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Understanding
Watersheds
Water
is an essential element for sustaining life. Rivers, streams and
lakes are the "lifeblood" of our environment. When our
waterways are polluted, we know the system is in need of repair.
When waterways are healthy, we know the environment can support
a diversity of plant and animal species. Adequate water supply
and the biological diversity that the watersheds' waters support
is the key to socially healthy and ecologically balanced futures.
If water
is the "lifeblood" of environment, the land that surrounds
that water is the "muscles and bones" of the environment.
Together, land and water make a watershed, a whole system. A "watershed"
is the term describing an area of land united by the flow of water,
nutrients, pollutants and sediments, moving downslope to the lowest
point, through a network of drainage pathways that may be underground
or on the surface. Generally, these pathways converge into a stream
or river system that becomes progressively larger as the water
moves downstream. Watersheds
can be large or small. Every stream, tributary, or river has an
associated watershed, and small watersheds aggregate together
to become larger watersheds. Watershed boundaries are delineated
using topographical maps showing the stream channel network. The
watershed boundaries will follow the major ridgeline around the
channels and meet at the bottom where the water flows out of the
watershed commonly referred to as the watershed mouth.
The connectivity
of the stream system is the primary reason why aquatic resources
need to be managed at the watershed level. Connectivity refers
to the physical connection between hillslopes and stream channels,
between surface water and groundwater, and between wetlands and
these water sources. Because the water moves downstream in a watershed,
any activity that affects the water quality, quantity, or rate
of movement at one location can change the characteristics of
the watershed at locations downstream.
Watersheds
also link human dwellers in intricate social-ecological relationships.
Both factors - the biophysical attributes and the policy and institutional
environments - shape people's livelihoods and interactions within
the watershed. A watershed is healthy when it is capable of maintaining
its self-organizing complexity and diversity through time. Managing
for healthy watersheds requires active participation of resource
users and other interested groups to collaborate in generating
information to guide management planning and action.
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