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as runoff, or immediately evaporates. Much of the water that
infiltrates or runs off eventually finds its way back to the
atmosphere via evaporation from soil, lakes, and streams. In
addition, some of the water that soaks into the ground is absorbed
by plants, which later release it into the atmosphere. This process
is called transpiration. Because both evaporation and transpiration
involve the transfer of water from the surface directly to the
atmosphere, they are often considered together as the combined
process of evapotranspiration.
More water falls on land as precipitation than is lost by
evapotranspiration. The excess is carried back to the ocean mainly
by streams—less than 1 % returns as groundwater. However, much
of the water that flows in rivers is not transmitted directly into
river channels after falling as precipitation. Instead, a large
percentage first soaks into the soil and then gradually flows as
groundwater to river channels. In this manner, groundwater
provides a form of storage that sustains the flow of streams
between storms and during periods of drought. When precipitation
falls in very cold areas—at high elevations or high latitudes—the
water may not immediately soak in, run off, or evaporate. Instead,
it may become part of a snowfield or a glacier.
In this way, glaciers store large quantities of water. If
present-day glaciers were to melt and release their stored water,
sea level would rise by several tens of meters worldwide and
submerge many heavily populated coastal areas. Over the past 2
million years, huge ice sheets have formed and melted on several
occasions, each time changing the balance of the hydrologic cycle.

Task 3. Answer the following questions (in written
form).
0. Water on Earth is found in many forms. What are they?
0. What process is called infiltration?
0. Much of the water that flows in rivers is not transmitted
directly into river channels. Where does it flow then?

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