MadSci Network: Earth Sciences

Re: How to conserve clean rivers?

Date: Tue Apr 15 09:39:02 2003
Posted By: Alex Barron, Graduate Student, Ecology(Biogeochemistry)
Area of science: Earth Sciences
ID: 1049395714.Es

Joe -
Rivers are important parts of healthy ecosystems and preserving them is an 
important job.  It is a difficult one too because rivers are influenced by 
a very large area - their watershed.  The watershed (or catchment) includes 
all of the area which eventually supplies water to a river.  The watershed 
of most rivers contains all sorts of different land-uses from urban land to 
farms to forests.  Anything that happens in the watershed can eventually 
have an impact on the river.  Fertilizers and pesticides applied to fields 
can run off the surface or seem into groundwater which eventually enters 
the river.  Large areas of "impervious surface" like pavement and roofs 
prevent storm water from seeping into the soil;  this can cause much more 
rapid and frequent flooding of the river.  Likewise, rivers occur in 
networks and impacts in small tributaries can all add up to a much larger 
impact on the main river.  Thus, to really protect a river, you have to 
have to carefully protect and manage everything upstream!  Over the last 
few decades policy work has shifted towards managing rivers at the scale of 
watersheds but there is still a lot of progress to be made.
	Of all the area in a river's catchment, the habitat nearest to the 
river can be critical.   This riparian habitat is important to many 
organisms which live in or around the river.  It can serve to slow the 
runoff of water or sediment into the river.  Riparian wetlands can even 
remove some pollutants, like excess nitrogen, from water before it reaches 
the river.  This is why one of the first steps in river conservation and 
protection is to secure and protect strips of land adjacent to the river.
     Another important part of conserving rivers involves recognizing their 
dynamic nature.  Heraclitus once said that you cannot step into the same 
river twice - because they are always changing.  Natural river systems 
experience a wide range of flow conditions from low flows during drought to 
high flows during floods.  These variations in flow play important roles in 
affecting the structure of the river including the shape of channels and 
the distribution of sediment (which are in turn important for many of the 
organisms which live in the river).   Dams are one example of an 
anthropogenic (human-caused) disturbance which can reduce important high 
flow events.  There is considerable debate in the Northwestern US about 
what to do about dams' influence on rivers.  On a smaller scale, attempts 
to prevent the river from naturally drifting in it's path (by installing 
concrete embankments or other measure) can also alter flows away from 
natural conditions.
You might want to check the websites of the Environmental Protection Agency 
 or US Geological Survey for more information.  You can learn about the 
river watershed where you live at:

Please feel free to contact me if I can help more,

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