The Hydrologic Cycle • Water occurs as a solid, liquid and gas • Amount of water is fixed • The places where water resides are called Reservoirs • Water constantly moves from one reservoir to another
The Hydrologic Cycle: Pathways • Evaporation • Evapotranspiration • Condensation • Precipitation • Runoff • Infiltration/Percolation
RESERVOIRS Comparison of the amount of water supply held in each of the major reservoirs If the total earth’s water supply was a 55 gallon drum
Groundwater • What happens to precipitation once it reaches the ground • infiltration • percolation • Water filling pore space, cracks & crevices in rocks- Porosity • Aquifer- Geologic unit that can store, transmit and yield appreciable amounts of water
Porosity and Permeability • Porosity • % of rock or sediment that is open (void spaces) • ability to hold water • Permeability- ability to transmit water
Movement of ground water • Moves in response to differences in water pressure & elevation • Velocity influenced by • Slope of water table • Permeability
Groundwater Movement • Darcy’s Law • Q= KA (h1-h2)/(l) • Where Q is discharge; A= BxW • K is hydraulic conductivity • (h1-h2)/(l) is hydraulic gradient
After pumping in a well stops, the water level slowly recovers its previous level and the cone of depression disappears
Water Use:Trends in population and freshwater withdrawals by source, 1950-2000.
Water Pollution • Degradation of water quality • Biological • Chemical • Physical • Based on the intended use of the water • Attainment vs. non-attainment
Clean Water Act Sec.304(a)(1) : • The Administrator, after consultation with appropriate Federal and State agencies and other interested persons, shall develop and publish, within one year after the date of enactment of this title (and from time to time thereafter revise) criteria for water quality accurately reflecting the latest scientific knowledge • (A) on the kind and extent of all identifiable effects on health and welfare including, but not limited to, plankton, fish, shellfish, wildlife, plant life, shorelines, beaches, esthetics, and recreation which may be expected from the presence of pollutants in any body of water, including ground water; • (B) on the concentration and dispersal of pollutants, or their byproducts, through biological, physical, and chemical processes; and • (C) on the effects of pollutants on biological community diversity, productivity, and stability, including information on the factors affecting rates of eutrophication and rates of organic and inorganic sedimentation for varying types of receiving waters.
Common Sources of Groundwater Pollution/Contamination • Leaks from storage tanks and pipes • Leaks from waste disposal sites (landfills) • Seepage from septic systems • Accidental spills • Agricultural activities • Intrusion of salt water • Mine spoils and tailings • Irrigation • Injection wells • Acid mine drainage • Runoff- urban, industrial, agricultural
Water Pollutants • Biological Oxygen Demand • Pathogenic Organisms • Nutrients • Oil • Chemicals • Heavy Metals • Radioactive materials • Sediments • Thermal Pollution
Pollution and Environmental Health World Health Organization(WHO); World Resources Institute(WRI); United States Environmental Protection Agency (USEPA); United States Geological Survey(USGS); Botkin & Keller
Contamination, Pollution and Toxicity • Any material that is above background level in the environment (introduced) • Any material that is above background level in the environment and that causes a deleterious effect on humans and ecosystems
Units of Measurement • Depending on whether it is found in water, soil or air • Reported as percent (%), ppm, ppb, ppt (parts per million, billion or trillion) • 0.01% = 100ppm = mg/kg or mg/L • Milligram (mg) (1/1,000 g) • Microgram (mg) (1/1,000,000g) • Reported as either volume, mass or weight
There are two very distinctquestion sets • Will a given material harm the environment? • Will a given material harm us?
Factors Influencing Toxicity • Additive 2 + 2 = 4 • Synergistic 2 + 2 = 10 • Antagonism 2 +2 = 0
What determines the impactof Exposure? • Length of, period of, time • Concentration - dose • Recurrence – is contact repeated • Frequency of recurrence – daily/yearly • Life cycle sensitivity differences - infant/adult • Physical condition of victim – robust/sickly • Presence of other hazards - synergism
Point vs. Non-Point Sources • As authorized by the Clean Water Act, the National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States • Point sources are discrete conveyances such as pipes or man-made ditches • Industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters • In most cases, the NPDES permit program is administered by authorized states
Point vs. Non-Point Sources • Non-point source (NPS) pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources • NPS pollution is caused by rainfall or snowmelt moving over and through the ground • As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and groundwater
Non-Point Source Pollutants • Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas • Oil, grease, and toxic chemicals from urban runoff and energy production • Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks • Salt from irrigation practices and acid drainage from abandoned mines • Bacteria and nutrients from livestock, pet wastes, and faulty septic systems • Atmospheric deposition are also sources of non-point source pollution
Federal Water Legislation • Refuse Act 1899 • Federal Water and Pollution Control Act 1956 • Fish and Wildlife Coordination Act 1958 • National Environmental Policy Act 1969 • Water Quality Improvement Act 1970 • Federal Water Pollution Control Act (Clean Water Act) 1972
Water Quality Standards • Under §303(c) of the Clean Water Act a water quality standard is described as comprising: (1) the designated beneficial uses (aquatic life, wildlife, recreation, fishing, agriculture, water supply, etc.) of a water body and (2) the criteria (numeric and narrative) necessary to protect these uses. States and Tribes are required by CWA §303(c)(2)(B) to adopt criteria for CWA §307(a) toxic pollutants for which EPA has published CWA §304(a) criteria, and/or recommendations and methodology based on the latest science.
Federal Water Legislation • Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) 1980 • Hazardous and Solid Waste Amendments to the Resource Conservation and Recovery Act (RCRA) 1984 • Water Quality Act 1987 • Safe Drinking Water Act 1996
Water Quality Standards • Maximum Contaminant Level- MCLs • Based on toxicity • Usually lethal dose (LD50) for some target organism or toxic dose (TD50) • Maximum Contaminant Level Goal-MCLGs
Categories of Pollutants • Biological- Infectious Agents • Heavy Metals • Organic compounds • Particulates • Radiation • Thermal
Biological Hazards • Of all the environmental hazards humans encounter, the most formidable adversaries remain the microorganisms -- viruses, bacteria, protozoa, and parasitic worms • Up to 17 million deaths per year are attributable to these infectious and parasitic agents, almost all in the developing world, along with hundreds of millions of cases of illnesses