Some precipitation infiltrates the ground and percolates downward through spaces in soil, gravel, and rock until an impenetrable layer of rock stops it. The water in these spaces is called groundwater—one of our most important sources of freshwater and a key component of the earth’s natural capital.
zone of saturation
The spaces in soil and rock close to the earth’s surface hold little moisture. Below a certain depth, in the zone of saturation, these spaces are completely filled with water.
The top of this groundwater zone
the freshwater from precipitation and snowmelt that flows across the earth’s land surface and into rivers, streams, lakes, wetlands, estuaries, and ultimately to the oceans.
reliable surface runoff
the amount of surface runoff that we can generally count on as a source of freshwater from year to year.
After a river is dammed, the river’s flow creates an artificial lake, or reservoir, behind the dam.
involves removing dissolved salts from ocean water or from brackish (slightly salty) water in aquifers or lakes for domestic use.
A flood happens when water in a stream overflows its normal channel and spills into the adjacent area, called a floodplain.
Movement of salt water into freshwater aquifers in coastal and inland areas as groundwater is withdrawn faster than it is recharged by precipitation.
An unconfined aquifer is an aquifer with a permeable water table.
A confined aquifer is bounded above and below by less permeable beds of rock where the water is confined under pressure
Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater.
Natural replenishment of an aquifer by precipitation, which percolates downward through soil and rock. See recharge area.
Land area that delivers water, sediment, and dissolved substances via small streams to a major stream (river).
Water flowing off the land into bodies of surface water. See reliable runoff.
Any area of land allowing water to pass through it and into an aquifer. See aquifer, natural recharge.
center pivot sprinkler
Water usually pumped from underground and sprayed from mobile boom with sprinklers.
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Seeding clouds with tiny particles of chemicals to increase rainfall towing icebergs or huge bags filled with freshwater to dry coastal areas have all been proposed but are unlikely to provide significant amounts of freshwater.
Sinking of land (subsidence) from overpumping
Low Energy Precision Application sprinklers. A type of center pivot sprinkler.
An artesian aquifer is a confined aquifer containing groundwater that will flow upward through a well, called an artesian well, without the need for pumping.
consumptive use of water
Water abstracted which is no longer available for use because it has evaporated, transpired, been incorporated into products and crops, or consumed by man or livestock.
nonconsumptive use of water
Water that can be treated and returned as surface water, such as sewage
zone of depression
In the tropics or subtropics, an organized, but non-frontal, system of convective clouds around a low-pressure centre, with closed isobars and circulation.
The process of extracting groundwater beyond the safe yield or equilibrium yield of the aquifer