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(c) McGraw Hill Ryerson 2007 10.3 Sources of Fresh Water Precipitation becomes run-off as gravity pulls water down into the groundwater, a lake or an ocean.

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Presentation on theme: "(c) McGraw Hill Ryerson 2007 10.3 Sources of Fresh Water Precipitation becomes run-off as gravity pulls water down into the groundwater, a lake or an ocean."— Presentation transcript:

1 (c) McGraw Hill Ryerson Sources of Fresh Water Precipitation becomes run-off as gravity pulls water down into the groundwater, a lake or an ocean basin. See page

2 Sources of Fresh Water Run-off increases if:  precipitation falls on rock, as soils allow water to soak in  heavy rainfall saturates the ground so water can’t soak in  long periods of rainfall saturate the ground so water can’t soak in  water can flow quickly down a steep slope, not having time to soak in  there is no vegetation, as plants help to absorb water and hold soil with their root systems  there is human development and no soils Human development often alters run-off (c) McGraw Hill Ryerson 2007

3 Drainage Basins Drainage basins are large areas where surface water all moves towards one main river  Run-off flows into streams and smaller rivers, which are tributaries of large rivers, forming a branching system  Large rivers are separated by very high ground called divides  The Rocky Mountains form the Continental Divide, which divides BC and Alberta See page 379

4 (c) McGraw Hill Ryerson 2007 Ground Water Ground water is water that soaks into the ground  Rock/ground with good porosity allows more water to enter  More pores (spaces in the rock/soil), the better the porosity  An aquifer is a layer of porous rock that allows ground water to flow, almost like a river below the surface. See page 380

5 Ground Water Humans get fresh water from  Reservoirs, natural or man-made  Wells, drilled into aquifers down to the water table, which is the top level of the zone of saturation.  The water table is very deep in deserts, but near the surface in swamps  The water table rises during wet seasons (c) McGraw Hill Ryerson 2007

6 Glaciers Almost 66% of all fresh water on Earth is in glaciers  Glaciers form from layers of snow falling over many years  Glaciers melt slowly under their own weight, and slowly flow downhill (c) McGraw Hill Ryerson 2007

7 Glaciers  Glaciers cover about 10% of the Earth’s surface  Alpine glaciers (aka valley) found in mountains  Continental glaciers (aka ice sheets) cover huge areas of land.  Eg. Greenland and Antarctia  Glaciers flow until they  reach an ocean, where crevasses open and icebergs fall off  reach an area where warm temps allow as much melting as re-freezing, or recede if they melt faster than they can freeze See page 381 Take the Section 10.3 Quizction 10.3 Quiz


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