Transcript WATER RESOURCES

WATER RESOURCES
Availability, Usage and Pollution
Usage
• World = 700 m3/year average per capita use
• N. America = 1850 m3/year average per capita
use
• Value very low and transportation expensive
• Source needs to be close to consumption
• Building canals and aqueducts expensive
Surface Water
Streams, rivers, lakes: accessible, cheap, easy extraction
Quantity related to:
• Climate (amount and timing of precipitation)
• Geology (porosity and permeability of ground)
• Biology (trees, plants, grazing animals)
• Geography (topography) conditions.
• Politics
• People settle on flood plains for fertile soils, available
water for irrigation, transport and waste disposal
• Settlement changes the flow processes of the river
causes increased flooding and pollution from industry,
farming, sewage and domestic waste
GROUND WATER
• Source is infiltration from precipitation, lakes,
streams, reservoirs
• Recharge time from days to millions of years
• Issues relate to pollution, ground subsidence
and excessive extraction especially when
aquifer crosses national boundaries
• Surface and Groundwater quantity and quality
are closely linked
Desalination
• Desalination of sea water by evaporation or osmosis
– sea water: 3.5% salt
– drinking water standards: 0.05 % salt
• Very expensive: 10 x cost of other water supplies
• Large scale evaporation plant requires energy to boil
water so often combined with a power plant
• California: emergency supplies in time of drought.
• Mexico: holiday resorts for foreigners
• Middle East: desalination of brackish ground water which
contains 0.5% salt
• Jebel Ali desalination and power plant
in Dubai will be the largest in the world.
It solves water shortage but discharge of
hot water may damage largest coral reef
in the Arabian Gulf
Water Shortage
• The world's supply of fresh water is
running out. Already one person in five
has no access to safe drinking water.
http://news.bbc.co.uk/hi/english/static/in_d
epth/world/2000/world_water_crisis
USA: ORME, Tennessee.
(© 2007 The Associated Press)
•
•
At twilight, the Mayor of Orme releases the community tank's water supply.
suddenly washing machines whir, kitchen sinks fill and showers run.
Three hours later, he returns and reverse the process, cutting off water to
the town's 145 residents.
•
The severe drought across the Southeast has threatened the water supply
of cities large and small, sending politicians scrambling for solutions. At
Orme, 150 miles NW of Atlanta, the water has run out.
•
The waterfall that fed the mountain hamlet has been reduced to a trickle,
and the creek running through the center of town is dry.
•
Three days a week, two volunteer fire trucks haul about 20,000 gallons of
water from the hydrant to Orme's tank.
•
Orme can survive as it has only 145 people.
•
Atlanta has 4.5 million people and only a few weeks of water left
CANADA: Hotels, other businesses closing as
water shortage hits Tofino, BC:
CBC Tuesday, August 29, 2006
•
There's a severe water shortage in Tofino on the west coast of Vancouver Island, generally
one of the wettest communities in B.C.
•
The municipality issued a public notice for all hotels, restaurants and other food services to
shut down by Friday to preserve what water supply remains.
•
All commercial water users including fish plants are not to use any water.
•
The district's main reservoir is very low because of the dry summer. The residential water
supply is being maintained with water from a creek. As a result, people are being asked to
boil their water.
•
the tourist industry will take a big hit on the eve of one of the busiest weekends of the year.
"For people in the restaurant industry, you can't wash your dishes. You can't clean any of
the linens if you're in a hotel business. You can't wash your hands. Your clients can't take a
shower and there's no other water source
The growth in tourism has been "fantastic," but all the development has put a severe strain
on the water resources.
•
Officials have said the order will stay in effect at least until there is significant rainfall.
•
Local hotel owners came together and trucked water from Ucluelet to save the Labor Day
weekend tourist trade
Europe: CATALONIA
• More than half of Europe's cities are
exploiting groundwater at unsustainable
rates.
• Chronic water shortages are already
affecting 4.5m people in Catalonia, where
authorities are pressing for the
construction of a pipeline to divert water
from the Rhone in France to Barcelona.
Mexico City:
Subsidence and pollution
Mexico city is sinking because of the amount of water
being pumped out from beneath its foundations.
One of the largest and most populous cities in the world, it
was once a lush land of lakes. But over the last 500
years the lakes have been drained and the surrounding
forests chopped down. As the city grew in size, the water
problem magnified.
With no adequate drainage system, today rainwater mixes
with sewage and is used for irrigation. The city is now at
serious risk of running out of clean water.
An estimated 40% of the city's water is lost through leaky
pipes built at the turn of the century.
Middle East Conflict
•
•
•
•
•
•
•
•
Water is the most precious resource in the Middle East, more important than oil.
There are four main drainage basins but each river crosses at least one
international boundary
Euphrates: Turkey, Syria, Iraq, Kuwait
Tigris: Iraq, Kuwait
Jordan: Jordan, Syria, Israel, Lebanon
Orontes: Turkey, Syria
Centuries of negotiations, treaties, discussions
As populations increase, water becomes more scarce, aggravating regional
tensions. e.g.
•
Turkey has been accused by Syria and Iraq of depriving them of much-needed
water, as it continues to build a series of dams along the Euphrates and Tigris.
•
•
Competition for water from the River Jordan was a major cause of the 1967 war.
Israelis in the West Bank use four times as much water as their Palestinian
neighbors.
•
The Lebanese have accused Israel of having designs on the waters of the River
Litani, and Syria accuses it of being reluctant to withdraw from the banks of the
Sea of Galilee, the source of up to 30% of Israel's water.
Africa
•
A United Nations report predicts that access to water may be the single biggest cause of
conflict and war in Africa in the next 25 years. Such wars are most likely to be in
countries where rivers or lakes are shared by more than one country.
•
Ghana, has become totally reliant on the hydro-electric output of the Akosombo dam on
the river Volta.
Mali, one of the poorest countries in the world, is dependent on the river Niger, which
flows from Guinea through Mali to Nigeria, for food, water and transport. But great
stretches of the river are now facing environmental catastrophe as a result of pollution.
In Nigeria, half the population has no access to clean water, and as in much of Africa,
many women walk for hours a day to fetch it.
•
•
•
•
•
•
•
The Nile There is already fierce national competition over water for irrigation and power
generation in the Nile river basin.
Cairo warned in 1991 that it was ready to use force to protect its access to waters of the
Nile, which also runs through Ethiopia and Sudan. If the populations of these countries
continue to rise, competition for the water could be fierce.
Zambezi River Basin in southern Africa is one of the most overused river systems in
the world.
Although the countries through which the river flows usually vie with each other to
harness the water power, at other times they are deluged by floods and heavy rain.
The region experienced the worst floods in living memory in March 2000, exacerbated
by Zimbabwe opening the Kariba dam gates.
India
•
THE GANGES The most sacred Hindu river, the
Ganges, is so depleted that the Sundarban wetlands and
mangrove forests of Bangladesh are seriously
threatened.
• It is also said to contain unacceptable levels of arsenic.
• As more trees are chopped down, and more buildings
erected along its banks, the glaciers supplying the river
have been melting, raising fears of shortages and
drought downstream.
• The river has been the subject of a long-running dispute
between India and Bangladesh, although recently
progress has been made in resolving the conflict.
Australia: the world's driest continent
•
•
•
•
•
A scheme to reverse the flow of the Snowy River has backfired
disastrously, threatening to deprive Adelaide of fresh water.
The region that the diverted Snowy River now feeds is bounded by
Australia's two longest rivers, the Murray and the Darling.
The water tables under this land are now rising, pushing deadly
quantities of salt to the surface.
The salt has already destroyed some of the country's most
productive farmland.
The Murray-Darling basin produces three-quarters of Australia's
irrigated crops.
Many of the basin's tributaries may be unusable for irrigation in 20
years time, let alone as a source of drinking water.
Northern China
• All three rivers feeding China's Northern Plain are
severely polluted, damaging health and limiting irrigation.
• The lower reaches of the Yellow river, which feeds
China's most important farming region, ran dry for 226
days in 1997.
• Northern China is home to two thirds of the country's
cropland but only one fifth of its water.
• As competing demands for water are made by cities,
industry and agriculture, the land is drying up.
• Between 1991 and 1996, the water table beneath the
north China plain fell by an average of 1.5 m/year.
Vanishing Aral Sea
•
•
•
•
•
•
•
•
The Aral Sea in Central Asia was once the
world's fourth biggest inland sea, and one of
the world's most fertile regions.
But economic mismanagement has turned the
area into a toxic desert.
The two rivers feeding the sea, the Amu Darya
and the Syr Darya, were diverted in a Soviet scheme to grow cotton in the
desert.
Between 1962 and 1994, the level of the Aral Sea fell by 16 metres.
Rich delta ecosystems were largely lost.
Rusted ships stranded on the desiccated seabed and ghost fishing villages
are a sad reminder of the once thriving fishing industry.
The surrounding region now has one of the highest infant mortality in the
world, and anaemia and cancers caused by chemicals blowing off the dried
sea bed are common.
Water control structures on both the Aral Sea and Syr Darya River had
either generated only temporary benefits or failed altogether.
Aral Sea Solution
• The World Bank helped build the 8 mile Kok-Aral Dam in 2005, which
separates the two parts of the Sea.
• This will allow the accumulation of over 29 km3 water in the Northern
Aral Sea or Small Sea and help to restore delta and river wetland
ecosystems.
• A sluice in the dike is periodically opened, allowing water to flow into
the largely dried-up Southern Aral Sea.
• Waterworks will raise the water supply for irrigation and restore fishing
lakes in the delta area, for hatcheries to restock the Northern Aral
Sea’s fish population.
• There is a reduction in diseases due to unhealthy drinking water.
• In a few years, the salt content in the Sea is expected to decline from a
current 23 to 10 g/L (1960 levels).
• The desertification of surrounding land is being mitigated
• Already, in Tastubek, a fishing village near the Small Sea, residents are
able to catch salt-resistant flounder introduced in the 1970s
• As the salt content of the Small Aral drops, many of the 24 fish species
that once supplied a thriving fishery will return.
• Work has begun in Uzbekistan, to restore the delta wetlands and lakes
• Sustainable results will take 10 years.
Future trends in the use of water
Increased shortage and conflicts especially in hot countries
due to:
• Change from small scale agrarian population to large
scale irrigated farming and industry
• Increase in population & rise in living standards
• Changes in global climate
•
•
•
•
•
Solutions: Value water
International treaties and economic water management
Improve water conservation technologies
Recycle water
Bank water during surplus sell it during drought
WATER POLLUTION
• Biochemical oxygen demand (BOD):
–
–
–
measure of oxygen used by anaerobic bacteria
mg/l of O2 consumed over 5 days at 20oC
increases with organic pollutants
• Organic matter: sewage, chemical &agricultural waste
Aerobic bacteria use oxygen to break it down until oxygen exhausted
then anaerobes produce reduced compounds such as H2S,
sulphides.
Organic spill in stream short lived problem:
time of residence is low
BOD can be reduced by aeration.
• Stagnant water: breeding grounds for pathogenic bacteria
• Eutrophication:
Phosphates or nitrates from fertilizers or sewage provide too much
nutrition for the plant life
Algal blooms cut sunlight to plants below which die, use up oxygen and
increase the BOD
WASTE WATER TREATMENT
• Organic pollutants: need to lower BOD, reduce
suspended solids, nasty bacteria, and organic
compounds
• Sewage Process:
(1) Screening of large solids
(2) Digesting of solid organic material by
anaerobic bacteria to form sludge which may be
used as fertilizer after treatment
Methane also produced and saleable
(3) Breakdown of soluble organics by aerobic
bacteria in aerated system
(4) Disinfectant of waste water with Cl
(5) Treatment to lower heavy metal content.
TREATMENT OF POLLUTION
•
SURFACE WATER
Point source: find and stop pollution and wait
General source: e.g. leaking sewage systems, not easy to stop, must treat water
Add air: allow aerobic bacteria work more efficiently
Filter through sand and gravel as bacteria work more efficiently in biofilms
Separate source of drinking water from polluted water
Use ion exchange methods such as zeolites or clays
•
•
•
•
•
•
•
•
GROUND WATER: Very difficult to clean as residence time of hundreds to thousands of years
Much less accessible than surface water
No oxygen available for aerobic bacteria
Some natural cleansing by passing through sand & gravel
•
Legislation
prevent dumping
make companies pay for remediation.
•
Ban pollutants such as DDT and PCB's
Map geology and aquifers as most aquifers not studied until problems arise
Identify contaminants and source
Possible remedies:
chlorinate well
pump out contaminated water and treat on surface
vapour extraction to remove volatile contaminants
inject bacteria and air into aquifer
build a permeable treatment bed within aquifer