Water Resources

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Water Resources
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Hydrologic Cycle

• Hydrosphere All the water at or near the surface
  of the earth
• Amount of water essentially constant and moves
  between different reservoirs
• 100 million billion gallons move through
  Hydrologic Cycle
• Oceans account for 96, Fresh water lakes and
  streams for only 0.016 of all water

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Distribution of Water
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Hydrologic Cycle
Thousands of km3/yr
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Ground water

• 22 of all fresh water occur underground
• Aquifer Underground formation that holds and
  yields water
• A good aquifer needs to be both porous and
  permeable

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Porosity and Permeability

• Porosity Proportion of void space pore space,
  cracks, vesicles
• Gravel 25-45 (1K - 10K), Clay 45-55(lt.01)
• sandstone 5-30 (0.3 - 3), Granite lt1 to
  5(.003 to .00003)
• higher porosity in well rounded, equigranular,
  coarse grained rocks
• Permeability Measure of how readily fluid passes
  through a material
• Depends on the size of the pores and how well
  they are interconnected
• Clay has high porosity but low permeabilty

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Less porosity
porosity permeability Clay 45-55 lt0.01
m/day sand 30-52 0.01 - 10 gravel 25 -
45 1000 to 10,000
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Subsurface Water

• Zone of Aeration or Vadose Zone or Unsaturated
  Zone Overlies Phreatic Zone. Pore spaces partly
  filled with water. Contains soil moisture.

Saturated Zone

• Zone of Saturation or Phreatic Zone saturated
  zone overlying impermeable bed rock. Water fills
  all the available pore spaces
• Water Table top of the zone of saturation where
  not confined by impermeable rock

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• Water table follows the topography but more
  gently
• Intersection of water table and ground surface
  produces lakes, streams, spring, wetlands
• Ground water flows from higher elevation to
  lower, from areas of lower use to higher use,
  from wet areas to dry areas.

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Darcys law

• Hydraulic Gradient Slope of the ground water
  table
• Rate of flow is proportional to the hydraulic
  gradient

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Aquifer

• Recharge Process of replenishment of Ground
  Water by infiltration, migration and percolation
• Aquifer A rock that holds enough water and
  transmits it rapidly. Porous and Permeable.
  Sandstone and Coarse Clastic Sedimentary rocks
  make good aquifers
• Aquitard and Aquiclude Rocks of low and very low
  permeability e.g., shale, slate
• Perched water table Local aquifer in Vadose Zone

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Confined and Unconfined Aquifer

• Unconfined Aquifer open to atmosphere e.g.,
  overlain by permeable rocks and soils
• Confined aquifer sandwiched between aquitards
• Artesian System Water rises above the level in
  aquifer because of hydrostatic pressure
• Potentiometric surface Height to which water
  pressure would raise the water.

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• Artesian System Water rises above the level in
  aquifer because of hydrostatic pressure
• Potentiometric surface Height to which water
  pressure would raise the water.

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Consequences of Ground Water Withdrawal

• Lowering of Water Table
• Cone of depression Circular lowering of water
  immediately around a well

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Consequences of Ground Water Withdrawal

• overlapping cones of depression causes lowering
  of regional water table
• Water mining rate of recharge too slow for
  replenishment in human life time

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Compaction and Subsurface subsidence
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Consequences of Ground Water Withdrawal.

• Compaction and Subsurface subsidence
• Building damage, collapse
• flooding and coastal erosion e.g., Venice,
  Galveston/Houston (80 sq km permanently flooded),
  San Joaquin Valley (9m subsidence)
• Pumping in of water no solution

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Land subsidence in San Joaquin Valley , California
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The High Plains Aquifer

• The High Plains is a 174,000-square-mile area of
  flat to gently rolling terrain that includes
  parts of eight States from South Dakota to Texas.
  
• moderate precipitation but in general has a low
  natural-recharge rate to the ground-water system.
• Unconsolidated alluvial deposits that form a
  water-table aquifer called the High Plains
  aquifer underlie the region.
• Since early 1800s, irrigation water pumped from
  the aquifer has made the High Plains one of the
  Nations most important agricultural areas.
• the intense use of ground water for irrigation
  has caused upto 100m decline in water-level in
  parts of Kansas, New Mexico, Oklahoma, and Texas.

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Changes in ground-water levels in the High Plains
aquifer from before ground-water development to
1997. (V.L. McGuire, U.S. Geological Survey,
written commun., 1998.)
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The Gulf Coastal Plain Aquifer System

• The Gulf Coastal Plain aquifer system underlie
  about 290,000 square miles extending from Texas
  to westernmost Florida, including offshore areas
  to the edge of the Continental Shelf.
• Water withdrawals from the aquifer system have
  caused
• lowering of hydraulic heads at and near pumping
  centers
• reduced discharges to streams, lakes, and
  wetlands
• induced movement of saltwater into parts of
  aquifers that previously contained freshwater
• and caused land subsidence in some areas as a
  result of the compaction of interbedded clays
  within aquifers.

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Land subsidence in Houston
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Flooding in coastal Galveston because of
subsidence
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• Saltwater Intrusion
• upconing below cone of depression
• Aquifer below Brooklyn, NY destroyed
• Serious problem in Gulf Coast and California

Salt water incursion in caostal aquifer
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Extent of salt water incursion in Miami-Dade
Salt water intrusion in Miami-Dade
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• Sinkholes
• forms in areas with abundant water and soluble
  bedrock (gypsum or limestone)
• collapse follows ground water withdrawal

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Stalagtites
Stalagmites
Dripstones in a cavern
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Interfering with the flood plain

• Asphalt and concrete reduces infiltration and
  hence the lag time
• Buildings in the flood plain increases flood
  heights (why?)
• Storm sewers quicken the flow to the river
• Exposed soils silt up the river channel

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Reducing Flood Hazards

• Avoid Flood Plains Not practicable
• Risk mapping identify areas endangered by
  different magnitude of flood
• Use higher risk areas for recreation purposes
  etc.
• Building codes e.g., on buildings on stilts

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Reducing Flood Hazards

• Retention ponds
• does not alter the channel, can be farmed
• Channelization
• Mississippi case history, Florida problems,
  Export of flooding
• Levees (Raised banks along the channel)
• Extensive damage if breached, alters
  sedimentation, upstream flooding
• Dams (irrigation, hydel, recreation)
• stream profile altered, habitat destroyed,
  seismic risk

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Channelization of Kissimmee River
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Kissimmee River Project

• Wetlands drained
• Dairy Farms and Sugar Plantation moved in
• Fertilizers and pesticides washed into Florida
  Bay
• Algal Bloom used up dissolved oxygen in water
• Excessive sedimentation smothered bottom
  communities and blocked sunlight in deeper water
• Death of corals, sponges and bottom-communities
• Loss of habitat of fish and fowls of wetland
• Loss of recharge of groundwater
• Loss of evaporation and drop in rainfall
• Exotic plants moved in
• Now the river is being restored to original
  channel

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Urbanisation and ground water

• Loss of Recharge
• Impermeable cover retards recharge
• Filling of wetlands kills recharge area
• Well planned holding pond can help in recharging
  ground water

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Water Quality

• Most freshwater contain dissolved substances
• concentrations are described in ppm or ppb
• TDSTotal Dissolved Solids
• 500 to 1000 ppm for drinking water
• 2000 ppm for livestock
• some solids (e.g., Iron, Sulfur) more harmful
  than others (e.g. calcium)
• synthetic chemicals can be toxic at ppb level
• Radioactive elements pose special hazard
• Uranium, Radium, Radon

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Hard water

• Hard Water
• Common in limestone country
• contains dissolved Ca and Mg problematic if gt100
  ppm
• problem with soap
• leaves deposits in plumbing and in appliances
• can be cured with water softener typically ion
  exchange through zeolites

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Water Use in US

• 4200 billion gallons of precipitation
• 2750 billion gallons lost by evaporation
• 1400 billion gallons available for consumption
• Biological need 1 gal/person/day
• US consumption 1800 gal/person/day 400
  billion gallons per day for the entire US

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• Offstream Use water diverted from source
  e.g.,for irrigation or thermal power generation
• Consumptive water used up
• For farming, drinking or lost by evaporation
• Instream water returns to flow e.g., for
  hydroelectric power generation

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Water Use contd

• Main Uses
• Thermoelectric Power
• Surface Ground water 6733
• Consumed 2, Return Flow 98
• Irrigation
• Surface Ground water 6333
• Consumed 56, Loss 20, Return Flow 24
• Industrial
• Surface 67 (saline 12), Ground water 15 (1
  saline), Public Supply 19
• Consumption 15, Return Flow 85
• Domestic
• Public Supply 86, Ground Water 13, Surface 1
• Consumption 23, Return Flow 77

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Irrigation and Ground water

• Thus, irrigation is the major consumer of ground
  water
• Western states are the major drawers of ground
  water causing serious environmental problems

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Most of the precipitation is in the eastern
states but
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Most of the water withdrawal is in the western
states (see also the next slide)
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• Total withdrawal increased from 1950 to 1980 and
  has held steady since then although population
  has increased by 16
• Withdrawal for thermoelectric power generation
  190,000 Mgal/day largest of any other category
• Higher water price, more public awareness,
  conservation, better farming and industrial
  techniques will keep water demand in check

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Water Rights

• Riparian Rights (Eastern USA)
• Every landowner can make reasonable use of lake
  or stream or water flowing through or bordering
  his property
• Municipalities have the right of eminent domain
  at times of scarcity, cities get their
  requirement first
• Sale of riparian rights allowed in some states
• Practical in regions of plentiful water

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Law of Prior Appropiation

• First come, first served
• Settlers can lay claim to certain amount of water
  which will be honored for perpetuity
• The oldest claim are honored first and any left
  over goes to the next claimant and so on..
• Los Angeles bought up water rights in 1900 from
  areas far and wide, some even from Arizona. Now
  people in those areas are very unhappy about the
  arrangement

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Story of Colorado River
The Colorado River flows through Utah to Lake
Powell, thence through the northwest corner of
Arizona to Lake Mead. From Hoover Dam it flows
southward to Mexico forming the border between
Nevada, California and Arizona, and yielding
major diversions to central Arizona and southern
California. The river is the lifeblood of the
southwestern US and its development and
management have been the focus of attention by
the member states for more than a century. Waters
of the Colorado River System have been
apportioned by a treaty with Mexico, compacts,
and a Supreme Court decree to the seven basin
states.
Colorado River basin
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Colorado River Compact

• The Colorado River Compact of 1922 divided the
  use of waters of the Colorado River System
  between the Upper and Lower Colorado River Basin.
  
• It apportioned in perpetuity to the Upper and
  Lower Basin, respectively, the beneficial
  consumptive use of 7.5 million acre feet (maf) of
  water per annum.
• It also provided that the Upper Basin will not
  cause the flow of the river at Lee Ferry to be
  depleted below an aggregate of 75 maf for any
  period of ten consecutive years.
• The Mexican Treaty of 1944 allotted to Mexico a
  guaranteed annual quantity of 1.5 maf. These
  amounts, when combined, exceed the river's
  long-term average annual flow.
• These apportions were decided during a
  particularly wet climatic period. At present, the
  flow in Colorado does not add up to all the
  apportionments

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Within Colorado water allocations are based on
the Doctrine of Prior Appropriation or the
First-in-Time, First-in-Right Doctrine. This
doctrine is found in most arid states because
when there is too little water to satisfy all
users, sharing of the remaining water would be of
little value to any user. But a large part of the
Colorado river water is diverted to Los Angeles
on the basis of this doctrine
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Conservation

• Shift water-hungry crops to regions with more
  rainfall
• Use drip irrigation to reduce evaporation loss
• Use pipes to reduce transport loss
• Water lawns in morning and evening or opt for no
  lawn
• Direct storm water in recharge basins

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Interbasinal transfer

• Transfer water from water-surplus regions to
  water-deficient regions
• California Los Angeles aqueduct moves 150
  million gallons/ day from east of Sierra Nevada
  to LA
• New York Water supply to NYC from Finger Lakes
  region
• political problems
• Desalination
• Filtration, distillation
• Expensive, limited