Overallocation, conflict, and water transfers

Grantham and Viers' article 100 years of California's water rights system: patterns, trends, and uncertainty Grantham and Viers (2014 Environ. Res. Lett. 9 084012) makes valuable contributions by mapping the disparities between California's legal allocations of water and actual water availability. This perspective article explains that those results both over- and understate the potential for conflict, but they nevertheless provide useful information for water policy analysts and educators. The results also provide compelling evidence of the need for water transfers and, unfortunately, the practical difficulties associated with achieving those transfers.