What effect would a change in our water usage have on dam levels?
We have analysed the data from the SCA on water usage and dam inflows in Sydney's dam and come up with the following analysis.
We have considered several alternate water usage scenarios. i.e. What would our dam levels be if our usage had been 20% (or 50%) less
than what it has been (since 2001). Such a drop (20%) in usage could be achieved through water efficient devices and rainwater tanks.
A drop of 50% would require more drastic changes in water usage.
|Hypothetical usage since 11.2001||Available water||% full all dams||1 year change GL(%)|
|20% More|| 1430.6||55.41
|As is || 2500.5
|20% Less|| 2551.8||98.84
|50% Less|| 2553.2||98.89
Of course if such a drop in water usage had occurred in 1998 when the dams last filled, the difference would be more dramatic.
What has been saved so far?
The NSW government has stated that the water restrictions so far have saved 12% on water usage. So, without these savings, the current dam levels would
be similar to the "20% more usage" levels as seen above. You can see the slight change in usage levels in the fact that the usage is dropping on
the following graph (smoothed out on a 1 year rolling average).
Overall, however, inflows have been considerably less than usage, despite this drop. In order to level out our dam levels a much more significant drop in
usage is required. You can see this from the hypothetical usage table above, but also from the following graph of cumulative usage and inflow. The graph
shows the total amount of inflow to our dams since 2001 verses the total amount of usage since 2001. The reduction in usage can be seen in the fact
that the usage graph (now) isn't as steep as what it was. In order to get dam levels back up to 80%, the two lines must meet again!
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