Water Use and Management

Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

Water Use and Management


Outline:

• Water Availability and Use

• Freshwater Shortages

• Water Management and Conservation


WATER RESOURCES

• Water, liquid and solid, covers more than 70% of world’s surface. More than 370 billion billion gallons.


Hydrologic Cycle


Sources of water

Surface fresh water: 3% of liquid fresh water,

which is 13% of all fresh water,which is 2.4% of all water


Groundwater

Second largest reservoir of fresh water.- Infiltration - Process of water percolating

through the soil and into fractures and permeable rocks.

Zone of Saturation - Lower soil layers where all spaces are filled with water.

Water Table - Top of Zone of Sat.


Groundwater


Groundwater Aquifer

Technologies for water collection

• Industrialized countries: Drill into aquifers Build dams across rivers to create reservoirs

(hold water in times of excess flow and release water in times of lower flow).

Water is piped to treatment plants. Water is distributed through the water system to

homes, schools, and industry. Water is collected by sewage-treatment plant,

retreated, and sent back out for distribution

Dam Impacts• Fresh water habitats lost, increased salt

concentration, etc. • US: 75,000 dams at least six feet in height,

another 2 million smaller structures.• Around the world: more than 45,000 large

dams (50ft high). 3,000 of these contain storage reservoirs

with volumes greater than 25 billion gallons

Why build dams?

• Combination of flood control, water storage, and hydropower.

Three Georges Dam

Water diversions from rivers

Yellow River (Huang He)In northern China

Three Georges Dam

• Yangtze River in China• Completed in 2006• Largest hydroelectric project in the world• Generates 22,000 MW of electricity• More than 1.2 million people have been

displaced• Critics point to the huge human, ecological, and

aesthetic costs of the dam and claim alternative sources of energy are cheaper


Diversion of rivers to the Aral Sea

• Once the 4th largest inland body of water in the world

A series of dams was built to irrigate cotton.

• Aral Sea reduced to about 25% of its 1960 volume, quadrupled the salinity of the lake and wiped out the fishery. Pollutants became airborne as dust, causing significant local health problems.

• The environmental damage caused has been estimated at $1.25 -$2.5 billion a year.

Colorado River Deltain U.S./Mexico

US Dam Removal

• 500 dams have already been removed in the US and many await the same fate.

• Pros for removal: reestablish historic fisheries and reestablish the river for recreational and aesthetic value

• Cons: massive sediment from upriver that will be washed downstream; difficult.

US water policy

• No federal US water policy • Clean water act and its subsequent

amendments authorize the US EPA to develop programs and rules to carry out its mandate for oversight of the nation’s water quality.

• EPA does not deal with water quantity.


U.S. Water Policy

• Through most of US history, water policies have generally worked against conservation. In well-watered eastern states, water

policy was based on riparian use rights. In drier western regions where water is

often a limiting resource, water law is based primarily on prior appropriation rights.

- Fosters “Use it or Lose it” policies.

OK Water Policy• “The Legislature hereby declares that, in order to protect Oklahoma

citizens from increased water supply shortages and groundwater depletions by the year 2060 in most of the eighty-two watershed planning basins in the state as described in the 2012 Update of the Oklahoma Comprehensive Water Plan, the public policy of this state is to establish and work toward a goal of consuming no more fresh water in the year 2060 than is consumed statewide in the year 2012, while continuing to grow the population and economy of the state and to achieve this goal through utilizing existing water supplies more efficiently and expanding the use of alternatives such as wastewater, brackish water, and other nonpotable supplies. Provided, however, that nothing in the Water for 2060 Act shall be construed as amending the provisions of law pertaining to rights or permits to use water.”



Ogallala Aquifer

High-capacitywellwithdrawals


Dried-up reservoir


WATER AVAILABILITY AND USE

• Renewable Water Supplies Made up of surface runoff and infiltration

into accessible freshwater aquifers. Readily accessible, renewable

supplies are 400,000 gal /person/year.


Types of Water Use

• Withdrawal - Total amount of water taken from a source.

• Consumption - Fraction of withdrawn water not returned to its source.


Quantities of Water Used

• Worldwide, humans withdraw about 10% of total annual renewable supply. Many societies have always treated water

as an inexhaustible resource.• Human water use has been increasing about

twice as fast as population growth over the past century. Average amount of withdrawn worldwide is

about 170,544 gal/person/year.


Global Water Use Growth


Precipitation Patterns


Water use

Agriculture

Industry

Household/municipal

How is there not enough?

• If the water cycle is sufficient to provide water for all human needs, why do some go without? Not distributed evenly Scarcity of water in many parts of the

world Deficit in infrastructure Expanding populations


FRESHWATER SHORTAGES

• Estimated 1.5 billion people lack access to an adequate supply of drinking water. Nearly 3 billion lack acceptable sanitation.

• A country where consumption exceeds more than 20% of available, renewable supply is considered vulnerable to water stress.

How can we make water use sustainable:

1. Capture more runoff2. Gain better access to groundwater aquifers3. Desalt seawater (microfiltration/reverse

osmosis)4. Conserve present supplies by using less

water. (drip irrigation)

Municipal water conservation

• Flushing 3-5 gallons• Showering 2-3 gallons per minute• Laundry 20-30 gallons per load• Conserve: fix leaky faucets, low-flow

shower heads and faucets, replace lawns with xeriscaping, ban use of water during draughts, gray-water recycling.


Typical US Household Water Use

Xeriscaping

• Landscaping with desert species that require no extra watering (lawn replacement)


Depleting Groundwater

• Groundwater is the source of nearly 40% of fresh water in the US. On a local level, withdrawing water faster

than it can be replenished leads to a cone of depression in the water table,

- On a broader scale, heavy pumping can deplete an aquifer.





• Withdrawing large amounts of groundwater in a small area causes porous formations to collapse, resulting in subsidence.

Sinkholes form when an underground channel or cavern collapses.

Saltwater intrusion can occur along coastlines


Saltwater Intrusion

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Water Use and Management