Water ResourcesWater Resources

Questions for Today:Questions for Today:

• What are the major reasons for the What are the major reasons for the decline of freshwater resources?decline of freshwater resources?

• What are the different ways to get What are the different ways to get freshwater?freshwater?

• How do we use freshwater more How do we use freshwater more sustain ably?sustain ably?

Decline of FreshwaterDecline of Freshwater

• Water is a renewable resource!Water is a renewable resource!– Tragedy of the Commons can take effect Tragedy of the Commons can take effect

though.though.

• Most of our usable water comes from Most of our usable water comes from groundwater sources like aquifers.groundwater sources like aquifers.– Decline in aquifer levels are due to over Decline in aquifer levels are due to over

pumping and wasteful irrigation. pumping and wasteful irrigation.

U.S. DepletionU.S. Depletion

• In the United States, Groundwater is In the United States, Groundwater is being drafter 4 times as faster than it being drafter 4 times as faster than it can be replenished.can be replenished.

• One of the largest overdrafts comes One of the largest overdrafts comes from the Ogallala Aquifer.from the Ogallala Aquifer.– Stretches from South Dakota to TexasStretches from South Dakota to Texas

Fig. 13-10, p. 323

WYOMINGSOUTH DAKOTA

NEBRASKA

COLORADOKANSAS

OKLAHOMANEW MEXICO

Miles

0

100TEXAS

Saturated thickness of Ogallala Aquifer

Less than 61 meters (200 ft.)61–183 meters (200–600 ft.)More than 183 meters (600 ft.) (as much as 370 meters or 1,200 ft. in places)

0

160Kilometers

Other problems due to Other problems due to overpumping:overpumping:

• Aside from economics due to Aside from economics due to overpumping, one of the biggest overpumping, one of the biggest secondary problems for over secondary problems for over pumping comes in land subsidence.pumping comes in land subsidence.

• Sinkholes can form from over Sinkholes can form from over pumping.pumping.– Occurred in Occurred in San Antonio San Antonio this year.this year.– Slanted Church in Slanted Church in MexicoMexico

What are different ways to get What are different ways to get new freshwaternew freshwater

• Build DamsBuild Dams– Refresh memoryRefresh memory– Dam Problems (HA!)Dam Problems (HA!)

•Colorado disappearing (14 dams)Colorado disappearing (14 dams)

• Transfer WaterTransfer Water– Aral Sea DisappearingAral Sea Disappearing

Natural Capital Degradation: The Aral Sea, Natural Capital Degradation: The Aral Sea, Shrinking Freshwater LakeShrinking Freshwater Lake

What are different ways to get What are different ways to get new freshwaternew freshwater

• Desalinate WaterDesalinate Water– Distillation– Reverse osmosis, microfiltration– ProblemsProblems

•High cost and energy footprintHigh cost and energy footprint

•Keeps down algal growth and kills many Keeps down algal growth and kills many marine organismsmarine organisms

•Large quantity of brine wastesLarge quantity of brine wastes

Living SustainablyLiving Sustainably

• Reduce Waste WaterReduce Waste Water– DomesticallyDomestically– AgriculturallyAgriculturally

Fig. 13-20, p. 335

Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA

sprinkler)Drip irrigation

(efficiency 90–95%)

Water usually pumped from underground and sprayed from mobile boom with sprinklers.

Gravity flow (efficiency 60% and 80% with surge valves) Above- or below-ground

pipes or tubes deliver water to individual plant roots.

Water usually comes from an aqueduct system or a nearby river.