 The drought-resilient interscale portfolio planning, DRIP, model was developed to optimize urban water supply portfolios during droughts. The model takes into account climate and hydrologic variability, available technology options, and demand reduction measures to determine the most cost-effective and reliable water supply portfolios. The model was applied to Santa Barbara, California, where it found that drought intensity, rather than duration or frequency, drives cost increases, reliability risk, and regret of overbuilding infrastructure. A diversified technology portfolio that includes both rapidly deployable, decentralized technologies alongside larger centralized technologies minimizes water supply cost, while maintaining high robustness to climate uncertainty. This article was authored by Marta Zanielo, Sarah Fletcher, and Megan S. Malter.