Natural Resources II: Water

Lecture 06

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Unit Organization:

• Water as a resource
• Water Supply
• Demand for Water
• Responses to Demand
• Social Implications of Water Demand
• The Quantitative MetaExperiment

Reading:

Textbook: Chapter 9

Ancillary Reading:

Water as a resource

Water is needed for personal use (drinking, cooking), for household uses (cleaning, sewage, garden), for consumer uses (almost every retail store, from restaurants to storehouses, use water), for industrial use (during the manufacturing process, clean-up, and removal of both solid and soluble wastes, and as waste output from the manufacturing process), and for agricultural use, mostly irrigation.

An important point here is that we consume this resource in two ways

• directly as fresh water
• indirectly as polluted water (which removes water from use just as does drinking it)

Water on a smooth Earth, would cover the planet to a depth of 2 miles, but almost all water is not immediately available as a resource:

The Water that is readily available is found in lakes, impoundments, rivers, and in some groundwater regions known as aquifers

• Oceans are salt water, as are some lakes
• Ocean composition is about 3.5% salt by weight (usually expressed as 35 parts per thousand or ppt)
  • 19.00 ppt Chlorine
  • 11.00 ppt Sodium
  • 03.00 ppt Sulphate
  • 01.00 ppt Magnesium
  • 00.50 ppt Calcium
  • 00.50 ppt Potassium
  • 00.05 ppt 30+ other ions

A problem for you:  The ratio (by weight) of sodium to chlorine in seawater is 1 Cl : 0.58 Na.  The ratio of these elements (by weight) in table salt (NaCl) is 1 Cl : 0.65 Na.  Why is there relatively less sodium in sea water than you would expect based on table salt? Solution in class (if some one is willing to enlighten us).

Physical properties of water:

You should be familiar with these: 

• Cohesion's effect on boiling point and solvency power, and surface tension of water along with the ideas of latent heat of vaporization and freezing
• Adhesion's effect on hydrophily
• Water's unusual density and the concepts of specific gravity and specific heat
• Expansion of water as it freezes causing ice to float and water to reach its greatest density at 4° centigrade

Water Supply

Fresh water is the most readily available water

• All fresh water comes from precipitation
• The fresh water we use can come from either renewable or non-renewable sources

Renewable Water Sources

What happens to precipitation that falls on land (if it falls on the ocean, it is lost as a source)?

• 65% runs off the land in floods and is lost as a resource
• about 1/3 of the rest falls on uninhabited land and is not used
• The rest (about 7,000 cubic km worldwide) remains in rivers, streams, and groundwater we can potentially use
• Impoundments (artificial lakes upstream of dams, sometimes called drowned rivers) have increased the total resource to about 9,000 cubic km worldwide
• Currently, direct consumption and pollution use up almost all of the 7,000 cubic km available without impoundments

Water supply is not evenly distributed world-wide because precipitation is not distributed evenly worldwide

• Deserts are the regions of poor rainfall and, thus, poor water supply
• Australia (driest continent) western US and most of Mexico (Great Basin, Sonoran, and Chihuahuan Deserts and Short grass Prairie regions), West of the Andes from 20° S to the equator (Atacama Desert), central Argentina (Chaco and Pampas), northeastern Brazil (Sertao and Caatinga regions), most of Africa above the Equator Sahara Desert), much of southern Africa (Kalahari and Namib Deserts), the Middle East, and Central Asia (Gobi Desert) are all dry areas

Surface Waters: Lakes and Rivers

Both are important water resources

• We won't bother trying to separate rivers from streams and creeks or lakes from ponds so all flowing water for us is in rivers and all basins filled with water are lakes (no mention of wetlands at all in this chapter)
• Many centers of early civilization were associated with water supplies
• Rivers and large lakes supplied water and food, replenished soil nutrients, and facilitated transport of goods while carrying away waste

When water falls on land, where it goes depends on the contour of the land

• Water collects in low areas and flows from low area to lower area
• Watersheds (Drainage Basins) are all of the land where precipitation flows into a particular river or lake
  • Thus, we can define the Cumberland River Watershed, which is part of the Tennessee River Watershed, which is part of the Mississippi River Watershed
  • Watersheds can either
    • empty into the sea (or empty into another river that eventually flows to the sea)
    • have no outlet other than evaporation (usually the lowest area is a lake but some closed watersheds have rivers that simply dry up)
  • Watershed boundaries rarely match well with political boundaries
• Dams store water and alter flow through the watershed
• Colorado River is an example of overuse of a watershed
  • 100 MYA, the region was Pacific Ocean but 50 MYA, the Rockies began to form and the Colorado was born as a much smaller river and, as more land accumulated in the Southwest, the Colorado grew until, about 5 to 12 MYA it began discharging into the Gulf of Mexico
  • Colorado River is over 1,450 miles long and drops over 10,000 feet along that course
    • Upper River is 200-500 feet wide and Lower River is 500-1000 ft wide with an average depth of 10 to 30 ft (now as low as 2 ft after water removal near mouth)
  • Colorado Watershed comprises the southwest corner of Wyoming, the western half of Colorado, the eastern half of Utah, the pointy bottom of Nevada, and all of Arizona
    • Colorado begins in the Colorado Rockies, runs west out of the mountains, into Utah where it flows southwest across the Colorado Plateau into Arizona near Lee's Ferry, across northern Arizona to where AZ, NV, and UT touch, then turns south, where it forms the boundary between California and Arizona, and crosses a narrow strip of Mexico before discharging into the uppermost part of the Sea of Cortez (= Gulf of California)
      • Lee Ferry marks the divide between the upper and lower basins of the watershed
    • Major tributaries are the Green, San Juan, Little Colorado, Virgin, and Gila Rivers
    • The river has carved many Canyons from the sedimentary rock over which it flows (Grand, Gore, Glenwood, De Beque, and Cataract Canyons are some - Black Canyon now Lake Mead)
  • Man has altered the flow with 29 major dams and hundreds of miles of canals
    • Largest dams are the Glen Canyon (Lake Powell), Hoover (Lake Mead), and Imperial Dams
      • Total capacity  of the dams is over 4 times average yearly flow
      • A drop of water entering the top of the watershed will be taken up and used 17 times by man before it gets to the Gulf
    • Water has irrigated previously non-productive land (Imperial Valley, CA and southwest Arizona)
      • Imperial Valley produces $350 million of crops per year
        • (ASIDE - Some of the Imperial Valley is, like Death Valley, below sea level.  The Colorado's delta built a dam across the upper end of the Gulf of California which turned the sea floor into land.  Early attempts to divert Colorado River water to Imperial Valley allowed flood waters from the river to flow into the valley, where they created the Salton Sea in 1905 and evaporation has increased the salinity to 44 ppt, greater than seawater)
      • Dams provide 12,000,000 kw of electricity per  year
  • Colorado is named for its once-red colored water
    • Due to the red rocks that provide the sediment but dams now trap the sediment and the water is green
  • From 1922 until 1973, the Colorado Water Compact was slowly negotiated by six states and Mexico, all of whom wanted water.
    • The negotiated total is 16.5 million acre-feet of water out of a total yearly discharge of 27.5 million acre-feet
      • The yearly total is an average based on measurements taken at Lees Ferry for 20 years before 1920

Colorado River Water Allocation
User		% of 16.5 maf taken
US		90.9%
	California		26.7%
	Colorado		23.5%
	Arizona		17.0%
	Utah		10.4%
	Wyoming		6.4%
	New Mexico		5.1%
	Nevada		1.8%
Mexico		9.1%
Total		100%

• Tree-ring studies suggest that those were some of the wettest years in the last 1000 years and that 13.5 is a more accurate average
  • Since 2000, the river has been at or above average volume only three years

• Environmental Impacts
  • Trapping sediment behind dams
    • Filling of impoundments
    • Lake Powell will fill in from 3 to 7 hundred years
  • Delta in Mexico is starved of sediment needed as nutrient for wetlands and algal growth in the Gulf
    • Loss of nutrients and nursery areas have severely reduced shrimp, fish and sea mammal populations
  • Reuse of water has increased saltiness of water
    • Once, the salinity of the lower basin was 50 ppm but is now over 2000 ppm
    • Salinity damages crops
    • Bureau of Reclamation estimates that, in 1997, $500,000,000 loss in US and $100,000,000 in Mexico
    • US built a large desalination plant near Yuma, AZ (1/4 billion $) and has just tested (2011-2012) the plant at 1/3 capacity for a year to satisfy treaty obligations with Mexico as the Colorado River water is now too salty to be useful for agriculture when it arrives in Mexico.
  • Dams release water from lower portion of lake, where water is cold
    • Normal temperature range is 32° in winter to 85° in summer, now almost always 46°
    • Recreational boaters now die in summer from hypothermia

Groundwater

• Precipitation that does not run-off percolates into soil and the underlying rock and is called Groundwater
• The rock must be porous (sandstone or fractured limestone or granite)
  • Layers of porous rock are Aquifers
    • Water in aquifers flows from areas receiving precipitation to discharge  into lakes and rivers
  • Zone of Saturation - lower zone, where water fills the voids in the rock
    • top of saturation zone is the top of the Water Table
  • Zone of Aeration - upper zone where walls of voids are wet but also contain air
  • Recharge areas are the source areas for the water (from precipitation)
• Man has added a second discharge:  withdrawal of water from wells
  • Wells create a Cone of Depression of the water table that is deepest at the well
• Current data indicates that most aquifers take up to 200 years to completely recharge (turn over the water once)
• Layers of rock that are not porous are called Aquicludes (shale, siltstone)
• Many areas have many layers of porous and non-porous rock
• Wells tap groundwater resource
• Artesian wells are those where water pressure from areas where the water table is high cause water to flow without pumping (in effect, man-made springs)

Problems with groundwater supply

• Groundwater pollution
  • Organic compounds, radioactive compounds, and excess salt have started to appear in US groundwater
    • Unlined landfills (or leaky lined landfills), leaky aboveground and underground storage tanks, old or poorly maintained septic tanks are common POINT sources of pollution
    • An additional source of point groundwater pollution was due to the practice of injecting pollutants into deep wells to store the pollutants
      • this practice was founded on the faulty assumption that once injected, the waste would stay put
      • Most states prevent this practice today but laws abroad are not so restrictive
    • Pesticides and fertilizers applied to agricultural lands (and, to a lesser extent, to suburban lawns) and road salt are important sources of NON-POINT source pollution
  • Flow is slow in groundwater (often no more than 50 ft per year), so pollutants remain concentrated in small areas for longer periods than polluted surface waters
  • Dickson, TN has a severe groundwater pollution problem from dumping TCE and PCE (tri- and perchloroethylene - either may cause cancer) in county landfill
    • Surrounding wells have been polluted and it may cost up to $1 billion to clean up
    • As most of those affected were African-Americans and most of those who authorized the dumping were not, the case has racial implications
    • Poor communities, often communities of color, often are chosen as places to discharge pollutants
• Overuse leading to depletion of groundwater and a lowering of the water table
  • Can dry up streams  where table is close to surface
  • Overuse can cause Land Subsidence
    • Some areas have subsided over 30 feet
    • Subsidence causes surface problems (foundations crack, roads fall apart, etc.)
    • Subsidence causes subsurface problems
      • Voids in the rock collapse, so that the rock ceases to be an aquifer and groundwater resource is reduced
    • Subsidence can have many causes:
      • Grounwater loss (pumping or extended drought)
      • Sink hole collapse of rock in Karst regions
      • Pumping of natural gas
      • Collapse of mines
      • Earthquakes causing Faulting
      • Faulting due to deeper motion in the Asthenosphere
        • The aesthenosphere responds to the deposition or loss of mass at the surface by depressing or rebounding
          • Lake Bonneville mass depressed the aesthenosphere 200 ft and, as the water had dried up, the aesthenosphere rebounded so that the center of the Bonneville flats are 200 feet above the edges (not so flat, huh?)
• Salt Water Intrusion - near the ocean, withdrawal of water can allow salt water to replace fresh, poisoning water supplies

Fossil-Water Aquifers

• Some porous layers of rock recharge very slowly or not at all because the porous rock, once exposed to recharge, is now sealed off by aquacludes
  • The water in the aquifer may have been stored there millions of years ago
  • There is little or no recharge for such an aquifer
  • Much of the agriculture of the US is irrigated with this "fossil" water
• Largest and most important fossil aquifer is the Ogallala Aquifer, now half depleted and the rate of withdrawal is  increasing
  • No viable plans exist to replace this water source with another once it is gone

Demand for Water

• Some startling figures:
  • US uses 408,000,000,000 gallons of water per day
  • That's 1,143 gallons per person
• Who do you know that drinks a thousand gallons of water per day?
  • Individual Use is a small portion of the per person per day figure
• Withdrawn Water - water taken from the source
  • The largest "withdrawer" of water are electricity generating plants, which use the water for cooling
  • This water is returned without much chemical alteration but is returned with another sort of pollutant:  waste heat
  • This heat can change the temperature of the body of water from which the water is drawn, altering a fundamental physical parameter that may alter the composition of the community in the generation plant's environment
  • This form of pollution can be mitigated by using cooling towers that heat the air
• Consumed Water - water taken from the source and not returned (a subset of withdrawn water)
  • logically, consumed water can equal but never exceed withdrawn water
  • Water that is returned may or may not be suitable for subsequent use depending on the quality of the returned water and the specific use (drinking or car washing?)
• What do we use water for?  From the use the consumes the most to the least:
  • Agriculture
  • Industry
  • Municipal (including water supply to residences)
  • Reservoir Losses (most to evaporation, some to groundwater)
• California agriculture uses about 1/3 of all US water and everyone in the US (and many in other countries) eats what those farmers produce

Responses to Demand

Efficiency and Conservation

• Consume less and preserve the resource
• Much water is supplied at less than cost to agriculture, so farmers do not invest in efficiency and conservation as much as they would if water were a greater cost
  • Drip Irrigation (Microirrigation) delivers water slowly to crop root zones and avoids run-off and evaporation losses
  • Irrigation canals and reservoirs lose water to evaporation and leakage back into the groundwater, so improved canals and covering canals can reduce loss
• When water costs rise to industry, the incentive often increases efficiency or promotes technological changes to reduce water consumption
• Meat is more costly (in terms of water) to produce than vegetation, so a less meat in the diet conserves water
  • The cost of a cow is the water needed by the cow plus the water needed to grow the cow's food
• Homes can reduce water usage per flush, flush less
• Xeriscaping (xeri- is a prefix meaning dry) can reduce suburban water use by using plants adapted for dry conditions

Desalination

• Using technology to remove salt from water
• Two approaches:
• Distillation - evaporated water leaves the salt behind
  • Cost is in the heat needed to get evaporation rate high enough to produce significant fresh water
  • If waste heat from electricity generation or from industrial processes is used, the efficiency of distillation can compare well with osmotic processes
• Osmosis
  • Reverse Osmosis- using hydraulic pressure to force water across a membrane that won't let salt pass
    • Normal osmosis resists this,  so lots of pressure is needed to make much water
    • Using straight sea water clogs membrane pores, so this process is much more efficient if brackish water is used
  • Forward Osmosis (newer technology) - Heat-labile salts are added to water to a concentration greater than seawater, so osmosis moves water out of seawater, across the membrane, and into the salter water (called the Draw Solution).  After absorbing as much water as it can, the draw solution is heated, which drives off the salts, leaving almost pure water behind
    • No pressurization is needed but energy cost is due to heat needed to drive off salts
    • Most efficient way to do this is to use waste heat from electricity generation or from some industrial process
• Both methods have environmental costs
  • Costs associated with energy needed to heat water or to apply pressure
  • Costs associated with disposal of salt produced

Waste Water Reclamation

• Much reclaimed water is reused but not for direct consumption
• Sewage treatment plants can reclaim water
  • Multi-step process:
    • Primary Treatment
      • Separates solids suspended in the water by sedimentation (settling out)
      • Skims off oils from top
    • Secondary Treatment in tanks that use natural recycling processes
      • Uses Aerobic Decomposition to remove dissolved and suspended organic material through bacterial digestion
      • Waste can now be released or, preferably, treated more
    • Tertiary Treatment
      • Chemical and physical (e.g. fine filtration) treatment to disinfect, clarify, and remove remaining dissolved pollutants
    • Treated fluid can be
      • released into a river or lake
      • released into a natural filtering system for further improvement in quality
        • Wetlands, sometimes constructed for this purpose, and some golf courses, can be used in this way
      • released into the groundwater for further filtration and natural processing
    • Solids, now called Sludge, are processed according to the types of material in the sewage (so not all sludge is treated alike) to disinfect it, remove pollutants, and to control odor
      • Sludge might be used to produce methane (natural gas) in Anaerobic Digesters and the gas used for electric generation
      • Sludge might be burnt, and the heat generated may be used to generate electricity
      • If the sludge meets standards for pollution and disinfection, it can be used as fertilizer
      • Sludge that does not meet criteria for combustion or agricultural use may simply be put in landfills (most sludge)
  • Designed to handle organic waste efficiently but other pollutants (heavy metals, man-made organics like PCBs) are less efficiently removed
• Industries can be required to treat their own water
• Sewage systems are often part of the overall Storm Water System
  • Good in that it forces storm runoff to be treated as sewage and not simply allowed to run into lakes and streams
  • Bad in that storms may produce so much runoff that the sewage system's storage capacity is overwhelmed and raw sewage may be released into lakes or rivers

New Dams, Canals and Reservoirs

• Building new dams and reservoirs will increase water resources by retaining more run-off for later use
  • Dams are not always built to increase water supply (hydroelectric power, flood control)
• Environmental Impact of dams
  • Removal of normal sediment load from rivers
    • sediments accumulate in reservoirs
    • sediments do not build deltas or fertilize wetlands and shallow offshore sea water
  • Increased erosion below dam
  • Reservoirs, especially those in hot, dry areas, lose lots of water to evaporation
  • Evaporation increases salinity of the water
  • Dam Breaks can cause disasters
  • Biological Disruptions (fish migration, alterations in fish, invertebrate and plankton communities due to temperature changes, etc.)
  • Alteration or destruction of natural and human communities
• Canals do not increase the supply but do redistribute it from areas of surplus to areas of scarcity
  • Canals often have large costs
    • reduce water available to natural systems (Florida Everglades)
    • destroy productive wetlands ("Drain the Swamp")
    • Social disruption caused by the diversion

Social Implications of Water Supply

Is there a "Water Crisis"?

• Certainly, water is in short supply in some parts of the Earth
• The Third World Center for Water Management claims that there is enough almost to satisfy the demand if sufficient technology and efficiency are applied
• Will efficiency and technology be able to meet future demand?  The center does little forecasting

Who pays for water?

• Agriculture often receives water subsidies in the form of lower prices for water
  • These are often less than 1/10 of what urban consumers pay
• Inexpensive resources get wasted, expensive resources get conserved
• As prices rise for water, farmers use less by increasing efficiency or choosing crops with lower water demand
  • This policy of charging those who use the resource the real price, with environmental costs included, puts pressure on farmers, industries, and households to reduce water consumption

Who controls water?

• Water is a resource that has a long legal and political history but the regulation of water usually pertains to surface water
  • Less is known about ground water movement
• Surface Waters:
  • Riparian Laws - empower those who own the banks of a river to withdraw water from it
    • usually requires that not so much water can be taken that would seriously reduce the water available for downstream owners
  • Riparian Laws come from common-law, practices built up over many years and eventually codified
  • Riparian Law is more common where water is relatively plentiful (eastern US)
  • Appropriation Laws predominate in the western US
    • The first to use the water has the right to it, and this right supercedes any rights due to ownership of the banks
      • Thus, a rancher who has pumped water from a stream has the right to the water and someone who moves in upstream must leave that water in the stream, even though he or she owns the banks of the stream
    • This means users have rights tied to time of first use, not rights tied to where they own land along a river
  • Beneficial Use Law gives the water to the user who makes the most beneficial use of it
    • These laws are similar to Eminent Domain laws, which allow the state to take property, with compensation, in order to use it for the general good (often an ill-defined concept)
    • Thus, if an industrial facility is using water but very wastefully, the state can take that water, with compensation, unless the industry agrees to cut the waste from its process
• Groundwater
  • Few laws but in may places, it is assumed that those who own the surface of the land can use the groundwater under it
    • However, wells can deplete water under adjacent owner's land and laws are accumulating that regulate the right to pump freely from a well on one's own property
  • Groundwater pollution is harder to regulate, as nothing can stop the lateral movement of the water and so, any pollution will eventually move to adjacent owners land

Case Histories of Water Use Disputes in the US

• The Everglades
  • The everglades are a shallow river system that flows from Lake Okeechobee in central southern Florida to the tip of Florida and discharges into the Florida Bay
    • The area was once coral reef and is very flat, which accounts for the river's odd dimensions
      • Coral is calcium carbonate, and so south Florida is composed of Marl (unconsolidated calcium carbonate) and coralstone (consolidated calcium carbonate)
  • These conditions are unique and the ecosystem that developed is also unique
    • Florida Bay is an important resource for shellfish, commercial, and sport fisheries
    • The everglades are home to the largest populations of water fowl in the US (or once were)
  • To develop the area, drainage canals were used to divert water to the ocean or gulf north of the everglades so that the water table would drop and expose land for construction
    • Much of this occurred in the 1950's and the area just south of the lake was turned into fields for sugarcane
    • The diverted water was used by households, industry or agriculture and the excess was simply released into the Ocean or the Gulf
    • The diversion of water exposed more land, which was mostly used for residential construction, and the increase in population used more and more of the water
  • Problems soon surfaced
    • The peat soils were mostly humus and, when exposed, crumbled and eroded such that the average soil depth when the canals were built (5 ft) has declined to less than 3 feet on average (cane needs 3 ft) and productivity had declined since the 1980's
    • Humans introduced exotic species of plants and animals that further damaged the system
      • Melaleuca, a species of fast-growing, root-sprouting tree from Australia, used as an ornamental, has overgrown many acres and it's high rate of evapotranspiration had lowered the water table where it grows in abundance (Florida natives are adapted to wet, not dry, soils)
      • Pythons have reduced mammal populations (deer, mustelids, raccoons, etc.) where they have become common (by as much as 90% for some species) (the largest one found so far was over 17 feet long and pregnant)
    • So little water was left in the glades that bird populations declined and some species left the area altogether
  • A coalition of public and private agencies put together a plan to restore flow to the glades but, according to an independent oversight committee involving the National Academy of Sciences, the plan has not gone forward quickly enough to prevent further damage to the system

• California Water Wars

• LA began looking for more water to support growth in the late 1800's and the Owens Valley, between the White and Sierra Nevada Mountains, had water and far fewer people
• The distance between LA and Bishop, the largest town in the Owens Valley is 250 miles due north
• LA acquired water rights (often through political influence at the state level but also by buying water rights from land owners) and built an aqueduct (canal) from the valley to LA by 1913
  • Many Owens Valley residents claim they were told that the water was for residential use only and not for agriculture (not true) and when the project began, LA residents were told that there was a water crisis (also not true but, if LA was to become LA, just proactive)
  • Promises to preserve Owens Valley agriculture were made but broken
• The aqueduct was costly to build and operate because it had to pump water over elevated land between the valley and LA
• By the 1920's, so much surface water was diverted to LA that agriculture in the valley, their main source of income, was severely affected
• Although residents sought to destroy the aqueduct, they were unsuccessful and by 1926 Owens Lake was gone
• By 1928, LA owned 90% of the water and agriculture ceased to be economically viable in the valley
• In 1972, a second canal was built to remove groundwater pumped for LA's use
• Owens valley springs and seeps dried up and desertification set in
• Lawsuits followed to make LA return some water and the Owens Valley won but LA has never returned enough water to stop the process of desertification in the valley

Fracking, gas production, groundwater and the law

• As we learned earlier, fracking involves the injection of a slurry of materials into deep layers of rock with trapped gas
  • The pressurized fracking liquid pulverized the rock and releases the gas
• Most of the fluid is returned to the surface and there are some regulations about handling this waste safely
• For the fluid in the ground, the energy industry claims that it is trapped in the shale by un-fracked layers of rock and will not mix with groundwater
  • This is not a well-tested (no pun intended) assumption and data is now being collected as fracking activity has skyrocketed since the discovery of significant amounts of shale gas
• If there are cracks in the "impermeable" layers of rock, then contamination can occur
  • The most likely crack is the one made by fracking - the bore hole drilled to get the fracking fluid to the shale layer
  • Currently, there are regulations about sealing that hole while fracking and once the fracking is completed but no one has tested thoroughly if the current methods really are an efficient seal or how long the seal lasts
• No one knows what the effects of earthquakes may be on these "sealed" fracking wells
  • It is known that fracking can cause (minor) earthquakes

s²₂

Last updated November 29, 2012