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Hydrosphere. Only planet with correct atmospheric pressure and temperature to allow water to exist in all its phases 97% water held in ocean basins 2% water frozen Only 1 % water fresh *. Figure 2-11 (Merritts et al., 1998). Image ID: corp1893, NOAA Corps Collection
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Hydrosphere • Only planet with correct atmospheric pressure and temperature to allow water to exist in all its phases • 97% water held in ocean basins • 2% water frozen • Only 1 % water fresh* Figure 2-11 (Merritts et al., 1998)
Image ID: corp1893, NOAA Corps Collection Location: Alaska Southeast Photo Date: August 1991 Photographer: Commander John Bortniak, NOAA Corps
The Hydrologic Cycle • Water continuously circulates from the ocean to the atmosphere to the land and back to the ocean. • Regardless of its physical form-solid,liquid, or vapor-every molecule of water eventually moves through the hydrologic cycle. Water sources for Earth included 1) water from icy comets, 2) volcanoes, and 3) minerals.
Hydrosphere residence times • Oceans = 3,100 years • Atmosphere = 9 days • Continents = 403 years • Rivers 12 - 20 days • These residence times are significant for evaluating environmental issues.
Water budget for the U.S. • ~15.9 trillion liters/day fall on the U.S. • 66% returned to atmosphere by evaporation and transpiration • 3% seeps into groundwater • 31% as runoff to rivers and lakes
Water Reservoirs • Rivers • Lakes • Wetlands • Groundwater • Oceans • “cryosphere” (glaciers)
Rivers: sources of flow • Rain falling on the surface of the Earth may infiltrate (to groundwater), runoff (to rivers), or evaporate/ transpirate (to atmosphere).
River discharge • Amazon, South America 212,400 m3/s • La Plata, South America 79,300 m3/s • Congo, Africa 39,600 m3/s • Yangtze, Asia 21,800 m3/s • Brahmapututra, Asia 19,800 m3/s • Ganges, Asia 18,700 m3/s • Mississippi, North America 17,300 m3/s • Colorado River, North Am. 300 m3/s
Rivers: Human influences • Commerce • Transportation • Irrigation • Waste disposal • Dams diversions
Lakes • Basins that collect water • Location of basins defined by geologic setting, presence of water based on climate (local or regional) • Most of the world’s freshwater resides in lakes
Lakes: Human influences • Pollution • Water diversion • Exotic species
Wetlands • Wetlands are usually inundated by water during some part of the year, are poorly drained, have low relief, and have high soil moisture. • Wetlands may appear along coasts as swamps or marshes (i.e. salt marshes) or in the continental interior as marshes, wet meadows, or prairie potholes, or peat moss bogs http://www.epa.gov/owow/wetlands/
Natural wetlands have distinct ecosystem functions to which society can assign a “value.” • nutrient storageremoval of fertilizing nutrients helping farmers to attain compliance with water quality targets • accumulation of organic material for fuel or agriculturestorage of carbon, source of peat • filtering of solids from waterswastewater and sewage treatment, trapping sediment
Natural wetlands have distinct ecosystem functions to which society can assign a “value.” • animal habitatsfishing, wildfowl hunting and fish and shrimp hatcheries. In addition, Wetlands are a home to a third of the nation’s threatened and endangered species. • plant habitatsforestry, agriculture • regulating water outflowflood and erosion protection • all functionsrecreation, research, and education
Wetland losses in the U.S.In the 1660’s, 220 million acres of wetlands were thought to exist in the U.S. By 1980, only 103 million acres remained. • Drainage • Dredging • Stream channelization • Diking, damming • Tilling • Logging • Levees, • Mining • nutrient levels • Pollution • Nonnative species http://www.epa.gov/owow/wetlands/
Groundwater • Water enters the ground as excess surface water • Water then seeps downward due to gravity and the porous nature of soil, rock, and sediment • Water ultimately seeks it’s base level (usually sea level)
Groundwater Depletion • Overdraft • Subsidence • Saltwater intrusion Groundwater Pollution • Contaminant transport
Environmental problems related to water usually involve problems with water quantity or water quality.