Tampering
with nature
Throughout the course of history,
mankind has attempted to conquer his environment sometimes
without understanding the full consequences of his actions
or the impacts that the changes could have on future generations.
In this respect, Manitoba's history is no different than the
history of many other places. The following article illustrates
how actions taken to address one set of challenges can create
new and different problems.
Several decades ago it was decided
that many of the natural waterways in Manitoba required straightening
in order to protect farmland, buildings, roads and other structures
from flooding during spring runoff or during heavy rains.
The adjoining map shows drainage activities around Lake Dauphin.
As can be seen the streams start
off as nice meandering waterways. They start in Riding Mountain
National Park, where the topography is steeper and where natural
boundaries are protected. However, as the streams leave the
National Park boundary and enter the flatter prairie topography,
some portions have been straightened. This was done to control
runoff.
The straightening of these streams
has caused an increase in the speed of the water during periods
of heavy flow and this increased speed has increased the sediment
carrying capacity of the water. This sediment, laden with
pesticides, fertilizers, animal waste and other pollutants,
ultimately ended up in Lake Dauphin.
Water quality in the lake has declined
dramatically. Until 1950, the lake supported a large commercial
and sport walleye fishery, but fish harvests have subsequently
dropped by 90 to 95 percent. This drop in fish populations
is due to the damage to fish habitat caused by the stream
alterations as well as to over-fishing.
Another consequence of increasing
the runoff rate means that surface water does not have as
much time as before to naturally infiltrate into the water
table. This results in slower aquifer recharges in some areas.
It also results in a reduction of stream baseflow.
The good news is that many of these
problems were recognized. A Stream Rehabilitation Program
was developed in 1992 to rehabilitate riparian zones and unstable
stream reaches within the seven major tributaries of the Lake
Dauphin watershed. Between 1993 and 1996, 36 kilometres of
straightened channels were rehabilitated and 14 cooperating
livestock producers implemented new farm layouts and practices.
Under a signed stewardship agreement, landowners committed
to maintain the project works and a minimum 10-metre riparian
corridor for at least 10 years.
This Stream Rehabilitation Program
has been adopted as a model for other watershed level management
programs throughout Manitoba. The program has raised public
awareness of fisheries, wildlife, recreation, agriculture
and land stewardship issues. |
