Water Chapter 14

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%) Affects Climate Without water, chemical reactions can’t occur Affects Climate Carves the Land Removes and dilutes wastes & pollutants Cycles continuously Despite it’s importance, water is one of our most poorly managed resources. We waste it, pollute it, & charge too little for making it available

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

Readily accessible fresh water Earth’s Water Budget All water Fresh water Readily accessible fresh water Groundwater 0.592% Biota 0.0001% Rivers 0.0001% Lakes 0.007% Fresh water 2.6% 0.014% Oceans and saline lakes 97.4% Atmospheric water vapor 0.001% Ice caps and glaciers 1.984% Soil moisture 0.005% Only about 0.024% of water is available as accessible, liquid freshwater! Fig. 11-2, p. 238

Availability of Water Resources Percent of world's water resources and population Continent 36% Asia 60.5% 10% Africa 14% Global Availability of Water Resources 8% Europe 11.3% 15% North and Central America 7.3% QUESTION: What two major conclusions can you draw from these data? 26% South America and Caribbean 6.4% 5% Oceania 0.5% Fig. 14-2, p. 307

Ground Water Water below the earth’s 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 Watertight layers of rock or clay below aquifers prevent water from sinking deeper into Earth.

Evaporation and transpiration Groundwater Systems Unconfined Aquifer Recharge Area Evaporation and transpiration Precipitation Evaporation Confined Recharge Area Runoff Flowing artesian well Recharge Unconfined Aquifer Stream Well requiring a pump Water table Infiltration Lake Infiltration Unconfined aquifer Less permeable material such as clay Confined aquifer Confining impermeable rock layer Fig. 11-3, p. 239

Accessing Aquifers

Aquifers Renewable Aquifers Nonrenewable 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 Watershed / Drainage Basin Precipitation that doesn’t 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) 2/3 surface runoff lost to floods, 1/3 makes up reliable runoff

Water Withdrawal Consumptive Use Nonconsumptive 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 Withdrawal – total amount of water we remove from a river, lake, aquifer, etc.

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.

Annual Precipitation determines who has & does not have water resources Precipitation NOT evenly distributed! Fig. 11-4a, p. 240

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 Drought – a prolonged period in which precipitation is at least 70% lower and evaporation is higher than normal

Stress on the World’s River Basins 1 in 6 don’t have access to adequate & affordable supply of clean water. Buy 2050 this could be 1 in 4. The Middle East is among the most water impoverished areas globally, already experiencing disagreements over water rights. By 2050, ~60 countries will be suffering from water stress.

Could you live on 1 gallon of water/day for all your needs? Hydrological Poverty Could you live on 1 gallon of water/day for all your needs? More than 2/3 of the world’s households do not have running water. When water is scarce, not much is used toward sanitation or hygiene.

Ways to Increase Freshwater Supplies Dams & Reservoirs Water Transfers Using Groundwater Dams & Reservoirs - Pro: cheap electricity / reduces flooding / increases freshwater supply - Con: disrupts downstream flow & upsets ecosystems / floods productive land Water Transfers - Pro: provides water to areas w/ little - Con: degrades rivers & disrupts ecosystems / use to grow water needy plants in areas w/ lil natural water - example: Aral Sea – created major ecological, economic & health disaster Using Groundwater - Pro: Renewable if not overpumped / cheap / available most places unless polluted or contaminated by salt - Con: US w/drawing @ 4x replacement rate / causes land to sink / unuseable once

Ways to Increase Freshwater Supplies Desalination Distillation & reverse osmosis Import food Waste Less Desalination - Con: high cost / no solution for what to do with resulting salt waste Importing food – reduces water waste used for crops / livestock - takes 1,000 tons of water to produce 1 ton of grain Waste Less - charge more to increase conservation - improve irrigation techniques - provide govt subsidies for improving water conservation in agriculture / industry - fix leaks in homes, businesses, infrastructure - install low-flow toilets, showers, etc

What are the advantages and disadvantages of withdrawing groundwater? 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. Currently provide about ¼ of world’s water

Effects of Groundwater Overpumping Contaminates freshwater aquifers near coastal areas with saltwater. Sinkholes form when drained aquifers collapse Sinkholes can also occur naturally in areas high in limestone. Aquifer waters can dissolve limestone causing a cave in.

Groundwater Contamination Example: Contamination from fracking

Withdrawing Groundwater Trade-Offs Withdrawing Groundwater Advantages Disadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Sinking of land (subsidence) from overpumping Available year-round Exists almost everywhere Polluted aquifers for decades or centuries Renewable if not overpumped or contaminated Saltwater intrusion into drinking water supplies near coastal areas No evaporation losses Reduced water flows into surface waters Cheaper to extract than most surface waters Increased cost and contamination from deeper wells Fig. 14-7, p. 313

Groundwater Depletion: A Growing Problem Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. Groundwater is being withdrawn 4x faster than it’s being replenished The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest). Figure 14-8

Groundwater Depletion Solutions Groundwater Depletion Prevention Control Waste less water Subsidize water conservation Raise price of water to discourage waste 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 Set and enforce minimum stream flow levels Do not grow water-intensive crops in dry areas Fig. 14-12, p. 316

Essential Question #4 What are the advantages and disadvantages of using dams to supply more water?

Beaver’s are Fans

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) Trade-offs: advantages (left) and disadvantages (right) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. Downstream flooding is reduced Migration and spawning of some fish are disrupted Fig. 14-13a, p. 317

Powerlines Reservoir Dam Powerhouse Intake Turbine River Fig. 14-13b, p. 317

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 (1/10th 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?

Desalination

Disadvantages Not Practical High cost / High Energy Disposal of waste salts / minerals / toxins Projects involving desalination by renewable energy means are underway.

Other Ideas: Unlikely Cloud Seeding Towing Icebergs Giant Water Bags Costly, no scientific evidence of success, unintended ecological consequences

How can we waste less water? 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

(efficiency 60% and 80% with surge valves) Improving Irrigation Gravity flow (efficiency 60% and 80% with surge valves) Figure 14.18 Major irrigation systems: because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new low-cost drip-irrigation systems may change this situation. Center pivot Drip irrigation (efficiency 80%–95%) (efficiency 90–95%) Above- or below-ground pipes or tubes deliver water to individual plant roots. Water usually pumped from underground and sprayed from mobile boom with sprinklers. Water usually comes from an aqueduct system or a nearby river.

Reducing Water Waste Charge more to increase conservation Improve irrigation techniques (drip irrigation) Give financial incentives (subsidies) for improving water conservation in agriculture / industry Government subsidies keep water prices artificially low to help the agriculture industry. Prices so low, there’s no incentive to invest in water saving technologies.

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

Rain Water Recycling Systems

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 Figure 14.21 Solutions: methods of reducing water waste in industries, homes, and businesses. QUESTION: Which three of these solutions do you think are the most important? • 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 Fig. 14-21, p. 327

What causes flooding, and what can we do to reduce flood risks? 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 Floodplain – areas in which flood waters spill into; typically contain wetlands that provide natural flood & erosion control

What causes flooding? Heavy Rain Rapid Snow Melt Removing Plants Destroying Wetlands Impervious Structures Pavement / Buildings Since the 1960’s, human activities have contributed to increased flooding: - damming & altering rivers w/ levees increase flood risks b/c can be easily overwhelmed - removing water-absorbing vegetation - draining & removing wetlands that act as natural sponges for flood water

Flooding After Deforestation of a Hillside Fig. 11-23, p. 253

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

Preserve forests on watersheds Solutions Reducing Flood Damage Prevention Control Preserve forests on watersheds Strengthen and deepen streams (channelization) Preserve and restore wetlands in floodplains Build levees or floodwalls along streams Tax all development on floodplains Figure 14.24 Solutions: methods for reducing the harmful effects of flooding. QUESTION: Which two of these solutions do you think are the most important? Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreation Build dams Fig. 14-24, p. 331

How can we use the earth’s water more sustainably ? Essential Question #9 How can we use the earth’s 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

What Can We Do? What Can You Do? Fig. 11-21, p. 251 Water Use and Waste 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. Fig. 11-21, p. 251

The Awesome Water Bottle http://www.youtube.com/watch?v=pzdBCxZhKpQ