THE IMPACT OF RESTRICTIONS ON REGIONAL URBAN DEMAND

摘要

The water savings achieved under water restrictions in Victoria were previously estimated by a VicWater technical working group. This group estimated that a 14%, 44%, 67% and 98% reduction in restrictable demand occurred at Stages 1 to 4 of restriction respectively. These figures were based on demand information collated for the Melbourne supply system prior to the 2006/07 drought and were recommended for application throughout Victoria. This paper presents information collated from a number of non-metropolitan urban water utilities to assess the water savings achieved under restrictions in recent drought years, including 2006/07, for comparison against the VicWater working group results. It also presents a simple but rigorous method for assessing the statistical significance of reductions in demand using two sample t-tests on residuals of observed minus estimated unrestricted demand. Whilst there was generally a greater reduction in restrictable demand under Stage 1 restrictions than anticipated, the wide range of consumer response to restrictions meant that there was insufficient evidence to alter the previous VicWater recommendations. The ability to draw firmer conclusions from the analysis could be improved by adopting a consistent assessment method across all water utilities in Victoria and Australia in the future.