Shaping the 2014 Colorado River Delta pulse flow: Rapid environmental flow design for ecological outcomes and scientific learning

In 2014, the United States and Mexico jointly delivered an environmental flow to the Colorado River Delta, as authorized in a 2012 binational water management agreement known as Minute 319. The agreement specified a volume of water, the source of the water, that the water should be delivered as a pulse flow, and that the objectives of the pulse flow were to pilot environmental restoration and learn about the hydrologic and ecological responses to water delivery into the Colorado River Delta. The Minute did not specify the characteristics of the pulse flow, but rather specified a process, calling on a group of stakeholders, including federal, state, and local water managers as well as non-governmental conservation organizations from both countries, to develop a flow delivery plan.The flow delivery plan was developed, approved, and executed in an exceptionally short period of time, with limited scientific data, under numerous operational constraints. The unique feature that made the hydrograph development a success is the exceptionally close interaction between policy makers, water managers, and scientists, driven by clear objectives for ecological outcomes and scientific learning. In describing this case study, we also document the inevitable tradeoffs that led to a flow design that best met the needs of all parties while fully meeting the needs of none. In so doing, we rationalize the characteristics of the flow delivery hydrograph.