With a six-fold increase in global water use over the last century, the availability of fresh water has emerged as a critical issue for environmental sustainability. Water scarcity is an issue that policymakers must address with urgency — states like California already face one of the worst droughts in history. The United Nations estimates that by 2025 over two-thirds of the world’s population will reside in regions considered water-stressed. Although policymakers have made great strides in developing new approaches to stave off this pending crisis, the traditional methods such as educational awareness campaigns and variable rate pricing have not always curbed people’s day to day water use as expected.

But what about using our knowledge of human behavior?

Given the successful application of behavioral interventions or “nudges” in other environmental contexts, such as reducing energy consumption using social norms, we might expect that that these tools could also work well for water conservation. However, there could be fundamental differences about water and energy consumption that would limit the applicability of interventions from one sector to another. Is water demand for the most part fixed – driven by necessity — or can we effectively nudge people’s behavior to reduce water consumption?

Together with the World Bank, ideas42 had an interesting opportunity to answer this question in Belén, Costa Rica in 2014. To better understand what was leading to high household water consumption, we first conducted focus groups with residents of Belén, which revealed key behavioral insights.  Participants discussed the importance of water conservation and the essential role that households play in water resource management. However, they did not have a good sense of how much water they were actually using, nor did they have concrete plans to reduce their own consumption. From these and other insights, we determined that there was scope to use nudges to change water use behavior.

Furthermore, in exploring Belen’s water use, we stumbled upon another compelling question: how do we design low-tech nudges in resource-constrained settings? Many previous interventions in reducing energy use have relied on personalized messages based on an individual household’s usage habits. Unfortunately, that was not possible in Belén. Because we had to make our nudges low-tech and even simpler, our final interventions featured stickers and postcards that could be placed on any utility bill without requiring personalization.

We tested our designs against a control group, and found remarkable results. Providing residents with feedback about how their water use compares to neighbors reduced monthly water consumption by up to 5.6%. Furthermore, prompting residents to take action on their intentions to conserve water also reduced monthly household consumption by up to 5.6%. If our treatments were scaled across all households in Belen, this would translate to a conservation of 6,720 cubic meters of water each month. That’s 94,080 washing machine loads, 188,000 showers or 222,000 dishwasher loads saved in a single month.

Outside of the incredible results, this study is significant for two reasons. First, it suggests that some behaviors translate across different settings and cultures. It is well-documented that the use of social norms is effective in curbing energy consumption in the United States. However, until now, that did not necessarily mean that such interventions would work in other contexts – perhaps there is something different about how people use water versus electricity, or the habits of people outside the United States. Our diagnosis of human behavior (and test results) in Belen revealed that we’re not that different after all. Using social norms for water consumption in Latin America had comparable effects to what we know works with energy conservation in the United States, providing evidence that human behavior is more similar than we often think.

Second, the study shows the massive potential for impact that behaviorally-informed solutions can have without using a lot of resources. By making simple, low-tech modifications to existing monthly billing letters, we were able to achieve effects that have only previously been demonstrated through highly customized and technology-intensive approaches.

If our behavioral intervention is scaled to millions of consumers, it could become part of an effective, low-cost approach to making global water use more sustainable for years to come. For full results from this study, click here.