Presentation on theme: "WATER RESOURCES Availability, Usage and Pollution."— Presentation transcript:
WATER RESOURCES Availability, Usage and Pollution
Usage World = 700 m 3 /year average per capita use N. America = 1850 m 3 /year average per capita use Value very low and transportation expensive Source needs to be close to consumption Building canals and aqueducts expensive
Surface Water Streams, rivers, lakes: accessible, cheap, easy extraction Quantity related to: Climate (amount and timing of precipitation) Geology (porosity and permeability of ground) Biology (trees, plants, grazing animals) Geography (topography) conditions. Politics People settle on flood plains for fertile soils, available water for irrigation, transport and waste disposal Settlement changes the flow processes of the river causes increased flooding and pollution from industry, farming, sewage and domestic waste
GROUND WATER Source is infiltration from precipitation, lakes, streams, reservoirs Recharge time from days to millions of years Issues relate to pollution, ground subsidence and excessive extraction especially when aquifer crosses national boundaries Surface and Groundwater quantity and quality are closely linked
Desalination Desalination of sea water by evaporation or osmosis –sea water: 3.5% salt –drinking water standards: 0.05 % salt Very expensive: 10 x cost of other water supplies Large scale evaporation plant requires energy to boil water so often combined with a power plant California: emergency supplies in time of drought. Mexico: holiday resorts for foreigners Middle East: desalination of brackish ground water which contains 0.5% salt Jebel Ali desalination and power plant in Dubai will be the largest in the world. It solves water shortage but discharge of hot water may damage largest coral reef in the Arabian Gulf
Water Shortage The world's supply of fresh water is running out. Already one person in five has no access to safe drinking water. epth/world/2000/world_water_crisis
CANADA: Hotels, other businesses closing as water shortage hits Tofino, BC: CBC Tuesday, August 29, 2006 There's a severe water shortage in Tofino on the west coast of Vancouver Island, generally one of the wettest communities in B.C. The municipality issued a public notice for all hotels, restaurants and other food services to shut down by Friday to preserve what water supply remains. All commercial water users including fish plants are not to use any water. The district's main reservoir is very low because of the dry summer. The residential water supply is being maintained with water from a creek. As a result, people are being asked to boil their water. the tourist industry will take a big hit on the eve of one of the busiest weekends of the year. "For people in the restaurant industry, you can't wash your dishes. You can't clean any of the linens if you're in a hotel business. You can't wash your hands. Your clients can't take a shower and there's no other water source The growth in tourism has been "fantastic," but all the development has put a severe strain on the water resources. Officials have said the order will stay in effect at least until there is significant rainfall. Local hotel owners came together and trucked water from Ucluelet to save the Labor Day weekend tourist trade
Europe: CATALONIA More than half of Europe's cities are exploiting groundwater at unsustainable rates. Chronic water shortages are already affecting 4.5m people in Catalonia, where authorities are pressing for the construction of a pipeline to divert water from the Rhone in France to Barcelona.
Mexico City: Subsidence and pollution Mexico city is sinking because of the amount of water being pumped out from beneath its foundations. One of the largest and most populous cities in the world, it was once a lush land of lakes. But over the last 500 years the lakes have been drained and the surrounding forests chopped down. As the city grew in size, the water problem magnified. With no adequate drainage system, today rainwater mixes with sewage and is used for irrigation. The city is now at serious risk of running out of clean water. An estimated 40% of the city's water is lost through leaky pipes built at the turn of the century.
Middle East Conflict Water is the most precious resource in the Middle East, more important than oil. There are four main drainage basins but each river crosses at least one international boundary Euphrates: Turkey, Syria, Iraq, Kuwait Tigris: Iraq, Kuwait Jordan: Jordan, Syria, Israel, Lebanon Orontes: Turkey, Syria Centuries of negotiations, treaties, discussions As populations increase, water becomes more scarce, aggravating regional tensions. e.g. Turkey has been accused by Syria and Iraq of depriving them of much-needed water, as it continues to build a series of dams along the Euphrates and Tigris. Competition for water from the River Jordan was a major cause of the 1967 war. Israelis in the West Bank use four times as much water as their Palestinian neighbors. The Lebanese have accused Israel of having designs on the waters of the River Litani, and Syria accuses it of being reluctant to withdraw from the banks of the Sea of Galilee, the source of up to 30% of Israel's water.
Africa A United Nations report predicts that access to water may be the single biggest cause of conflict and war in Africa in the next 25 years. Such wars are most likely to be in countries where rivers or lakes are shared by more than one country. Ghana, has become totally reliant on the hydro-electric output of the Akosombo dam on the river Volta. Mali, one of the poorest countries in the world, is dependent on the river Niger, which flows from Guinea through Mali to Nigeria, for food, water and transport. But great stretches of the river are now facing environmental catastrophe as a result of pollution. In Nigeria, half the population has no access to clean water, and as in much of Africa, many women walk for hours a day to fetch it. The Nile There is already fierce national competition over water for irrigation and power generation in the Nile river basin. Cairo warned in 1991 that it was ready to use force to protect its access to waters of the Nile, which also runs through Ethiopia and Sudan. If the populations of these countries continue to rise, competition for the water could be fierce. Zambezi River Basin in southern Africa is one of the most overused river systems in the world. Although the countries through which the river flows usually vie with each other to harness the water power, at other times they are deluged by floods and heavy rain. The region experienced the worst floods in living memory in March 2000, exacerbated by Zimbabwe opening the Kariba dam gates.
India THE GANGES The most sacred Hindu river, the Ganges, is so depleted that the Sundarban wetlands and mangrove forests of Bangladesh are seriously threatened. It is also said to contain unacceptable levels of arsenic. As more trees are chopped down, and more buildings erected along its banks, the glaciers supplying the river have been melting, raising fears of shortages and drought downstream. The river has been the subject of a long-running dispute between India and Bangladesh, although recently progress has been made in resolving the conflict.
Australia: the world's driest continent A scheme to reverse the flow of the Snowy River has backfired disastrously, threatening to deprive Adelaide of fresh water. The region that the diverted Snowy River now feeds is bounded by Australia's two longest rivers, the Murray and the Darling. The water tables under this land are now rising, pushing deadly quantities of salt to the surface. The salt has already destroyed some of the country's most productive farmland. The Murray-Darling basin produces three-quarters of Australia's irrigated crops. Many of the basin's tributaries may be unusable for irrigation in 20 years time, let alone as a source of drinking water.
Northern China All three rivers feeding China's Northern Plain are severely polluted, damaging health and limiting irrigation. The lower reaches of the Yellow river, which feeds China's most important farming region, ran dry for 226 days in Northern China is home to two thirds of the country's cropland but only one fifth of its water. As competing demands for water are made by cities, industry and agriculture, the land is drying up. Between 1991 and 1996, the water table beneath the north China plain fell by an average of 1.5 m/year.
Vanishing Aral Sea The Aral Sea in Central Asia was once the world's fourth biggest inland sea, and one of the world's most fertile regions. But economic mismanagement has turned the area into a toxic desert. The two rivers feeding the sea, the Amu Darya and the Syr Darya, were diverted in a Soviet scheme to grow cotton in the desert. Between 1962 and 1994, the level of the Aral Sea fell by 16 metres. Rich delta ecosystems were largely lost. Rusted ships stranded on the desiccated seabed and ghost fishing villages are a sad reminder of the once thriving fishing industry. The surrounding region now has one of the highest infant mortality in the world, and anaemia and cancers caused by chemicals blowing off the dried sea bed are common. Water control structures on both the Aral Sea and Syr Darya River had either generated only temporary benefits or failed altogether.
Aral Sea Solution The World Bank helped build the 8 mile Kok-Aral Dam in 2005, which separates the two parts of the Sea. This will allow the accumulation of over 29 km 3 water in the Northern Aral Sea or Small Sea and help to restore delta and river wetland ecosystems. A sluice in the dike is periodically opened, allowing water to flow into the largely dried-up Southern Aral Sea. Waterworks will raise the water supply for irrigation and restore fishing lakes in the delta area, for hatcheries to restock the Northern Aral Seas fish population. There is a reduction in diseases due to unhealthy drinking water. In a few years, the salt content in the Sea is expected to decline from a current 23 to 10 g/L (1960 levels). The desertification of surrounding land is being mitigated Already, in Tastubek, a fishing village near the Small Sea, residents are able to catch salt-resistant flounder introduced in the 1970s As the salt content of the Small Aral drops, many of the 24 fish species that once supplied a thriving fishery will return. Work has begun in Uzbekistan, to restore the delta wetlands and lakes Sustainable results will take 10 years.
Future trends in the use of water Increased shortage and conflicts especially in hot countries due to: Change from small scale agrarian population to large scale irrigated farming and industry Increase in population & rise in living standards Changes in global climate Solutions: Value water International treaties and economic water management Improve water conservation technologies Recycle water Bank water during surplus sell it during drought
WATER POLLUTION Biochemical oxygen demand (BOD): –measure of oxygen used by anaerobic bacteria –mg/l of O 2 consumed over 5 days at 20 o C –increases with organic pollutants Organic matter: sewage, chemical &agricultural waste Aerobic bacteria use oxygen to break it down until oxygen exhausted then anaerobes produce reduced compounds such as H 2 S, sulphides. Organic spill in stream short lived problem: time of residence is low BOD can be reduced by aeration. Stagnant water: breeding grounds for pathogenic bacteria Eutrophication: Phosphates or nitrates from fertilizers or sewage provide too much nutrition for the plant life Algal blooms cut sunlight to plants below which die, use up oxygen and increase the BOD
WASTE WATER TREATMENT Organic pollutants: need to lower BOD, reduce suspended solids, nasty bacteria, and organic compounds Sewage Process: (1) Screening of large solids (2) Digesting of solid organic material by anaerobic bacteria to form sludge which may be used as fertilizer after treatment Methane also produced and saleable (3) Breakdown of soluble organics by aerobic bacteria in aerated system (4) Disinfectant of waste water with Cl (5) Treatment to lower heavy metal content.
TREATMENT OF POLLUTION SURFACE WATER Point source: find and stop pollution and wait General source: e.g. leaking sewage systems, not easy to stop, must treat water Add air: allow aerobic bacteria work more efficiently Filter through sand and gravel as bacteria work more efficiently in biofilms Separate source of drinking water from polluted water Use ion exchange methods such as zeolites or clays GROUND WATER: Very difficult to clean as residence time of hundreds to thousands of years Much less accessible than surface water No oxygen available for aerobic bacteria Some natural cleansing by passing through sand & gravel Map geology and aquifers as most aquifers not studied until problems arise Identify contaminants and source Possible remedies: chlorinate well pump out contaminated water and treat on surface vapour extraction to remove volatile contaminants inject bacteria and air into aquifer build a permeable treatment bed within aquifer Legislation prevent dumping make companies pay for remediation. Ban pollutants such as DDT and PCB's