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Fresh Water

What we will cover The Hydrologic Cycle River systems Floods Groundwater Caves and Karst Topography Hot springs

Distribution of water in the hydrosphere Reservoir (%) Oceans Glaciers and other ice Ground water Lakes Freshwater Lakes Saline Lakes Soil moisture Atmosphere Rivers 97.2 2.15 0.61 0.009 0.008 0.005 0.001 0.0001

Hydrologic Cycle Hydrologic cycle - the movement and interchange of water between the sea, air, and land Evaporation Solar radiation provides energy Precipitation Rain or snow Transpiration Evaporation from plants Runoff Water flowing over land surface Infiltration Water soaking into the ground

The Hydrologic Cycle IG4e_15_01

River Systems A river or stream is any body of water that is flowing downhill in a well defined channel River systems consist of a main channel and all its tributaries

Path of desire or path of least resistance? Desire Path: A term in landscape architecture used to describe a path that isn t designed but rather is worn casually away by people finding the shortest distance between two points. http://www.yourdailyawesome.com/

River terminology Headwaters - upper part of stream near its source in the mountains Mouth - place where a stream enters sea, lake or larger stream Channel - a long, narrow depression eroded by a stream into rock or sediment Stream banks - sides of channel Streambed - bottom of the channel Floodplain - flat valley floor composed of sediment deposited by the stream

Drainage basin River Systems The area of land that is drained by a certain river drainage system All the water in that area eventually finds its way into one of the rivers in the system Drainage divide Boundaries that separate one drainage basin from another Continental Divide separates the streams that flow into the Pacific from those that flow into the Atlantic and Gulf of Mexico

Mississippi River Drainage Basin

Powder River Drainage Basin

Yellowstone River Drainage Basin

Missouri River Drainage Basin

Mississippi River Drainage Basin

http://waterdata.usgs.gov/mt/nwis/uv?site_no=06214500

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Urban flooding Paved areas and storm sewers increase runoff by inhibiting infiltration Rapid delivery of water to streams increases peak discharge and hastens occurrence of flood Flooding

Mississippi River flood: Iowa

Mississippi River flood: Iowa

Mississippi River flood: Iowa

The Hydrologic Cycle IG4e_15_01

Ground Water precipitation either runs off or infiltrates into the soil as runoff, it flows into streams as infiltration, it either returns to the air through evapotranspiration or seeps downward to become ground water

Ground Water Figure 15.3, p. 514

Ground Water the water table marks the top of the saturated zone of ground water - highest under hilltops and divides, and it slopes to intersect the surface at lakes, marshes, and streams. Figure 15.4, p. 515

Ground Water an aquifer is a layer of rock or sediment that contains abundant, freely flowing ground water aquicludes are beds of clay and shale which are relatively impermeable a perched water table is an accumulation of water suspended or perched above the main water table Figure 15.5, p. 515

Springs and Streams Spring - a place where water flows naturally from rock or sediment onto the ground surface Gaining streams - receive water from the saturated zone Losing streams - lose water to the saturated zone Stream beds lie above the water table

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Porosity and Permeability Porosity - the percentage of rock or sediment that consists of voids or openings Measurement of a rock s ability to hold water Loose sand has ~30-50% porosity Compacted sandstone may have only 10-20% porosity Permeability - the capacity of a rock to transmit fluid through pores and fractures Interconnectedness of pore spaces Most sandstones and conglomerates are porous and permeable Granites, schists, unfractured limestones are impermeable unless fractured

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Ground Water Movement Movement of ground water through pores and fractures is relatively slow Flow velocity depends upon: Slope of the water table Permeability of the rock or sediment

Problems of Ground Water Management wells drawdown the water table at a point, creating a cone of depression as many wells exploit an aquifer, their cones of depression merge to create a general lowering of the water table Figure 15.12, p. 519

Problems of Ground Water Management sanitary landfills can release pollutants and toxic compounds that infiltrate to the water table, causing ground water contamination that renders adjacent well waters unfit for consumption Figure 15.13, p. 520

What water does to Limestone

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Groundwater Erosion Groundwater chemically weathers & erodes the bedrock through dissolution Subsurface dissolution forms: Caves Sinkholes Karst topography

Caves, Sinkholes, and Karst Caves - naturally-formed underground chambers Acidic ground water dissolves limestone along joints and bedding planes Caves near the surface may collapse and produce sinkholes Rolling hills, disappearing streams, and sinkholes are common in areas with karst topography

Karst Topography Karst topography is found in areas that have carbonate, sulfate, or salt beds at or near the ground surface Characterized by: Solution valleys Disappearing streams Sinkholes

Karst Topography

Sinkholes

Sinkholes

Thermal Springs & Geysers Geysers and hot springs require: Hot rock bodies to heat groundwater Fractures system to transmit water Large supply of groundwater Geysers such as Old Faithful are the results of this process

Thermal Springs & Geysers Hot water contains thermal energy and dissolved ions Geothermal energy taps heat source Many mineral deposits are produced by hot water interacting with cooling igneous intrusions

Hot Water Underground Hot springs - springs in which the water is warmer than human body temperature Ground water heated by nearby magma bodies or circulation to unusually deep (and warm) levels within the crust Hot water is less dense than cool water and thus rises back to the surface on its own Geysers - hot springs that periodically erupt hot water and steam Minerals often precipitate around geysers as hot water cools rapidly in the air

Geothermal Energy Geothermal energy is produced using natural steam or superheated water No CO 2 or acid rain are produced (clean energy source) Some toxic gases given off (e.g., sulfur compounds) Can be used directly to heat buildings Superheated water can be very corrosive to pipes and equipment

Surface Water as a Natural Resource human society is heavily dependent on fresh surface water for irrigation, potable water supplies, and industrial consumption artificial dams can increase freshwater supplies and generate power, but may have environmental costs Figure 15.28, p. 538