Wasting H2O
- Mohamed ElAshry of the World Resosurces institute estimates that 65-70% of the water people use throughout the wolrd is lost through evaporation, leaks. and other losses.
- The US does slightly better still loses about 50% of the water it withdraws.
How to reduce the H2O waste
El-Ashry
Waters' importance
- Believes that it is economically and technically feasible to reduce such water loss to 15%, thereby meeting most of the worlds water needs for the foreseeable future.
- This will involve greatly increased the use of water saving tech. and practices that do more with less water.
- According to water resource experts, three major causes of water waste are
- Government subsides of water supply project that creates artificially low water prices.
- Water laws
- Fragmented watershed management
- Globally, only about 40% of the water used reaches crops.
- Most irrigation systems distribute water form groundwater well or a surface water source and allows to to flow by gravity through unlined ditches in crop fields so that the water can be absorbed by crops.
- This flood irrigation method delivers far mire water than needed for crop growth and typically allows only 60% of the water to reach crops b/c of evaporation, seepage, and runoff.
Cloud seeding
- Water covers 71% of the Earth's surface
- Water plays a key role in
- Sculpting the earth's surface
- moderating climate
- diluting pollutants
- The US have been experimenting with seeding the clouds with tiny particles of chemicals such as Silver iodide.
- However cloud seeding is not useful in very dry area and would introduce large amounts of the cloud seeding chemical into soil and water systems , possibly harming people, wildlife, and agricultural productivity.
Water Resources
Properties of H2O
Water waste can be reduce by using more efficient irrigation systems.
- Strong forces are by the hydrogen bonds
- water exist over a wide temp. range
- water can dissolve a variety pf compounds
- water filters put wave lengths of UV radiation that would harm some aquatic organisms
- Center-pivot low pressure sprinklers
- which typically allow 80% of the water input to reach the crop
- Low-energy precision application (LEPA)
- allows 90-95% to reach the crops
- Using surge or time-controlled vavles in conventional gravity flow irrigation system
- rise irritation efficiency to 80%
Cont. irrigation efficient
- Using soil moisture detector to water crops only when they need it
- Farmers using to can use 33-66% less irrigation water with no change in crop yield
- Drip irrigation and solution
- water efficiency to 90-95% and reduces by 37-70%
Cause and effects of floods
Cont. of properties
Taking H2O from groundwater pros/cons
How to increase freshwater supplies
- Takes a large amount of heat to vaporize the water to vapor
- H2O molecules can ionize or beak down into [H+] and [OH-] which helps maintain the acids and bases
- water expands when it freezes
- Natural flooding by streams is caused mainly by heavy rain or rapid melting of the snow
- This causes water in a stream to overflow its normal channel and flood the adjacent area called floodplain
- Provide natural flood and erosion control
- maintain high water quality
- recharge groundwater
- Pumping groundwater from aquifers has several pros over tapping more erratic flows from streams
- Ground water can be removed as needed year-round, and is not lost by evaporation and usually is less expensive to develop than surface water systems
- However, overuse of ground water can cause several problems such as water table lowering, aquifer depletion, aquifer subsidence, intrusion of salt into aquifers, drawing of chemical contamination in groundwater toward wells, and reduce the flow of the stream
- Large dams and reservoirs have benefits and drawbacks
- the main purpose of them are controlling floods, producing hydroelectric power, and supplying H2O for irrigation
- However its hard to come to a balance b/c
- the time in year
- conditions such as drought and higher than normal precipitation
- pollution loads
- habitat needs of aquatic life
- and values people place on the wildlife, fisheries and recreational use of river basins
How much do we use? (fresh)
Fresh H2O
- Worldwide 70% of all water withdrawn each year from rivers, lakes, and aquifers is used to irrigate 17% of the world's cropland.
- Industry uses about 20% of the water withdrawn for the cites and residents to use
Cont. sustainable
Cont. desalination
Fresh H2O shortage
Fresh H2O in the US resources
- Only a tiny fraction of the planet's abundant water is available to us as freshwater
- most of the remaining 2.6% that is fresh is locked up in ice caps or glaciers
- 0.014% is available for humans to use
- 97.4% by volume is found in oceans and is too salty for humans to use
- Blue revolution
- Irrigating crops more efficiently
- using water-saving tech. in industrial and homes
- improving and integrating management of water basin and groundwater pipes
- Water experts contend that not developing such strategies will eventually lead to economic and health problems, increased environmental degradation and loss of biodiversity, heightened tensions and perhaps armed conflicts over water supplies , larger numbers of environmental refuges and threats to national and global military, economic and environmental security.
- Its expensive b/c it takes large amounts of energy
- It produces large quantities of waste water containing high levels of salt and other minerals
- In the US the eastern coast has water problems such as flooding, occasional urban shortage, and pollution
- In the Us the western coast has water problems such as low precipitation, high evaporation, and recurring prolonged drought.
Surface H2O
- A dry climate, drought, desiccation, and water stress are 4 causes of water shortage.
- A # of environmental, political, and economic analysts believe that access to water resources, already a key foreign policy and environmental security issue for water short countries, will become even more important over the next 10-20 years
Ground H2O
- We use freshwater that first arrives as a result of precipitation
- 2/3 of the world annual runoff is lost by seasonal floods and is not available for human use
- 1/3 is reliable runoff that generally can be counted on a stable source of H2O
- Some Precipitation infiltrates the ground and percolates downward through voids in soil and rock
- Ground H2O moves from recharged through an aquifer and out to a discharged area (well, spring, lake geyser, stream or ocean) as part of the hydrogen cycle.
How useful is desalination?
How much are we using? ( Reliable)
- Two main method of desalination
- Distillation which involves heating salt salt water until it evaporates and condenses as freshwater
- reverse osmosis in which salt water id pumped at high pressure through a thin membership whose pores allow water molecules but not salt to pass through
How to reduce flood risk
Three Gorges Dams
Achieving a more sustainable water future
- 20% of all water running to the sea each year is in rivers to remote to supply cites and farming areas.
- Downpours of rain that cannot be collected make up 50% of the global runoff so it leaves about 30% of the runoff for human use
- A channelization in which a section of a stream is deepened, widened or straightened to allow more rapid runoff
- Channelization can reduce up steam flooding but increase flow of water can also increase upstream bank erosion and downstream flooding and sediments deposition.
- Channel also reduces habitats for aquatic wildlife
- remove bank vegetation
- increase stream velocity
- eliminating rest and hiding places for fish and other aquatic life
- Critics also charge that the dam and reservoir will
- radically change the region's entire ecosystem
- increase H2O pollution
- expose .5 million people to severe flooding if the reservoir fills up with sediment and overflows
- reduce annual deposits of nutrient rich sediments below the dam
- promote satlt water intrusion into drinking water supplies near the mouth of the river.
- When completed, China's Three Gorges project on the mountainous upper reaches of the Yangtze River wwill be the world's largest hydroelectric dam and reservoir.
- Not depleting aquifers
- preserving ecological health of aquatic system
- integrated watershed management
- wasting less water
- slowing population growth
- decreasing government subsides for supplying water