This study examines the relative water demand and potential streamflow impacts of cannabis cultivation, residential use, and non-cannabis agriculture in rural northern California watersheds. While cannabis has received much attention for its potential impact on sensitive aquatic species, the relative contribution to overall water demand in watersheds where cannabis is farmed remains poorly understood. Using spatial and temporal analyses across multiple watersheds, this study assesses how water use for cannabis cultivation compares to other major water users in terms of total demand, spatial distribution, and interannual fluctuations.