Essential Question #1 Why is water so important, how much fresh water is available to us, and how much of it are we using?
Why is Water Important Major part of organisms (60%) – Without water, chemical reactions cant occur Affects Climate Carves the Land Removes and dilutes wastes & pollutants Cycles continuously
Where is Freshwater Available? 97.4% salt water, 2.6% freshwater Of that 2.6% freshwater: – 75% is frozen – 90% of melted freshwater is in lakes, soil & air
Fig. 11-2, p. 238 All waterFresh waterReadily accessible fresh water Oceans and saline lakes 97.4% Fresh water 2.6% Groundwater 0.592% Ice caps and glaciers 1.984% Soil moisture 0.005% Biota 0.0001% Rivers 0.0001% Atmospheric water vapor 0.001% 0.014% Lakes 0.007% Earths Water Budget Only about 0.024% of water is available as accessible, liquid freshwater!
Fig. 14-2, p. 307 Continent Percent of world's water resources and population Asia 60.5% 36% Africa 10% 8% Europe North and Central America 7.3% South America and Caribbean 6.4% 26% 15% 5% Oceania 11.3% 0.5% 14% Global Availability of Water Resources
Ground Water Water below the earths surface, stored in spaces in soil, gravel, sand & rock – Water table – top of ground water layer (zone of saturation) Rises & falls w/ precipitation changes – Aquifers – deep layers of porous rock holding water 1/3 of world pumps water from aquifers
Evaporation and transpiration Evaporation Stream Infiltration Water table Infiltration Unconfined aquifer Confined aquifer Lake Well requiring a pump Flowing artesian well Runoff Precipitation Confined Recharge Area Recharge Unconfined Aquifer Less permeable material such as clay Confining im permeable rock layer Unconfined Aquifer Recharge Area Fig. 11-3, p. 239 Groundwater Systems
Aquifers Renewable Aquifers – Natural Recharge – precipitation percolates down to refill (slow process) – Lateral Recharge – refilled from side by streams/rivers Nonrenewable Aquifers – Receive little to no recharge
Surface Water Surface Runoff – Precipitation that doesnt evaporate or soak into ground – 2/3 lost to seasonal flooding Watershed / Drainage Basin – The region where runoff flows into water bodies Reliable Runoff – The amount of runoff we can count on as a stable source of fresh water *(1/3 of surface runoff)
Water Withdrawal Consumptive Use – Does not return water to original source – ~70% of withdrawn water Nonconsumptive Use – Temporarily removes water from source – Ex: Power plant using water for cooling
How much water do we use? 70% = Irrigation 20% = Industrial Use 10% = Cities & Residencies (1lb of beef = 6 months of showers!)
How much water do we use? We currently withdraw 34% of reliable runoff. But to meet demands of growing population we may be using 70-90% by 2025.
Fig. 11-4a, p. 240 Annual Precipitation determines who has & does not have water resources
Freshwater Resources in the United States 17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife. Figure 14-5
Cooperation? No cooperative agreements exist for 158 of 263 watersheds shared by two or more countries Conflicts likely to increase as population & demand continue to rise
Question #2 What causes freshwater shortages, and what can be done to increase freshwater supplies?
Causes of Freshwater Shortages Dry Climate Drought Large Population Poverty
Stress on the Worlds River Basins 1 in 6 dont have access to adequate & affordable supply of clean water. Buy 2050 this could be 1 in 4.
Hydrological Poverty Could you live on 1 gallon of water/day for all your needs?
Ways to Increase Freshwater Supplies Dams & Reservoirs Water Transfers Using Groundwater
Ways to Increase Freshwater Supplies Desalination – Distillation & reverse osmosis Import food Waste Less
Essential Question #3 What are the advantages and disadvantages of withdrawing groundwater?
Withdrawing Groundwater To Increase Supplies Aquifers are Renewable as long as NOT: Overpumped Contaminated Groundwater depletion for Irrigation is a growing problem At least one-fourth of the farms in India are being irrigated from overpumped aquifers.
Effects of Groundwater Overpumping Contaminates freshwater aquifers near coastal areas with saltwater. Sinkholes form when drained aquifers collapse
Groundwater Contamination Example: Contamination from fracking
Fig. 14-7, p. 313 Trade-Offs Withdrawing Groundwater AdvantagesDisadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Available year- round Sinking of land (subsidence) from overpumping Exists almost everywhere Polluted aquifers for decades or centuries Renewable if not overpumped or contaminated Saltwater intrusion into drinking water supplies near coastal areas Reduced water flows into surface waters No evaporation losses Cheaper to extract than most surface waters Increased cost and contamination from deeper wells
Groundwater Depletion: A Growing Problem The Ogallala, the worlds largest aquifer, is most of the red area in the center (Midwest). Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. Figure 14-8
Fig. 14-12, p. 316 Solutions Groundwater Depletion Prevention Control Waste less water Raise price of water to discourage waste Subsidize water conservation Ban new wells in aquifers near surface waters Tax water pumped from wells near surface waters Buy and retire groundwater withdrawal rights in critical areas Do not grow water- intensive crops in dry areas Set and enforce minimum stream flow levels
Essential Question #4 What are the advantages and disadvantages of using dams to supply more water?
Fig. 14-13a, p. 317 Provides water for year-round irrigation of cropland Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Provides water for drinking Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Risk of failure and devastating downstream flooding Can produce cheap electricity (hydropower) Downstream flooding is reduced Migration and spawning of some fish are disrupted
Fig. 14-13b, p. 317 Powerlines Reservoir Dam Powerhouse Intake Turbine River
The Colorado Basin – an Overtapped Resource The Colorado River has so many dams and withdrawals that it often does not reach the ocean. 14 major dams and reservoirs, and canals. Water is mostly used in desert area of the U.S. Provides electricity from hydroelectric plants for 30 million people (1/10 th of the U.S. population).
The Colorado River Basin The area drained by this basin is equal to more than one-twelfth of the land area of the lower 48 states. Figure 14-14
Dam Removal Since 1998, U.S. Army Corps of Engineers no longer building dams / water diversion projects in US Many dams being removed b/c of age or ecological reasons – Difficult & Expensive
Essential Question #5 What are the advantages and disadvantages of transferring large amounts of water from one place to another?
Advantages of Water Transfer Makes unproductive areas more productive Promotes investment / jobs / economy
Disadvantages of Water Transfer Encourages unsustainable use in water scarce areas Reduces water availability from source Examples: – Aral Sea Disaster – California Water Project – South-to-North China Water Diversion Project ($58 billion)
Essential Question #6 How can removing salt from water solve our water supply problems? Why or why not?
Disadvantages Not Practical – High cost / High Energy – Disposal of waste salts / minerals / toxins
Other Ideas: Unlikely Cloud Seeding Towing Icebergs Giant Water Bags
Essential Question #7 How can we waste less water?
Water Waste 65-70% of water used is lost to evaporation, leaks, & other losses About 60% of water used for crop irrigation is lost due to inefficient methods
Center pivot Drip irrigation 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. (efficiency 90–95%) (efficiency 80%–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers. Improving Irrigation
Reducing Water Waste Charge more to increase conservation Improve irrigation techniques (drip irrigation) Give financial incentives (subsidies) for improving water conservation in agriculture / industry
Reducing Water Waste Fix leaks in homes, businesses, infrastructure Install low-flow toilets, showers, etc Used recycled water (gray water) for watering home Plant drought tolerant plants
Fig. 14-21, p. 327 Solutions Reducing Water Waste Redesign manufacturing processes Repair leaking underground pipes Landscape yards with plants that require little water Use drip irrigation Fix water leaks Use water meters Raise water prices Use waterless composting toilets Require water conservation in water- short cities Use water-saving toilets, showerheads, and front loading clothes washers Collect and reuse household water to irrigate lawns and nonedible plants Purify and reuse water for houses, apartments, and office buildings Don't waste energy
Essential Question #8 What causes flooding, and what can we do to reduce flood risks?
What is a flood? When water leaves its normal channel and spills into its adjacent floodplain
What causes flooding? Heavy Rain Rapid Snow Melt Removing Plants Destroying Wetlands Impervious Structures – Pavement / Buildings
Fig. 11-23, p. 253 Flooding After Deforestation of a Hillside
How can we reduce flood risks? Straighten & deepen rivers/streams Build Levees Build Dams – These solutions have ecological problems Can increase erosion Can be overwhelmed by excess flood water
How can we reduce flood risks? Preserve & Restore Wetlands (best solution) – Act as a natural sponge for flood waters Better identify flood plains & think about where we live
Fig. 14-24, p. 331 Solutions Reducing Flood Damage PreventionControl Preserve forests on watersheds Strengthen and deepen streams (channelization) Preserve and restore wetlands in floodplains Tax all development on floodplains Build levees or floodwalls along streams Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreation Build dams
Essential Question #9 How can we use the earths water more sustainably ?
Sustainable Water Use Improve monitoring of water sources to improve management Protect ecosystems involved in water cycle Regulate withdrawals Change subsidies to promote water conservation Improve wastewater treatment Slow population growth & thus demand
Fig. 11-21, p. 251 Use water-saving toilets, showerheads, and faucet aerators Shower instead of taking baths, and take short showers. Repair water leaks. Turn off sink faucets while brushing teeth, shaving, or washing. Wash only full loads of clothes or use the lowest possible water-level setting for smaller loads. Wash a car from a bucket of soapy water, and use the hose for rinsing only. If you use a commercial car wash, try to find one that recycles its water. Replace your lawn with native plants that need little if any watering. Water lawns and garden in the early morning or evening. Use drip irrigation and mulch for gardens and flowerbeds. Use recycled (gray) water for watering lawns and houseplants and for washing cars. What Can You Do? Water Use and Waste What Can We Do?