Transcript Chapter 17: Water Use and Management

Chapter 17: Water Use
and Management
Shutian Lu, Siri Nycklemoe, Jonathan Olsen, and
Jeffrey Gruba
Water Resources
● Water is a renewable resource; however, limitless exploitation of water
resources will lead to disaster.
● 2 billion people now live in countries with insufficient fresh water. And
the number could double in 25 years.
● War over water?
● Water resources are not unevenly distributed.
Uneven Distribution
● Three factors control global water
distribution:
1. Global atmospheric circulation
→ Hadley cell & Ferrell cell
→ high pressure, low
precipitation
→ major desserts are on
30° belt
1. Proximity to water resources;
1. Topography;
mountains & rain
Major Water Compartments
● Redistribution of water often is described in terms of interaction between
different water compartments.
Compartment
Proportion to The Total
Average Residence Time
Ocean
96.5%
3,000 to 30,000 years
Ice and snow
1.76%
1 to 100,000 years
Groundwater(saline and fresh)
1.69%
Days to thousands of years
Lakes (saline and fresh)
0.013%
One to hundreds of years
Soil moisture
0.001%
2 weeks to 1 year
Atmosphere
0.001%
1 week
Marshes, wetlands, rivers
0.0012%
1 week to years
Global Ocean Currents
“Global warming”
does not mean
“warmer”!
Ocean currents act as a global conveyor system, redistributing
warm and cold currents around the globe.
Easily Available Freshwater is
Scarce
Frozen Water
● 87.2% of total freshwater is tied
up in glaciers, ice caps and
snow fields;
● Meltwater replenishes rivers;
● Colorado river gets water from
snowpeck on Rocky mountain,
and decreasing snowfall has
caused drought in the western
United States;
● Climate change further disrupts
the pattern.
Groundwater System
●
12% of total freshwater is
groundwater
● Infiltration
→ the process that precipitation
percolates through permeable rocks
● zone of aeration
→ upper soil that holds water
and air
● zone of saturation
→ filled with water
● water table
→ the top of the zone of saturation
● aquifer
→ porous layers of sand, gravel or
rock lying below the water table
Groundwater System
●
●
artesian well/spring
recharge zones
→ where water infiltrates into an aquifer
Northfield Water Supply
“Water within the Northfield city limits is supplied from a groundwater
source via four wells that range in depth from 365 to 410 feet. Water is
drawn from the Jordan aquifer.”
Surface Water
● 0.8% of total freshwater
● Rivers
o precipitation, meltwater
replenish streams;
o discharge rate is used to
measure the size of river
● Lakes
o contain nearly 100 times as
rivers and streams
● Wetlands
o stabilize soil
o hold runoff
o allow time for infiltration
Water Availability
● Freshwater: essential for life
○ settlement
● Renewable Water Supply:
○ from surface runoff & aquifers
■ ⅔ of water transported in rivers = flood water
■ dependable source = stable runoff
● provides 400,000 gallons per person per
year
Water Scarcity and Stress
● Water Scarcity: demand exceeds supply or restricted
use
● Water stress: renewable water supply cannot meet
fundamental ecosystem/human needs
○ competition
● Per capita Supply:
○ highest: wet, low population density
■ Iceland
○ lowest: dry, high pop. density
■ Bahrain, Egypt
Water Scarcity and Stress
● Drought: frequent in semi-arid climate
○ water shortage
■ Dust Bowl
● 1931-39
● lack of soil conservation practice
● plowing & wheat planting, no growth
● dried soil carried by wind
○ dust filled farms & homes
● throughout plains
Drought in the US
Dust Bowl
John Wesley Powell
● First expedition on Colorado River
● US Geological Survey
○ Concluded: not enough water to support large,
concentrated populations
■ Oasis settlements
■ Pop. in each jurisdiction → area water source
○ Denver, Los Angeles, Las Vegas, Phoenix
John Wesley Powell
Water Use
● Use is increasing 2x as fast as population growth
○ Industrialized vs. Developing Countries
● Withdrawal: total amount taken from body of water
○ most can be returned to circulation or reused
■ 170,544 gallons
● US vs Haiti
● Consumption: loss of water due to evaporation,
absorption, and contamination
○ Libya, Yemen, Israel
Water Use By Sector
● Agriculture: ⅔ worldwide withdrawal
○ 85% of consumption
■ India, Kuwait, US
● Aral Sea: Kazakhstan & Uzbekistan
○ 1975 to 2000, 75% surface area loss, 90% decrease
in volume
■ Soviet Union: tributaries diverted
● Salt concentration doubled
○ Small Aral reclamation
Aral Sea
Reduction
over Time
Water Use By Sector
● Lake Chad: 60,000 years ago → Caspian Sea
○ 1960s → Lake Erie
○ Irrigation, drought
○ former lake bed = Bodele Depression
● Irrigation: inefficient practices
○ 1% of world cropland is watered by drip irrigation
● Domestic: only 1% worldwide withdrawal
○ domestic consumption = 10% on avg.
● Industry: 20% global withdrawal
Typical Household Water
Use in the US
Lake Chad
Freshwater
Shortages
Causes of Water Shortages
● Natural defects
● Over consumption by agriculture or industry
● Inadequate funds for purifying and delivering
good water
Many People Lack Access to Clean Water
● One billion people lack access to clean water and 2.5 billion people don’t
have adequate sanitation
● Every year there are hundreds of millions of water related illnesses and
five million deaths caused by lack of clean water
● However in recent years there has been improvements:
o In 1990, 800 million people gained access to clean water
o The percentage of rural families with safe drinking water has risen
from 10% to 75%
Groundwater
● Groundwater is the source of about 40% of the fresh
water for domestic and agricultural uses in the US
● Half of Americans rely on groundwater for drinking
● Overuse problems
o Drying of well and natural springs
o Disappearance of surface waters (wetlands, rivers
and lakes)
The Ogallala Aquifer
● Ogallala Aquifer underlies 8 states
between Texas and North Dakota
● Once held more water than all the
freshwater rivers and streams on earth
● Heavy pumping has dried up wells and
whole towns are being abandoned
● It will take thousands of years to refill
Consequences of Aquifer Depletion
● Subsidence: settling of the porous formations causing them to
collapse
o San Joaquin Valley (CA) has sunk about 33 feet (10 m) in the
last 50 years because of excess groundwater pumping
o Mexico City has sunk about 26 feet which has caused ancient
Aztec temples
o Also leads to flooding in coastal cities
● Saltwater Intrusion: when saltwater from ancient oceans along
coastlines intrude into aquifers because of excess use of
freshwater reserves
Saltwater Intrusion
Case Study: Lake Mead
● Because of drought, climate change, and
urban development Lake mead is estimated
to possibly reach levels where they will not
be able to produce power or provide water
for agriculture
o Lake levels have been dropping about 12
feet per year
Lake Mead
China’s South-Water-North Project
● Because of similar water loss, Northern China is getting drier, so much so
that the Gobi Desert is moving Eastward towards Beijing, so China
embarked on a water distribution project called South-Water-North
o This proposed to build a canal to bring the water from the Yangtze
River to northern China
o However this may worsen pollution problems
 Dry up wetlands, possibly alter ocean circulation and climate
along China’s eastern coast
● Some people believe it may be beneficial to do something like this from the
Great Lakes to the South Western states, others disagree
Dams Often Have Severe Impacts
● Pros:
o Provide hydraulic power and water to distant cities
● Cons:
o Evaporation
o Force people from their homes and land
o Can trigger earthquakes if in seismically active locations
o Lethal to migratory fish
o Sediment can block dams which decreases the life of the dam and
have many environmental impacts
 China’s Sanmenxia Dam on the Yellow River
 Clean Canyon and Boulder Dams on the Colorado River
Major Transboundary River
Basins
●
Water around the
world is unevenly
distributed
Average Annual Precipitation
Water and Climate Change
● May exacerbate water shortages caused by population growth, urban
sprawl, wasteful practices, and pollution
● Drought is the most likely result of climate change
o People will have to leave their towns because of too little drinking
water or will become undernourished because lack of water and food
o Could also lead to war and conflict to nations
 Examples:
● Israel and its neighbors because of the Jordan River
● Nomadic tribes in Kenya fought over water resources
● Caused genocide in Darfur
● Sadam Hussein cut off water flow to his enemies
Getting By with Less Water
● In 2010, an agreement was made for the Klamath River in California to
keep fish populations stable.
● The agreement asked farmers to conserve 10 to 25% of the water they
have used for irrigation in the past and in return would receive a one-time
payment to finance conservation measures.
● This way, farmers can save more water over time so that the water doesn’t
have to be shut off when fish are endangered.
● With clearer guidelines, farmers can grow low-value crops (like alfalfa) and
use a little land for high-value crops during dry years.
Increasing Water Supplies
● Researchers have been trying to make it rain with a variety of techniques
● For example, seeding clouds with dry ice or potassium iodide particles has
been tested with mixed results
● More recently, researchers have been having more success using
hygroscopic salts which is being tested all over the world
● One kind of technology that shows potential is desalination of ocean water
or brackish saline lakes and lagoons.
Desalination Statistics
● Worldwide, there are 13,080 desalination plants that produce more than 12
billion gallons of water a day. This is expected to grow to about 26 billion
gallons per day by 2015.
● The largest producer is Saudi Arabia at one-third of the world total. The
U.S. is second, at one-fifth.
● Middle Eastern oil-rich states produce about 60 percent of desalinated
water.
● Desalination is 3 to 4 times more expensive than other ways to get
freshwater but totally worth it for countries with very little fresh water.
How We Can Conserve
●
●
●
●
Take a shorter shower
Stopping leaks
Washing cars, dishes, and clothes as efficiently as possible
Invest in low-volume showerheads and efficient dishwashers and washing
machines
● Buy a waterless or low volume toilet (the largest U.S. domestic water use
is toilet flushing).
https://www.youtube.com/watch?v=4LrUc0C7vW0
Water Recycling
In California, water
recovered from treated
sewage constitutes the
fastest-growing water
supply, growing 30
percent per year.
Purified sewage effluent
is being used for
everything from
agricultural irrigation to
flushing toilets.
Prices and Policies
● Throughout U.S. history most policies in U.S. have generally worked
against conservation
● In the eastern United States where water is common, those who lived
along a river bank had the right to use as much water as they wanted as
long as it didn’t interfere with quality or availability for those downstream
● In the drier western regions policy those who owned the water first can
block the water from anybody else on the stream so long as the water is
used for economic use. Under this system, water rights can be bought and
sold.
● Now, with growing recognition that water is a finite resource, the United
States and other countries are encouraging the most beneficial uses and
discourage wasteful water uses by water pricing and allocation policies.
Water Conservation at Olaf
● Buildings like Regents have water
saving toilets
● Also have motion-activated sinks in
many buildings to make sure no
water is not turned off
● The dishwashers at the cafeteria
use circulated water so they don’t
use as much water