Do the theories of planned behaviour and protection motivation provide probabilistic sufficient and necessary conditions for residential water conservation? Combined use of PLS-SEM and NCA.

Understanding the key determinants of residential water conservation is crucial for designing effective water demand management policies in arid and semiarid regions. While extant literature has frequently identified such determinants using statistical significance and correlations, there is a growing emphasis on understanding these determinants using probabilistic sufficiency and deterministic necessity logics. Integrating these two logics to test an integrated model of the Theories of Planned Behaviour (TPB) and Protection Motivation (PMT), this study identifies and differentiates the probabilistic sufficient and necessary conditions or "must have" factors that need to exist for residential water conservation intentions and behaviours to occur. Combining partial least square structural equation modeling (PLS-SEM) and necessary condition analysis (NCA) to analyse 346 responses from residents in Australia's Northern Territory (NT), we found that attitude, self-efficacy, perceived vulnerability, and response efficacy are probabilistic sufficient and necessary conditions for water conservation intention. Self-efficacy and intention further provided probabilistic sufficient and necessary conditions for water conservation behaviour. Based on the findings, the TPB-PMT constructs are categorised into four groups and the bottleneck table is used to indicate the minimum levels of the identified necessary conditions that must exist to realise the highest levels of water conservation intention and behaviour. This study further draws on these two logics to conduct a combined importance-performance map analysis (cIPMA) to provide guidelines for policymakers and water authorities on how to better prioritise water management actions to improve residential water conservation intentions and behaviours.