WaterWater

Resources, Use, PolicyResources, Use, Policy

WaterWater

• QuantityQuantity

• Sources & DistributionSources & Distribution

• Hydrological Cycles & Ecosystem Hydrological Cycles & Ecosystem HealthHealth

• Patterns of use & recuperationPatterns of use & recuperation

• IrrigationIrrigation

• DamsDams

How Much Water is There?How Much Water is There?

• Though most of the earth is covered Though most of the earth is covered by water, only 2.6% of all the water by water, only 2.6% of all the water is freshwateris freshwater

• If we scaled all the water on the If we scaled all the water on the planet to = 100 gallons then all the planet to = 100 gallons then all the freshwater would = 9.6 teaspoons!freshwater would = 9.6 teaspoons!

Distribution of WaterDistribution of Water

Freshwater CycleFreshwater Cycle

Dynamic of Rivers and Dynamic of Rivers and OceanOcean

• Infiltration of seawater depends upon Infiltration of seawater depends upon strength of freshwater current and volumestrength of freshwater current and volume

• In summer season greater seawater In summer season greater seawater penetrationpenetration

• In drought years, even greater penetrationIn drought years, even greater penetration

• E.g., saltwater wedge from Gulf of Mexico E.g., saltwater wedge from Gulf of Mexico known to penetrate the Mississippii more known to penetrate the Mississippii more than 200 milesthan 200 miles

Dynamic of Rivers and Dynamic of Rivers and OceanOcean

• Infiltration of seawater can have Infiltration of seawater can have serious consequences for agriculture, serious consequences for agriculture, ranching and drinking waterranching and drinking water

• Exacerbated by human reduced Exacerbated by human reduced flows in rivers and watershedsflows in rivers and watersheds

Flooding is beneficial!Removes salts from soils!Brings in new nutrients!

Prevention of Flooding bydykes, levees, channelization, river

diversion is expensive and usually leads to increased erosion downstream

Humans Living in Flood Humans Living in Flood ZonesZones

• Billions of $US spent annual on flood relief Billions of $US spent annual on flood relief and insuranceand insurance

• Floods beneficial for agricultureFloods beneficial for agriculture

• Farming yes, but permanent residences?Farming yes, but permanent residences?

Missouri River 1992 Missouri River 1993

Freshwater UsageFreshwater Usage

Freshwater UsageFreshwater Usage

Water for Products Water for Products (virtual water)(virtual water)

Water for ProductsWater for Products

Water in the West – The Water in the West – The ColoradoColorado

Water in the West – The Water in the West – The ColoradoColorado

Colorado R. Water is Siphoned Colorado R. Water is Siphoned OffOff

Colorado R. Water & Colorado R. Water & AgricultureAgriculture

• The Imperial Valley of California is one of the major producing regions of fruits and vegetables in the US

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Delta of the Colorado

River:

BONE DRY!

Stress Stress ononaquifersaquifers

Water Water shortageshortage

IrrigationIrrigation• Takes water from rivers or Takes water from rivers or

aquifersaquifers

• In US > 21 million hectaresIn US > 21 million hectares

• Increased rate of water loss to Increased rate of water loss to evaporationevaporation

• Costs do not include depletion Costs do not include depletion of freshwater resourcesof freshwater resources

Depletion of Depletion of aquifersaquifers

Ogallala Ogallala AquiferAquifer

Should we be Should we be irrigating the irrigating the most arid lands most arid lands in the USA???in the USA???

• Soybeans require ca. 25 inches (=.64 m) of water when grown on arid soils• A hectare is 10,000 sq. m

• each hectare of soybeans requires 6,400 m3 of water

• 100,000’s hectares of soybean agriculture in arid western US (e.g., eastern Oregon, Nevada, Colorado, Wyoming, etc.)