Freshwater Resources and Water Pollution

Transcription

1 Visualizing Environmental Science Freshwater Resources and Water Pollution Chapter 10 Copyright

2 The Importance of Water Life on Earth would be impossible without water All living organisms contain water Humans are approximately 70% water Uses include drinking, cooking, washing, agriculture, transportation, manufacturing, mining, energy production, waste disposal

3 The Importance of Water 97% is salty Less than 3% of Earth s water is fresh Uneven distribution - serious regional supply issues across the globe By 2025, more than 1/3 of humans will live in areas with inadequate supply of fresh water for drinking and irrigation

4 Properties of Water The chemical structure of water gives it unique physical properties Each individual molecule of water (H 2 O) contains one oxygen and two hydrogen atoms held together by strong (covalent) bonds Water molecules are considered polar molecules The O end of the molecule has a negative charge The H end of the molecule has a positive charge

5 Properties of Water Hydrogen bonds Each end of every water molecule is attracted to opposite charges on adjacent water molecules This attraction forms weak chemical bonds (hydrogen bonds) between the molecules of H 2 O Responsible for many physical properties of water High freezing/melting point High boiling point High heat capacity Ability to act as a solvent

6 Water Resources Surface water Precipitation that remains on the surface of the land and does not seep down through the soil Runoff Drainage basin/watershed

7 Water Policy Central Ridge Area Florida unique system, water belongs to everyone in the state equally Water is allocated based on a permit system administered by the water management districts System aims to prevent waste, provide certainty to existing users, provide equal rights irrespective of economic power, and protect natural resources

8 Water Resources Groundwater The supply of fresh water that is stored in underground aquifers (underground reservoirs) Considered a non-renewable resource; takes 100s 1000s of years to form Rain-fed aquifers begin at recharge zones

9 Freshwater Resources

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

11 Water Resource Problems Too much water Flooding Occurs when a river s discharge cannot be contained within its normal channel Humans are drawn to flood plains Construction replaces flood-protecting plant cover with paved areas that do not absorb water

12 Land Development Changes the Natural Flow of Water

13 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

14 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

15 Water Resource Problems Overdrawing of surface waters Saltwater intrusion Wetlands dry up Water shortages have great economic and ecological ramifications

16 Water Resource Problems Salinization of irrigated soil Gradual accumulation of salt in soil, often as a result of improper irrigation methods Normally, precipitation runoff would carry salts away, but in arid and semiarid areas there is little precipitation, so the salts remain in the soil Salt accumulation becomes poisonous for plants, and over time this salinization may render soil unfit for crop production

17 Water Wars Cooperation between countries that share common watersheds is essential to ensure clean water availability for all The river Nile the source of wealth and prosperity for Egypt Other countries are considering dam projects Egypt is fighting this This represents just the first of many such international and even interstate disagreements over shared water sources.

18 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

19 Water Management Dams and reservoirs Dams generate electricity and ensure year-round supply of water Costs vs. benefits Columbia River - 4 th largest in North America More than 100 dams generate electricity and provide water Negative impact on fish populations Three Gorges Dam (China) largest in the world

20 Water Management Water conservation Reducing agricultural water waste Reducing water waste in industry Reducing municipal water waste

21 Reducing Water Use

22 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

23 Water Pollution BOD is a critical factor in the health of a waterway Large amounts of organic material (sewage) deposited in water enables the growth of large numbers of microorganisms These microorganisms deplete dissolved oxygen, causing fish and the microbes themselves to then die Anaerobic microorganisms then flourish, producing toxins and other chemicals that further reduce water quality

24 Eutrophication of Lakes, Rivers and Streams: An Enrichment Problem Oligotrophic Unenriched, clear water, supports small populations of aquatic organisms

25 Eutrophication of Lakes, Rivers and Streams Eutrophic Cloudy water due to large numbers of algae and cyanobacteria Water is enriched with inorganic nutrients such as nitrogen and phosphorous This can be a natural, long-term process, or Artificial eutrophication Overnourishment of an aquatic ecosystem by nutrients from agricultural runoff and sewage treatment plants

26 Water Pollution Sources of water pollution Point sources Pollutants can be traced to specific sources, such as pipes, sewers, ditches from specific sites Nonpoint sources Pollutants enter a body of water over large areas rather than a specific, single point of entry, i.e. precipitation washes pollutants out of soil and into the water: polluted runoff

27 Water Pollution Groundwater pollution Half of the U.S. obtains drinking water from groundwater sources Quality is a concern Pesticides, fertilizers, organic compounds seep into groundwater from landfills, storage tanks, backyards, golf courses, etc. Cleanup is not always technically feasible Very costly

28 Sources of Groundwater Contamination

29 Improving Water Quality Removing contaminants from water supply before and after use Purification of drinking water Municipal water supplies are treated before water is used Turbid water treated with chemical coagulant to clump and settle out particles Filtration through sand to remove microorganisms Disinfection (chlorine, ozone, UV) to kill any remaining disease-causing organisms

30 Is Bottled Water Safer? Bottled water standards are lower than that for municipal water. About one-quarter of all bottled water in the United States is simply reprocessed municipal water, and much of the rest is drawn from groundwater aquifers, which may or may not be safe. A recent survey of bottled water in China found that two-thirds of the samples tested had dangerous levels of pathogens and toxins. Trailer: Tapped

31 Improving Water Quality Artificial wetlands to treat reclaimed water Orlando Wetland Park 16 million gal per day, on 1220 acres Wetlands absorb and assimilate contaminants Provides wildlife habitat

32 Improving Water Quality Controlling water pollution Legislation is effective on point sources Two very successful laws, but much work is still needed Safe Drinking Water Act Uniform federal standards for drinking water Guarantees safe drinking water supply EPA must determine maximum contaminant levels allowed 1996 amendment requires municipalities to inform which contaminants are present and in what amount Clean Water Act Quality of rivers, lakes, aquifers, estuaries, and coastal waters Attain water quality levels that are safe for fishing and swimming

33 Preventing Water Pollution at Home Individuals produce very little, but collective effect is large

34 Water Pollution in Developing Countries 1.4 billion people in the world do not have access to safe drinking water 2.9 billion don t have access to sanitation systems 250 million cases of water-related illness each year 5 million or more result in death

35 Improving Water Quality Sewage from densely populated cities is dumped directly into rivers and coastal harbors Ganges River-India s holy river Used for bathing and washing clothes Very polluted by untreated sewage and industrial waste, and ashes of 35,000 humans/year