ESSPM Climate and water
Water for the world
Take away ideas and understandings:
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Water is crucial for a large range of natural processes on Earth, including
life.
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A large fraction of fresh water flow on Earth is now controlled by humans.
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Water use has increased globally in a dramatic way.
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Factors that influence the demand for water: population growth, urbanization,
growth of agriculture and industry.
Introduction
The role of water is central to most natural processes
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transport
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Earth's climate
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energy balance, transport of heat, high heat capacity
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ca 80% of the atmospheric greenhouse effect is caused by water vapor
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life
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for most terrestrial life forms, water determines
where they may live; man is exception
'Hydrology'
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literally "water science," encompasses the study of the occurrence and
movement of water on and beneath the surface of the Earth
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finite though renewable resource
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finite in quantity, unlimited in supply, use rate
is limited by 'recycling times'
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use of water in 20th century has grown dramatically (Fig)
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hydrologic sciences have pure and applied aspects
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how the Earth works
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scientific basis for proper management of water resources
Hydrology and water resources
History
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Vitruvius, writing during the second half of the first century BC, often
is credited with first recognizing that groundwater is derived primarily
from infiltration of rain and snowmelt, rather than upwelling of subterranean
water from great depths
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ancient Arabian wells, the Persian kanats, the Egyptian and Mesopotamian
irrigation projects, the Roman aqueducts, and the Chinese irrigation systems,
canals, and flood control works
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Leonardo da Vinci wrote what is likely the earliest complete statement
of the hydrological cycle (da Vinci CD)
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since 1950s, more rigorous mathematical treament of the subject
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20th century has seen most extensive manipulation
of water, dams, groundwater schemes
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13% of global riverflow is now controlled by mankind!
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solutions to problems involving water supply, flood control, water quality
control, recreation, and navigation require an understanding of hydrology
Water resources in the US
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in US, 1500 km3/year are withdrawn for offstream use (1990)
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how does this compare to the discharge of the Hudson
River (13,500 ft3/s)?
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how does it compare to the water use of NYC (1.5
bill gal/d)?
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the fraction of renewable freshwater resources withdrawn on an annual basis
is approximately 18%.
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case study: Water
use in the United States, 1990 Distribution
of the use (Fig) (Where
is groundwater important?)
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sources, use and disposition of freshwater in the
US (Fig)
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case study: Trends
in Water Use in the United States, 1950-1990
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major issues: water quantity and quality
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in many areas of the US more water is withdrawn than is renewed
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global warming
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floods, hurricanes
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groundwater and surface water contamination
Water resources in the world
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global water use is increasing steadily (Fig)
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global concerns as expressed at the UN Water conference
in Dublin, January 1992:
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poor state of water resources assessment throughout
most of the world
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withdrawal rates approaching the renewal rate (or
example, 41% for Spain, 88% for Israel, 97% for Egypt, and 164% for Saudi
Arabia) (Table)
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increasing numbers of aquifers that are being exploited
at rates exceeding their recharge rate
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in 1990, 1.8 billion people still had no access to sanitation services,
1.3 billion people still lacked access to clean water
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in the developing world 80% of all disease is waterborn!
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fears of global warming
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increasing pressure on resources
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prospects of 'Water Wars'
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many countries depend on other countries on water supply (Table)
=> great potential for wars
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the increase in demand is due to population growth and 'mulipliers'
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population growth and urbanization
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population growth: 1900: 1.5bill, 1990: 5bill, 2000:
6bill, 2025: 8.5bill (Fig)
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doubling time ~ 50 years
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improvement in quality of life
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expansion of cities and centralized sewerage
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demand for more industrial, commercial, and agricultural
products
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basic metabolism: 1l/d
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2/3rd of population live on less than 50 l/d/p
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rural consumption less than 200 l/d/p globally
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demand in cities: 300-600 l/d/p (NYC 1.5 bill gal/d,
7mill inhabitants -> ca 800 l/d)
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4% of population consumed more than 300l/d/p in 1980,
will be 17% by 2000
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industrial factor
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amounts of water used higher with older technologies,
with heavy manufacturing industry, and in warmer climates
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industrial use in Europe and North America as a whole
may increase by only 20-30% during last 20y vs. 300-500% in developing
countries
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agricultural factor
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main user of water supplies, mostly for irrigation
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one t of grain, feeding 6 people for one year, requires
3200m3 of water
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50% of world food production by value is grown on
irrigated land, covers only 15% of cultivated land area
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Asia contains three-quarters of the world's irrigated
area (400 mill ha), mostly in river valleys
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human population is similarly concentrated on those
floodplains, and is both the driving force and the consequence of irrigated
agriculture
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irrigated agriculture expanded rapidly, doubled during
last 30y
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by the early part of 21st century, irrigated land
will reach the environmental potential of 470 mill ha, then decline
Water as hazard
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flood risk for property and humans
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climate change
Hydrologists are needed!!
Resources