A Sensitivity Analysis of an Investment Model Used to Determine the Economic Benefits of Rainwater Tanks

The community-based investment model created by Coombes et al. [2000a; 20021 that allows economic comparisons between a traditional base scenario for urban water cycle services and alternative scenarios that include rainwater tanks is examined. The economic benefits derived from the use of rainwater tanks vary with the price of mains water and the cost to augment mains water supply headworks systems. The magnitude of the economic benefits accruing to the community from widespread installation of rainwater tanks was dependent on real interest rates, the value of stormwater savings that result from the use of rainwater tanks and the installation costs of rainwater tank systems. Nonetheless it was shown that the use of rainwater tanks provided greater economic benefits to the community than the traditional water supply and stormwater management options in the majority of cases considered.