Chapter 13 Water Resources

Will We Have Enough Usable Water?

FRESHWATER 71% of Earth’s surface is either liquid or frozen H2O Water accounts for 60-90% of the total body mass of living organisms Freshwater is our most important resource & our most poorly managed one (waste & pollution) Freshwater only accounts for about 3% of all the surface (or slightly subsurface) water on the planet While most marine animals have body structures to deal with excess salt accumulation, no one is really sure how marine mammals handle this

Girl Carrying Well Water Over Dried Out Earth During a Severe Drought in India ACCESS TO WATER IS: A global health issue ~3900 children under age 5 die each day from waterborne diseases An economic/women’s and children’s issue: water is vital for producing food & energy which reduces poverty; lack of available water requires that women and girls spend 4-6 hours a day and walk an average of 4 miles to collect it A national and global security issue: increasing tensions within and between nations over access to limited water resources they share

Most of the Earth’s Freshwater Is Not Available to Us So, if ALL precipitation is freshwater, why is just 3% of the surface water fresh? Freshwater availability: 0.024% Groundwater, lakes, rivers, streams Hydrologic cycle provides a constant supply of freshwater in the form of precipitation Movement of water in the seas, land, and air Driven by solar energy and gravity People divided into Water haves: Canada (0.5% of world’s population; 20% of the available freshwater) Water have-nots: China (19% of the people; 7% of the water) Asia (60% of the people; 30% of the water)

Hydrologic Cycle Figure 3.16: Natural capital. This diagram is a simplified model of the water cycle, or hydrologic cycle, in which water circulates in various physical forms within the biosphere. Major harmful impacts of human activities are shown by the red arrows and boxes. Question: What are three ways in which your lifestyle directly or indirectly affects the hydrologic cycle? Fig. 3-16, p. 67

Groundwater Terminology Water in the spaces between soil, gravel and rock Percolation The movement of water from the surface into the ground Zone of saturation Area below ground where substrate is completely filled with water Water table Top of zone of saturation (fluctuates with wet and dry seasons) Aquifers Geological layers below the zone of saturation; typically caverns & underground lakes that hold water Enclosed in watertight zones of solid rock or clay that keep the water from moving deeper Natural recharge-precipitation falls directly over the area above the aquifer, percolates downward & is collected in aquifer Lateral recharge-water moves sideways into the aquifer from nearby streams, rivers or lakes

Surface Water Terminology Freshwater from precipitation and snow melt that flows across earth’s surface into rivers, lakes, streams, marshes, estuaries, wetlands and, ultimately, the ocean Our most important freshwater resource Surface runoff Precipitation that does not evaporate or percolate Watershed/Drainage Basin Area of land from which surface runoff drains into a body of water Much of this land is often designated as a flood plain Example: Colorado River Basin

Colorado River Basin

We Use Much of the World’s Reliable Runoff 2/3 of the surface runoff: lost to larger bodies of water further away from the area where the rain fell due to seasonal floods 1/3 is usable (reliable runoff): collects locally in bodies of water such as lakes, ponds, streams World-wide freshwater use averages Domestic: 10% Agriculture: 70% Industrial use: 20%

Water Footprints and Virtual Water Volume of water we use directly and indirectly Average American uses 260 liters per day Flushing toilets, 27% Washing clothes, 22% Taking showers, 17% Running faucets, 16% Wasted from leaks, 14% World’s poorest use 19 liters per day More water is used indirectly (virtual water) Hamburger, 2400 liters Virtual water often exported/imported Grains and other foods

EXAMPLES OF VIRTUAL WATER USE

Freshwater Resources in the United States More than enough renewable freshwater but it is unevenly distributed and often polluted Freshwater Resources in the United States Eastern States have ample precipitation Most of the freshwater is used for power plant cooling & manufacturing Most serious water problems are flooding, occasional water shortages from pollution & drought Western States are arid (having little to no rain) or semi-arid Irrigation accounts for almost 85% of the water used Most serious water problems are a shortage of runoff from reduced precipitation, high evaporation and recurring prolonged drought

Average Annual Precipitation and Major Rivers, Water-Deficit Regions in U.S. Figure 13.4: The top map shows the average annual precipitation and major rivers in the continental United States. The bottom map shows water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (shaded areas). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey) Fig. 13-4, p. 322

Water Hotspots in 17 Western U.S. States Figure 13.5: This map shows water scarcity hotspots in 17 western states that, by 2025, could face intense conflicts over scarce water needed for urban growth, irrigation, recreation, and wildlife. Some analysts suggest that this is a map of places not to live in the foreseeable future. Question: Which, if any, of these areas are found in the Colorado River basin (Figure 13-1)? (Data from U.S. Department of the Interior) Fig. 13-5, p. 322

Natural Capital Degradation: Stress on the World’s Major River Basins Figure 13.6: Natural capital degradation. The world’s major river basins differ in their degree of water scarcity stress, the measurement of which is based on a comparison of the amount of water available with the amount used by humans (Concept 13-1B). Questions: If you live in a water-stressed area, what signs of stress have you noticed? In what ways, if any, has it affected your life? (Data from World Commission on Water Use in the 21st Century) Fig. 13-6, p. 323

Extracting Groundwater

Trade-Offs: Withdrawing Groundwater, Advantages and Disadvantages Figure 13.7: Withdrawing groundwater from aquifers has advantages and disadvantages. Questions: Which two advantages and which two disadvantages do you think are the most important? Why? Fig. 13-7, p. 325

Aquifer Depletion in the United States Ogallala aquifer: second largest known aquifer Irrigates the Great Plains Very slow recharge Water table dropping Government subsidies to continue farming deplete the aquifer further Biodiversity threatened in some areas California Central Valley: serious water depletion

Natural Capital Degradation: Areas of Greatest Aquifer Depletion in the U.S. Figure 13.9: Natural capital degradation. This map shows areas of greatest aquifer depletion from groundwater overdraft in the continental United States. Aquifer depletion is also high in Hawaii and Puerto Rico (not shown on map). See an animation based on this figure at CengageNOW. Questions: Do you depend on any of these overdrawn aquifers for your drinking water? If so, what is the level of severity of overdraft where you live? (Data from U.S. Water Resources Council and U.S. Geological Survey) Fig. 13-9, p. 326

Deep Aquifers: Future Water Supply? The Ogallala Aquifer is between 50 and 300 feet below the surface. Deep aquifers are anywhere from 1.5-2 miles below the surface (5280 ft = 1mile) May contain enough water to provide for billions of people for centuries Major concerns Nonrenewable Little is known about the geological and ecological impacts of pumping deep aquifers Some flow beneath more than one country Costs of tapping are unknown and likely quite high

Building More Dams

Large Dams and Reservoirs: Advantages and Disadvantages Main goal of a dam and reservoir system Capture and store runoff Release runoff as needed to control: Floods Generate electricity Supply irrigation water Recreation (reservoirs)

Large Dams and Reservoirs: Advantages and Disadvantages Increase the reliable runoff available Reduce flooding Grow crops in arid regions Displaces people Flooded regions Impaired ecological services of rivers Loss of plant and animal species Fill up with sediment Can cause other streams and lakes to dry up

Transferring Water From One Place to Another

California Transfers Water from Water-Rich Areas to Water-Poor Areas Water transferred from north to south by Tunnels Aqueducts Underground pipes California Water Project: One of the World’s Largest Water Transfer Projects Inefficient water use Environmental damage to Sacramento River and San Francisco Bay

Southern California Lettuce Grown with Northern California Water Figure 13.15: This lettuce crop is growing in the Imperial Valley of central California. This and other water-intensive crops are grown in this arid area mostly because of the availability of cheap, government-subsidized irrigation water brought in from northern California, but also because the weather allows for growing crops year round in this valley. Question: Have you ever checked to see where your lettuce and other produce that you eat come from? Fig. 13-15, p. 331

The California Water Project and the Central Arizona Project Figure 13.16: The California Water Project and the Central Arizona Project transfer huge volumes of water from one watershed to another. The red arrows show the general direction of water flow. Questions: What effects might this system have on different areas on this map? How might it affect areas from which the water is taken? Fig. 13-16, p. 331

Converting Seawater to Freshwater

Removing Salt from Seawater Is Costly, Kills Organisms & Creates Briny Wastewater Desalination Removing dissolved salts Distillation: evaporate water, leaving salts behind Reverse osmosis, microfiltration: use high pressure to remove salts 14,450 plants in 125 countries Saudi Arabia has the highest number of plants including the world’s largest Problems High cost and energy footprint Keeps down algal growth and kills many marine organisms Large quantity of brine wastes If dumped into nearby coastal waters it raises the salinity of that water to dangerous levels Disposing of it on land could contaminate the limited surface and groundwater supplies

How Can We Use Water More Sustainably?

Reducing Water Waste Has Many Benefits One-half to two-thirds of water is wasted Subsidies mask the true cost of water Water conservation Improves irrigation efficiency Improves collection efficiency Uses less in homes and businesses

We Can Cut Water Waste in Irrigation Most Common Method: Gravity Flow/Flood irrigation Delivers far more water than can be absorbed before it is lost to evaporation About 60% of the water used worldwide for irrigation does not reach its intended crop More Efficient Options: Center pivot, low pressure sprinkler (80% efficient) Low-energy, precision application sprinklers (90-95% efficient) Drip or trickle irrigation (90-95% efficient)

Major Irrigation Systems Figure 13.18: Several different systems are used to irrigate crops. The two most efficient systems are the low-energy, precision application (LEPA) center-pivot system and the drip irrigation system. Because of high initial costs, they are not widely used. The development of new, low-cost, drip-irrigation systems may change this situation. Fig. 13-18, p. 335

Solutions: Reducing Irrigation Water Waste Figure 13.19: There are a number of ways to reduce water waste in irrigation. Questions: Which two of these solutions do you think are the best ones? Why? Fig. 13-19, p. 336

We Can Cut Water Waste in Industry and Homes Recycle water in industry Fix leaks in the plumbing systems Use water-thrifty landscaping: xeriscaping Use gray water (sinks, showers and washing machines) Pay-as-you-go water use

How Can We Reduce the Threat of Flooding?

Floodplains Flood plains Highly productive wetlands Provide natural flood and erosion control Maintain high water quality Recharge groundwater Benefits of floodplains Fertile soils Nearby rivers for use and recreation Flatlands for urbanization and farming

We Can Reduce Flood Risks/Damages Rely more on nature’s systems Wetlands Natural vegetation in watersheds Rely less on engineering devices Dams Levees Channelized streams Reconsider how we design structures: