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

TotalSurface waterGround water

*Figure has error in textbook

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.

WetlandsGeneral 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.

Threatened Groundwater of Long IslandAbundant groundwater contained in two “outstanding” aquifers:1.Upper, young glacial deposits yielding abundant supply at shallower than 30 m depth2.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.

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.

Coral Reefs – An indicator of human pollution?

Hanauma Bay, Oahu, is in poor ecological shape as a result of:1.Oceanic warming2.Excessive coastal development3.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.

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

Pathogenic OrganismsWaterborne 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.

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.

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.

Nutrients