Unisa Study Notes



LEARNING UNIT 7: RIVERS, LAKES AND WETLANDS7.3 RIVER POLLUTIONName three types of fluid organic waste that pollute water. Indicate the source of each of these types of waste.Three types of waste:Excess nutrients (sewage and soil erosion)Pathogens (sewage)Heavy metals and synthetic organic compounds (industry, mining and agriculture) (p166)Explain how aquatic life is affected by organic waste.In your answer, you should refer to:Breakdown of organic waste by bacteria in the presence of oxygenBiological oxygen demand (BOD)Decline in fish and aquatic plants as dissolved oxygen decreasesHigh volumes of organic waste can exhaust all the dissolved oxygen in a river (p166)Name three examples of liquid inorganic waste. Three examples:CadmiumLead Mercury (p166)Which types of water pollution proved to be a serious problem during the Industrial Revolution?Waste from domestic sources (p168)Which types of water pollution replaced this particular form of water pollution as the major threat to human existence on earth for the remainder of the 19th century? Industrial pollution, especially nutrient pollution and sewage disposal linked to cholera epidemics in London (p168)Name the worst harmful effects of water pollution.Reduces amount of dissolved oxygen in waterIncrease in undesirable forms of algaeReduced reproduction and growth of some species of fishHeavy metals can bioaccumulate up in the food chain and damage human healthSpread of diseases (diarrhoea, cholera and polio)Cholera epidemicsDeath of aquatic plants and animals (p166-167)Name the pollutants that are dumped in rivers as a result of agricultural activities.Pollutants from agricultural activities:SedimentsPesticides Nutrients (nitrogen and phosphorus)What can the nitrate levels in rivers over the past few decades be attributed to, and what are the consequences thereof?In your answer you should refer to:Ploughing of permanent grassland reduces soil organic matter and releases soil nitrogenConversion of grassland to arable farming and its effect on nitrate concentrations in the Thames RiverPollution from sewage (p167)Do you think that it is possible to reverse the damage that pollution causes to rivers? Substantiate your answer by referring to an example.In your answer you can refer to the examples of:Thames RiverRhine River (p167)7.4 LAKESWhat were the ecological implications of the introduction of the exotic Nile perch (a type of fish) into Lake Victoria? Ecological implications:Dramatic decline of endemic fish called cichlidsApproximately 200 cichlid species were driven to extinction (p177)What were the economic implications? Economic implications”Nile perch suddenly increased Nile perch generated considerable benefits – expanding the fishery into a multimillion dollar export industry for Nile fillets and improving incomes of lakeside communitiesAnnual fish landings rose from 40,000 tons in the 1970s to 500,000 tons in the 1980s (p177)What do you think should carry more weight in decisions about introducing exotic species into lakes: the ecological implications or the economic implications? Briefly substantiate your viewpoint.This is your own answer.Which human activities can increase eutrophication in permanent bodies of water such as lakes and dams? How do these human activities affect aquatic life?Human activities:Wastewater dischargeRunoff of fertilizers from agricultural landChanges in land use that increase runoff (Effects on aquatic life:Algal blooms, altered thermal conditions, turbidity and low dissolved solids can cause impairment of drinking water quality, fisheries and water volume or flow.Health problems can range from skin irritations to bilharzia, schistosomiasis and diarrhoea (p176)*You should also be aware of how lakes are affected when the flow patterns of rivers are altered by people. Lake Owens and Lake Mono (California, USA)Irrigation and water export systems diminished the water levels in Lake OwensThe lake, which was 7,6m deep in 1912, disappeared by 1930The dry lake bed became a source of dust storms, which severely affected highway and aviation traffic and increased deaths among people suffering from emphysema, asthma and chronic bronchitisBy 1941, the water export system started using water from Lake MonoBy 1990, the water levels in Lake Mono had fallen by 14m, water salinity doubled and freshwater habitats such as marshes and lagoons were severely damagedThe California Supreme Court ordered the restoration of Lake Mono and its damaged habitats, which also resulted in an increased water level and decrease in salinity levelsThe Aral Sea (Kazakhstan and Uzbekistan, Central Asia)The diversion of water from the Amu Darya and Syr Darya rivers in Kazakhstan and Uzbekistan (under the governance of the Soviet Union at the time) for irrigation of cotton plantations, has resulted in the diminishing water levels of the Aral Sea.In 1960, the Aral Sea was the fourth largest lake in the world, but its surface area has shrunk by 75%, it has lost 90% of its volume and its water level has dropped by more than 25m.Average water level in 1960 was 53m above sea level, by 2003 it was 30m above sea level.This has resulted in salinization.In some parts of the Aral Sea, the water is several times saltier than the sea water in the open ocean.Drainage from salinized areas can increase the concentration of salts in streams, rivers and wetlands, which negatively affects biodiversity and aquatic organisms The Aral Sea commercial fishing industry ceased to exist, since most of the native organisms died outThe diversion of river water also resulted in widespread lowering of groundwater levelsThe receding sea affected the local climate – the exposed sea bed has become a dust bowl from which tons of saline material is deposited on surrounding areas The dust contaminates agricultural land and may have negative effects on human healthThe irrigated cropland has also been subject to salinization and waterlogging due to poor managementDrainage water from the irrigation schemes also contain high salinity and high concentrations of fertilizer and pesticide residues.Regional climate changes took place: the climate has warmer summers and cooler winters, later spring frosts and earlier autumn frosts than previously occur, there has been a decrease in humidity and a shorter growing season.The desire to be self-sufficient in textiles, combined with the Soviet belief that humans were capable of complete domination over nature overrode any fears of the associated environmental impacts.The Aral Sea tragedy is regarded as the most extreme example of human-induced environmental degradation in the modern era. It is also an example of the dangers of an extreme technocentric approach to the environment (p103, 173-175, 244).7.5 LAKE MANAGEMENTName the various considerations that should play a role in the management of lakes.Basic principles in the management of lakes are:The geographical focus for management – includes the lake and the entire catchmentCitizen and stakeholder involvement throughout the planning and management processMechanisms to promote cooperation among government and civil society organisations in the catchment (p178)Explain the role of legislation in the conservation/management of lakes. Can lakes be protected/managed without legislation?In your explanation, you should refer to:The management of the North American Great LakesThe balance between political and economic interests with the natural ecosystemsExamples: Collingwood Harbour, Canada and Oswego River, USA (p178-179).7.6 WETLANDSName and briefly discuss at least one example of each of the following factors leading to the destruction of wetlands:agriculturedisease preventionminingurban expansionwater utilisationthe exploitation of energy sources (eg collection of wood for fuel)In your discussion you should have referred to:AgricultureUSA (Great Lakes, lakes in the Mississippi River, along the Gulf of Mexico and Chesapeake Bay)Belarus (Marshes along the Pripyat River)Botswana (Okavango delta)Disease preventionAlbania (fight against malaria)Mining – this should rather be land reclamationNetherlandsUrban expansionMexico CityWater utilisationSouth Sudan (Sudd Swamps drained)The exploitation of energy sources (eg collection of wood for fuel)Central America, Africa and Asia (mangroves)Northern European countries such as Irland, Russia, Finland and Belarus (production of peat) (p180-182)Why do wetlands generally have a positive effect on the quality of water?Wetlands act as giant water filters, trapping and recycling nutrients and other residues.*Other benefits of wetlands are:They act as temporary water stores, which helps to mitigate river floods downstream, protects coastlines from erosion and recharges aquifersWetlands provide habitats for a wide variety of plants and animalsSome wetlands can also act as significant carbon sinks which helps mitigate global climate changeWhat can be regarded as the main cause of the destruction of wetlands in the world?The clearance of land for agriculture (p179)What happened to the numerous wetlands in and around Mexico City? Why did this happen?Urban sprawl caused the desiccation of four wetlands and only one small wetland remains. This small wetland is threatened by the city’s declining water table (p181)7.7 WETLAND PROTECTIONWhich international convention has as its goal the protection of wetlands?The Ramsar Convention, also known as the Convention on Wetlands of International Importance.Discuss the degree of success of the Ramsar Convention.In your discussion, you should refer to:The 2056 sites in 163 countriesThe lack of power of the Convention, which relies on persuasion and moral pressure to achieve its aimsPressure from growing populations and to expand agricultural activitiesAddressing the drivers of wetland loss and degradationExample of the Azraq Wetland Reserve in Jordan (p183-185). ................
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