Water

WATER //The most essential element to life on Earth// Water covers about 70% of the Earth's surface, but over 97% is saltwater. Only a tiny fraction of the 3% freshwater is available for human use. Water availability used to determine the best places to live, which explains why many major cities are located near waterways.


 * Potable Water:** unpolluted freshwater that is suitable for drinking.

25% of the world population does NOT have access to safe drinking water, which results in 5-10 millions deaths each year.

Moisture in the atmosphere condenses into droplets that fall to the Earth as rain or snow, supplying all living things with its life-sustaining properties. Water, flowing over the Earth as a surface water or through soil as groundwater, returns to the oceans, where it evaporates back into the atmosphere to begin the cycle again. __Important terms of the Hydrolic Cycle:__ Runoff: surface water that moves across the surface of the land and enters streams and rivers. Groundwater: the water that fills teh spaces in the substrate (pores in layers of sediment or rock). Aquifer: the porous layer that becomes saturated with water. unconfined aquifer: usually occurs near the land's surface where water enters the aquifer from the land above it. confined aquifer: bounded on both the top and bottom by layers that are impervious to water and is saturated with water under greater-than-atmospheric pressure. Water table: the top of the layer saturated with water. Aquiclude: an impervious confining layer. Aquitard: a confining layer through which water can pass. Porosity: a measure of the size and number of the spaces in the substrate.
 * THE HYDROLIC CYCLE**

Increases in tourism and urbanization affect coastal cities. Evaporation is faster when water is used in power plants, reservoirs, or for irrigation. Removing vegetation (logging, agriculture, etc.) increases runoff, decreases infiltration. In cities where there is a lot of pavement there is increased runoff and decreased infiltration.
 * Human Influences on the Water Cycle:**

In North American urban areas, most of the domestic water comes from a municipal water system, whereas rural areas can use clean, untreated water from wells. Domestic uses include drinking, air conditioning, bathing, washing clothes, washing dishes, flushing toilets, and water lawns and gardens. The average North American uses about 100 gallons of domestic water a day. Groundwater accounts for about 37% of the water used in agriculture, surface water about 63%. Irrigation is the biggest comsumptive use -- accounts for about 80% of all water consumption in North America. Amount of water used for agriculture is always increasing. 4 types of irrigation: surface/flood, spray, trickle, subirrigation. Maintaining the structures (dams, canals, pipes, etc.) is expensive, even though the construction costs are typically low due to government aid. Irrigation requires a ton of energy! Accounts for almost half the water withdrawals in the U.S. Accounts for less than 20% of water consumed in U.S. Ex. Electric-power generating plants use water to cool steam so that it changes back to water, but many can use saltwater. Does not remove water but makes use of it in its channels and basins. Mainly used for hydroelectric power, recreation, and navigation. Something about dams. Over 25,000 miles of commercial waterways. Transport of resources
 * Kinds of Water Use**
 * Domestic
 * Agricultural
 * Industrial
 * Clean Water Act -- protects the waters of the U.S. from pollution. It sets water-quality standards for surface water and limits effluent discharges into the water.
 * In-Stream

SEE CHART ON PAGE 347 Problem of providing clean drinking water AND disposing of waste. Wastes from home are mainly organic matter from garbage, food preparation, cleaning of clothes/dishes, & human wastes.
 * Kinds and Sources of Water Pollution**
 * Municipal Water Pollution