water resources “it is not until the well runs dry, that we know the worth of water.” benjamin...

Water Resources

“It is not until the well runs dry, that we know the worth of water.”

Benjamin Franklin

Properties of Water Strong hydrogen bonds Remains liquid over wide temp range High heat capacity

Protect living things from temp fluctuations Moderates climate Excellent coolant

Properties of Water video Water-Liquid Awesome, Crash Course

Properties of Water con’t Need a lot heat to evaporate water Excellent solvent Water molecules can ionize into H+ and OH- to

help maintain balance between acids and bases in the cells

Filters out UV radiation from aquatic organisms Capillary action Expands when it freezes/ice has lower density

Fresh Water? 97% too salty Most of 3%

freshwater is locked up in ice caps or too deep to be used

.024% easily available

Unconfined & Confined Aquifer

Groundwater System Surface runoff Watershed or drainage basin Groundwater Zone of Saturation Water table Zone of aeration Aquifer Recharge area

Groundwater System

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Evaporation and transpiration

Evaporation

Stream

Infiltration

Water tableInfiltration

Unconfined aquifer

Confined aquifer

Lake

Well requiring a pump

Flowingartesian well

Runoff

Precipitation

ConfinedRecharge Area

Aquifer

Less permeable materialsuch as clay

Confining permeable rock layer

Unconfined Aquifer Recharge Area

Figure 14-3Page 315

Uses of World’s Fresh Water 70% of water withdrawn=irrigation

About 57% of irrigated water evaporates or seeps into groundwater

20% of water withdrawn=energy production & industrial processing, cleaning, and waste removal

10% domestic and municipal use

Causes of Freshwater Shortages Dry climate Drought Desiccation Water stress

Causes of Flooding Removal of water

absorbing vegetation Living on floodplains Urbanization-roads,

buildings, parking lots

Reduce Risk of Flooding Channelization Building levees and dams Restoring wetlands Floodplain management to keep people out

of flood prone areas = experts view this as best approach

Increase Water Supplies Dams and reservoirs to store runoff Bringing in surface water from other areas Withdrawing groundwater Desalination Improving the efficiency of water use

Dams and Reservoirs Used to capture and store runoff and release it as

needed to Control flooding Produce electricity Supply water for irrigation Reservoirs used for recreation

1950-2000 number of large dams has increased from 5,700 to more than 45,000

24% of world’s freshwater fish species are threatened or endangered

Dams and Reservoirs cont ½ of the world’s major rivers either run dry

part of the year and fail to reach the sea or have little water left in them

Major rivers that run dry: Colorado, Rio Grande, Yellow in northern China, Nile in the Middle East, Ganges and Indus in South Asia, and Amu Darya and Syr Darya in counties of the former Soviet Union

Transferring Water Uses tunnels, aqueducts, and underground

pipes One of world’s largest transfer projects is

the California Water Project which transfers water to Southern California

Compare the transfer projects for the James Bay Watershed and the Aral Sea

Aral Sea

Advantages of Groundwater Removed as needed Water not lost to evaporation Less expensive to use than surface water

systems Aquifers provide drinking water for 1/3 of

world’s population In U.S. 51% of water used for drinking &

43% used for irrigation

Disadvantages of Groundwater Lowering of water table Depletion of aquifer Aquifer subsidence Intrusion of salt water into aquifers Case Study: Mining Groundwater: The

Shrinking Ogallala Aquifer Ogallala Aquifer

Using Water More Efficiently Reduce water subsidies Use more efficient irrigation practices Xeriscaping-replace green lawns in arid & semiarid

regions with vegetation adapted to that environment Fix water leaks Use water meters & charge for all municipal water

use Raise water prices Water-saving toilets, showerheads, & washers