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Environmental Science
Jovan Stefanovic

Discussion on sept 30 & nov 4 Continuation of last week… Distribution of Water on Earth  Water is only substance that naturally occur as a liquid , solid, or gas  Earth contains 1.39billion km3 of water o The oceans make our earth look blue against the black background of the atmosphere  Not evenly distributed and varies season to season and year to year Consequences  Such disparities lead to water shortages and the need to do: o Store water in reservoirs during wet periods o Rely on groundwater resources if available o Transport water supplies to great distances Oceans  Covers70% of earth’s surface  Uneven distribution of land and oceans is caused by plate tectonics?  Salty or saline (3.5% dissolved salts by weight; salts are: Na, Ca, Mg, and CI)  Human tolerance for salt is less than 2% o Agriculture & industry cannot use salt water  Nearly 97% of earth’s water is salty – difficult, expensive to utilize for drinking, agriculture and industry  If all seawater evaporated  seafloor will be covered with 56m of salt (75% of this salt is common table salt – NaCI) Surface Ocean Currents  Persistent prevailing winds blowing over the ocean produces currents  Prevailing winds generate gyres – circular ovean currents  Coriolis effect (due to Earth’s rotation) influences the paths of surface or shallow ovean currents Glaciers, permanent snow, sea ice, and polar ice caps  Glaciers are created when deep snow recrystallizes due to the weight of overlaying snow  When snow and ice becomes so thick and heavy gravity causes the frozen mass to move  30% of Earth’s surface is in the cryosphere (cold and frozen sphere) : presently 10% are glaciers and 20% permanently snow – covered and frozen ground (permafrost)  Polar ice caps generate cold, dense water that creates deep ocean circulation  Ocean currents affects world’s climate by altering ocean temperatures Groundwater (GW)  Water stored under Earth’s surface  Replenished when precipitation falls on land surface and seeps down into an aquifer o Aquifer: a rock, sand or gravel layer that can store and yield significant amounts of water  GW is 30% of total freshwaters  The quality of GW ranges from salty (3%-30000ppm) in some coastal areas to relatively mineral-free in Iceland  GW is often the main source of water to sustain ecosystems, riparian zones, lakes and rivers (also potable water for approximately 30% of Canadians)  The largest GW deposit in the world is the Ogallala Aquifer  Problems of river waters and surface waters o For fresh water which one will you choose?  Ground water  Pure + easier to transfer into drinkable water  Less expensive o After couples of years, you get less and less water  The timing it takes to recharge the GW Rivers  Surface water transport system  4.8 million km of river channels in the US alone  .0001% fo the world’s water  rivers varies in size, discharge, speed of current, aquatic population, water quality and temperature (T)  Think about T, oxygen level & sediments of the Amazon R. flowing toward the Atlantic Ocean and in headwaters in the Peruvian Andes Mountains o Nile river brings many sediments and is good for the water o More oxygen in the winter o When water is turbulent, there are more oxygen (ex mountain rivers) compared to flat smooth stream  Types of rivers: o Ephemeral streams: not fed by any continuous water source or they flow only after storm events  Ex. dry rivers in Australia  No GW o Intermittent streams  Fed by storm water + GW  Ground water is continuous o Influent or losing rivers  Dry condition when water lever is lower than level of GW o Effluent or gaining rivers  GW discharges to the stream Lakes  Inland body of water found in a topographic depression  Canada contains nearly half of the world’s lakes o part due to the ice sheets that carved depressions in the landscape some 10 000 – 12 000 years ago  Ways to use our water o Our waters come from the lake Ontario through giant pipes o Temperature is always 5-6 degrees o Use this water for cooling purposes  Put pipes around the building  Lake Stratification o There is a layer of water temperature difference, sometimes in the summer the surface is warmer than deeper o Whereas spring there is no stratification because there is a good mix of water temperature throughout, even deeper down o Density versus temperature curve for water Wetlands (natural sponges)  Swamps, marsh, fen, peatland, bog, moor or estuary  Areas which are saturated by surface or GW for long enough periods of time to develop characteristic wetland soils and vegetation  70% - 80% of original wetlands in S. Ontario have been lost since European settlements  Important functions o Flooding or potential areas to treat waste water o Habitat, food, breeding and nesting  What can we use the wetland for?  What can you expect below the wetland? o GW Atmosphere  Gaseous envelope that surrounds a planet  Water vapor moves into the air through evaporation from land and waterbodies  Only 0.1% of the world’s water is found in the atmosphere at any one time, but it is critical to the replenishment of water supplies as precipitation Watersheds  The topographic area within which apparent surface water drains to a specific waterbody  No matter where you live, you are in a watershed  Can cover multiple states, provinces, territories or countries  Why is it important o When calculating the river, you can know the limit and boundaries of the rivers  Conservation Authority Watersheds are in charge and take care of rivers, etc Human Effects on Freshwater Ecosystem  Dam construction, river water diversions and poor water quality alter river regimes and cause degradation of wetlands  Population growth can lead to land conversion for increased food production o Ex. wetlands are drained  Land conversion to urban or other uses can results: o Altered runoff patterns o Siltation of rivers, lakes and wetlands o Loss of aquatic habitats  Pollution caused by population growth can alter the chemistry and ecology of waterbodies Global Population Growth and Human Proliferation  don’t need to know the #’s Settlement Patterns  MEGACITIES – massive, densely populated, urban centers of 10 million or more – increasingly found in less-developed regions  Create environm
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