States throughout the West have rushed to legalize marijuana over the last four years. The biggest by far is California, where recreational use of the drug became legal on January 1. The states are clamoring for the tax revenue in these new markets, but they seem less concerned with how they may affect water resources. Even now, no state regulators can answer a basic question about marijuana cultivation: How much water will this new industry consume?  Yet state and local governments are permitting tens of thousands of indoor and outdoor marijuana farms without such answers.