hillside. In (B) the spring discharges from a solution
passageway in limestone. Example (C) illustrates how water from deeper aquifers can flow to the surface
along faults or fractures.

Cone of depression Long Description
A pumping well in an unconfined aquifer (A) draws in water and creates a cone of depression in the water
table. A well in a confined aquifer (B) creates a cone in the potentiometric surface, which in this case lies
above the land surface. Such a drawdown cone can pull contaminants into a well and reduce the flow of
water to nearby rivers or springs.

Modern water well Long Description
Diagram showing the construction of a modern water well. Note the clay seal and concrete placed around
the well casing to prevent surface contaminants from moving down into the well. Photo showing a
completed well and pressure tank at the surface.

Impacts of Groundwater Withdrawals Long Description
Aerial view of Tucson, Arizona, a city of over a half-million people located in a desert environment and
almost totally dependent on groundwater. The inset map shows how this booming city has been rapidly
expanding since 1945. Unfortunately, most of the groundwater recharge occurred thousands of years ago
under more humid and cooler climatic conditions. Today groundwater mining poses serious problems for the
city’s future.

Massive Cone of depression Long Description
Large pumping withdrawals from a confined aquifer along the Georgia coast have resulted in a massive
cone of depression. Contours show the potentiometric surface before and after major pumping began. Note
how the areas of upward artesian flow (in blue) have been dramatically reduced.

Salt water intrusion Long Description
Under natural conditions (A), coastal aquifers contain both freshwater and salt water, which flow toward a
mixing zone, the position of which depends on the hydraulic head and water density in the various aquifers.
Large pumping withdrawals (B) will alter the hydraulic head within the system, causing the position of the
mixing zone to move toward the well and allowing saltwater to contaminate the water supply.

Ogallala Aquifer Long Description
Map showing where the Ogallala Aquifer lies beneath the surface in the semiarid region of the United States
known as the High Plains. Groundwater withdrawals from this vast and complex aquifer system have
transformed the region into the nation’s top grain producer, but have also resulted in dramatic water-level
declines, threatening long term agricultural production.

Subsidence Long Description
Illustration (A) showing how land subsidence occurs when pumping in a confined aquifer creates a cone of
depression, causing leakage and a reduction in pore pressure within the system. Most of the subsidence is
due to compaction of highly compressible, clay-rich aquitards. Photo (B) shows the casing from a well in
Mexico City that became exposed when heavy pumping withdrawals across the city caused the land surface
to subside.

Selecting a Water-Supply Source Long Description
Municipal water-supply systems may use a combination of surface and groundwater sources, with surface
water requiring far more filtration and disinfection. After being treated, drinking water is pumped into a
storage tank. The elevated nature of the tank creates the water pressure (hydraulic head) necessary to
move water through the distribution system.

Alternative Sources (1) Long Description
Aerial view showing Israel’s reverse osmosis plant at Ashkelon, which is one of the largest in the world.
Plants such as this produce highly saline wastewater, which can disrupt marine ecosystems if discharged
directly into the ocean.

Alternative Sources (2) Long Description
Rainwater harvesting systems involve collecting rainwater from a roof, then storing it either above or below
ground in a tank called a cistern. With modifications to a building’s plumbing system, cistern water can be
used in place of drinking water for certain applications.

Irrigation systems Long Description
In older irrigation systems (A) as much as 30% of the water evaporates and never reaches the
ground. Systems can be retrofitted (B) so that water is directed toward the ground, which greatly
reduces evaporative
losses.
Drip-irrigation systems, like this one in a vineyard in New Mexico, are the most efficient as water
is applied only to the root zone of each plant. However, irrigating in this manner is labor-intensive
and involves considerable material costs.

Xeriscaping Long Description
Large reductions in home water use can be realized through landscaping changes. Xeriscaping involves
using native plants (A) rather than nonnative vegetation (B) that requires extensive irrigation.

ENV 101 Ch11 lecture ppt_a

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