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BI 105A Environmental Biology. Professor Jill Nissen Montgomery College Fall 2006. Water: A Limited Resource. Chapter 14. Why study water?. We depend on water for our survival and convenience Drinking Cooking Washing Travel over water Agriculture

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bi 105a environmental biology

BI 105AEnvironmental Biology

Professor Jill Nissen

Montgomery College

Fall 2006

why study water
Why study water?
  • We depend on water for our survival and convenience
    • Drinking
    • Cooking
    • Washing
    • Travel over water
    • Agriculture
      • Irrigation accounts for the greatest percentage of the world’s water usage (71%)
    • Manufacturing
    • Mining
    • Energy production
    • Waste disposal
water supply on earth
Water Supply on Earth
  • Water covers ¾ of the Earth’s surface, but
    • 97.5% of water is saltwater
    • Most of the fresh water is frozen (ice caps and glaciers)
    • Less than 1% of water is available for humans
    • The available fresh water is distributed unevenly, leading to regional water supply problems
water terms
Water Terms
  • Surface Water
    • Fresh water in streams, rivers, lakes, ponds, reservoirs, and wetlands:
      • Areas of land that are covered with water all or part of the year
    • Replenished by runoff:
      • The movement of fresh water from precipitation and snow melt to rivers, lakes, wetlands, and ultimately, the ocean
water terms con t
Water Terms (con’t)
  • Watershed (also called a drainage basin)
    • The area of land drained by a single river or river system
  • Groundwater
    • The supply of fresh water under Earth’s surface stored in aquifers:
      • Underground caverns and porous layers of sand, gravel, or rock in which ground water is stored
  • Water Table
    • The upper surface of the saturated zone of groundwater
water resource problems
Water Resource Problems
  • Too much water
  • Too little water
  • Poor water quality (Chapter 22)
too much water
Too much water
  • Flood plains are areas bordering a river that are subject to flooding
  • Humans have caused increased flooding and damage by flooding by removing plant cover and developing along flood plains
too little water
Too Little Water
  • Approximately 40% of the worlds population lives in arid or semiarid lands, primarily Asia and Africa
  • Population growth intensifies the problem:
  • More food = more irrigation, more grazing
overdrawing surface waters
Overdrawing Surface Waters
  • When surface water is overdrawn (greater than 30%), the organisms in fresh water ecosystems suffer, wetlands dry up, and estuaries become saltier
aquifer depletion
Aquifer Depletion
  • Aquifer depletion is the removal of more groundwater than can be replenished by precipitation or snow melt
    • Lowers the water table
    • Drains the aquifer dry, loss of water source
    • Leads to
      • Subsidence
      • Sink holes
      • Saltwater intrusion
saltwater intrusion
Saltwater Intrusion
  • Saltwater intrusion is the movement of seawater into a freshwater aquifer located near the coast; caused by aquifer depletion
  • The result is water that is unfit to drink
  • Salinization is the gradual accumulation of salt in the soil; usually caused by improper irrigation
  • The result is decreased soil productivity
water problems in the u s
Water Problems in the U.S.
  • Mono Lake
    • Surface water diverted to Los Angeles had lowered water level and increased salinity
    • In 1994, the state of CA required the L.A. Department of Water and Power to reduce water export by 20%
  • The Colorado River Basin
    • Population growth in Colorado, Utah, and Wyoming threatens the regions water supply
    • The water available for Mexico is insufficient
  • The Ogallala Aquifer
    • This is the largest groundwater deposit in the world, but farmers are drawing water from it 40 times faster than nature can replenish it
water management
Water Management
  • Providing a Sustainable Water Supply
  • Sustainable water use seeks to provide water to future generations without damaging ecosystems.
dams and reservoirs
Dams and Reservoirs
  • Dams and Reservoirs
    • most dams are designed to form reservoirs from which the flow can be regulated
    • Benefits
      • Ensure a year round supply of fresh water for human use
      • Control floods in downstream areas
      • Generate electricity (renewable energy source)
    • Drawbacks
      • Alter the quantity and quality of water upstream and downstream of dam, leading to habitat degradation or destruction
      • Interfere with fish migration
water recycling
Water Recycling
  • Water recycling, also known as water reclamation or water reuse, is reusing treated wastewater for beneficial purposes such as agricultural and landscape irrigation, industrial processes, toilet flushing, and replenishing a ground water basin.
  • Source:
environmental benefits of water recycling
Environmental Benefits ofWater Recycling
  • Decreases diversion of freshwater from sensitive ecosystems (e.g., Mono Lake)
  • Decreases discharge to sensitive water bodies
  • Can be used to create or enhance wetlands and riparian (stream) habitats
  • When used for agriculture, naturally stimulates production which reduces fertilizer use
  • Source:
reducing water waste
Reducing Water Waste
  • Techniques for reducing agricultural water waste
    • Microirrigation (=trickle irrigation)
    • Planting level fields
    • Scheduling irrigation according to rainfall and soil moisture
    • Using reclaimed water for irrigation
  • Techniques for reducing industrial water waste
    • Recycling water
    • Implementing stricter pollution control laws
reducing water waste1
Reducing Water Waste
  • Techniques for reducing water waste in homes and buildings
    • Educating consumers in water conservation methods
    • Using water-saving fixtures
    • Developing economic incentives to save water
    • Charging for water according to usage
    • Charging what the water actually costs
water facts
Water Facts
  • The average household uses 350 gallons of water per day, or 127,400 gallons per year
    • If all U.S. households installed water-saving fixtures, water use would decrease by 30 percent, saving an estimated 5.4 billion gallons per day.
    • This would result in dollar-volume savings of $11.3 million per day or more than $4 billion per year!
  • More than 50% of household water is used outdoors to maintain the lawn!
    • Xeriscaping is a method of landscaping with rocks and plants that need very little water.
    • Traditional landscaping requires large amounts of water, fertilizer, and pesticides - Time and Money!
  • Source:
review objectives
Review Objectives

The Importance of Water• Describe surface water and groundwater, using the following terms in your descriptions: wetland, runoff, drainage basin, aquifer, and water table.

Water Use and Resource Problems• Describe the role of irrigation in world water consumption.• Define flood plain and explain how humans exacerbate flood damage.• Relate some of the problems caused by overdrawing surface water, aquifer depletion (including saltwater intrusion), and salinization of irrigated soil.

Water Problems in the United States• Relate the background for each of the following U.S. water problems: Mono Lake, the Colorado River Basin, and the Ogallala Aquifer.• Define reclaimed water.

Water Management• Define sustainable water use.• Contrast the benefits and drawbacks of dams and reservoirs.

Water Conservation• Give examples of water conservation by agriculture (including microirrigation), industry, and individual homes and buildings.