CHAPTER 21: WATER SUPPLY, USE AND MANAGEMENT

WATER

To understand water, we must understand its characteristics, and roles:

Water has a high capacity to absorb and store heat. Water is the universal solvent.Water has a high surface tension.Water is the only compound whose solid form is lighter than its liquid form.

Sunlight penetrates water to variable depths, permitting photosynthetic organisms to live below the surface.

A BRIEF GLOBAL PERSPECTIVE

We are facing a growing global water shortage linked to the food supply.

Global hydrologic cycle Transfers water from the atmosphere, to land, to oceans and back to

atmosphere 97% in oceans 2% in ice Only 0.001% in atmosphere

A BRIEF GLOBAL PERSPECTIVE

At Earth’s surface water can be found in liquid, solid or gaseous form.

Residence time varies from a few days to thousands of years

Amount of water for which all people, animals and plants compete is < 1%

Industrial production increases water use Mass of water used 1000x total production of minerals

GROUNDWATER AND STREAMS

Groundwater refers to the water below the water table Where saturated conditions exist Locations where surface waters move into the ground are recharge

zones Places where it flows or seeps out are discharge zones (points) Area where water seeps through pore spaces known as vadose zone

GROUNDWATER AND STREAMS

Aquifer is an underground zone from which groundwater can be obtained

When water is pumped from an aquifer forms a cone of depression

STREAMS

Effluent streamFlow is maintained during the dry season by seepagePerennial stream

Influent streamEntirely above the water table and flows only in direct response to precipitation

Ephemeral stream

A given stream can have reaches that are both or intermittent at varying times of year.

INTERACTIONS BETWEEN SURFACE WATER AND GROUNDWATERShould be considered part of the same resource.

Nearly all surface water environments have linkages w/ ground water

E.g. withdrawal of groundwater can lower stream flow or lake levels Pollution can spread from one source to the other

WATER SUPPLY: A US EXAMPLE

Water supply at any point on the land surface depends on several factors in the hydrologic cycle,

including the rates of precipitation, evaporation, transpiration

stream flow subsurface flow

Water budgetA model that balances the inputs, outputs, and storage of water in a system.

Precipitation - evaporation = runoff

WATER SUPPLY: A US EXAMPLE

Amount of water vapor passing over the US every day ~ 152,000 million m3

10% falls as precipitation (66% of which is evaporated or transpired) Only 34% enters surface or groundwater

In developing water budgets for water resources management it is useful to consider annual precipitation and runoff patterns.

Potential problems can be predicted in areas where average runoff and precip low

Total storage of runoff not possible because of evaporative losses

PRECIPITATION AND RUNOFF PATTERNS

DROUGHTS

Because there are large annual and regional variations in stream flow, even areas with high precipitation and runoff may suffer from droughts.

GROUNDWATER USE AND PROBLEMS

½ the people in the US use groundwater as a primary source of drinking water

20% of water used In many parts of the country withdrawal from wells exceeds natural

inflow Overdraft Nonrenewable resource Problems include damage to river basins and land subsidence

DESALINATION AS A WATER SOURCE

Seawater is 3.5% salt

Desalination- a technology to remove salt from water Must be reduces to 0.05% to be fresh water Requires large amount of energy, tied to fuel prices Has place value- price increases quickly with transport distance Discharge may affect local salinity

WATER USE

Off-stream use Refers to water removed from its source for use May be returned to source after use Or consumptive use- water enters tissues, product or evaporates

during use and not returned

WATER USE

In-stream use The use of the river for navigation, hydroelectric power, fish and

wildlife habitats, and recreation. Multiple uses can create controversy

WATER USE

Another problem with off stream use is how much water can be removed w/o damaging the stream ecosystem.

E.g. Aral Sea. Diverting water for agriculture caused sea to dry up Surface area of sea reduces 90% in 50 years

ARAL SEA

Salt content of the water has increased

Dust storms from dry salt flats

Climate changes Winters colder, summers warmer Loss of fishing and decline of tourism

TRANSPORT OF WATER

Ancient civilizations constructed canals and aqueducts to transport water

From distant river to where it is needed

In modern civilization water moved from areas of abundant rain and snow fall to areas of high usage

E.g. California moves water from north to south E.g. New York City has had to obtain water from farther and farther

away

SOME TRENDS IN WATER USE

Withdrawal of surface water far exceeds withdrawal of groundwater

Since 1980 use has decreases and leveled off Suggests improvement in water management and conservation

SOME TRENDS IN WATER USE

Trends in freshwater withdrawals by water-use categories suggests that:

1. The major uses of water are for irrigation and the thermoelectric industry.

2. Water use for irrigation increased from 1950-1980. It decreased and leveled off from 1985-2000 due to better irrigation efficiency, crop type and higher energy

costs.

SOME TRENDS IN WATER USE

3. Water use by thermoelectric industry decreased slightly in 1980, and stabilized in 1985. Due to reticulating water for cooling

4. Water for public and rural supplies continued to increase through the period from 1950 to 2000 presumably related to the increase in human population.

WATER CONSERVATION

The careful use and protection of water resources Involves the quantity of water used and the quality Important component of sustainable water use Expected that a number innovations will reduce the total withdrawals

AGRICULTURAL USE

Improved irrigation could reduce agricultural withdrawals by 20 to 30%

Tremendous savings because ag is the biggest user

AGRICULTURAL USESuggestions for conservation:Price agricultural water to encourage conservation

Use lined or covered canals that reduce seepage and evaporation.

Use computer monitoring and schedule release of water for maximum efficiency.

Integrate the use of surface water and groundwater to more effectively use the total resource.

AGRICULTURAL USE

Irrigate at times when evaporation is minimal, such as at night or in the early morning.

Use improved irrigation systems, such as sprinklers or drip irrigation, that more effectively apply water to crops.

Improve the soil to increase infiltration and minimize runoff.

Encourage the development of crops that require less water or are more salt tolerant.

DOMESTIC USE

Accounts for about 10% of total national water withdrawals But concentrated in urban areas May pose major local problems

DOMESTIC USEWater use can be substantially

reduced by:In semiarid regions, replace lawns with decorative gravels and native plants.

Use more efficient bathroom fixtures.Turn off water when not absolutely needed.

Flush the toilet only when really necessary.

Fix all leaks quickly.

DOMESTIC USE

Purchase dishwashers and washing machines that minimize water consumption.

Take a long bath rather than a long shower. Sweep sidewalks and driveways. Using gray water to water vegetation. Water lawns and plants at cool times to reduce evaporation.

DOMESTIC USE

Use drip irrigation and place water-holding mulch around garden plants.

Plant drought-resistant vegetation.Learn how to read the water meter to monitor for unobserved leaks and record your conservation successes.

Use reclaimed water

INDUSTRY AND MANUFACTURING USE

Water conservation measures that can be taken by industry:

Using cooling towers that use little or no water

In-plant water treatment and recycling

PERCEPTION AND WATER USE

Perception of water is based partly on its price and availability.

If water is abundant and inexpensive, we don’t think much about it.

If water is scarce or expensive, it is another matter.

E.g. people in Tucson pay about 100% more for water than people in Phoenix.Tucson residence use less water per person per day

SUSTAINABILITY AND WATER MANAGEMENTFrom a water supply use and

management perspective, sustainable water use defined as:

use of water resources by people in a way that allows society to develop and flourish into an indefinite future

W/o degrading the various components of the hydrologic cycle or the ecological systems that depend on it.

SUSTAINABLE WATER USE

General criteria:Develop water resources in sufficient volume to maintain human health and well-being.

Provide sufficient water resources to guarantee the health and maintenance of ecosystems.

Ensure minimum standards of water quality for the various users of water resources.

SUSTAINABLE WATER USE

Ensure that actions of humans do not damage or reduce long-term renewability of water resources.

Promote the use of water-efficient technology and practice.

Gradually eliminate water pricing policies that subsidize the inefficient use of water.

GROUNDWATER SUSTAINABILITY

Sustainability involves a long term perspective

For groundwater even longerEffects of pumping might not be seen immediately

Long-term approach involves balancing withdrawal with recharge

WATER MANAGEMENT

Management of water resources is a complex issue that will become more difficult as demand for water increases in the coming years.

Especially in areas like the Southwestern US and other semi arid regions

WATER MANAGEMENT

Options for minimizing potential problems:

Alternating water supplies and managing existing supplies better

Towing icebergsAs price goes up many innovative programs are possible.

VARIABLE-WATER-SOURCE APPROACH

A MASTER PLAN FOR WATER MANAGEMENTNew management philosophy is that surface water and

groundwater are both subject to natural flux with time. In wet years, there is plenty of surface water, and the near-surface

groundwater resources are replenished. During dry years, specific plans to supply water on an emergency

basis must be in place and ready to use.

A MASTER PLAN FOR WATER MANAGEMENTAdvanced planning may include Drilling to wells that are presently isolated Reuse of waste water Develop surface water and use groundwater in dry years In wet years pump excess surface water underground to recharge

groundwater

WATER MANAGEMENT AND THE ENVIRONMENTOften a good deal of controversy surrounds water development Dams, canals, wetlands modification Resolution of development involves input from a variety of

government and public groups

WETLANDS

Wetlands is a comprehensive term for landforms such as salt marshes, swamps, bogs, prairie potholes, and vernal pools.

Common feature is that they are wet at least part of the year Have a particular type of vegetation and soil

TYPES OF IRRIGATION

- flood: flooding an area, inexpensive, but very wasteful, more that 50% of water is lost to evaporation.

- Furrow irrigation: also called ditches, found between crops, more efficient than flooding, however, high rate of evaporation and accumulation of mineral salts

TYPES OF IRRIGATION CONTINUED

Overhead irrigation: sprinkler systems are the most common. Efficiency decreases with strong wind. Drip or trickle, developed in Israel, uses tubing to deliver small amounts directly to the root system, very expensive, but very efficient.

Sub irrigation: water is introduced naturally or artificially beneath the soil.

NATURAL SERVICE FUNCTIONS OF WETLANDSFreshwater wetlands are a natural sponge for

water.Reducing flooding.

Many freshwater wetlands are important as areas of groundwater recharge or discharge.

Wetlands are one of the primary nursery grounds for fish, shellfish, aquatic birds, and other animals.

Wetlands are natural filters that help purify water.

NATURAL SERVICE FUNCTIONS OF WETLANDSWetlands are often highly productive and

are places where many nutrients and chemicals are naturally cycled.

Coastal wetlands provide a buffer for inland areas from storms and high waves.

Wetlands are an important storage site for organic carbon.

Wetlands are aesthetically pleasing to people.

WETLANDS

Freshwater wetlands are threatened in many areas. Over the past 200 years > 50% of all wetlands have disappeared,

90% of freshwater wetlands Diked, drained or filled SF bay estuary considered the most modified by human activity

WETLANDS

Mississippi River delta includes major coastal wetlands Historically maintained by flooding Accretion processes counter natural subsidence If accretion decreases area of open water increases and wetland in

reduced Levees block sediments and costal wetlands are being lost

RESTORATION OF WETLANDS

Number of projects have attempted to restore wetlands. In freshwater marshes recovery linked to availability of water Salt marshes more complex EPA of 1969 states if wetlands destroyed by development must be

replaced elsewhere

RESTORATION OF WETLANDS

Constructing wetlands to clean up ag waste Natural ability to remove excess nutrients, break down pollutants,

and cleanse water. In Florida, human-made wetlands designed to intercept and hold

nutrients so they don’t damage the Everglades.

DAMS AND THE ENVIRONMENT

Dams and their accompanying reservoirs generally are designed to be multifunctional structures.

Used for recreational activities Generating electricity Providing flood control Ensuring a more stable water supply

Often difficult to reconcile various uses at a given site.

DAMS AND THE ENVIRONMENT

The environmental effects of dams include the following: Loss of land, cultural resources, and biological resources in the

reservoir area. Larger, dams and reservoirs produce a potential serious flood hazard

should they fail Storage behind the dam of sediment that would otherwise move

downstream to coastal areas.

DAMS AND THE ENVIRONMENT

Downstream changes in hydrology and in sediment transport that change the entire river environment and the organisms that live there.

Fragmentation of ecosystems above and below a dam. Restrict movement upstream and downstream or organic material,

nutrients and aquatic organisms.

DAMS AND THE ENVIRONMENT

Many people vehemently against building new dams. But if present water use practices continue we will need new dams. Few acceptable sites for dams Expensive to build and operate, many people don’t want tax dollars

spent on subsidized water.

CANALS

Water from upstream reservoirs may be routed downstream by way of natural water ways or canals and aqueducts.

Not hydrologically the same as creeks Smooth, steep banks; water moves fast Canals can spread and carry disease

schistosomiasis

REMOVAL OF DAMS

Recent dam removals include Edwards Dam in Maine Marmot Dam in Oregon After removal both river saw return of fish as they migrated upstream

Large fish runs transport nutrients upriver from ocean to forest ecosystems.

REMOVAL OF DAMS

Trapped sediment behind dams must be dealt with in dam removal.

If released quickly it could damage downstream ecosystem and fill pools.

Slower release minimizes damage.Matilija Dam in Ventura County cost $300,000 to build but 10 times that to remove.

Removing dams is simple in concept but involves complex problems relating to sediment and water.

CHANNELIZATION AND THE ENVIRONMENTChannelization of streams consists of straightening,

deepening, widening, clearing, or lining existing stream channels.

Engineering technique that has been used to control floods, improve drainage, control erosion, and improve navigation

CHANNELIZATION AND THE ENVIRONMENTAdverse environmental effects, including

the following:Degradation of the stream’s hydrologic qualities;

nearly all riffle flow, resulting in loss of important fish habitats.

Removal of vegetation along the watercourse, which removes wildlife habitats and shading of the water.

Downstream flooding where the channelized flow ends.

Damage or loss of wetlands.Aesthetic degradation.

CHANNELIZATION AND THE ENVIRONMENTCase study in problems w/ Channelization Kissimme River in Florida Meandering river turned into straight ditch Failed to provide flood protection, damaged wildlife habitat, water

quality problems and aesthetic degradation. In 1990 efforts to restore river began.

THE COLORADO RIVER: WATER RESOURCES MANAGEMENT AND THE ENVIRONMENT

The history of the Colorado River emphasizes linkages among physical, biological, and social systems that are at the heart of environmental science.

Major river of the southwestern US Ends in the Gulf of California

THE COLORADO RIVER

For its size has a modest flow but is one of the most regulated and controversial bodies of water in the world.

Total flow was apportioned among various users in 1922 No water allowed for environmental purposes Water rarely flows into the Gulf, all stored and used upstream.

Damaged delta

THE COLORADO RIVER

Two largest reservoirs- Hoover Dam and Glen Canyon Dam Stored about 80% of total in the basin Represents a buffer of several years water supply. Changing hydrology of the river changed other aspects

Rapids, sediment load, and vegetation

THE COLORADO RIVER

Record snowmelt in the Rocky Mountains in 1983 forced the release of water from Glen Canyon Dam

Three times normal but similar to spring floods before the dam was built.

Beneficial to the river, highlighted the importance of floods in maintaining a natural state.

THE COLORADO RIVER

As an experiment “flood” waters released in 1996 Two weeks at full flood As a result 55 new sandbars formed and 75% of existing sandbars

increased in size, rejuvenated marshes and backwaters. Hailed a success; hoped that what was learned can help restore other

river impacted by dams.

GLOBAL WATER SHORTAGE LINKED TO FOOD SUPPLYBoth surface water and groundwater

are being stressed and depleted:Groundwater in the United States, China, India, Pakistan, Mexico, and many other countries is being mined used faster than it is being renewed

Large bodies of water—for example, the Aral Sea—are drying up.

Large rivers, including the Colorado in the US and the Yellow in China, do not deliver any water to the ocean in some seasons or years.

GLOBAL WATER SHORTAGE LINKED TO FOOD SUPPLYAs human population grows there is growing concern that

there won’t be sufficient water to grow the food to feed 8-9 billion people.

Food shortage linked to water resources a real possibility. Water also linked to energy (fuel to pump) as energy cost goes up so

does cost of food.

GLOBAL WATER SHORTAGE LINKED TO FOOD SUPPLYSolution Control human population growth Conserve and sustain water resources Need to be proactive now before significant food shortages develop.

WATER TREATMENT

- Desalination (covered)

- Distilation: salt water is heated to boiling, evaporated water is collected

- Reverse osmosis: salt water is forced through a strainer trapping the salt, fresh water passes through

- Freezing: salt water is frozen (only the fresh water freezes) an ice and brine slucs is created, fresh water is in solid form and removed

- Sedimentation and filtration: screens remove debris, settling tanks allow more to settle, coagulants may be added to help remove particles to small to settle.

WATER TREATMENT CONTINUED

Aeration and sterilization

-Exposure of water to air and sunlight (aeration)

-Bacteria are often utilized to break down organic matter, and oxygen is mixed in with it.

-Sterilization is used to kill off the bacteria, via heat or with chemicals

- Chlorine: one used to kill off- Ozone: more efficient that chlorine