Chapter 10: Water: Hydrolic Cucle and Human Use Flashcards
How much volume did the Aral Sea lose?
90%
How many feet did the Aral Sea water level drop by?
53 feet
What percent of all water is salt water?
97.5%
Fresh water
contains < 0.1% salt
What percent of fresh water is bound up in ice caps and glaciers?
67%
What contains water?
- streams
- rivers
- ponds
- lakes
- swamps
- estuaries
- groundwater
- bays
- oceans
- atmosphere
What have humans constructed to control water?
huge infastructures
What will challenge water management infastructure?
Increasing population
What will affect the hydrologic cycle?
Climate change
Hydrologic (water) cycle
the cycling of water through the Earth
Evaporation
water molecules leave liquid state and enter gaseous state
Transpiration
loss of water vapor from plants through leaf pores
Condensation
the collecting of water molecules in the gaseous state to form the liquid state
Precipitation
water returns to the land and oceans
Green water
water in vapor form
Blue water
water in liquid form
Humidity
amount of water vapor in air
Relative humidity
the amount of water vapor as a percent of what the air can hold at a particular temperature
What is the opposite of evaporation
Condensation
Aerosols
microscopic liquid or solid particles
What happens when condensing intensifies?
Droplets become larger, gravity pulls them to Earth as precipitation
Trade winds
Earth’s rotation deflects winds east and west
Rain shadow
the dry region downwind of a mountain range
Where do deserts occur on mountains?
The leeward side
Infiltration-runoff ratio
the amount of water that soaks into the ground compared with the amount that runs off
Watershed
all the land area contributing to a stream or river
Surface waters
ponts, lakes, streams, rivers, etc. on the Earth’s surface
Capillary water
held in the soil, according to the soil’s capacity
Evapotranspiration
the combination of evaporation and transpiration
Gravitational water
is not held in the soil
Percolation
trickling of water through pores or cracks in the soil under the pull of gravity
Groundwater
water accumulated in the earth
Water table
the upper surface of groundwater
What does groundwater lie on top of?
an impervious layer of rock or clay
Aquifers
layers of porous material through which groundwater moves
Recharge area
the area where water enters an aquifer
Seep
water flows out in a wide area
Spring
water flows from a small opening
Four categories of human impacts on the hydrologic cycle
- changes to Earth’s surface
- changes to Earth’s climate
- Atmospheric pollution
- Withdrawls for human use
What is water’s largest use for?
Irrigation, then industry and direct human use
What are most increases in withdrawl of water due to?
Increases in agriculture
How much does irrigation account for of freshwater consumption in the U.S.?
65%
What percent of domestic water comes from groundwater sources?
37%
What percent of demestic water comes from surface water?
63%
Where do rural people in developing nations get water?
Wells, rivers, lakes, rainwater
- women often have to walk long distances
Whater in developing nations is often…
polluted with waste
How many people use polluted water?
1.1 billion
How many people die each year due to polluted water?
1.6 million (mostly children
Millennium Development Goal 7
increase access to safe drinking water
The Ogallala aquifer
supplies water to seven U.S. states (20% of the irrigated land in the U.S.)
How much have the water tables in the Ogallala aquifer dropped and how much does it continue to drop a year?
30-60 m (100-200ft)
6ft/year
What does sustainability depend on?
balancing withdrawal rates with recharge rates
Land subsidence
gradual setting of the land
Sinkhole
another kind of land subsidence
What five possibilities exist to meet the future water needs?
- Capture more runoff water
- Tapping more groundwater
- Desalting seawater
- Using less water
- Making food production more efficient
How can more runoff water be captured?
New dams
How many new dams become operational each year?
260
What river was China’s Three Gorges Dam constructed across?
Yangtze River
The centerpiece of the Chinese government’s efforts to industrialize
Three Gorges Dam
The largest hydroelectric project in the world
Three Gorges Dam
Groundwater depletion
the greatest threat to irrigated agriculture
What else is polluting groundwater?
fertilizers, pesticides, animal waste, and industrial chemicals
Desalination
desalting of seawater for domestic use
Most people in the U.S. can afford…
desalinized water
How many gallons/person/day do people in developing nations use?
1
How much water do people in the U.S. use per day?
100 gallons per day (380 liters)
Instead of thinking about how much water is available and where we get it, what should we be thinking?
How much water is available and how we can best use it
Why has the rate of water use dropped?
Conservation
Current flood or center-pivot irrigation…
wastes huge amounts of water
What does the drip irrigation method use?
pipes with holes to drip water at the base of each plant
What does the drip irrigation method do?
wastes less water, retards salination, increases yields
Why don’t farmers switch to drip irrigation?
It’s cheaper to use traditional method than switch
How does the government try to get people to switch to drip irrigation?
it pays $400 per acre in subsidies
What would reducing subsidies do?
encourage water conservation through using more efficient irrigation technologies
Who cannot afford irrigation?
Rural poor in developing countries
What do low-cost treadle pumps allow farmers to do?
irrigate fields
How does the dreadle work?
like a step exercise machine
Xerscaping
planting plants that don’t require watering
50 million U.S. low-flow toilets save…
600 million gallons/day
Gray water
slightly dirtied water from sinks, showers, tubs, and laundry
What does conservation tillage enhance?
rainfall retention and soil fertility
What does conservation tillage decrease?
erosion
Water wars
conflicts between using water for drinking and using it for agricutlure
What does the U.S. need?
A water policy to collect data on water resources and problems and issue recommendations
What must be the primary strategy for meeting future needs
Water efficiency
Water subsidies
must be reduced or eliminated
Polluters
must be charged according to their effluents
Dams
must be operated to maintain river flow that simulates natural flow regimes
The U.S. must provide…
international development aid
