water: resources and pollution
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DESCRIPTIONWater: Resources and Pollution. Chapter 23. Outline:. Hydrologic Cycle Water Compartments Water Availability Freshwater Shortages Increasing Water Supplies Water Management and Conservation Water Pollution Water Quality Today Water Pollution Control Water Legislation. WATER RESOURCES. - PowerPoint PPT Presentation
Water: Resources and PollutionChapter 23
Outline:Hydrologic CycleWater CompartmentsWater AvailabilityFreshwater ShortagesIncreasing Water SuppliesWater Management and ConservationWater PollutionWater Quality TodayWater Pollution ControlWater Legislation
WATER RESOURCESHydrologic CycleDescribes the circulation of water as it:Evaporates from land, water, and organisms. (Transpires from plants)Enters the atmosphere.Condenses and precipitates back to the earths surfaces.Moves underground by infiltration or overland into rivers, lakes and seas.
Mean Annual Precipitation
MAJOR WATER COMPARTMENTSGroundwaterSecond largest reservoir of fresh water.Infiltration - Process of water percolating through the soil and into fractures and permeable rocks.Zone of Aeration - Upper soil layers that hold both air and water.Zone of Saturation - Lower soil layers where all spaces are filled with water.Water Table - Top of Zone of Sat.
GroundwaterAquifers - Porous layers of sand, gravel, or rock lying below the water table.Artesian - Pressurized aquifer intersects the surface. (Water flows without pumping)Recharge Zone - Area where water infiltrates into an aquifer.Recharge rate is often very slow.Presently, groundwater is being removed faster than it can be replenished in many areas.
Question 11. Define: hydrologic cycle.
Describes the circulation of water as it:Evaporates from land, water, and organisms. (Transpires from plants)Enters the atmosphere.Condenses and precipitates back to the earths surfaces.Moves underground by infiltration or overland into rivers, lakes and seas.
Major Water CompartmentsRivers and StreamsPrecipitation that does not evaporate or infiltrate into the ground runs off the surface, back toward the sea.Best measure of water volume carried by a river is discharge.The amount of water that passes a fixed point in a given amount of time.Usually expressed as cubic feet per second.
Question 22. Compare and contrast: aquifer and artesian.
Aquifers - Porous layers of sand, gravel, or rock lying below the water table.Artesian - Pressurized aquifer intersects the surface. (Water flows without pumping)
Question 33. What is the best way to measure the water volume of a river or stream? Does the season matter? Why?
Discharge. ( example: cubic feet per second)
Yes. Stream discharges usually vary over the year.
Upper Chatahoochee Watershed
Major Water CompartmentsWetlandsPlay a vital role in hydrologic cycle.Lush plant growth stabilizes soil and retards surface runoff, allowing more aquifer infiltration.Disturbance reduces natural water-absorbing capacity, resulting in floods and erosion in wet periods, and less water flow the rest of the year.
Major Water CompartmentsThe AtmosphereAmong the smallest water reservoirs.Contains 0.001% of total water supply.Has most rapid turnover rate.Provides mechanism for distributing fresh water over landmasses and replenishing terrestrial reservoirs.
Question 44. Off the major water compartments, which has the greatest volume? The least?
Greatest: the oceans
Least: the atmosphere
WATER AVAILABILITY AND USERenewable Water SuppliesMade up of surface runoff and infiltration into accessible freshwater aquifers.Water-Rich ad Water-Poor CountriesWater availability usually measured in per capita terms.Highest per capita generally found in countries with moist climates and low population densities.
Water UseWithdrawal - Total amount of water taken from a source.Consumption - Fraction of withdrawn water made unavailable for other purposes (Not returned to its source).Degradation - Change in water quality due to contamination making it is unsuitable for desired use.
Quantities of Water UsedWater use has been increasing twice as fast as population growth over past century.Worldwide, agriculture claims about 70% of total water withdrawal.In many developing countries, agricultural water use is extremely inefficient and highly consumptive.Worldwide, industry accounts for about 25% of all water use.Cooling water for power plants is single largest industrial use.
Question 55. State the three modes of water use and briefly describe them.
Withdrawal - Total amount of water taken from a source.Consumption - Fraction of withdrawn water made unavailable for other purposes (Not returned to its source).Degradation - Change in water quality due to contamination making it is unsuitable for desired use.
FRESHWATER SHORTAGESEstimated 1.1 billion people lack access to an adequate supply of drinking water.2.4 billion lack acceptable sanitation.A country where consumption exceeds more than 20% of available, renewable supply is considered vulnerable to water stress.Globally, water supplies are abundant, but, along with capital resources, are unevenly distributed.
A Precious ResourceCurrently, 45 countries, most in Africa or Middle East, cannot meet the minimum essential water requirements of their citizens.More than two-thirds of worlds households retrieve water from outside the home.Availability does not automatically equate to affordability.Sanitation levels decline when water is expensive.
Depleting GroundwaterGroundwater is the source of nearly 40% of fresh water in the US.On a local level, withdrawing water faster than it can be replenished leads to a cone of depression in the water table, On a broader scale, heavy pumping can deplete an aquifer.Ogallala AquiferMining non-renewable resource.
Ogallala AquiferThe Ogallala Aquifer within the boundaries of the North Plains Groundwater Conservation District is declining at an average of 1.74 feet per year (1,082,631 acre ft).The aquifer is cut off from natural recharge sources.http://www.npwd.org/Ogallala.htm
Depleting GroundwaterWithdrawing large amounts of groundwater in a small area causes porous formations to collapse, resulting in subsidence.Sinkholes form when an underground channel or cavern collapses.Saltwater intrusion can occur along coastlines where overuse of freshwater reservoirs draws the water table low enough to allow saltwater to intrude.
Sink Holes and Karst TopographyCaCO3 + H2SO4 CaSO4 + H2O +CO2http://www.soils.umn.edu/academics/classes/soil2125/doc/1-snkle.htm
Question 66. Compare and contrast: water table and cone of depression.
The water table is the upper surface of the zone of saturation.
On a local level, withdrawing water faster than it can be replenished leads to a cone of depression in the water table.
INCREASING WATER SUPPLIESSeeding Clouds Condensation NucleiTowing IcebergsCost Desalination Most common methods are distillation and reverse osmosis.Three to four times more expensive than most other sources.
Flow Diagram of a reverse osmosis system (courtesy of USAID). (Kahn, 1986.) In RO, feedwater is pumped at high pressure through permeable membranes, separating salts from the water.. The feedwater is pretreated to remove particles that would clog the membranes. The quality of the water produced depends on the pressure, the concentration of salts in the feedwater, and the salt permeation constant of the membranes.http://www.coastal.ca.gov/desalrpt/dchap1.html
New desalination technology taps waste heat from power plants GAINESVILLE, Fla. --- Desalination is often touted as one solution to the world's water woes, but current desalination plants tend to hog energy. Now University of Florida researchers have developed a technology that can tap waste heat from electrical power plants as its main source of energy, an advance that could significantly reduce the cost of desalination in some parts of the world.
Increasing Water SuppliesDams, Reservoirs, and Canals - Trap excess water in areas of excess and transfer it to areas of deficit. Environmental CostsUpsets natural balance of water systems.Ecosystem LossesLoss of wildlife habitat.Reservoir SizeWater Quality
Dams, Reservoirs, and CanalsDisplacement of PeopleThree Gorges Dams in China will force relocation of over a million people.Evaporation, Leakage, SiltationEvaporative losses from Lake Mead and Lake Powell on the Colorado River is about 1km3 per year (264 billion gallons).Dams slow water flow, allowing silt (nutrients) to drop out.Loss of Free-Flowing Rivers
Question 77. Why is the energy cost so high for reverse osmotic plants? What may be a solution?
To over come the osmotic pressure of seawater ( about 30 atm) requires a higher pressure and therefore, a very high energy cost.
The waste heat from power plants may provide a cheaper alternative energy source.
Price Mechanisms and Water PolicyThroughout most of U.S. history, water policies have generally worked against conservation.Eastern - Riparian Use RightsWestern - Prior Appropriation RightsIn most federal reclamation projects, customers have been charged only for the immediate costs of water delivery.
WATER MANAGEMENT AND CONSERVATIONWatershed ManagementWatershed - All the land drained by a stream or river.Retaining vegetation and ground cover helps retard rainwater and lessens downstream flooding.Additionally, retaining crop residue on fields reduces flooding and minimizing plowing and forest cutting on steep slopes protects watersheds.
Domestic ConservationEstimates suggest many societies could save as much as half of current domestic water usage without great sacrifi