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Water is Unique
• High heat capacity (climate)• Universal solvent (dissolves compounds)• High surface tension (physical and biological
process)• Solid lighter than liquid (impact biosphere)• Sunlight penetrates to various depths
(biosphere)
Groundwater and Streams• Groundwater
– Water found below the Earth’s surface, within the zone of saturation, below the water table
– Water table, recharge zones, discharge zones, aquifer, cone of depression
• Effluent Stream (perennial)– A type of stream where flow is maintained during the
dry season by groundwater seepage into the channel
• Influent Stream (epheremal)– A type of stream that is everywhere above the
groundwater table and flows in direct response to precipitation
Water Supply: A U.S. Example
• Water budget – a model that balances the inputs, outputs and storage of
water in a system.– precipitation=evapotranspiration and runoff– Defines the natural variability and availability of water
• Over 99% of the Earth’s water is unavailable or unsuitable for beneficial human use
• It is expected that the total water withdrawn from streams and groundwater in the U.S will decrease but the consumptive use will increase
Precipitation and Runoff
• Arid and Semiarid areas
• Runoff not stored• shortages• Droughts:
– large annual and regional variations in stream flow
• Groundwater Use and Problems:– nearly ½ US
population use GW as primary source for drinking water
– “overdraft”
Desalination as a Water Source
• Desalination: a technology to remove salt from water
• Increased cost• “Place value”• Environmental impacts
– discharge– damage ecosystems
Water Use
• Off-stream use:– water removed from it's source for use
• Consumptive use: – consumption by plants and animals or used in
industrial processes
• In-stream use: – the use of rivers for navigation, hydroelectric
power generation, fish and wildlife habitats and recreation (Example – Aral Sea)
Transport of Water
• Often moved long distances from areas of abundant rainfall and snow to areas of increased usage
• Example: New York City– Hudson River
• paved areas increase surface runoff to sea
– 1842: 1st large dam produced– 1900: 2nd dam produced
Water Conservation
- the careful use and protection of water resources
- Agricultural Use- Domestic Use- Industry and Manufacturing Use- Perception and Water Use
Sustainable Water Use
• The use of water resources by people in a way that allows society to develop and flourish into an indefinite future without degrading the various components of the hydrologic cycle or the ecological systems that depend on it
Sustainable Water Use
• General criteria includes:– develop water resources in sufficient volume– guarantee health and maintenance of ecosystems– ensure minimum standards of water quality for
various user of water resources– ensure actions of humans don't damage or reduce
long-term renewability of water resources– promote use of water-efficient technology– gradually eliminate water pricing policies that
subsidize inefficient use of water
Wetlands• Areas that are inundated by water or where
the land is saturated to a depth of a few centimeters for at least a few days per year
• Wetlands serve a variety of functions that benefit ecosystems and people
Natural Functions of Wetlands• Natural sponge for water• Groundwater recharge• Nursery grounds• Natural filters• Highly productive and places where nutrients
and chemicals are recycled• Buffer zones• Storage site for organic carbon• Aesthetically pleasing
Dams and the Environment
• Proponents of:– recreation; generating electricity; flood control
• Environmental effects:– loss of land and biological resources; sediment
disruption; downstream changes in hydrology and sediment transport; fragmenting ecosystems
• Few accept sites for new dams• Economical effects:
– expensive to guild and operate
Removal of Dams
• Edwards Dam, August, Maine– fish migration
• Glines Canyon Dam, Washington (2010)– fish– beaches at river's
mouth
Channelization and the Environment
• Channelization: – An engineering technique that consists of
straightening, deepening, widening, clearing, or lining existing stream channels
– Purpose:• Control floods, improve drainage, etc.
Adverse environmental effects:
• Degradation of the stream's hydrologic qualities
• Removal of vegetation along the watercourse• Downstream flooding where the channelized
flow ends• Damage of loss of wetland• Aesthetic degradation
Flooding
• The most universal natural hazard in the world
• The frequency and severity are increased by urbanization
• Avoid building on floodplains• Most common control - Dams
Colorado River: Management and Environment
• Most regulated and controversial
• 7 U.S. states and Mexico (1922)– allocated no water
for environmental purposes
• Today:– ecosystems of lower
river and delta are damaged
– canals and aqueducts– “input” uncertainties
• winter precipitation; snow-melt; t-storms
– Hoover and Glen Canyon Dams