Water Resources Chapter 13

13-1 Will We Have Enough Usable Water?  Concept 13-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource.  Concept 13-1B One of every six people does not have sufficient access to clean water, and this situation will almost certainly get worse.

ALL water Fresh water Water available to humans 13-1 Will We Have Enough Usable Water?

 Our planet is 70% water.  Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle. Most of the Earth’s Freshwater Is Not Available to Us

 Access to water is: A global health issue – lack of clean water is the world’s single largest cause of illness An economic issue – it is vital for reducing poverty and producing food, energy A women’s and children’s issue – poor women/girls are responsible for finding and carrying daily water supplies A national and global security issue – increasing tensions between nations over limited water supplies An environmental issue – excessive withdrawal from rivers and groundwater, pollution, shrinking lakes, loss of wetlands, decreasing fish populations, declining water quality, degradation of ecological services provided by aquatic systems Freshwater Is an Irreplaceable Resource That We Are Managing Poorly

The Hydrologic Cycle

 Surface water includes all of the water contained in rivers, streams, ponds, lakes, wetlands, etc.  Some precipitation infiltrates the ground and is stored in soil and rock as groundwater. The top of this groundwater zone is called the water table.  Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water.  The land from which the surface water drains into a body of water is called its watershed or drainage basin. We Get Freshwater from Groundwater and Surface Water

Watershed or Drainage Basin

 An aquifer is a saturated formation of rocks or sediments that contains enough water to yield significant quantities of water to wells and springs. Usually found in layers of sand and gravel, sandstone, limestone, or fractured igneous rock.  Renewable aquifers are replenished by precipitation percolating down from above (natural recharge) or through the ground form nearby rivers or streams (lateral recharge).  Nonrenewable aquifers are found very deep underground and get very little, if any, recharge. We Get Freshwater from Groundwater and Surface Water

Groundwater System: Unconfined and Confined Aquifer

We Use a Large and Growing Portion of the World’s Reliable Runoff  2/3 of the surface runoff: lost by seasonal floods  1/3 is called reliable surface runoff – the amount of surface freshwater we can count on from year to year  We currently use 34% of the world’s surface water and could be using 70% by  Uses of water from lakes, rivers, and aquifers: Agriculture (irrigation) : 70% Industrial use: 20% Domestic (cities and homes): 10%

Average Annual Precipitation and Major Rivers, Water-Deficit Regions in U.S.  Average precipitation (left) in relation to water-deficit regions and their proximity to metropolitan areas (right).

Case Study: Freshwater Resources in the United States  The U.S. has more than enough renewable freshwater, but it unevenly distributed and much of it is contaminated by agriculture and industry.  The Eastern U.S. has plenty of water and most is used for energy generation, power plant cooling, and industry.  In the Western U.S., 85% of what little water they have is inefficiently used for irrigation.

Water Hotspots in 17 Western U.S. States  17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife.  The climate isn’t meant to support the high population and growing certain crops.

Water Shortages Will Grow  The main factors causing water scarcity: Dry climate Drought Too many people using a normal supply of water Wasteful use of water  The poorest people bear the brunt of water shortages: According to a 2005 UN study, 1.1 billion people lack regular access to enough clean water for drinking, cooking, washing and 2.6 billion didn’t have access to even basic sanitation.

 There is controversy over whether water supplies should be owned and managed by governments or by private corporations.  Countries are importing grain as a way to reduce their water use.  Inevitably, this will lead to conflicts over water usage and availability.  Our water options are: 1.Get more water from aquifers and rivers 2.Desalinate ocean water 3.Waste less water Who Should Own and Manage Freshwater Resources?

13-2 Is Extracting Groundwater the Answer?  Concept 13-2 Groundwater that is used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.

 Aquifers provide drinking water for nearly half of the world’s people.  Most aquifers are renewable resources unless water is removed faster than it is replenished or if they are contaminated. Areas of Greatest Aquifer Depletion in the U.S. Water Tables Fall When Groundwater Is Withdrawn Faster Than It Is Replenished  Groundwater depletion is a growing problem mostly from irrigation of cropland.

 Irrigation systems from the nonrenewable aquifer appear as green dots. Brown dots are wells that have gone dry Natural Capital Degradation: Irrigation in Saudi Arabia Using an Aquifer

Case Study: Aquifer Depletion in the United States  Ogallala aquifer: world’s largest known aquifer Irrigates the Great Plains Water table lowered more than 30m in some places High cost of pumping has eliminated some farmers Government subsidies to continue farming deplete the aquifer further Biodiversity threatened

 A cone of depression can also form Water is pumped out too quickly and the water table dips Nearby shallow wells can go dry  Groundwater overpumping can cause contamination of wells near coastal areas with saltwater Groundwater Overpumping Has Other Harmful Effects

 Subsidence is the sinking of the land when water is removed from an aquifer too quickly.  Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater. Groundwater Overpumping Has Other Harmful Effects

Trade-Offs: Withdrawing Groundwater, Advantages and Disadvantages

13-3 Is Building More Dams the Answer?  Concept 13-3 Building dam and reservoir systems has greatly increased water supplies in some areas, but it has disrupted ecosystems and displaced people.

Large Dams and Reservoirs Have Advantages and Disadvantages  A dam is a structure built across a river to control the river’s flow. A reservoir is a large artificial lake that forms once the river is dammed.  The GOAL of a dam is to capture and store runoff. It is also useful for: Controlling floods Generating electricity Supplying irrigation water Recreation (reservoirs)  Dams are a major disruption to the hydrologic cycle

Large Dams and Reservoirs Have Advantages and Disadvantages

 A dam over the Euphrates river in eastern Turkey Large Dams and Reservoirs Have Advantages and Disadvantages

Case Study: The Colorado River Basin – An Overtapped Resource  This river flows for 2,300 km through 7 U.S. states The area drained by its basin is equal to more than 1/12 th the land area of the lower 48 states.  14 Dams and reservoirs  Water is supplied mostly from snowmelt – Rocky Mountains  Supplies water/electricity for more than 25 million people  Irrigation of crops  Recreation

 Four Major problems: The SW U.S. has a very arid climate. The river basin includes some of the driest lands in the U.S. The river only has modest water flow for its size Legal pacts allocated more water for human use than the river can supply Amount of water flowing to the mouth (end) of the river has sharply dropped Many times it does not reach the ocean. Case Study: The Colorado River Basin – An Overtapped Resource

Case Study: China’s Three Gorges Dam  World’s largest hydroelectric dam and reservoir 2 km long dam across the Yangtze River Reservoir is 670km long! (same as distance from SF to LA) Construction started in 1994, completed in 2006, started production in 2012.

 Benefits Electricity-producing potential is huge = 22,500 MW At full capacity = same as 22 coal/nuclear plants Enough power for 10 cities the size of Los Angeles Holds back the Yangtze River floodwaters Allows cargo-carrying ships  Harmful effects Displaces about 5.4 million people (1,350 cities) Built over a seismic fault Rotting plant and animal matter producing CH 4 Worse than CO 2 emissions Case Study: China’s Three Gorges Dam

13-4 Is Transferring Water from One Place to Another the Answer?  Concept 13-4 Transferring water from one place to another has greatly increased water supplies in some areas, but it has also disrupted ecosystems.

The California Water Project and the Central Arizona Project  Water transferred by: Tunnels Aqueducts Underground pipes  Used for: Irrigation Domestic use  Transferring water from water-rich Northern California water-poor Southern California.

Case Study: The Aral Sea Disaster  Large-scale water transfer project in dry central Asia  Once the world’s fourth largest freshwater lake, now it barely exists  Caused by too much withdrawl, drought, evaporation Salinity increased Wetlands destroyed Fishing industry collapse

13-5 Is Converting Salty Seawater to Freshwater the Answer?  Concept 13-5 We can convert salty ocean water to freshwater, but the cost is high, and the resulting salty brine must be disposed of without harming aquatic or terrestrial ecosystems.

 Desalination – the creation of freshwater by removing salt from seawater. Distillation: heating saltwater until it evaporates, leaves behind salt in solid form. Reverse osmosis: uses high pressure to force saltwater through a membrane filter. Removing Salt from Seawater Seems Promising but Is Costly

 There are 15,000 plants in 125 countries Saudi Arabia: highest number  Removing salt from seawater by current methods is expensive, consumes a large amount of energy, and produces large amounts of salty wastewater that must be disposed of safely. Removing Salt from Seawater Seems Promising but Is Costly

13-6 How Can We Use Water More Sustainably?  Concept 13-6 We can use water more sustainably by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release water.

 We waste 65-70% of the water we use throughout the world through evaporation, leaks, and other losses, but we could cut this waste to 15%.  Water conservation: Improves irrigation efficiency Improves collection efficiency Uses less in homes and businesses  Water is underpriced - it is cheap The lack of government subsidies for improving the efficiency of water use contributes to water waste. “Its cheap, so I don’t mind if I waste a little” Tragedy of the Commons Reducing Water Waste Has Many Benefits

 Remember, 70% of the world’s water is used for agriculture…mostly for irrigation.  Sixty percent of the world’s irrigation water is currently wasted, but improved irrigation techniques could cut this waste to 5-20%. Flood irrigation - very wasteful Center pivot, low pressure sprinkler Low-energy, precision application sprinklers Drip or trickle irrigation, microirrigation – costly, but less water waste We Can Cut Water Waste in Irrigation

 Xeriscaping – Landscaping that uses plants that need very little water.  Gray water – slightly dirty water from bathtubs, sinks, showers, washers, that can be used for watering lawns, washing cars, etc.  Saving $ as an incentive not to waste water. When meters are used, water use per person drops by 40%. A 10% increase in water prices cuts domestic water use by 3-7%...maintain low lifeline rates for the poor We Can Cut Water Waste in Industry and Homes

Solutions: Sustainable Water Use

13-7 How Can We Reduce the Threat of Flooding?  Concept 13-7 We can lessen the threat of flooding by protecting more wetlands and natural vegetation in watersheds and by not building in areas subject to frequent flooding.

 Heavy rainfall, rapid snowmelt, removal of vegetation, and destruction of wetlands cause flooding.  Floodplains, adjacent flat areas, usually include highly productive wetlands, help provide natural flood and erosion control, maintain high water quality, and recharge groundwater. Some Areas Get Too Much Water from Flooding

St. Louis, Missouri  To minimize floods, rivers have been narrowed with levees and walls, and dammed to store water.  Human activities have contributed to flood deaths and damages. Removal of water absorbing vegetation Draining and building on wetlands which naturally absorb water Some Areas Get Too Much Water from Flooding

Solutions: Reducing Flood Damage  Rely more on natural systems like wetlands and natural vegetation  Rely less on engineering devices like dams and levees