Drought Attribution Studies and Water Resources Management

February 28, 2023

Drs. Rolf Olsen (recently retired from the US Army Corps of Engineers, Institute for Water Resources), Mike Dettinger (CW3E) and Jason Giovannettone (Sisters of Mercy of the Americas Inc.) have published an essay titled “Drought Attribution Studies and Water Resources Management” in the 2021-and-2022 issue of the American Meteorological Society’s special report series Explaining Extreme Events from a Climate Perspective (EEE). This report series annually (in normal times) presents detailed assessments of whether, and how, human-caused climate change has affected the strength and likelihood of specific extreme events in the previous year(s). These assessments generally are highly technical statistical analyses of observations of the particular extreme weather events studied in the context of climate-model simulations of climate conditions under current atmospheric greenhouse-gas concentrations. Typically, their aim is to determine “Has this extreme event (storm, heat wave, drought, or whatever) during the past year been made more likely or extreme by climate changes to date? If so, by how much?” The new essay shares information about how droughts are managed by water managers with climate-change attribution scientists in an attempt to help scientists to focus—when possible—on aspects of droughts and drought management that matter most to resource managers. Like the old story of the man looking for his keys under the street light because it’s easier to see there, it is easy for analysts to end up focusing on aspects of drought (and other extremes) that are the most readily evaluated or attributed to climate change; this essay amounts to a request, with some background information, for attribution analysts to focus the questions they address on the most actionable aspects of drought, both recent and future.

Specifically, well-focused attribution studies can provide insights into changing drought processes in ways that help inform plans and responses in the form of improved future water-supply estimates, reservoir-management decisions (like FIRO), and triggers used to initiate immediate drought responses in various state to local drought-management plans. The essay discusses each of these management challenges, and then surveys several recent droughts around the US, each of which illustrates a relevant drought mechanism that is likely to be worsened in future droughts by ongoing climate changes. Specifically, the recent droughts discussed include the mechanisms and responses to long-term precipitation deficits in recent California droughts; the various forms (and impacts) that snow droughts now take, e.g., in Washington State; and the high-temperature-driven 2017 drought in the northern Great Plains. In each case, knowing (a) what it was about those droughts and mechanisms that made them more impactful on water supplies and stores, and (b) how water managers go about addressing those conditions, can help researchers to design future attribution studies to be most action-able by resource managers. The essay’s authors are members of the American Meteorological Society’s Water Resources Committee, and this drought-focused essay is a “sequel” to a similar EEE essay by committee members that addressed flood-management issues and information needs for attribution studies (Vano et al. 2018).

Olsen, J. R., Dettinger, M. D., & Giovannettone, J. P. (2023). Drought Attribution Studies and Water Resources Management, Bulletin of the American Meteorological Society, 104(2), E435-E441. doi: https://doi.org/10.1175/BAMS-D-22-0214.1

Vano, J. A., Miller, K., Dettinger, M. D., Cifelli, R., Curtis, D., Dufour, A., Olsen, J. R., & Wilson, A. M. (2019). Hydroclimatic Extremes as Challenges for the Water Management Community: Lessons from Oroville Dam and Hurricane Harvey, Bulletin of the American Meteorological Society, 100(1), S9-S14. doi: https://doi.org/10.1175/BAMS-D-18-0219.1