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Water Words

Terms and definitions relating to watersheds and the hydrologic (water) cycle

 

Ahupua'a

the Hawaiian equivalent of a watershed; a strip of land, usually between two ridges, that reaches from summit to sea

 

Aquifer

water bearing rock

 

Artesian well

a well drilled through impermeable strata to reach water; pushed by pressure from the underground aquifer, this water naturally rises to the earth’s surface

 

Boiling point

the temperature at which a liquid boils; for water this is 212 degrees Fahrenheit (100 degrees Celsius)

 

Desalination

removal of salt from seawater using a semi-permeable membrane; the membrane prevents the passage of salts as the water is forced through it

 

Dew

water vapor that condenses on sold surfaces that have cooled below the condensation point of water

 

Dew point

temperature at which water vapor condenses into cloud droplets

 

Dike

underground water barrier formed of nonporous, dense volcanic bedrock (basalt); can form water storage chambers

 

Erosion

the process by which soils loosen from the earth due to exposure to the elements; this topsoil eventually washes into the ocean, polluting the sea

 

Evaporation

conversion of liquid water through heat energy into water vapor

 

Fog drip

water vapor which condenses on cooler surfaces such as rocks and plants without falling to earth as rain

 

Ghyben-Herzberg lens

freshwater aquifer below a tropical ocean island; rainwater percolates through the island and floats above the surrounding seawater; this groundwater forms a root shape beneath the island, usually 40 times as thick below sea level as above.

 

Groundwater

any water beneath the earth’s surface; or a region of subsurface water that forms a saturation zone in which all pore spaces are filled with water

 

Hydrologic

concerning water on the earth’s surface, in the soil and underlying rocks and in the atmosphere

 

Intermittent stream

surface water that flows seasonally or only after heavy storms

 

Non-potable

lower quality water with high mineral content; safe for occasional inadvertent human consumption, conforms to state and federal requirements for this level

 

Orographic lifting

winds push moist air up against mountains or cliffs to produce clouds and precipitation

 

Percolation

rainwater slowly sinks through the island’s soil and porous volcanic rock; passage of a raindrop from mountain top to aquifer takes roughly 25 years.

 

Perched water

smaller volumes of groundwater trapped between layers of porous and less porous material

 

Perennial stream

permanently flowing water, fed by consistent rainfall

 

Porous

having small pores or holes through which materials such as water can pass

 

Potable

drinkable water of excellent quality, conforms to state and federal requirements

 

Precipitation

rain, snow, dew, frost, sleet, or hail condensed from atmospheric water vapor (clouds) and falling to earth

 

Pump

in relation to a forested watershed with cool and cloudy conditions, plants act as a pump to put water back into the soil

 

Rain shadow

area sheltered from prevailing winds and rain by adjacent high ground or mountains and hence an area of low rainfall

 

Soil anchor

roots of trees and plants serve as an anchor to hold soils in place and prevent erosion

 

Sponge

the soil, roots, mosses, ferns and leaves of a forested watershed act as a sponge that soaks up precipitation.  When the sponge is fully saturated, it slowly releases water into underground water tables and streams

 

Spring

water that emerges from an underground source to feed streams or release freshwater directly into the ocean

 

Surface water

water flowing or collecting at the level of the earth’s surface, such as streams, rivers, springs, or lakes

 

Transpiration

evaporation of water from the surface of a plant

 

Umbrella

Trees and plants serve as an umbrella to intercept rain and wind, thus reducing the erosive capacity of precipitation and storms

 

Water table

level under the ground in permeable or porous rock below which the ground is completely saturated with water