Water Use and Management
EVPP 111 Lecture
Dr. Largen
Outline
- World’s Water Supply
- Hydrologic Cycle
- Types of water
- Water Use
- Water Pollution
- Wastewater Treatment
- Water Use Planning
Water Use and Management
- World’s water supply
- Importance of water
- Life
- Physical properties:
- Distribution of Water
- ~75% earth’s surface is covered by water
- ~97.5% - seawater
- ~ 2.5% - fresh water
- ~1.97% - ice caps and glaciers
- ~0.53% - lakes, rivers, soils, moisture, atmosphere
- >99% unavailable to humans
- <1% accessible to humans
- global variations in water supply
- differences in annual precipitation
- vulnerability to water shortages
- high annual precipitation = low vulnerability
- low annual precipitation = high vulnerability
constant water recycling process
- precipitation
- evaporation
- evapotranspiration
- condensation
- infiltration
- runoff
- Types of water
- Surface water
- fresh water on earth’s surface
- streams, rivers, lakes, ponds, reservoirs, wetlands
- replenished by runoff
- considered renewable, though finite, resource
- drainage basin
- area of land drained by single river
- watershed
- area of land drained by a river and all its tributaries
- water that fills spaces in soil and subsurface material
- moves downward until it reaches an impervious layer of rock
- accumulates in porous strata called an aquifer
- that becomes saturated with water
- aquifer
- two types
- unconfined aquifer
- usually near land’s surface
- lower boundary is impermeable layer of clay or rock
- upper limit, below which ground is saturated with water, is water table
- atmospheric pressure
- recharged by rainfall and percolation
- flows in direction of water table’s slope
- vadose zone
- below surface, above water table, not saturated with water
- confined aquifer
- bounded on top and bottom by impermeable layer
- water is trapped, often stored under high pressure
- water is recharged from a geologic recharge zone
- land from which water percolates to replace the groundwater
- artesian well
- non-flowing artesian well
- flowing artesian well
most is considered nonrenewable resource
takes hundreds or thousands of years to accumulate
only small portion is replaced each year by percolation or precipitation
- Water use
- varies considerable around the world
- depending on
- availability of water
- degree of industrialization
- non-consumptive (water withdrawal)
- withdrawing water, returning to original source.
- consumptive (water consumption)
- withdrawing water and incorporating it into a product, or otherwise moving it to another area so it does not make it back to its original source.
- domestic
water use
- accounts for
- ~12% of total water use in North America
- ~100 gallons per person per day
- ~7% of total water use world wide
- ~8% of global freshwater is withdrawn for
- more domestic water is wasted than consumed
- ~ 60% of domestic water returned to rivers as wastewater
- major source of loss is public attitude
- as long as water is considered limitless & cheap, little effort will be made to conserve it
- agricultural
water use
- major consumptive use of water in most parts of world
- accounts for
- ~40% of total water use in North America (text has typo)
- ~70% of total water use world wide
- irrigation
- requires large amount of energy
- many methods are wasteful
- increasing water costs will stimulate conservation - i.e. trickle irrigation
- increasing water costs or a water shortage can lead to devaluation of land
- industrial
water use
- accounts for
- ~48% of total water use in North America
- ~23% of total water use world wide
- ~90% of water is used for cooling
- returned to source
- little actually consumed
- to dissipate and transport waste materials.
- results in stream and lake degradation
- in-stream
water use
- does not remove water but makes use of it in its channels and basins
- all are non-consumptive
- major in-stream uses are
- hydroelectric power
- recreation
- navigation
- hydroelectric power
- produce ~13% of electricity generated in US
- does not consume water
- does not add waste to water
- controls flooding and creates electricity
- has drawbacks.
- high construction costs
- habitat destruction
- retard stream flow and silt deposition
- impounded water has high evaporation rate
- recreation
- often associated with reservoirs created by dams
- requires water of reasonably good quality
- overuse or inconsiderate use can cause degradation
- navigation
- US has 40,000km (25,000mi) of commercially navigable waterways
- must have sufficient depth
- in past, economical aspects of navigation projects often outweighed environmental concerns
- Water pollution
- occurs when something enters water that
- changes natural ecosystem
- interferes with water use by segments of society
- in industrialized societies
- not feasible to maintain completely unpolluted water
- water pollutants
can be divided into several categories
- toxic chemicals
- kill organisms
- make water unfit for human use
- persistent
- bioaccumulate in some individual organisms
- biomagnify in some food chains
- dissolved organic matter
- decays in water
- microorganisms naturally present in water break down organic matter, use up available dissolved oxygen from water
- if too much dissolved oxygen is used, aquatic organisms may die
- biochemical oxygen demand (BOD)
- amount of oxygen required to decay a certain amount of organic matter
- disease-causing organisms
- found in untreated or inadequately treated human or domesticated animal waste
- reduced by sewage and drinking water treatment systems in developed world
- nutrients
- in form of nitrogen and phosphorous compounds
- generally present in limited amounts in unpolluted freshwater
- are a limiting factors for aquatic plants and algae
- cause increase in rate of growth of aquatic plants and algae
- upon their decay, BOD can increase
- physical particles
- alter clarity
- cover spawning sites
- act as abrasive that injure organisms
- carry toxic materials
- contribute to changes in other physical characteristics of waterway
sources of pollution
classified as
point
source can be readily identified
has definite place where it enters water
such as waste discharge pipes
nonpoint
- diffuse pollutants
- source cannot be readily identified
- such as agricultural land, urban paved surfaces, acid rain, runoff, urban lawns
categories of pollution
municipal pollution
municipalities must provide
suitable drinking water
dispose of wastes
municipal wastes include
storm water runoff
industrial wastes
residential wastes
commercial wastes
municipal pollution
residential wastes include
garbage
food preparation
cleaning (clothes, dishes, etc.)
human wastes
- fecal coliform bacteria (generic term for bacteria found in human intestines)
agricultural pollution
agricultural activities are primary cause of water pollution problems
eutrophication of aquatic habitats
- due to excessive use of fertilizers
contamination of groundwater
runoff from agricultural feedlots
- bacteria from animal waste
silt
industrial pollution
some discharge wastes into municipal waste disposal systems
some discharge wastes directly into bodies of water
wastes may include
organic materials
pertroleum products
metals
acids
organisms
nutrients
particulates
toxic materials
thermal pollution
occurs when an industry
- removes water from a source
- uses water for cooling purposes
- returns heated water to its source
significant because some aquatic organisms are very sensitive to minor temperature changes
once it occurs, its very difficult to remedy
major sources include
agricultural products
underground storage tanks
landfills
septic tanks
surface impoundments
agricultural products
pesticides
- from leaks, spills runoff
- 73 pesticides have been detected in groundwater of Canada and US
animal-feeding operations
fertilizer applications
underground storage tanks
leaks from tanks containing gasoline and other hazardous substances
- 4 liters of gasoline can contaminate water supply for 50,000 people
landfills
recently constructed landfills have special liners and water collection systems
~90% of landfills in US have no liners
~96% have no system to collect leachate
~60% have no restrictions on waste accepted
septic tanks
poorly designed and inadequately maintained septic systems have contaminated groundwater with
- nitrates, bacteria, toxic cleaning agents
~20 million septic are in use in US
- up to 1/3 have been found to be operating improperly
surface impoundments
>225,000 pits, ponds, lagoons are used in North America to store or treat wastes
71% of these are unlined
only ~1% use plastic or other non-soil liners
99% have no leak detection system
73% have no restrictions on the waste placed in the impoundment
- Wastewater treatment
- wastewater treatment facilities
- maintained by most companies and municipalities in developed world
- percentage of sewage treated varies greatly throughout world
- treatment of sewage is classified as
- primary treatment
- primarily physical process
- removes large particles via filtration
- pumps remaining water into settling ponds and lakes
- after settling, water is drawn off the top and is either released to
- environment
- subsequent stage of treatment
- secondary treatment
- biological process
- involves holding wastewater until organic matter has been degraded by bacteria and other organisms
- combination of primary and secondary treatment is most common in US.
- discharged water must still be disinfected
- usually via chlorine due to ease and cost
tertiary treatment
involves variety of techniques
additional stage to remove
more dissolved pollutants, such as phosphorous and nitrogen
- some municipalities use natural or constructed wetlands
specific problem materials
extremely costly
Water use planning
metropolitan areas must deal with variety of issues and maintain extensive infrastructure to provide
- three basic water services
- water supply for human and industrial needs
- wastewater collection and treatment
- storm-water collection and management
- failure to provide these services will lead to serious conflicts about water issues causing
- social, economic, environmental losses at both local and international levels
water diversion
physical process of transferring water from one area to another
can differentially affect areas
extensive draining can lead to wetland drainage and habitat loss
groundwater mining
refers to removing water from an aquifer faster than it can be replenished.
extended periods of mining can lead to
land subsidence
lowering of the water table
salt-water intrusion of wells in coastal areas
salinization
increase in salinity caused by increased salt concentrations in soil
primarily a problem in areas where irrigation has been practiced for decades
The End