Preserving Freshwater Resources: Challenges and Solutions

1. Chapter 15: Freshwater Resources Natural System, Human Impact and Conservation www.aw-bc.com/Withgott

2. A: Freshwater Systems • glaciers • icecaps • underground aquifers • rivers & lakes

3. www.aw-bc.com/Withgott Wetlands • diverse ecological systems • slow runoff • reduce flooding • recharge aquifers • filter pollutants • combinations of freshwater and dry land • marshes: plants are allowed to grow above water level • swamps: same as marshes but present in forest areas • bogs: ponds roughly covered by vegetation

4. Lakes and Ponds • open standing water • ecosystems vary according to depth • littoral zone~ shores • benthic zone~ bottom of lake • limnetic zone~ away from shores, top of lake • profundal zone~ similar to benthic, no sunlight

5. Diversity of Ecosystems in Lakes and Ponds www.aw-bc.com/Withgott

6. Groundwater • precipitation that percolates through the soil • 20% of Earth's freshwater • unequal distribution • climate change causing water shortage

7. Aquifers • porous spongelike formation of rock, sand and gravel formed by • zone of aeration: not completely saturated • zone of saturation: saturated with water • water table: limit between zones of aeriation and saturation • confined aquifer: rain cannot get to it by filtration • unconfined aquifer: no upper layer that confines it

8. Average Water Usage • world wide→ 170,616 gal/yr/person • U.S.A.→ 509,000 gal/yr/person • poor countries→ 16,425 gal/yr/person • source: U.N. Environmental Program 2002

9. Water Usage • altering environmental systems • dams • canals • diversions • consumptive use~ water is consumed • irrigation • nonconsumptive use~ water is returned to the system after use • hydroelectric

10. Dam's Drawbacks • risk of failure • Three Gorges dam cracks and sedimenting • blocks flow of water • fisheries fail (salmon in Columbia river) • sedimentation (Answar dam in Egypt) • population displacement (Three Gorges dam) • affects ecosystems • Hoover dam was recently opened to restore the ecosystem www.northlasvegaschamber.com

11. Dam's Benefits ~prevents floods ~provide drinking water ~facilitate irrigation ~generates electricity ~emissions drop ~shipping geochange.er.usgs.gov/.../natural/codrought/

12. Dikes and Levees • flood prevention • along banks of rivers • can fail • flooding is a natural process • heavy rain • snow melt • spreads nutrient-rich sediments

13. Today's Problems Caused by Overuse • major rivers' deltas are dry • Rio Grande, Colorado, Yangze between others • causes tidal erosion • Yangze delta is eroding due to tides • affecting industry and population • Aral sea shrinking and salinating • fishing industry • agricultural industry

14. Ground Water Depletion • we are overusing it • 160 km³ = 100 cubic miles of water used that is not replaced by rain • water table is dropping • causing salt intrusion at deltas • salt water can get to aquifers making water undrinkable • drop of water table causes sinkholes

15. Solutions to Water Depletion • reducing demand • conservation • xeriscaping • water lawn at night • efficiency • showers • washing machine • dishwasher • low-flow faucets • toilets www.aw-bc.com/Withgott

16. Solutions • desalination plants • freshwater from sea water • expensive • requires energy • creates large amounts of salty waste

17. Solutions • reduce agricultural demand • choose crops that match the land and climate • improve efficiency of irrigation systems • drip irrigation • low pressure spray • target individual plants •genetic modification

18. Economic Approaches for Water Conservation • end subsidies to inefficient practices • let water become a commodity • privatization of water supplies • decentralization of control over water • education

19. B: Water Pollution • nutrient pollution: eutrophication oligotrophic eutrophic www.aw-bc.com/Withgott

20. Pollution • pathogens and waterborne diseases: contamination by human or animal waste • cholera • diphtheria • Escherichia coli • salmonella

21. Pollution • toxic chemicals: synthetic chemicals • toxic metals • pesticides • petroleum based products • acids from mining drainage • acid rain

22. Pollution • sediment • mining • clear-cutting • careless cultivation • thermal pollution • too warm can cause oxygen depletion • too cold can cause invasive species to thrive

23. Sources of Water Pollution • point sources • oil spills • industrial waste • sewage plants • non-point sources • animal feedlots • fertilizers from farms, homes and clubs • pesticides from farms, homes and clubs • herbicides from farms, homes and clubs • salt and sand on winter roads • chemicals from urban runoffs

24. Water Quality Indicators • biological • presence of fecal coliform bacteria • disease causing pathogens • physical • turbidity→ presence of sediments • color→ indicates presence of certain chemicals • temperature→ can affect biological processes

25. Groundwater Pollution • extremely difficult to monitor • non-point sources • retains contaminants until they decompose • decomposition can take decades • less O2 • less microbes • less organic matter

26. Sources of Groundwater Pollution • natural • occur naturally in the environment • can cause toxicity in water • arsenic in Bangladesh water wells

27. Sources of Groundwater Pollution • human activity • pathogens and pollutants • underground liquid hazardous waste • septic tanks • tanks of industrial chemicals • oil/gas tanks • nitrates from agriculture fertilizers • cancer • miscarriages • blue-baby syndrome • industrial and military waste

28. http://oceanservice.noaa.gov/education/kits/pollution/media/supp_pol02d.html Legislation • Federal Water Pollution Control Act (1972) • later Clean Water Act (1977) • illegal to discharge pollution from a point source unless permit was given • standards for wastewater • standards for contaminant levels • funds for sewage treatment plants

29. Prevention vs. Mitigation • prevention is cheaper • consumer choice • phosphorus-free detergents • environmentally friendly products • local groups of volunteers collect pollutant data • state and federal regulation

30. Wastewater • water that has been used • sewage • showers • washing machines • dishwashers • manufactures • businesses cleaning processes • storm water runoff

31. Treatments • Municipal wastewater • septic systems in rural areas • underground • microbes break organic matter • needs to be taken to landfill periodically • emits gases lawcoswm.org/septictank.htm

32. bcn.boulder.co.us Treatments • sewer systems in populated areas • primary treatment • physical removal of up to 60% suspended solids • secondary treatment • water is aerated to promote bacteria activity • 90% of solids are removed • chlorine and UV rays applied to kill all bacteria • water is piped back to rivers/lakes/ocean • reclaimed water used as "grey water" • leftover sludge is disposed, incinerated or used as fertilizer

33. Treatments • artificial wetlands • primary treatment is done in a conventional manner • microbes, aquatic plants, fishes, algae • filter and clean the water • biosolids used for energy • problems may happen • prairie dogs The End www.aw-bc.com/Withgott