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Water Resources. 1. Hydrologic Cycle and Water Reservoirs 2. Floods and Flood Control 3. Use of Water 4. Water Composition 5. Water Problems. Hydrologic Cycle. Plop Plop plop. Distribution of Water (from your text book-based on 1972 data).
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Water Resources • 1. Hydrologic Cycle and Water Reservoirs • 2. Floods and Flood Control • 3. Use of Water • 4. Water Composition • 5. Water Problems
Hydrologic Cycle • Plop • Plop plop
Distribution of Water(from your text book-based on 1972 data)
Distribution of Waterhttp://ga.water.usgs.gov/edu/waterdistribution.html (1997 data)
Bibliographical Acknowledgment referenced publication for content development Peixoto and Kettani, 1973 The Control of the Water CycleScientific American - Vol. 228 - pp. 46-6
Heat Capacity of Water • This means that water has the ability to absorb and hold heat with a minimal change in temperature • Why? • When water evaporates it takes 540 cal/gm. This means that evaporation creates a cooling effect. • Ice going to water releases 80 cal/gm, thus releasing heat
Precipitation/Evaporation patterns • http://weather.msfc.nasa.gov/GOES/
World water resources http://www.worldmapper.org/
Evaporation (mean annual U.S.) http://geochange.er.usgs.gov/sw/changes/natural/et/
http://ga.water.usgs.gov/edu/watercycleevapotranspiration.htmlhttp://ga.water.usgs.gov/edu/watercycleevapotranspiration.html Evapotranspiration
When ppt >>> e/t • Then we get rivers and streams • Eastern NA—water surplus • Western US—water deficiency • Plays a role in population density in U.S. and Canada
Freshwater Reservoirs • Rivers and Streams • Lakes • Icecaps • Groundwater
Groundwater • Much greater in volume than either lakes or streams • Non-renewable in our lifetime
Water Table • Surface below which pores and fractures of rocks and overburden are water filled
What is an aquifer? • Geologic formation that possesses porosity and permeability
Water Resources • 1. Hydrologic Cycle and Water Reservoirs • 2. Floods and Flood Control • 3. Use of Water • 4. Water Composition • 5. Water Problems
Surface Water/Floods/Flood Control • Surface water is water that flows off the land in streams and rivers • What is it dependent upon??
Amount of rainfall • Slope and Length of drainage basin • Rock and soil type of drainage basin • Vegetation • Extent of impermeable areas
When does flooding occur? • When surface run-of exceeds a normal stream channel’s capacity and water spreads out onto the flood plain • Is this a problem?
What do we do to minimize flooding? • 1. build dams • 2. build levees • 3. create channels (channelization) • 4. Moveable dams—Thames
Dams: pro • 1. Do help with flood control • 2. Supply electricity • 3. Provide recreation • 4. Sources of water for irrigation • 5. Increases groundwater • Does anyone see some inconsistency here?
Dams: con • 1. Sediment catchment • 2. Increased evaporation • 3. Loss of land • 4. Interruption of river transport and fish migration • 5. Environmental alteration
Some Dams • Aswan High Dam
Channelization • Replacement of a meandering stream by a deeper, straighter channel
Drawbacks • Transfer of flooding • Flood plain doesn’t get new sediment
Drawbacks of Channelization • Increased erosion • Transfer of flooding downstream • Reduced natural filtering of water and drainage basin • Loss of wetlands • Reduction in available water for general use • Less evapotranspiration • Less infiltration • Lower ground water levels • Larger variations in flow rates • Reduction in wildlife