William & Mary Environmental Law and Policy Review
Abstract
Climate change is shifting seasons. Spring comes earlier, fall comes later, rainy seasons are shorter and more intense, and summers are hotter and longer. In the American West, winter precipitation increasingly falls as rain, leading to a smaller snowpack and an earlier, more intense runoff followed by a longer and drier dry season. For irrigators— the highest volume water users—growing seasons are shifting earlier, weather is less predictable, and precipitation is increasingly inconsistent. The end of a relatively static climate marks the end of static water rights. The shifting seasons pose serious challenges to our ability to manage water systems.
The legal infrastructure of water management is ill-suited for a changed climate. Western water right systems were built on an assumption of climate stationarity that is no longer true. Everything from basin adjudications based on outdated annual flows to the design of western water rights themselves may have to change to accommodate our shifting climate.
In this Article, we examine the seasonality of water rights. Water rights allow diversion during a particular time of year, often the historic growing season or peak runoff season. These restrictions are an inherent part of the water right, as important as the total volume or rate of water withdrawal. As the shifting climate alters runoff patterns, many water rights will be left high and dry with insufficient water available during the allowed season of diversion.
Although state water agencies have begun to think about new conditions on future water rights, the real problem is addressing existing water rights to accommodate the shifting seasons. Here, we examine a selection of sixty-one water rights in the Sacramento River watershed, California’s largest river system. These water rights show weaknesses in California’s current approach to managing water rights for a changing climate. Based on this examination, we consider options for western states to improve their water right resilience in the face of our new climate reality.