Reducing Waste Outflow to Motivate Water Conservation

Resource-consumption systems can be defined by a resource inlet, a control volume where the resource is used, and a waste outlet. Specific to water, many existing conservation strategies focus on reducing the in-flow of water into a control volume. Instead, this work explores reducing waste out-flow, which causes accumulation in the control volume. This strategy aims to motivate users to reduce resource in-flow in response to accumulation in the control volume, and thus modify behavior. To test this strategy, Amazon Mechanical Turk workers completed three randomly ordered handwashing simulations with different sink-outflow rates online. Study participants (N = 74) significantly reduced consumption of water when it accumulated quickly in the sink (p < 0.0001). Participants reduced water consumption, on average by 14% at lower outflow rates, as they decreased inflow rates to prevent sink overflow. Many pro-environmental behavior interventions are limited in their reliance on user motivation and intention to reduce resource consumption. In contrast, the reduced-outflow intervention significantly reduced water usage (p < 0.001) of individuals, regardless of self-reported daily pro-environmental behavior. This result suggests that the developed intervention relies less on user intention. Overall results support that reducing outflow can increase sustainable user behavior when properly executed. In-person testing is discussed as future work.