If Stationarity is Dead, What Do We Do Now?1

Abstract

Galloway, Gerald E., 2011. If Stationarity Is Dead, What Do We Do Now? Journal of the American Water Resources Association (JAWRA) 47(3):563‐570. DOI: 10.1111/j.1752‐1688.2011.00550.x Abstract: In January 2010, hydrologists, climatologists, engineers, and scientists met in Boulder, Colorado, to discuss the report of the death of hydrologic stationarity and the implications this might have on water resources planning and operations in the United States and abroad. For decades planners have relied on design guidance from the Interagency Advisory Committee on Water Data Bulletin 17B that was based upon the concept of stationarity. After 2½ days of discussion it became clear that the assembled community had yet to reach an agreement on whether or not to replace the assumption of stationarity with an assumption of nonstationarity or something else. Hydrologists were skeptical that data gathered to this point in the 21st Century point to any significant change in river parameters. Climatologists, on the other hand, point to climate change and the predicted shift away from current conditions to a more turbulent flood and drought filled future. Both groups are challenged to provide immediate guidance to those individuals in and outside the water community who today must commit funds and efforts on projects that will require the best estimates of future conditions. The workshop surfaced many approaches to dealing with these challenges. While there is good reason to support additional study of the death of stationarity, its implications, and new approaches, there is also a great need to provide those in the field the information they require now to plan, design, and operate today’s projects.

Analyzing the effects of excess rainfall properties on the scaling structure of peak discharges: Insights from a mesoscale river basin

“…It is important to stress that regional floodfrequency equations are used to predict future floods in terms of their probability of exceedance under the assumption that the hydroclimate system has been stationary and will remain so in the future and, as a result, the flood quantile scaling exponent and intercept, shown in equation (1), are assumed to remain unchanged. However, this assumption is currently under debate [e.g., Galloway, 2011;Lettenmaier et al, 1994;Milly et al, 2005Milly et al, , 2008Stedinger and Griffis, 2011;Villarini and Smith, 2010;Villarini et al, 2009]. Moreover, even if the stationarity assumption remains valid, regional flood-frequency equations cannot be used for predictions in basins that are located within ungauged regions because of the lack of historical peak discharge data required to estimate the flood quantile scaling intercept and exponent.…”

A Governing Framework for Climate Change Adaptation in the Built Environment

“…Although the issue continues to be debated within professional circles (Huitema et al 2009, Galloway 2011, nonstationarity is being incorporated into practice in the United States (Levin 2010 . The death of stationarity has important implications that go well beyond the evaluation of development projects.…”

Hydrologic Drought Decision Support System (HyDroDSS)

“…Interpretation of results of the retrospective streamflowdepletion analysis is based on the standard assumption that the historical record of streamflow can be used to estimate future conditions (known as stationarity), but recent research indicates that streamflow regimes may be changing with time Slack, 1999, 2005;McCabe and Wolock, 2002;Hayhoe and others, 2007;Milly and others, 2008;Lins and others, 2010;Hodgkins and Dudley, 2011;Galloway, 2011). Results for different flow percentiles are mixed, but streamflow-trend studies generally indicate that low flows have increased or are increasing at many index gages in the northeastern United States.…”