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Lecture 3

Lecture 3 - Freshwater Resources & The Environment (1).pdf

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Earth Sciences
Luc Bernier

Freshwater Resources & The Environment Part 1 - Landscape and Water Resources  There are close natural links between landscape and water resources  Water that condenses contributing to cloud formation reaches the ground in the form of precipitation and returns to the atmosphere through transpiration and evaporation  Water that has reached the ground can infiltrate, percolate and be reabsorbed by plants  The water will also lead to the formation of groundwater and a water table  Rocks and soils will be saturated with water and eventually water that flows as groundwater will form springs as the water connects with the topography  The surface runoff will eventually lead to the ocean  Precipitation contributes to the formation of groundwater  The groundwater saturates rocks and soil and eventually flows to springs and eventually the ocean Habitat Destruction and Water  The global international water's assessment report has studied these linkages between landscape and water  The destruction of habitats is involved in 18% of the cases of regions facing water related issues  For 75% of the population facing water related issues pollution is involved  The absence of Cyprus swamps destroyed by logging and saltwater intrusions by man- made canals is among the factors that lead to the flooding of New Orleans (2005) following hurricane Katrina Engineering of the landscape  Intensive deforestation results in major problems  Large scale irrigation results in major problems  Agriculture results in major problems Freshwater Resources & The Environment Indicators of Ecosystem Health  The impact of these changes can be tracked by indicators of ecosystem health  For freshwater systems fish are good indicators because they are acclimated and in sync with this environment  There are problems with using fish  Overfishing  Another factor in the destruction of aquatic habitat  River engineering focused on flood prevention removes shallow backwaters where fish may breed or hide from predators Blue and Green Waters  Water resource management has focused on rainfall and runoff of blue water because of its potential commercial value  Evapotranspiration is considered a loss even though this is the life blood of crops and terrestrial plants  Green water is directly used by the biosphere  It is a direct important for agriculture and economy  The FAO has adapted this dichotomy between blue and green water when discussing water related issues Blue Water  Baseflow: o Fair weather flow in rivers  Baseflow is one of the forms of blue water  It takes into account groundwater seepage and river flow  It accounts for 11% of the fate of annual precipitation  Stormflow: o Flow in rivers from rain events  Stormflow is the other form of blue water  It accounts for the fate of 27% of annual precipitation  1.5% of all blue water is used for irrigation but only half goes back to rivers Green Water  Green water is considered lost as water vapor but now it is incorporated into concepts of virtual water and water footprints  The majority of water supplied to crops is green water  Crops use 4% of global precipitation  Forests account for 17% of global precipitation  Grasslands account for 31% of the fate of total global precipitation  While 2/3 of human withdrawals are for irrigated agriculture this is relatively limited compared to the fate of natural watering Freshwater Resources & The Environment Part 2 - Agriculture and Water Resources Irrigation and Dissolved Salts  Because of the presence of dissolved salts in freshwater irrigation may be a source of major problems in arid areas and also an ancient one o E.g. Iraq  Farm culture is now being lost to salinization in Iraq  It is also a problem near the Aswan high dam where irrigated land is also being lost  It is also a problem in the Aral Sea Basin where it has been impacted by years of unsustainable diversion of water away from the sea to irrigation in land Indicators of Salinity  Electrical Conductivity: o Indicates general level of dissolved substances in water  Elevated levels are seen in Mexico, Middle East and North America due to problems with the Colorado River due to unsustainable irrigation Freshwater Resources & The Environment  Salinity in water may come from natural sources such as Gypsum  It can be due to human pollution  Industrial activity or road salts Salinity and Soil Fertility  High levels of salt negatively impact soil fertility  In Spain irrigation plays a large role in agriculture  There has been a steady rise in salinity between the 1950s and 1990 in the Aral basin one of the major rivers of the country  Salinized soils in Spain  As a result there has been a gradual reduction in fertility as soils have become salinized  To counter this the latest developments are the replacement of traditional ditch and flood irrigation by sprinklers Eutrophication  Process taking place in water bodies: o Characterized by a development towards an environment rich in nutrients  Levels of nutrients are also an indicator of ecosystem health  Eutrophication is an indication of high levels of pollution and major problems for surface waters  It is characterized by high nutrient supply, dense growth of plankton in the surface waters, turbulence of water columns high nutrient supply in relation to the receiving body of water  The result is a degraded ecosystem where fish die and biodiversity is reduced because the water is almost exclusively defined by algae Freshwater Resources & The Environment Hypoxia and Eutrophication  Status of waters that have: o A Dissolved Oxygen (DO) concentration of less than 2 mg/L  In the summer bottom waters become hypoxic due to stratification  If dissolved oxygen concentration reaches 0 mg/L then the water is considered to be anoxic  Due to the excess nutrient supply biological productivity is intense leading to depletion of oxygen  Dead algae is sinking to the bottom and organic matter is decomposed by bacteria which consume the oxygen  Stratification prevents oxygen from reaching the bottom Eutrophication worldwide  Algae bloom in China caused by eutrophication  Fish such as trout suffocate in massive numbers and are replaced by large amounts of filamentous algae  This is a major problem in the US where 60% of rivers are damaged due to this process as well as 50% of lakes Danube Delta and Algal Growth  Eutrophication has increased in the Delta where the largest wetlands can be found in Europe  This is due to the gradual decrease in the ability of Delta to store nutrients  This problem is due a reduction in the surface area covered by wetlands in the Delta and changes in floodplain storage upstream  There has been over the years of intensification of agriculture, there is more flooding now of heavily farmed fields and there is an increased use of fertilizers  This is combined with reduced flushing of pollutants because of dams upstream  Can see from space the result of this process  Algal blood in the Sea of Azov Biological Oxygen Demand  Amount of oxygen: o Consumed by bacteria as they are feeding on organic waste  It indicates the level of pollution of the water with organics Freshwater Resources & The Environment  e.g. sewage o Raw sewage has a BOD of 600mg/L of oxygen consumed whereas unpolluted water has a BOD of 5 mg/L or less  On this map in general BOD levels are pretty good  There are growing problems due to manure from livestock entering major rivers e.g. Danube Delta in Europe  This leads to BOD levels ten times higher than those for water Part 3 - Thermal Pollution and Acidification Thermal Pollution  Aquatic life is highly sensitive to water temp which has been increasing in rivers because of engineering  This has led to a reduction in oxygen levels in water which can be detrimental if combined with pollution  Loire River, France o Has increased in average temperature by 1 degree Celsius over the past 120 years Freshwater Resources & The Environment  Westport, Kentucky o The Ohio river provides the large amount of water used by the coal-fired power plants o Thermal pollution is evaded by the tower which emits only steam o Emission of the smoke stack is largely steam it still contains pollutants Acidification of Surface Waters  The acidification of surface waters is due to release of acidic gasses (sulphur dioxide) carried by wind and dissolved in rain water to cause acids rain  This rain kills plant life and pollutes rivers/streams  This problem has received a lot of attention at the start of the 1980’s but less not due to climate change concerns  Tacking acidification has led to the reduction in emission of acidic gasses in atmosphere  Targets haven’t been fully met as of yet  The reduction of emissions in acid gasses has yet to be fully achieved  One problem with mission targets is that they don’t apply to ships at sea which aren’t controlled yet and have very dirty exhausts Rehabilitation of Ecosystems  Acid rain has caused a lot of damage to forests in Scandinavia in Sweden  Once it enter s the system it takes time to flush out the acid and this reduced fish population downstream  Sweden has added lime by helicopter to water bodies impacted by acid rain to increase pH and neutralize acid  Long term effects? Freshwater Resources & The Environment Part 4 - Forests and Wetlands Disappearing Forests  FAO estimates for start of 21st cent2ry: o Net global loss of 73, 000 km in forested areas  All of Africa has lost a lot of forest  The Midwest of the US and throughout Europe has also lost quite a bit  The loss in the area of the Salah is important in Africa  Forests can regulate the flow of rivers by storing water Loss of Tropical Forests  1,350 tons of water/hectare  Hundreds and thousands of people are dying because of floods due to deforestation  Amazon forest: loss of 600.000 km since 1970/s  Nearly 50% from agriculture  14% has been from logging and forest fires Droughts and Forest Fires  Usually fires follow prolonged droughts  E.g.: Australia and California, in 2009  There has been less water in these areas for fire fighters because of the rising population Loss of Wetlands  Accelerated rate over the last 20 years  USA: nearly 50% since end of the 18th century  Germany, Netherlands: 50% over the last 50 years  By removing these huge natural sponges it makes it more problematic in controlling the water  Much of the wetland loss has been deliberate  It was believed for a long time that wetlands caused diseases Freshwater Resources & The Environment  The wetlands were located downstream from dam products so by removing the rivers feeding the wetlands they dries up  In other cases they were removed because it was thought that it would control floods Wetlands in Canada  Ramsar Convention: o International treaty for the conservation and sustainable utilization of wetlands  Canada is blessed to have an abundance of wetlands  There are different types of wetlands: Bogs, Floodplains, etc.  The total world area of wetlands is ~2,900,000 km2  Canada plays an important role in preserving these resources because 3 of the 10 largest wetlands are located in Canada  Wetlands preserve water resources and biodiversity  Wetland loss causes more flooding and less groundwater recharge  The Everglades in Florida  With urbanization and release of chemicals from the city there has been contamination of the water which has lowered the water table and salt-water intrusions  Salt water is percolating into the ground Freshwater Resources &
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