Taking roof loads out of the stormwater system would certainly reduce
the flash flooding in urban waterways.
Presumably the water in residential tanks would to some degree replace
water that is extracted from the waterways feeding the urban water
system.
Regards, Laurie.
On 25/08/2008, at 11:47 AM, Peter Shute wrote:
There is, apparently, a proposal to "drop" water tanks as part of
Victoria's water strategy. This is front page news in today's Age:
http://www.theage.com.au/national/desal-and-water-tank-wars-20080824-41et.html
and there is a full page about it in the Opinion and Analysis
section of the paper (not online yet).
They suggest that previous studies underestimated the amount of
water household tanks could collect by 2/3, so their installation
should be encouraged, not halted.
The main article says:
"Tanks can be important in reducing stormwater run off, which
damages and pollutes waterways."
Does this sound right? I would have thought that if you remove the
fairly clean roof component of the flows in urban waterways, but
still allow runoff from the roads, then the water that does reach
the local creeks will be far more polluted than before.
I've been wondering what effect it would have on the volumes
reaching local waterways if all roof runoff was removed, as the tank
proponents seem to be advising. I'm guessing at least a 10%
reduction, far more in inner urban areas. So are we really "saving"
water by doing this, or just stealing it from the local crakes and
rails (etc)?
Does anyone have any thoughts about this, and whether I need to
worry about it at all? Should this issue be part of the water tank
debate, or is the possible effect too small to matter?
Peter Shute
www.birding-aus.org
birding-aus.blogspot.com
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