 The health of a water system is determined by the balance between physical, chemical, and biological variables.

 Physical Variables  Temperature  Turbidity  Water movement  Chemical Variables  Dissolved Oxygen (D.O.) and other gasses  pH  Nitrates and phosphates  Salinity

Biological Variables  Looking at bioindictors : organisms such as the types of fish, insects, algae, plants, and other aquatic life (macro invertebrates).

 Temperature of the water determines how much oxygen can be held. Warmer waters hold less dissolved gasses. Colder water holds more dissolved gasses.  Very warm water may not be able to hold enough oxygen for organisms to be able to survive.  Ex. Thermal pollution- Warm water from industry being dumped into lakes and rivers causing organisms to die. Runoff from hot asphalt.

 The measure of how clear water is.  Suspended solids in water.  Can be associated with organic pollution that might include pathogenic materials.

Sediment-laden water from an inflow stream entering a much clearer lake. Tuscaloosa, Alabama, USA

 Oxygen that is dissolved in Water (DO)  Gets there by diffusion from the air, and byproduct of photosynthesis in algae and aquatic plants.  In surface water, used by all forms of aquatic life.  Measured to assess the health of lakes and streams.  Can vary with seasons.  When DO levels go down, sensitive animals move away, weaken, or die.  High DO levels make potable (drinkable) water taste better.

 7 neutral  acid  base (alkaline)

 Impact of minerals such as iron, aluminum, ammonia, or mercury is amplified or diminished based on the pH of the water.  When acidic waters come into contact with certain chemicals and metals, it makes them more poisonous than normal.  Especially important in water treatment processes. Have to maintain a certain range.

 Both are essential plant nutrients, but can pose a threat to humans if levels are high in drinking water.  Also, can cause algal blooms in lakes.  Sources of nitrates in surface water:  Runoff contaminated with fertilizers, septic tank leakage, sewage, etc…  Sources of phosphates in water:  Human and animal waste, laundry detergents and cleaning supplies, industrial waste.

 Run off from nitrates and phosphates into fresh water lakes and streams can lead to Eutrophicaton -an increase in nutrients in a pond or lake. Leads to algal blooms and decrease DO.

1. Treatment makes water safe for drinking.  People get water from a variety of sources, including wells, reservoirs, lakes, and rivers  The EPA (Environmental Protection Agency) sets standards for safe drinking water and determines the concentration of various substances that can be in drinking water.  Water treatment plants make water safe for drinking by removing harmful substances and killing harmful organisms.

2. Wastewater is treated and released.  Sewage system – collects and treat huge amounts of wastewater from cities and towns.  Septic system – treats wastewater from an individual home or business. Solids are broke down by bacteria or settle to the bottom of the septic tank.

3. Water pollution comes from many sources.  Human activities add so many chemicals, minerals or organisms to a water supply that cannot be made safe to drink, it is considered to be polluted.  Point-source pollution – enters water from known source, such as factory that spills chemicals into a river  Nonpoint-source pollution – pollution whose source is hard to find or is scattered, such as runoff from streets or farms

4. Water pollution can be prevented  Business and individuals can do a number of things to prevent or reduce water pollution.  Industry and Transportation – factories and shippers can reduce the use of toxic materials and recycle or reuse wastes.  Agriculture – farmers can grow crops without pesticides and keep animals away from water sources.  At home – people can properly dispose of hazardous wastes, uses non toxic materials, and eat organic food so that lower amounts of pesticides and herbicides enter the water supply.

1. Water shortages are a global problem  Some dry parts of the world, such as northern African and the Middle East, have a constant water problem.  Other areas may experience water shortages during droughts.  People in regions that are affected by drought or that do not have enough water must import food they cannot grow themselves.  Jordan imports 91%, Israel 87%, Egypt 40% of grain needed.

2. Overuse can cause water shortages  As the population grows, water is becoming scarcer.  Most fresh water worldwide is used in agriculture.  Overuse of ground water for irrigation is depleting aquifers faster than they can be refilled.

3. Fresh water can be conserved  Each American uses an average of 168 liters of water each day.  Knowing how you use water is the first step toward conserving it.  Water can be conversed in homes, businesses, and schools and on farms.

4. People can balance water needs and uses  Different people often have different opinions on how to use water.  Public officials and experts can help to manage water use and enforce fair laws.  When there is not enough water for a country to grow food, international organizations help to provide food for people.