Freshwater Resources and Water Pollution

Freshwater Resources and Water Pollution Chapter 10

Drought in Australia • The Murray-Darling Basin supports the city of Adelaide and provides 65% of water used by Australia’s agriculture • Currently threatened after 8 years of drought • About 40% of Australia’s crops are raised in this semi-arid region • Farmers compete with city residents • Environment is changing • Lakes become salty, native species die, wetlands become toxic, ethnologically important plants and animals have been lost • Environmental and economic damage

The Importance of Water Learning Objectives: • Explain how processes of the hydrologic cycle allow water to circulate through the abiotic environment • Describe the structure of a water molecule and explain how hydrogen bonds form between adjacent water molecules • List the unique properties of water

The Importance of Water • Life on Earth would be impossible without water • All living organisms contain water • Humans are approximately 60% water • Uses: • Drinking, cooking, washing, travel on it, agriculture, manufacturing, mining, energy production, waster disposal • Less than 3% of Earth’s water is consumable • 97% is salty • Uneven distribution - serious regional supply issues • By 2025, more than 1/3 of humans will live in areas with inadequate supply of drinking/irrigation water

The Importance of Water

The Importance of Water • The Hydrologic Cycle and Our Supply of Freshwater • Water circulates in the environment • Provides balance of water in ocean, land, atmosphere • Renews supply of freshwater on land

The Importance of Water • Surface Water: • Precipitation that remains on the surface of the land and does not seep down through the soil • Runoff: • Drainage basin/watershed: • Groundwater: • The supply of freshwater that is stored in underground aquifers (underground reservoirs) • Considered a non-renewable resource, takes 100s–1000s of years to form

The Importance of Water • Properties of Water • Molecules of H2O • Polar molecules • The O end of the molecule has negative charge • The H end of the molecule has positive charge • Hydrogen bonds • Form between 2 molecules of H2O due to opposite charges of the two ends of each molecule • Responsible for many physical properties of water

Global Climate Change • What is surface water? • How do hydrogen bonds form between adjacent water molecules? • What are the unique properties of water?

Water Resource Problems Learning Objectives • Relate some of the problems caused by aquifer depletion, overdrawing of surface waters, and salinization of irrigated soil • Relate the background behind the water problems of the Ogallala Aquifer and the Colorado River Basin • Briefly describe the role of international cooperation in managing shared water resources

Water Resource Problems Three categories: • Too much water • Too little water • Poor-quality water

Water Resource Problems • Flooding • Occurs when a river’s discharge cannot be contained within its normal channel • Humans remove water-absorbing plant cover and construct buildings on flood plains • Area bordering a river channel that has the potential to flood • Construction replaces flood-protecting plant cover

Water Resource Problems

Water Resource Problems • Too little water • Arid lands: desert • Plant growth is limited by lack of precipitation • Semiarid lands: • Receive more precipitation than deserts, but have long periods of drought • Farmers use irrigation to increase agricultural productivity of arid and semi-arid lands • Amount of irrigated land has tripled • 71% of world’s total water is used for irrigation

Water Resource Problems • Aquifer Depletion • Results form excessive removal of groundwater, faster than it can be recharged by precipitation or melting snow • Lowers the water table • The upper surface of the saturated zone of groundwater • Subsidence (sinking of the land) • In areas with porous sediments • Saltwater intrusion • Movement of seawater into a freshwater aquifer near the coast

Water Resource Problems • The Ogallala Aquifer • Largest groundwater deposit in the world • Farmers are drawing water 40 times faster than it can be replaced by nature • Water table has been lowered 30m (100ft) • Water conservation esp. through water-saving irrigation will postpone aquifer depletion

Water Resource Problems • Overdrawing of Surface Waters • Wetlands dry up • Estuaries become saltier • Serve as breeding grounds for many species • Play vital role in water cycle • Water shortages have great economic and ecological ramifications • Water supply and Water quality problems • West and Southwest US, Florida

Water Resource Problems • Colorado River Basin • Serious water problems in US • Provides water for 30 million people • Provides irrigation for 3.5 million acres • International and State laws and agreements • Insufficient water supply for upper Colorado populations and Mexico - violates agreements • Colorado river water is saltier than the ocean in some places • California has agreed to reduce the amount of water withdrawn

Water Resource Problems • Salinization of Irrigated Soil • Gradual accumulation of slat in soil, often as a result of improper irrigation methods • Normally, precipitation runoff would carry away salts • Salt accumulation becomes poisonous for plants • May render soil unfit for crop production

Water Resource Problems • Global Water Issues

Global Climate Change • What problems are associated with overdrawing surface water? With aquifer depletion? • What issues surround water problems of the Ogallala Aquifer? The Colorado River basin? • How does international cooperation affect shared water resources?

Water Management Learning Objectives: • Define sustainable water use • Contrast the benefits and drawbacks of dams and reservoirs • Give examples of water conservation in agriculture, industry, and individual homes and buildings

Water Management • Sustainable water use: • The wise use of water resources, without harming the essential functioning of the hydrologic cycle or the ecosystems on which present and future humans depend • Conservation: • Includes reusing and recycling water, improving water use efficiency. • Important part of sustainable use • Economic Policies: • If water is cheap, it tends to be wasted

Water Management • Dams and Reservoirs: • Dams generate electricity and ensure year-round supply of water • Costs vs. Benefits • Columbia River - 4th largest in North America • More than 100 dams generate electricity and provide water • Negative impact on fish populations

Water Management

Water Management • Water Conservation • Reducing agricultural water waste • Reducing water waste in industry • Reducing municipal water waste

Water Management

Global Climate Change • What is sustainable water use? • What are the benefits of dams on the Columbia River? The drawbacks? • How can individuals conserve and manage water resources?

Water Pollution Learning Objectives: • Define water pollution • Discuss how sewage is related to eutrophication, biochemical oxygen demand (BOD), and dissolved oxygen • Distinguish between the two types of pollution sources and give examples of each • Describe sources of groundwater pollution

Water Pollution • A physical or chemical change in water that adversely affects the health of humans and other organisms • Sewage • Disease-causing agents • Sediment pollution • Inorganic plant and algal nutrients • Organic compounds • Inorganic chemicals • Radioactive substances • Thermal pollution

Water Pollution

Freshwater Resources and Water Pollution