Thursday, Sep 07, 2006 at 13:34
JohnR - Your on the money.
Just looked at you pics -
the desert wheel alignment one is interesting. Is it a result of a roll over?
To further the post - some hydrology 101.
Before rivers start to flow you need
water to start flowing across the land to channels - runoff . Runoff only occurs once the land and vegetation between where the rain fell and the channel can not absorb or store the
water received. In an urban area you can see this on your concrete driveway - the first few broad sprays with the hose result in wetting of the concrete - but no visible pooling or flow. All the little holes in the concrete absorb and store the
water, once they are full you get flow.
Concrete can be considered to be a
water proof surface compared to native bush land, so the trees, grasses and land can soak up quite a bit of
water before it runs off.
Similar to watering you garden, when you
water slowly all the
water is absorbed. Low intensity rainfall can be easily absorbed by the bush. Hi intensity rainfall ( like a jet on a hose rather than a spray) delivers to much
water for the slow absorption process to work - thus it gets converted run off quickly.
The other factor, assuming that there was sufficient rainfall to convert to runoff is travel time. I takes time for
water to travel across the land, down rivers and into storages. It's not quite as fast as tipping
water into he bath and seeing an instantaneous rise in level.
Of course the other explanation is that the data on he dam could be out of date or the instrumentation stuffed :)
You could probably check the inflow rivers to the dam to see if any
water is on its way. www.waterinfo.nsw.gov.au/drr/index.shtml
Cooee Paul
BTW - 0.000000001% change would probalby be beyond the accuracy (precision) of the measuremnt systems in place.
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