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Water Use – Instream vs. Offstream vs. Consumptive

Water Use – Instream vs. Offstream vs. Consumptive. Definitions Consumptive use : use, but don’t return (ag. products) 1995: US = 100 bgpd In-stream use : used in source (navigation, hydro, recreation) Off-stream use : use and return (irrigation, livestock, etc.). Trends in Water Usage.

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Water Use – Instream vs. Offstream vs. Consumptive

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  1. Water Use – Instream vs. Offstream vs. Consumptive Definitions • Consumptive use: use, but don’t return (ag. products) 1995: US = 100 bgpd • In-stream use: used in source (navigation, hydro, recreation) • Off-stream use: use and return (irrigation, livestock, etc.)

  2. Trends in Water Usage Surface water withdrawals exceed ground water withdrawals Water withdrawals leveled off ~1980, but population has continued to increase = better water management practices Thermoelectric is greatest fraction of use by category. Total Surface water Ground water *Figure has error in textbook

  3. Wetlands General term referring to swamps, marshes, bogs, prairie potholes, vernal pools. Operational definition – land that is either inundated by water or is saturated to a depth of a few centimeters for at least a few days most years. Perform many functions: buffer against coastal erosion, natural filters of sed/nutrients/pollution, natural sponge – floodwater storage, habitat for diverse flora/fauna, groundwater recharge/discharge regions. The point – removal of water “upstream” may decrease functionality of wetlands.

  4. Threatened Groundwater of Long Island • Abundant groundwater contained in two “outstanding” aquifers: • Upper, young glacial deposits yielding abundant supply at shallower than 30 m depth • Lower, interbedded sands, clays, and silts (the Magothy formation) – artesian conditions in places. • Problem #1: Population stresses on supply – groundwater pumping has decreased fresh water table and promoted salt water intrusion to deep aquifer beneath Nassau county. • Problem #2: Upper aquifer pollution from urbanization. Landfills located on permeable sandy soils.

  5. Q: What is water pollution?A: Degradation of water quality as measured by bio., chem., or phys. criteria.Q: What is a pollutant?A: Any substance of which an identifiable excess is known to be harmful to desirable living organisms.

  6. Coral Reefs – An indicator of human pollution? • Hanauma Bay, Oahu, is in poor ecological shape as a result of: • Oceanic warming • Excessive coastal development • Pollution of nearshore waters • Coral reefs thrive in clear, nutrient-poor waters. • Rising nutrients assist coral-preying organisms. • Sediment (developmental runoff) blocks sunlight. • 60% of world’s coral reefs are threatened – indicating the ocean is much more sensitive than previously thought.

  7. Oxygen-demanding waste Dead stuff decays, i.e. is consumed by bacteria which need oxygen. So, in a stream, when there is an excess of dead stuff, the high bacteria activity needed will lower oxygen levels driving further death (fish, etc.) What kind of feedback is this? positive or negative? Commonly measure B.O.D. (Biochemical Oxygen Demand) to assess water quality. BOD=mg/Liter of Oxygen consumed in 5 days at 20˚ C

  8. Pathogenic Organisms • Waterborne Human diseases: cholera, typhoid infections, hepatitis, dysentery • Monitor pathogens by a proxy – human fecal coliform bacteria • common constituents of human intestines and waste • most, but not all, are harmless • Examples: • * E. coli outbreak of 1993 – contaminated meat from Jack-in-the-Box franchises around the western US (Wash., Calif., Nevada, Idaho) • * 1993 – 400,000 cases of cryptosporidiosis near Milwaukee • Waterborne illness still kills thousands outside the U.S. where separation of sewage and drinking water is not well-practiced.

  9. Nutrients Phosphorus & Nitrogen – two examples Related to land use Released from fertilizers, detergents, and sewage treatment plants. High concentrations result in eutrophication – rapid increase in abundance of plant life/algae, which block sunlight, killing plants below, which drives higher B.O.D. further killing living organisms in natural waters.

  10. Nutrients In Hawaii, marine eutrophication along the coast, resulting from agricultural practices may be killing the goose that has laid the golden egg – the beaches are becoming covered with dead algae that has washed up on shore to rot and serve as a home for irritating insects.

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