"Nature Guide Journal"
2 November 2000
Water, water everywhere!
Every school child draws the water cycle: water evaporating from the sea, then blown
inland, forming clouds that rain down to journey back to the sea.
This is no small issue. Planet-wide, something on the order of 10 million billion
gallons of water are transported through the water cycle each year. (That's a one with 16
But there's more to that simplistic view we remember from childhood. The water cycle
involves the soil, plants, and animalsincluding us. This life-giving circle is
better viewed as a complex three-dimensional circuit with nearly infinite branches and
off-shoots that involves most of the atmosphere and the upper levels of earth's crust.
Probably the most complex section of the water cycle is what happens when the rain (or
snow, or hail, or sleet) reaches the ground. Certainly, much of it runs off our trees and
roofs and down our hills and sidewalks. But quite a bit of itusually most of
itsoaks into the ground.
Under the surface, the water binds itself to the soil particles until the soil is
saturated. Or until a plant takes it up. The water picked up by plant roots is either
chemically converted into more plant or is passed through the leaves back into the air.
Water is pulled deeper underground until it meets a barrier. The water collects above
of the barrier; the "water table" is the top of that layer of water.
Rivers, streams, and lakes are not just "where the water collects on the
land," they're usually more accurately described as "where the water table
breaks through the surface."
Wetlands occur where the water table is at or near the surface. Long thought to be
"wastelands," we now know wetlands perform many vital functions. The life and
chemistry of wetland soils clean impurities out of the water. Wetland soilsand the
wetland's position in the cyclecollect and hold floodwaters, then slowly disperses
them. Wetlands along the edges of open waters buffer the shoreline from erosion. Wetlands
produce and recycle huge amounts of plant and animal life, much of which is passed on to
adjacent land and water habitats. Further, rich wetland ecosystems are critical permanent
or nursery habitat for myriad species of plants and animals.
And while we may envision a water cycle that takes in whole continents at a regular
pace, that's not always the case. The cloud/ground/cloud loop can be quite short. For
example, ground or pavement moistened by evening fog may readily evaporate in the next
morning's sun, the water producing frail wisps as it dissipates back to the air.
Conversely, some water may be locked up in places of the water cycle for millions of
years; in ice or deep underground.
So here we are, an intimate part of the water cycle, as we step over puddles of surface
water, eat plants that grew on soil water, drink water stored in lakes or deep below the
surface, and enjoy wildlife nurtured in wetlands.
Related articles on this site include salmon,
wetland functions, and ponds and lakes.