Cannabis Home Cultivation and Residential Water Use: Evidence from New Mexico

On June 29, 2021, cannabis home cultivation of up to six plants per person became legal in the water-scarce, desert state of New Mexico in the southwestern United States. This study explores the likely effects of this policy change on residential water use, a topic on which the existing literature is silent. Survey data on home cultivation, associated water use and growing decisions and substitution with dispensary-sourced cannabis were collected from 532 New Mexicans in Spring 2023 to assess how legalization changed home cultivation behaviors, including water use. Residential water utility data, collected between January 2017 and April 2022 and consisting of 2,073,751 month-level observations from 35,351 households located in the state capital, Santa Fe, were used to study monthly residential water use pre- and post-HCL. The survey responses suggest increased water use following HCL, and that such effects are likely to persist and even increase in the future with 12% of respondents reporting past home cultivation, 19% reporting current home cultivation and 40% of respondents intending to home cultivate in the future. Retention rates in home cultivation are high — 90% of current home cultivators intend to home cultivate in the future, despite increasing access to dispensary-sourced cannabis. An increasing number of home cultivators grow indoors, most home cultivators use public utility water and dispensary-sourced cannabis is a substitute for many home cultivators. Regression analyses of the residential water use data show a modest increase in water use of around 105 gallons per household per month, following HCL, but lingering effects of the COVID-19 pandemic in Summer 2021 may exist. More specifically, residential water use was declining prior to COVID, experienced a surge during Summer 2020 and then continued its overall decline but at a slower rate following HCL. Associations between HCL and water use exhibit significant heterogeneity by Census-Tract-level per capita income and population density. These descriptive results highlight the need for future causal analyses of primary water utility data in order to disentangle the relationship between legalization of home cultivation and water use. In the meantime, educating home cultivators on water-saving cultivation methods, e.g., growing indoors, could help reduce any impact of legalizing cannabis home cultivation on water use, of particular importance to geographic areas with limited water resources. Survey responses indicate that increasing dispensary prices or decreasing dispensary access will increase home cultivation, with the relative amount of water used by commercial versus home cultivators also a topic for future research.