Additional Information Resources of Mt. Desert Island, Maine
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Without the water cycle, Earth would be a barren waste. No mosses, no flowers, no trees, no butterflies, no frogs, no birds, no squirrels, no deer, no fish, no towns, no people. Everything we value most depends on water. And water depends on water vapor in the atmosphere condensing as skywater, falling, collecting, flowing, creating the lifeblood of our planet.

To nourish life, water must not only fall from the sky, it must collect where plants can use it, in the soil. Water in the soil picks up dissolved nutrients from the minerals and organic matter it flows through, delivering those nutrients to plants through their roots. Without soil to hold water and to share it with plants through the growing season, the families of life on which we depend would not exist.

The value of a stream or pond extends beyond its banks across the valley that collects skywater, stores it for plant and animal use, and allows the excess to seep into a channel and be carried away for the benefit of life in streams, ponds, estuaries, bays, gulfs, and the ocean.

The land basin that collects and stores water on which plants and animals depend, and later delivers a portion of that water into an associated stream system for the benefit of water-borne life-is called a watershed. Some of the water falling on a watershed sinks down and is stored as groundwater in underground reservoirs known as aquifers.

A great deal of skywater evaporates, especially if it collects on the surface faster than the soil can absorb it. Evaporation carries water into the atmosphere as vapor, an invisible gas, where it is recycled, eventually condensing on wind-borne particles such as dust and spores, and falling as precipitation again, and again, and again. Evaporation is a purifying process that prevents pollutants from rising into the air. Evaporation assures the long-term stability of climate itself, and the survival of all forms of life.

In the green, heavily forested State of Maine, much of the water that falls on a watershed flows through the stems of trees and other plants into their leaves. There, after helping sunlight turn carbon from the air into sugar and starch by the process of photosynthesis--the source of all life as we know it--it returns to the air as vapor by the process of transpiration, the evaporation of internal fluids from a plant's leaves or needles. Transpiration lowers pressure in a plant's leaves so that a flow of moisture from the roots is drawn upward to replace what is lost to the air.

Skywater that falls on a watershed and is not stored as groundwater, doesn't evaporate, and isn't returned to the air by transpiration, this water flows through the soil according to the pull of gravity and the lay of the land, to seep into the banks of a stream, pond, or wetland lower down in the watershed.

A watershed receives, stores, recycles, and delivers water to the roots of plants through the growing season, and feeds water into streams, ponds, estuaries, and ultimately the ocean.

A given water molecule may stay in the ocean for a million years or more, but sooner or later it will evaporate, probably when currents bear it to the surface of one of the warmer parts of the ocean near the equator. There, rising currents of warm air create great circulating spiral winds of moist air which, when they cool, fill with drops of water. When they grow large enough, those drops fall to earth as rain, landing in the ocean or in a watershed on land, driving the water cycle, maintaining life on land, in streams, ponds, and wetlands, and in the ocean.

The flow of water is the flow of life. The water cycle is the story, not only of a colorless fluid, but of all plant and animal life on our colorful planet. To protect life on Earth, it is essential to protect the flow of water at every stage of the cycle.