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Freshwater Resources Chapter 15

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Ch 15 Freshwater Resources Rivers feeding estuaries are freshwater resources How do we use water? From where do we draw our drinking water (we, us, here?) How does our use of freshwater resources alter those systems? Why is our water supply dwindling? How would you address this problem? Our freshwater is being degraded. How has that happened? Are there solutions for mitigation or restoration of those systems? How is wastewater treated?

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Limited resource: only 2.5% of all water is fresh

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Water is unequally distributed across Earths surface Different regions possess vastly different amounts of groundwater, surface water, and precipitation Many areas with high population density are water- poor and face serious water shortages

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Areas where water use exceeds supply

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Some terms to guide your study Lentic waters-slow moving or no moving waters-ponds, lakes, bogs, etc Lotic waters-moving water-creeks, streams, rivers Floodplain-land within the floodwaters of a river Watershed-all the land to one side of a fall line that drains into a body of water; the area of land drained by a river and its tributaries Aquifer-water trapped between layers of rock or between layer of rock and clay Groundwater-water in aquifer reservoirs Water table-upper limit of an aquifer Recharge an aquifer-replace water lost or used in aquifer-water needs to infiltrate land to recharge the aquifer Riparian = riverside areas that are productive and species-rich

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A typical aquifer

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Freshwater wetlands Usually ecotones between aquatic and terrestrial ecosystems Marsh-along edges of streams/rivers, may be perched, may be tidal or nontidal, dominant vegetation is grass Swamps-dominant vegetation is trees, water may be deep-a few feet Bogs-shallow body of water covered with vegetation- frequently sphagnum moss, can be over permafrost Prairie potholes-cyclical nontidal marsh found in the Dakotas

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Freshwater systems Water may seem abundant, but drinkable water is rare Freshwater = relatively pure, with few dissolved salts Only 25% of Earths water is fresh Most freshwater is tied up in glaciers and ice caps

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How do we use water? From where do we draw our drinking water (we, us, here?) Residential/municipal-10% of freshwater used Industrial use-20% of freshwater used Agriculture-70% of freshwater used (Ogallala aquifer) Arid countries use water for agriculture Developed countries use water for industry Consumptive use: irrigation, industrial, residential- water is not returned to aquifer/surface waters Nonconsumptive use: hydroelectric dams some industrial uses-returns water Our drinking water: CB, reservoirs, rivers, aquifers, desalinization plants (reverse osmosis)

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Ogallala Aquifer

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How does our use of freshwater resources alter those systems? Alter entire ecosystems: dams, canals, diversions Colorado river, Yangtze river 60 % of the worlds largest 227 rivers have been strongly or moderately affected Depleting surface waters-Aral sea Irrigation (Salinization) Groundwater depletion Salt water intrusion, sinkholes DEGRADATION

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Plumbing the Colorado River The 2,330 km Colorado River begins in the Rocky Mountains and trickles into the Gulf of California Dams and irrigation provide water to millions of people in 7 states Las Vegas, Nevada, is growing rapidly, and needs more water The other states are allowing Las Vegas to drill for underground water, even though it threatens the areas ecology and people

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We divert and deplete surface water People have long diverted water to farm fields, homes, and cities The once mighty Colorado River has been extensively dammed and diverted

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Can the Aral Sea be saved? People may have begun saving the northern part of the Aral Sea

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Yangtze River

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Three Gorges Dam The dam, on the Yangtze River, is the largest in the world 186 m (610 feet) high, 2 km (1.3 mi) wide Its reservoir stretches for 616 km (385 mi) Provides flood control, passage for boats, and electricity

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A typical dam

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Benefits and drawbacks of dams Benefits: Power generation Emission reduction Crop irrigation Drinking water Flood control Shipping New recreational opportunities Drawbacks: Habitat alteration Fisheries declines Population displacement Sediment capture Disruption of flooding Risk of failure Lost recreational opportunities

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Saltwater intrusion

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Freshwater pollution sources

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Water pollution Nutrient pollution-excess N and P Pathogens; waterborne diseases: viruses, bacteria, protists (Giardia) Biological hazards: giardiasis, typhoid, hepatitis A Toxic chemicals (Cuyahoga river) Sediment loading Thermal pollution Point vs nonpoint pollution

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Nutrient pollution Pollution = the release of matter or energy into the environment that causes undesirable impacts on the health and well-being of humans or other organisms Nutrient pollution from fertilizers, farms, sewage, lawns, golf courses Leads to eutrophication Solutions Phosphate-free detergents Planting vegetation to increase nutrient uptake Treat wastewater Reduce fertilizer application

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Sediment pollution Sediment can impair aquatic ecosystems Clear-cutting, mining, poor cultivation practices Dramatically changes aquatic habitats, and fish may not survive Solutions: better management of farms and forests; avoid large-scale disturbance of vegetation

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Pathogens cause massive human health problems Currently, 1.1 billion people are without safe drinking water 2.4 billion have no sewer or sanitary facilities Mostly rural Asians and Africans An estimated 5 million people die per year Solutions: Treat sewage Disinfect drinking water Public education to encourage personal hygiene Government enforcement of regulations

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Toxic chemicals From natural and synthetic sources Pesticides, petroleum products, synthetic chemicals Arsenic, lead, mercury, acid rain, acid drainage from mines Effects include: poisoning animals and plants, altering aquatic ecosystems, and affecting human health Solutions: Legislating and enforcing more stringent regulations of industry Modify industrial processes Modify our purchasing decisions

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Cuyahoga River 1 of at least 13 fires

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Indicators of water quality Scientists measure properties of water to characterize its quality Biological indicators: presence of fecal coliform bacteria and other disease-causing organisms Chemical indicators: pH, nutrient concentration, taste, odor, hardness, dissolved oxygen Physical indicators: turbidity, color, temperature

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Groundwater Any precipitation that does not evaporate, flow into waterways, or get taken up by organisms Groundwater makes up one fifth of the Earths freshwater supply Groundwater becomes surface water through springs or human-drilled wells Groundwater may be ancient: the average age is 1,400 years

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Groundwater pollution Doesnt flush Persistent toxins trapped No O2, low microbes, low organic material decomposition SLOW Some toxics naturally occurring, Fl in Smithfield, Al, NO3 (causes cancers, miscarriages, blue-baby syndrome), SO4, As Anthropogenic sources: industrial, agricultural and urban wastes Heavy metals, petroleum products, industrial solvents, pesticides, pathogens (E.coli), BOCs, leakage from landfills, leakage from septic tanks, industrial chemical tanks, gas and oil tanks

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Climate change will cause water shortages Climate change will cause Altered precipitation patterns Melting glaciers Early season runoff Intensified droughts Flooding Increasing probability that there will be still less water for more people Even if water stays the same, the population doesnt-7 billion people now populate the Earth

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Are there solutions for mitigation or restoration of those systems? Use less use less use less use less Dont pollute from the beginning Legislation has reduce point source pollution Clean water act Lowering demand Politically difficult in the short term Offers better economic returns Causes less ecological and social damage Increasing supply Water can be transported through pipes and aqueducts It can be forcibly appropriated from weak communities

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Agricultural demand can be reduced Look first for ways to decrease agricultural demand Lining irrigation canals Low-pressure spray irrigation that spray water downward Drip irrigation systems that target individual plants Match crops to land and climate Selective breeding and genetic modification to raise crops that require less water

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Residential demand can be reduced Install low-flow faucets, showerheads, washing machines, and toilets Water lawns at night, when evaporation is minimal Eat less meat Xeriscaping = landscaping using plants adapted to arid conditions

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Industrial demand can be reduced Shift to processes that use less water Wastewater recycling Excess surface water runoff used for recharging aquifers Patching leaky pipes Auditing industries Promoting conservation/education

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Economic approaches to water conservation End government subsidies of inefficient practices Let the price of water reflect its true cost of extraction Industrial uses are more profitable than agricultural Less developed countries suffer Privatization of water supplies May improve efficiency Firms have little incentive to provide access to the poor Decentralization of water control may conserve water Shift control to the local level

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It is better to prevent pollution It is far better to prevent groundwater contamination than correct it Other options are not as good: Removing just one herbicide from water costs $400 million Pumping, treating, and re-injecting it takes too long Restricting pollutants above aquifers would shift pollution elsewhere Consumers can purchase environmentally friendly products Become involved in local river watch projects

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Treating wastewater Wastewater = water that has been used by people in some way Sewage, showers, sinks, manufacturing, storm water runoff Septic systems = the most popular method of wastewater disposal in rural areas Underground septic tanks separate solids and oils from wastewater The water drains into a drain field, where microbes decompose the water Solid waste needs to be periodically pumped and landfilled

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Municipal sewer systems In populated areas, sewer systems carry wastewater Physical, chemical, and biological water treatment Primary treatment = the physical removal of contaminants in settling tanks (clarifiers) Secondary treatment = water is stirred and aerated so aerobic bacteria degrade organic pollutants Water treated with chlorine is piped into rivers or the ocean Some reclaimed water is used for irrigation, lawns, or industry

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A typical wastewater treatment facility

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HRSD

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HRSD: Hampton Roads Sanitation District 9 major treatment plants 231 million gallons per day Wastewater flows from municipal piped systems to HRSDs interceptor system of pipes and pump stations to our treatment plants. One of my former students is a scientist with HRSD. He samples water throughout the district for toxins.

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Waste Water Treatment Preliminary Treatment: Removes grit (sand), debris, and manmade objects. Primary Treatment: Allows for the settling and flotation of organics and solids. Heavy solid particles such as food waste sink to the bottom, and lighter organics such as oil and grease float to the top. About 35% of the organics and 50% of the solids are removed. Secondary Treatment: Uses naturally occurring microorganisms to remove additional organics and solids such as sugars, starches, proteins, detergents, and soaps. Nutrient Removal: Eliminates at least 2/3 of the phosphorus and 1/3 of the nitrogen from wastewater. Those treatment plants with Biological Nutrient Removal eliminate an additional 1/3 of the nitrogen. Disinfection: Kills disease-causing bacteria. Effluent is typically chlorinated and then dechlorinated before it is released to local waterways, making it safe for aquatic life.

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Artificial wetlands Natural and artificial wetlands can cleanse some waste water After primary treatment at a conventional facility, water is pumped into the wetland Microbes decompose the remaining pollutants Cleansed water is released into waterways or percolated underground Constructed wetlands serve as havens for wildlife and areas for human recreation More than 500 artificially constructed or restored wetlands exist in the U.S.

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Lake and pond zonation Benthic zones: Littoral Sublittoral Profundal Limnetic, pelagic zones Epilimnion (mesolimnion) hypolimnion

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Lake Classification Trophic ClassificationNutrient concentrationBiological productivity OligotrophicLow MesotrophicModerate EutrophicHigh hypereutrophicExtremely highVery high