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Explore the dynamics of water sources, hydrological cycles, and ecosystem health for sustainable water management. Learn about freshwater distribution, irrigation impacts, and the challenges of water scarcity and depletion in agriculture.
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Water Resources, Use, Policy
Water • Quantity • Sources & Distribution • Hydrological Cycles & Ecosystem Health • Patterns of use & recuperation • Irrigation • Dams
How Much Water is There? • Though most of the earth is covered by water, only 2.6% of all the water is freshwater • If we scaled all the water on the planet to = 100 gallons then all the freshwater would = 9.6 teaspoons!
Dynamic of Rivers and Ocean • Infiltration of seawater depends upon strength of freshwater current and volume • In summer season greater seawater penetration • In drought years, even greater penetration • E.g., saltwater wedge from Gulf of Mexico known to penetrate the Mississippii more than 200 miles
Dynamic of Rivers and Ocean • Infiltration of seawater can have serious consequences for agriculture, ranching and drinking water • Exacerbated by human reduced flows in rivers and watersheds
Flooding is beneficial! Removes salts from soils! Brings in new nutrients!
Prevention of Flooding by dykes, levees, channelization, river diversion is expensive and usually leads to increased erosion downstream
Humans Living in Flood Zones Missouri River 1993 Missouri River 1992 • Billions of $US spent annual on flood relief and insurance • Floods beneficial for agriculture • Farming yes, but permanent residences?
Colorado R. Water & Agriculture • The Imperial Valley of California is one of the major producing regions of fruits and vegetables in the US
Delta of the Colorado River: BONE DRY!
Irrigation • Takes water from rivers or aquifers • In US > 21 million hectares • Increased rate of water loss to evaporation • Costs do not include depletion of freshwater resources
Depletion of aquifersOgallala AquiferShould we be irrigating the most arid lands 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.)