Mandatory urban rainwater harvesting: learning from experience.

Rainwater harvesting is effectively mandated in several urban areas of New Zealand. To understand the costs and benefits of rainwater harvesting from an end-user perspective, semistructured interviews were conducted with 14 homeowners in northern Auckland affected by these regulations. Residents report differences in four aspects of urban rainwater infrastructure - security of supply, water quality, the learning process and financial costs - that could represent key values for public acceptance. When responses are examined from the perspective of experience that has built empirical knowledge, participants explained how their satisfaction with rainwater harvesting increased over time. We hypothesise that for those lacking experience, urban rainwater consumption is a function of empirical knowledge and has initially rising marginal utility. Regulation that recognises the costs of social learning is likely to be a more effective pathway towards maximising the social benefits associated with integrated urban water management.