Research and Planning
What factors affect water supply?
A number of key planning variables underpin ACTEW's water planning. It is important to take these all into account so that changes to climate or population for example are incorporated when making predictions of our future water needs or when introducing new levels of water restrictions.
The six key planning variables outlined below are reviewed yearly:
- climate change and variability;
- impact of bushfires on inflows to ACT reservoirs;
- future population growth in Canberra and Queanbeyan and the possibility of
servicing additional areas in NSW;
- reduction targets in per capita water use set by the ACT Government in Think
water, act water;
- environmental flow requirements; and
- acceptable levels for the duration, frequency and severity of water restrictions
during times of drought.
Climate change and variability have now become an integral part of water security planning across Australia. Based on advice from the CSIRO, ACTEW, in its 2004-05 Future Water Options studies, took a conservative approach by assuming that the CSIRO 2030 worse case scenario in terms of climate had already occurred – a reduction of 30% in inflows. In a more recent review, remodelling using current extremely low inflows, gave an almost 50% reduction in average long-term inflows. The ACT has recently experienced inflows reduced by about 60% (see below).
Responding to Climate Change
Climate change and variability have now become an integral part of water security planning across Australia. Based on advice from the CSIRO, climate variability was predicted for the year 2030. This information is used with rainfall and climate data spanning over 100 years. In its 2004-05 Future Water Options studies, ACTEW took a conservative approach by assuming that the CSIRO 2030 worse case scenario in terms of climate had already occurred – a reduction of 30% in inflows. In the recent review, remodelling using current extremely low inflows, gave an almost 50% reduction in average long-term inflows. The ACT has recently experienced inflows reduced by about 60% (see below).
To put the level of inflows into perspective, in 2006 the ACT had approximately 26 gigalitres (GL) of inflows into the reservoirs, yet 62 GL was used.
In contrast, the historical inflows had averaged about 200 GL per year. One important factor in the historical inflows is the very high level of variability (see below).
There is increasing evidence that the recent climatic patterns have resulted in significant
declines in inflows and may now occur more frequently and with greater variability. It is also possible however that the current situation is no more than a temporary decline within the CSIRO forecast and resultant average decline in inflows. Even if the chance of severe reductions continuing is small, ACTEW must plan ahead for long-term reductions.
This drought has resulted in significant water restrictions being imposed in Canberra and Queanbeyan. This combined with the current low storage levels highlight the uncertainty when predicting future water requirements. As such, it is prudent to obtain greater certainty in the amount of water available for consumption by creating more supply than living with high level restrictions for extended periods.
What is ACTEW currently doing to secure water supply?