15-Freshwater Resources

15-Freshwater Resources - FreshwaterResources...

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Freshwater Resources Environmental Problems Biol. 1305
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Freshwater systems Water may seem abundant, but drinkable water is  rare Freshwater  = relatively pure, with few dissolved  salts Only 25% of Earth’s water is fresh Most freshwater is tied up in glaciers and ice caps
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Rivers and streams wind through  landscapes Water from rain, snowmelt, or springs forms streams,  creeks, or brooks These merge into rivers, and eventually reach the ocean Tributary  = a smaller river slowing into a larger one Watershed  = the area of land drained by a river and its  tributaries Floodplain  = areas nearest to the river’s course that are  flooded periodically Frequent deposition of silt makes floodplain soils fertile Riparian =  riverside areas that are productive and  species-rich Water of rivers and streams hosts diverse ecological 
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Wetlands include marshes,  swamps, and bogs Wetlands  = systems that combine  elements of freshwater and dry land Freshwater marshes  = shallow  water allows plants to grow above  the water’s surface  Swamps  = shallow water that  occurs in forested areas Can be created by beavers Bogs  = ponds covered in thick  floating mats of vegetation 
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Wetlands are valuable Wetlands are extremely valuable for wildlife They slow runoff  Reduce flooding Recharge aquifers Filter pollutants People have drained wetlands, mostly for agriculture Southern Canada and the U.S. have lost more than half of their  wetlands
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Lakes and ponds are  ecologically diverse
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Lakes vary in nutrients and  oxygen Oligotrophic  lakes and ponds = have low nutrient and  high oxygen conditions Eutrophic  lakes and ponds = have high nutrient and low   oxygen conditions Inland seas  = large lakes that hold so much water, their  biota is adapted to open water
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Groundwater plays a key role Groundwater  = any precipitation that does not evaporate, flow  into waterways, or get taken up by organisms Groundwater is 1/5 of the Earth’s freshwater supply Aquifers  = Porous sponge-like formations of rock, sand, or gravel  that hold groundwater  Zone of aeration  = pore spaces are partially filled with water  Zone of saturation  = spaces are completely filled with water Water table  = boundary between the two zones Aquifer recharge zone  = any area where water infiltrates Earth’s  surface and reaches aquifers
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A typical aquifer
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There are two categories of  aquifers Confined or artesian  =  water-bearing, porous  rocks are trapped between layers of less permeable  substrate (i.e., clay)  Is under a lot of pressure
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This document was uploaded on 10/27/2011 for the course BIO 1305 at Texas Tech.

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15-Freshwater Resources - FreshwaterResources...

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