Water Cycle

Hydrologic Cycle
Water is always on the move. Rain falling
where you live may have been water in the ocean
just days before. And the water you see in a river
or stream may have been snow on a high
mountaintop.
Water can be in the atmosphere, on the land,
in the ocean, and even underground. It is
recycled over and over through the water cycle.
In the cycle, water changes state between liquid,
solid (ice), and gas (water vapour).
Most water vapour gets into the atmosphere
by a process called evaporation. This process
turns the water that is at the top of the ocean,
rivers, and lakes into water vapour in the
atmosphere using energy from the Sun. Water
vapour can also form from snow and ice through
the process of sublimation and can evaporate
from plants by a process called transpiration.
The water vapour rises in the atmosphere
and cools, forming tiny water droplets by a
process called condensation. Those water
droplets make up clouds. If those tiny water
droplets combine with each other they grow
larger and eventually become too heavy to stay
in the air. Then they fall to the ground as rain,
snow, and other types of precipitation.
Most of the precipitation that falls becomes
a part of the ocean or part of rivers, lakes, and
streams that eventually lead to the ocean. Some
of the snow and ice that falls as precipitation
stays at the Earth surface in glaciers and other
types of ice. Some of the precipitation seeps into
the ground and becomes a part of the
groundwater.
Water stays in certain places longer than
others. A drop of water may spend over 3,000
years in the ocean before moving on to another
part of the water cycle while a drop of water
spends an average of just eight days in the
atmosphere before falling back to Earth.