Water Resources

1
Water Resources

• Chapter 14

2
Waters Importance

• We live on a water planet about 71 of the earth
  is covered in water mostly salt water
• All organisms are made of water
• We need water to survive
• Water supplies us with food, shelter, and other
  needs and wants.
• Water sculpts the earths surface, moderates the
  climate, and dilutes pollutants

3
Waters Unique Properties

• Polarity and hydrogen bonding causes properties
• Water is a liquid at a variety of temperature
  ranges
• Liquid water changes temperature slowly - high
  heat capacity
• Universal solvent
• Water molecules can break down into hydrogen ions
  and hydroxide ions which helps maintain a balance
  between acids and bases
• Water filters out wavelengths of ultraviolet
  radiation that would harm some aquatic organisms
• Water has high surface tension and a high wetting
  ability --- allows for capillary action (movement
  up a tree)
• Unlike most liquids, water expands when it
  freezes ice has a lower density than water and
  can float

4
How Much Fresh Water Is Available?

• About 97.4 of water is too salty for drinking,
  irrigation, or industry.
• 2.6 is locked up in ice caps or glaciers or in
  groundwater too deep or too salty
• Only about .0014 of the earths total volume of
  water is easily available to us as soil moisture,
  usable groundwater, water vapor, and lakes and
  streams
• Our usable water is continuously collected,
  purified, recycled, and distributed in the solar
  hydrologic cycle as long as we dont overload it
  with wastes or withdraw it from underground
  supplies faster than it is replenished

5
Surface Water

• Surface Water precipitation that does not
  infiltrate the ground or return to the atmosphere
  by evaporation (including transpiration)
• 2/3 of the worlds annual runoff is lost by
  seasonal floods and is not available for human
  use
• 1/3 is reliable runoff which can be used
• Watershed is a region from which water drains
  into a stream, lake, reservoir, wetland, or other
  body of water

6
Ground Water Terms

• Groundwater some precipitation that infiltrates
  the ground and percolates downward through voids
  (pores, fractures, crevices, and other spaces) in
  soil and rock
• Zone of Saturation the voids are completely
  filled with water
• Water Table located at the top of the zone of
  saturation falls during dry weather and rises in
  wet weather
• Zone of Aeration an unsaturated zone that lies
  above the water table pores of rock and soil
  contain air and may be most but not saturated
  with water
• Aquifers porous, water-saturated layesr of
  sand, gravel, or bedrock through which
  groundwater flows like large elongated sponges
  through which groundwater seeps
• Recharge Area area of land through which water
  passes downward or literally into an aquifer
• Natural Recharge precipitation that percolates
  downward through soil and rock

7
Withdrawing Groundwater

• Global water withdrawal has increased about
  ninefold irrigations is the largest increase in
  water withdrawl
• Withdraw about 35 of the worlds reliable runoff
• 20 of this runoff is left in streams to
  transport goods by boats, dilute pollution, and
  sustain fisheries and wildlife
• Global withdrawal rates
• Will at least double in the next two decades
• Exceed the reliable surface runoff in a growing
  number of areas
• Water runoff does not match up with distribution

8
Using the Freshwater

• About 70 of all water withdrawn each year from
  rivers, lakes, and aquifers is used to
• Irrigate 18 of the worlds cropland
• Produce about 40 of the worlds food
• 20 used by industry
• 10 used by cities and residences
• Consumptive Water Use occurs when water is
  withdrawn and becomes unavailable for reuse in
  the basin from which it was removed mostly due to
  evaporation or contamination

9
Freshwater in the US

• Most of the fresh water is in the wrong place at
  the wrong time or it is contaminated by
  agriculture and industrial practices
• Western states have too little precipitation
  Eastern states have ample precipitation
• East water is used for energy production,
  cooling, and manufacturing
• West water is used for irrigation
• Most serious water problems are
• Flooding
• Occasional urban shortages
• Pollution
• Water problems caused by
• Low precipitation
• High evaporation
• Recurring prolonged drought
• Urban areas that are located in areas without
  enough water.

10
Freshwater Shortages

• Four causes of scarcity
• Dry climate
• Drought a period of 21 days or longer in which
  precipitation is at least 70 lower and
  evaporation is higher than normal
• Desiccation drying of the soil because of such
  activities as deforestation and overgrazing by
  livestock
• Water Stress low per capita availability of
  water caused by increasing numbers of people
  relying on limited runoff levels

11
Water Stressed and Scarcity

• Water Stressed when the volume of its reliable
  runoff per person drops to below about 1,700
  cubic meters (60,000 cubic feet) per year
• Water Scarcity when yearly per capita water
  availability falls below 1,000 cubic meters
• 500 million people live in countries that are
  water-scarce or water-stressed
• By 2025, there may be 2.3 2.4 billion people in
  such countries
• Largest rivers are far from agricultural and
  population centers.
• Those that dont make enough money live in
  hydrological poverty
• No safe drinking water supplies
• Must collect water from unsafe sources
• Must buy water from vendors who receive their
  water from polluted rivers
• Drought kills 24,000 people per year and creates
  millions of environmental refugees

12
Increasing Freshwater Supplies

• Build Dams and reservoirs to store runoff
• Bring in surface water from another area
• Withdraw groundwater
• Convert salt water to fresh water (desalination)
• Waste less water
• Import food to reduce water use

13
Purpose of Dams and Reservoirs

• Main Purpose to capture and store runoff and
  release it as needed for
• Controlling floods
• Producing hydroelectric power
• Supplying water for irrigation and for towns and
  cities
• Recreational activities such as swimming,
  boating, and fishing.

14
Adv. Of Large Dams and Reservoirs

• Downstream flooding is reduced
• Reservoir is useful for recreation and fishing
• Can produce cheap electricity (hydropower)
• Provides water for year-round irrigation of
  cropland

15
Disadv. Of Large Dams and Reservoirs

• Impairs the important ecological services
  deliver nutrients to the sea, deposits silt,
  purifies water, renew and nourish wetlands,
  provide habitats for aquatic life, conserve
  species diversity
• Large loses of water through evaporation
• Flooded land destroys forests of cropland and
  displaces people
• Downstream cropland and estuaries are deprived of
  nutrient-rich silt
• Migration and spawning of some fish are disrupted

16
Tunnels, Aqueducts, and Underground Pipes

• Tunnels, aqueducts, and underground pipes can
  transfer steam runoff collected by dams and
  reservoirs from water-rich areas to water-poor
  areas
• California Water Project one of the worlds
  largest watershed transfer projects
• Uses a maze of giant dams, pumps, and aqueducts
  to transport water from water-rich northern
  California to heavily populated areas and to air
  and semiarid agricultural regions

17
James Bay Watershed Transfer Project

• 60 billion, 50-year scheme to harness the
  rivers that flow into Quebecs James and Hudson
  Bays to produce electric power for Canadian and
  U.S. consumers
• construct 600 dams and dikes that will reverse
  the flow of 19 rivers
• Flood an area of boreal forest and tundra
• Displace thousands of indigenous people
• After 20 years, the 16-billion phase I has been
  completed.
• The second phase has been postponed.

18
Adv. Of Withdrawing Groundwater

• Can be removed as needed year round
• Is not lost by evaporation
• Usually is less expensive to develop than surface
  water systems
• Provides drinking water for almost 1/3 of the
  worlds people
• In the US supplies 51 of the drinking water
  and 43 of irrigation water

19
Disadv. Of Withdrawing Groundwater

• Lowers water table exceeds the rate of recharge
  from precipitation
• ? Tragedy of the Commons
• Overpumping a new phenomenon since 1950 because
  of the development of increasingly powerful
  electric and diesel pumps
• Increasing the gap between rich and poor
• Farmers must drill deeper wells, buy larger pumps
  to bring water to the surface, use more
  electricity to run the pumps
• Causes salt water to intrude into the aquifer if
  near a coast ? can contaminate drinking water,
  supplies of many towns and cities along the
  coastal areas.
• Depletes aquifers
• Causes aquifer subsidence (sinking of land where
  groundwater is withdrawn)
• Intrusion of salt water into aquifers
• Drawing of chemical contamination in groundwater
  toward wells
• Reduced stream flow

20
Desalination

• Desalination removing dissolved salts from
  ocean water or brackish (slightly salty)
  groundwater
• Distillation involves heating salt water until
  it evaporates and condenses as fresh water
• Reverse Osmosis salt water is pumped at high
  pressure through a thin membrane whose pores
  allow water molecules, but not dissolved salts,
  to pass through.
• Disadvantages
• Not enough produced
• It is expensive and takes a lot of energy
• Produces large quantities of watstewater (brine)
  containing high levels of salt and other minerals

21
Cloud Seeding and Towing Icebergs

• Experiments to seed clouds with tiny particles
  of chemicals (such as silver iodide). The
  particles form water condensation nuclei and
  produce more rain over dry regions and more snow
  over mountains.
• Not very useful in very dry areas because there
  are few rain clouds
• Would introduce large amounts of the chemicals
  into soil and water systems
• Legal disputes over the ownership of water in
  clouds
• Towing icebergs to arid regions and then pumping
  the water from the melting icebooks ashore.

22
Reducing Water Waste

• 65 70 of the water people use throughout the
  world is lost through evaporation, leaks, and
  other loses
• US loses only about 50 of the water it
  withdraws.
• People believe it is economically and technically
  feasible to reduce such water losses to 15
• Decrease the burden on waste-water plants
• Reduce the need for expensive dams and water
  transfer projects that destroy wildlife habitats
  and displace people
• Show depletion of groundwater aquifers
• Save energy and money.

23
Why We Waste Water

• Water subsidy policies governments and
  international agencies often provide subsidies
  for development of water supply programs such as
  dams and large-scale water transfer schemes. ?
  Creates low water prices and does not improve
  efficiency
• Some say that they promote settlement and
  agricultural production in arid and semiarid
  regions
• Stimulate local economies
• Help lower prices of food, manufactured goods,
  and electricity for consumers
• Buying and selling water at profits
• Water laws determine the legal rights of water
  users in countries
• Fragmented Watershed Management

24
Wasting Less Water in Irrigation

• Flood Irrigation Method distribute water from a
  groundwater well or surface water source and
  allow it to flow by gravity through unlined
  ditches in crop fields so the water can be
  absorbed by crops.
• Delivers more water than is needed for crop
  growth
• Allows only 60 of the water to reach crops
  because of evaporation, seepage, and runoff
• Examples of environmentally sound irrigation
• Center-pivot low-pressure sprinklers allow 80
  of the water input to reach crops and reduce
  water use
• Low energy precision application sprinklers
  allows 90-95 of the water input to reach crops
  by spraying it closer to the ground and in larger
  droplets use 20 30 less energy and use 37
  less water
• Use surge or time-controlled valves on
  conventional gravity flow irrigation systems
• Uses soil moisture detectors to water crops only
  when they need t
• Drip irrigation systems

25
Irrigation News

• Israel has slashed irrigation water waste by
  about 84 while irrigating 44 more land treats
  and reuses 30 of its sewage water for crop
  production and plans to increase to 80 by 2025.
• Has one of the highest costs for irrigation water
• Imports most of its water-intensive wheat and
  meat
• Concentrates on growing fruits, vegetables, and
  flowers that need less water.
• Bad news
• More efficient sprinklers are used on only 10
  and drip irrigation on only 1 of the worlds
  irrigated cropfields
• Most poor farmers cannot afford the modern
  technology they have their own low-cost
  traditional technologies
• Pedal-powered treadle pumps to move water through
  ditches
• Animal-powered irrigation pumps
• Buckets with holes for drip irrigation
• Small dams, ponds, and tanks to collect rainwater
  for irrigation
• Terracing
• Cultivating seasonally waterlogged wetlands,
  delta lands, and valley bottoms

26
Ways to Waste Less Water

• Replacing green lawns in arid regions with
  vegetation adapted to a dry climate xeriscaping
  ? reduces waster by 30 85 and decreases labor,
  fertilizer, and fuel
• Water meters
• 50 75 of water used in bathtubs, showers,
  bathroom sinks, and cloths washers could be used
  as gray water for irrigating lawns and nonedible
  plants
• Fix water leaks
• Raise water prices
• Landscape yards with plants that require little
  water
• Use water-saving toilets, showerheads, and
  front-loading clothes washers
• Collect and reuse household water to irrigate
  lawns and nonedible plants
• Purify and reuse water for house, apartments, an
  office buildings

27
Flooding

• Floodplain where water in a stream overflows
  its normal channel and flood the adjacent area
• Produce highly productive wetlands
• Provide natural flood and erosion control
• Maintain high water quality
• Recharge groundwater
• Advantages
• Fertile soil
• Ample water for irrigation
• Flat land suitable for crops, buildings,
  highways, and railroads
• Availability of nearby rivers for transportation
  and recreation
• Recharge groundwater
• Refill wetlands

28
How Humans Have Increased Floods

• Removing water-absorbing vegetables
• Draining wetlands that absorb floodwaters and
  reduce the severity of flooding
• Living on floodplains
• Urbanization

29
Reducing Flood Risks

• Strengthen and deepen streams
• Building levees contain and speed up stream
  flow, but increase water damage downstream and do
  not protect against unusually high and powerful
  floodwaters
• Building dams
• Restoring wetlands
• Identifying and managing flood-prone areas
  prohibiting certain types of building or
  activities, elevating or floodproofing buildings,
  constructing a floodway that allows floodwater to
  flow through the community with minimal damage

30
Achieving a More Sustainable Water Future

• Irrigate crops more efficiently
• Use water-saving technologies in industries and
  homes
• Improve and integrate management of water basins
  and groundwater supplies

31
What Will Happen If We Dont Change?

• Economic and health problems
• Increased environmental degradation and loss of
  biodiversity
• Heightened tensions and perhaps armed conflicts
  or economic competition over water supplies and
  food imports
• Larger numbers of environmental refugees from
  water-scarce areas.