Chapter 14Water: A Fragile Resource

http://www.nrdc.org/water/drinking/uscities/contents.asp

http://water.usgs.gov/http://www.ametsoc.org/amsedu/WES/home.html

http://ga.water.usgs.gov/edu/mearth.html

Water: A Fragile Resource

• Approximately 3/4 th’s of the Earth’s surface is comprised of water.

• Only 2.5% is available as fresh water

• Hydrologic Cycle: Is the pathway of water through the environment.

Hydrologic Cycle

A. Properties of Water

• High heat capacity (It does NOT heat up easily)• High dissolving ability (the universal solvent)• Water is a polar molecule (Due to 105

0

bond angle)

• Hydrogen bonding occurs between water molecules.

• Adhesion: H2O molecules bonded to other materials.

• Cohesion: H2O molecules bonded to each other.

Composition of 1 Kg of Sea water

Distribution of water on the Earth

Major Uses of Water on the Earth

• Irrigation- 68.3 %

• Industry- 23.1 %

• Domestic & Municipal consumption- 8.6%

Basic Water Vocabulary

• Surface Water is fresh water found in streams, rivers, ponds, lakes, and wetlands. (renewable resource)

• Wetlands: areas covered with water for at least part of the year. Wetlands serve as sponges and act like the kidneys of an ecosystem. (filtration)

• Surface waters are replenished by runoff of precipitation from the land.

Surface Water-

• The area of land drained by a single river is its drainage basin.

• Watershed: the entire river system including the area of land drained by a river and its tributaries.

Water Vocabulary (Continued…)

• Groundwater occurs in aquifers, underground concentrations of water in caverns and porous layers of rock. (Percolates to an impenetrable layer.)

• Unconfined aquifers: have porous layers of rock above them. The upper limit of an unconfined aquifer is the water table. The rock layers above are porous

• Confined Aquifers (artesian aquifer): have impermeable layers of rock above them. The water in a confined aquifer is trapped (sandwiched between impermeable layers) and is often under pressure.

Water Vocabulary (Continued)…

Artesian Wells- No Pump!!

Flooding- occurs as a result of too much fresh water entering an area.

Flood damage is exacerbated by the deforestation of hillsides & mountains, and by urban development.

Flooding

• Flood Plains: areas bordering a river that are subject to flooding. (fertile crescent, Nile, Amazon, Yellow river)

• Flood plains not only “absorb” excess water, they also slow its flow, and allow for mineral deposition.

Straightened river

How development changes the natural flow

Case in Point: The Floods of 1993

• Severe flooding of nine Midwestern states which is considered by many to be the worst flood in U.S. History.

Water Resource Problems

• Although there is enough fresh water to support life on earth, it is not evenly distributed. Some areas are barely able to support human life because of the shortage of water.

Water Resource Problems

I. Aquifer Depletion: human removal of more groundwater than can be recharged by precipitation of melting snow.

• Aquifer depletion from porous rocks can cause subsidence (sinking land.)

• Saltwater intrusion is the movement of seawater into a freshwater aquifer.

Water Resource Problems

II. Salinization: the accumulation of salt in the soil due to evaporation. (irrigation)

• Salinization results in a decline in productivity of agricultural soil.

Groundwater

“Lower 48” water budget

http://www.ijc.org/php/publications/html/11br/english/report/

Population Growth and Water Problems

• Many areas in the United States have severe water shortages.

• Population growth in California, Nevada, Arizona, & Florida has placed great demands on water supplies.

• Mono lake in eastern California has surface water diverted to Los Angeles, lowering its water level & increasing its salinity.

Mono Lake

http://www.monolake.org/naturalhistory/stats.htm

Population Growth and Water Problems

• In 1989 California decided that water could no longer be diverted from Mono Lake. Eventually, it should return to a “near normal” level.

• Instead, Los Angeles will develop reclaimed water, (treated wastewater), that will be reused in some way, to replace water supplies from Mono Lake.

Population Growth and Water Problems

• Colorado river basin is seriously over-diverted for human consumption.

• The lower Colorado supplies water to Tucson & Phoenix AZ, and to San Diego and Los Angeles CA.

• Recent population growth in the upper Colorado region ( Colorado, Utah, & Wyoming) threatens the lower Colorado’s water supply.

• The amount of water available from the Colorado River for Mexico, is insufficient according to international standards.

Population Growth and Water Problems

• The Ogallala Aquifer on the High Plains is the largest groundwater deposit in the world.

• The depletion of the Ogallala Aquifer for irrigation has lowered the water table in some places by more than 30m.

• Water experts (Hydrologists) predict that groundwater in the Ogallala Aquifer will eventually drop to a level that is uneconomical to pump.

Global Water Problems• The distribution of water resources in relation to human

populations exacerbates global water problems.• People in many developing countries lack access to to safe

(potable) drinking water and wastewater disposal. • 1.4 billion people lack potable water globally.• 2.9 billion lack proper wastewater disposal. (W.H.O.)• Population growth is outstripping water supplies in

countries such as India, China, & Mexico….

Are we on the verge of water wars?????

Global Water Problems (Continued…)

• The Aral Sea in Kazakhstan has been over-diverted for irrigation of farmland.

• Once the world’s 4th largest freshwater lake, the Aral Sea has declined in area by 50%.

• Airborne salt from the dry lake bed may be adversely affecting the health of millions of people living near the Aral Sea.

Providing a Sustainable Water Supply

• The long-term goal of water management is to provide a sustainable supply of high quality water, not to provide water in limitless supply.

• Sustainable Water Use: means that humans can use water resources into the future without harming the functioning of the hydrologic cycle or ecosystems.

Providing a Sustainable Water Supply

• Dams ensure a year-round supply of water in areas that have seasonal precipitation or snowmelt.

• Many people think that the drawbacks of dams outweigh any benefits they provide.

• The Columbia River has more than 100 dams. The river is used for shipping, hydroelectric power, municipal and industrial water, recreational sports, and commercial fishing.

• Dam impoundments along the Columbia River have adversely affected salmon populations.

Case in Point: The Columbia River

Providing a Sustainable Water Supply

• The Missouri River has been embroiled in a heated battle over water rights, particularly use of the water stored in upstream reservoirs.

• Water diversion is sometimes used to increase the supply of water to a particular area.

• Water is transported via aqueducts and streams.

• Water diversion concentrates pollutants in the remaining water & harms fishes & other organisms.

Providing a Sustainable Water Supply by turning to Sea water

• Desalinization (desalination): the removal of salt from seawater or salty groundwater.

• Distillation: heating salt water until water evaporates, leaving behind salt, the steam is then condensed and collected.

• Reverse Osmosis: an economical form of desalinization that forces salt water through a semi permeable membrane.

Water Conservation

• Water conservation measures can make the present supply adequate, as opposed to trying to increase the available amount of water.

• Agriculture (irrigation) is the single largest user of water. Although irrigation increases agricultural productivity, it can contribute to water pollution, soil salinization, & depletion of water supplies.

• Micro irrigation (drip or trickle irrigation) a water conservation method using small holes and subterranean piped to deliver water directly to root systems.

Water Conservation

• Field leveling can also cut agricultural water consumption.

• After agriculture, the 2 largest users of water are industry and domestic/municipal water use.

• Water Conservation, including recycling and reuse, can reduce both industrial and municipal water consumption.

• Xeriscaping: using rocks and plants that require little to no water in landscaping.

• Xero= dry (think Xerox dry copies)

Success on the Rhine River in Germany

• In 1986 30 tons of dye, pesticides & Hg spilled in the river.

• Today the Rhine is almost pure, Atlantic Salmon have returned after a 30 year hiatus.

Some web links of interest…

• Current stream flow-•  http://water.usgs.gov/waterwatch/•  •  Drought-• http://water.usgs.gov/waterwatch/?m=dryw&w=m

ap&r=us•  • Trends in water use in US-• http://ga.water.usgs.gov/edu/totrendbar.html