P

pH-measure of the relative acidity or alkalinity of water. A pH of 7 is neutral, lower is increasing acidity, higher is increasing alkalinity or more basic.
Per capita use-average amount of water used per person over a 24 hour day.
Percolation-movement of water into openings or pores in rock or soil and its downward movement by gravity; contributes to ground water replenishment.
Permeable-ability of a material to allow the passage of a liquid, such as water, through sands and gravels or rocks. Water moves more quickly through sands, whereas clay is impermeable.
Porosity-the water-bearing capacity of subsurface soil or rock.
Potable water-(Greek for “river”); water of a quality suitable for drinking.
Precipitation-rain, snow, dew, frost, hail and sleet.
Public water system-by law, a drinking water system that serves 15 or more connections or 25 or more people; must meet EPA standards for treatment and water quality. http://www.epa.gov/ebtpages/watedrinkingwater.html
Public water use-from a public water supply, used for firefighting, municipal parks and pools, and landscaping and other public city uses.

R

Raw water-water in its natural state, prior to any treatment for drinking.
Recharge-water naturally added to an aquifer by infiltration or percolation into the ground; can also occur through man made projects. (See artificial recharge.)
Reclaimed water-treated water from wastewater treatment facilities that can be used for irrigation, landscaping purposes or to recharge aquifers.
Recycled water-used more than one time before it passes back into the hydrologic system. (See gray water, reclaimed water.)
Reservoir-pond, lake or basin (natural or artificial) for the storage and control of water. Lake Pleasant, Saguaro, Apache, Canyon and Roosevelt Lakes are some of the reservoirs for storing the Valley's water.
Resource-something valuable that can be used to support life or make it easier. Water is a naturally occurring resource, and part of the “Basic 3” needed to live (food, water and shelter).
Riparian-the land and habitat, plants and animals adjoining a stream or river.
River-flow of water of considerable volume in a water course, larger than a brook, creek, stream, wash, rillito, or pantano.
Runoff-the water that falls as precipitation in a watershed and runs off into rivers and streams. May be stored in lakes and reservoirs and contributes to recharge where it infiltrates into the soil. In Phoenix, runoff enters sewers to wastewater plants for treatment and further use as reclaimed water.