Water

• In the U.S. agriculture accounts for 80% of water usage and in many western states it is over 90%.
• Irrigation has led to water scarcity in many regions; 40% of U.S. farms must bring in water from off their farm.
• Water for agriculture is often priced well below that of other market sectors.
• As water price increases, technological and conservation methods will be implemented to save water and money.  Various techniques include:  improved irrigation technology, fallowing land, crop shifting, no-till agriculture.

Sources:
-Calzadilla, A., Rehdanz, K., and Tol, R.S.J.  2008.  Water Scarcity and the Impact of Improved Irrigation Management:  A CGE Analysis.  Working Paper FNU-160.
-Gollehon, N. and Quinby, W.  2006.  “Chapter 2.1 Irrigation Resources and Water Costs.”  Agricultural Resources and Environmental Indicators, 2006 Ed.  EIB 16.  Economic Research Service; USDA.  
-National Geographic.  2010.  A Special Issue:  Water Our Thirsty World.  April 2010. 
-National Wildlife Federation (NWF).  Save Water Save Rivers Save Money:  The Potential of Municipal Water Conservation in Texas. 
-Pryor, R. 2006.  Switching To No-till Can Save Irrigation Water.  University of Nebraska Extension.  EC196-3.

• Consumptive use of water is much greater for agriculture than any other sector; about 80% of total consumption.  This is because a large share of applied irrigation water is taken up by plants and converted to biomass or lost through evaporation and transpiration. (Transpiration: the passage of watery vapor through the pores of a leaf)  Little returns to local surface and groundwater. 
  
• An example of groundwater depletion is the Ogallala aquifer.  It is located in the high plains for the western U.S. and covers >156,000 square miles.  Over 90% of the aquifer is pumped to irrigate crops and in some areas the water is withdrawn at 8-10 times the rate of recharge.  It is considered to be a non renewable resource because the recharge rate is so slow.  This aquifer generates $20 billion/year in food and fiber revenue and is considered to be a sole source aquifer (more than 50% of the population depends on it for their water supply).

Ogallala Aquifer

• Irrigation has led to water scarcity in many regions.  40% of US farms must bring in water from off their farm.  Gravity irrigation has efficiencies that range on average from 40-65%.  Pressure systems efficiencies range from 50-95%.
• Because agricultural water is generally priced very low, farmers don’t have an incentive to conserve.  If water prices are increased, farmers will be motivated to increase efficiency.  As population increases, food production will also need to increase and water conservation will only become that much more crucial.