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6.1 Water resources and usage (freshwater availability (distribution of…
6.1 Water resources and usage
freshwater availability
distribution of earth's water
total global water:
oceans: 96.5%
freshwater: 2.5%
saline ground water: 0.93%
saline lakes: 0.07%
freshwater:
glaciers and ice caps: 68.6%
groundwater: 30.1%
surface water and other freshwater: 1.3%
surface water and other freshwater:
ice and snow: 73.1%
lakes: 20.1%
soil moisture: 3.52%
swamps and marshes: 2.53%
rivers: 0.46%
biological water: 0.22%
atmospheric water: 0.22%
freshwater is a scarce resource. only 0.024% of earth's water supply is available to us. the world's freshwater supply is recycles, purified and distributed in the earth's hydrologic cycle
groundwater is our biggest source of drinkable water.
aquifier is an underground layer of water bearing permeable rock, rock fractures or unconsolidated materials such as gravel, sand and silt.
unconfined aquifiers are the ones in which water seeps from the ground directly above the aquifier.
confined aquifiers are the ones where water seeps into the aquifier from farther away
freshwater use
it is being used unsustainably. we overload it with water pollutants and withdraw water from water supplies faster than in replenishes
problems caused by unsustainable water use
environment: falling water tables, dwindling river flows, shrinking lakes, disappearing wetlands
economy: threats to food production and energy
national and global security: increasing tensions between some nations
global health: 4100 people on avg die from waterborne infectious diseases
equality and poverty: just 52% of the world's people have water piped to their homes
the freshwater supply is getting smaller bc of climate change
depletion of aquifiers
most aquifiers are renewable resources but we are using them faster than they can refill. some aquifiers are contaminated by industries like mining
withdrawing groundwater pros and cons
pros: useful for drinking and irrigation
exists almost everywhere
renewable if not overpumped or contaminated
cheaper to extract than most surface water
cons: aquifier depletion from overpumping
sinking of land from overpumping
some deeper aquifiers are nonrenewable
pollution of aquifers lasts decades or centuries
solutions to groundwater depletion
prevention: use water more efficiently
subsidize water conservation
limit number of wells
stop growing water-intensive crops in dry areas
control: raise price of water to discourage waste
tax water pumped from wells near surface water
build rain gardens in urban areas
use permeable paving material on street, sidewalks and driveways
increase freshwater availability: water transfers
water transfers: dams, pumps and lined canals are used for water transfers.
desalinization: the process of removing dissolved salts from ocean water. distillation and reverse osmosis
dams: they capture and store the surface runoff from a river's watershed. they can generate electricity and even tourism