Chapter 14 Water: A Limited Resource Importance of Water o o o Cooking Washing Use large amounts for: • • • • • o Agriculture Manufacturing Mining Energy production Waste disposal Use of freshwater is increasing Properties of Water o o o o Composed of 2 Hydrogen and 1 oxygen Exists as solid, liquid or gas High heat capacity Polar • o One end has (+) charge, one end has (-) charge Forms Hydrogen bond between 2 water molecules • H-bonds define water’s physical properties Properties of Water o o o Water is never completely pure in nature Content of seawater (left) Many substances water dissolves cause water pollution Hydrologic Cycle Distribution of Water o o o Only 2.5% of water on earth is freshwater 2% is in the form of ice! Only ~0.5% of water on earth is available freshwater Freshwater Terminology o Surface water • o Runoff • o Land area that delivers water into a stream or river system Groundwater • o Movement of surface water to lakes, rivers, etc. Watershed (drainage basin) • o Precipitation that remains on the surface and does not seep into soil Freshwater under the earth’s surface stored in aquifers Aquifer • Underground caverns and porous layers of sand, gravel and rock in which groundwater is stored Freshwater Aquifer Water Use and Resource Problems o Fall into Three Categories • • • Too much water Too little water Poor quality/contamination (discussed in Chapter 22) Too Much Water o Flooding • o Modern floods are highly destructive because humans: • • o Both natural and human-induced Remove water-absorbing plant cover from soil Construct buildings on floodplains Floodplain • Area bordering a river channel that has the potential to flood Urban vs. Pre-Urban Floodplains Floodplain o Government restrictions on building • o Levees can fail Rather than rebuild levees adjacent to rivers, experts suggest allowing some flooding of floodplains during floods • (next slide) Left: Traditional levees adjacent to river Right: Suggested levee style, set back from river Case-In-Point Floods of 1993 Too Little Water o o Typically found in arid land Problems • • • Drought Overdrawing water for irrigation purposes Aquifer depletion • • Subsidence Sinkholes Too Little Water o Problems (continued) • Saltwater Intrusion Water Problems In US and Canada o o US has a plentiful supply of freshwater Many areas have a severe shortages • • Geographical variations Seasonal variations Water Problems in US and Canada o Water shortages in West and Southwest • Water is diverted and transported via aqueducts Water Problems in US and CanadaSurface Water o Mono Lake (Eastern CA) • • • o Rivers and streams that once fed this lake are diverted to Los Angeles (275mi away) Becoming highly saline Court ordered water diversion reduction Colorado River Basin • • • Provides water for 27-million people Numerous dams for Hydropower Colorado River no longer reaches ocean Colorado River bed in Mexico Water Problems in US and CanadaGroundwater o Aquifer Depletion Ogallala Aquifer Global Water Problems o Amount of freshwater on planet CAN meet human needs • o BUT, it is unevenly distributed and some places lack stable runoff Problems: • • • • Climate Change Drinking Water Population Growth Sharing Water Resources Among Countries Global Water Problems o Water and Climate Change • • Climate change affects the type and distribution of precipitation Potential issues: • • Reduced snowfall will impact water resources downstream Sea level rise will cause saltwater intrusion into drinking water supplies Global Water Problems o Drinking Water Problems • o Many developing countries have insufficient water to meet drinking and household needs Population Growth • • • Increase in population means an increase in freshwater requirements Limits drinking water available Limits water available for agriculture (food) Global Water Problems o Sharing Water Resources Among Countries • Rhine River Basin (right) • • • Countries upstream discharged pollutants into river Countries downstream had to pay to clean the water before they could drink it Aral Sea (next slide) • Water diversion for irrigation has caused sea to become too saline Aral Sea 1967 1997 Global Water Problems o Potentially Volatile International Water Situations • • Jordan River Nile River Water Management o Main Goal: Provide sustainable supply of high-quality water • o o o Requires humans to use resource carefully Dams and Reservoirs Water Diversion Projects Desalinization Dams and Reservoirs o Benefits: • • • o Ensure year-round supply of water with regulated flow Generate electricity Provide recreational activities Disadvantages • • Alter the ecosystem Reduce sediment load Dams and Reservoirs o Glen Canyon Dam • o Regulated flow has changed ecosystem To rectify situation • • • Canyon has been flooded several times Small floods compared to natural floods Still helps rebuild habitat Dams and Reservoirs o o Salmon Population in Columbia R. very low due to dams that impede migration Fish ladders help, but are not effective enough Water Diversion Projects o o o Requires diverting water to areas that are deficient by pumping through a system of aqueducts Much of CA’s receives its water supply from diverted water from Northern CA Controversial and expensive Desalinization o o Removal of salt from ocean or brackish water Two methods: • • o Distillation- salt water is evaporated, and water vapor is condensed into freshwater (salt left behind) Reverse Osmosis- involves forcing salt water through a membrane permeable to water, but not salt Very expensive Water Conservation o Reducing Agricultural Water Waste • • Agriculture is very inefficient with water Microirrigation- irrigation that conserves waster by piping to crops through sealed systems • Also called drip or trickle irrigation Water Conservation o Reducing Industrial Water Waste • Stricter laws provide incentive to conserve water • • • Recycling water within the plant Water scarcity (in addition to stricter pollution control requirements) will encourage further industrial recycling Potential to conserve water is huge! Water Conservation o o Reducing Municipal Water Waste Gray Water • o o Can be used to flush toilets, wash car or water lawn Water saving household fixtures Government incentives Population Increases (1990-2000) Population increases from 1990-2000 in % Annual electricity consumption growth rates from 1988 to 1998 (%) Source: California Energy Commission, Electricity Analysis Office Population Projections Population Projections (2000-2030) Greatest increases expected in the driest states. Source: U.S. Census Bureau NEEDS: FRESH WATER! Snow Survey and Water Supply Forecasting Program o o o o 12 western states including Alaska 60 FTE (36 Field, 24 NWCC) 25.5M acres of irrigated agriculture $51.1B in annual market value (Ag. Census, 2002) NRCS SNOTEL Network o o SNOTEL network • 12 western states • 730+ sites • 16 million observations (2005) • 16.1 million downloads 920 manual snow courses Meteor-burst Technology SNOTEL Site Augmented Data Array o o o o o o o o Snow water content Precipitation Temperature Snow depth Relative humidity Wind speed/direction Solar radiation Soil moisture / temperature NWCC Webpage Mt. Rose SNOTEL Data Water Supply Forecasts o Water Year 2006 • 740 locations forecast Jan-Jun with NWS • • Over 11,534 forecasts issued by states to users Over 1.9M visits to WSF pages New Products - WSF Rapid changes in snowpack affect water supply forecasts New Products – Climate Maps o Maps of snowpack, precipitation, temperature Oregon State University http://www.ocs.orst.edu/prism/