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Round and Round and
Round It Goes …
Note: This is the first of a series of articles
that will explore our water resources, their natural qualities and tendencies, and the way that human
activities affect their quantity and quality.
There is a fixed amount of water on the earth and in the
atmosphere. Among the many places that water is temporarily
stored are the air, soil, plants, wetlands, lakes, oceans, groundwater
reservoirs and glaciers. However, that water is far from
static. Water makes its rounds, moving from the atmosphere
to the earth’s surface through plants back to the atmosphere, or
through the soil into deep groundwater reservoirs or aquifers, or into
rivers which carry it on a long pathway toward the ocean where it again
evaporates back to the atmosphere so that it can begin another
journey. This never-ending journey is called the Water Cycle, or
hydrologic cycle (see figure).
Water begins its journey from the atmosphere
to the earth as precipitation. Some water that reaches the
ground soaks into, or infiltrates, the soil. The water that makes
it into the soil can take one of many pathways but is primarily “lost”
as evaporation from the bare soil surface, taken up by plants which
transpire the water back to the atmosphere, or moves past the depth of
plant roots into groundwater reservoirs known as aquifers.
Because of our heavy clay soils and shale/limestone bedrock not much
water in Clermont County makes it into aquifers.
That part of precipitation that doesn’t soak
into the soil runs off of the surface into ditches, streams or
rivers. These surface channels eventually deliver the water to
lakes or oceans from which it eventually evaporates back to the
atmosphere.
In Clermont County, we receive about 43
inches of precipitation  annually
(see distribution of rainfall in figure). Of that, about 15
inches run off the land surface directly to streams and rivers, 2 – 3
inches are temporarily retained on the surface in puddles and the like
(and then evaporate), and about 26 inches enter or percolate into the
soil. Of the 26 inches that infiltrate the soil, about 24 inches
is returned to the atmosphere by evaporation from the soil or
transpiration through plants. The remaining 2 inches becomes part
of the groundwater system.
Human activities change the way that water is
transported, transformed and stored, sometimes by plan, other times by
accident. For example, humans intentionally dam rivers to store
water for drinking, recreation, and power generation. Conversely,
human activities may compact or harden the soil surface which reduces
the amount of water that can infiltrate or soak in. This type of
surface hardening (also called impervious area) increases the amount of
surface run-off which increases the amount of water being carried to
ditches and streams. Increasing the flow in our surface channels
may result in the unintended consequences of increased soil and
streambank erosion, and downstream flooding.
In the next article, we will explore the way
that nature manages the quantity and quality of run-off. In what
ways does nature manage how quickly water is released to creeks?
In what ways does nature treat stormwater?
For
more reading about the Water Cycle, check out:
Websites
for kids at:
http://www.kidzone.ws/water/
http://www-k12.atmos.washington.edu/k12/pilot/water_cycle/
http://www.epa.gov/OGWDW/kids/index.html
Water Resources of Clermont County and Ohio’s Hydrologic Cycle fact
sheets at: http://ohioline.osu.edu/aex-fact/
The Hydrologic Cycle and Precipitation in Ohio fact sheets at:
http://www.dnr.state.oh.us/water/pubs/fs_div/
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