Water Policy (Dec 2021)
On the need for streamflow drought frequency guidelines in the U.S.
Abstract
Extreme drought and resulting low streamflows occur throughout the U.S., causing billions of dollars in annual losses, detrimentally impacting ecosystems, as well as agricultural, hydropower, navigation, water supply, recreation, and a myriad of other water resource systems, leading to reductions in both the effectiveness and resiliency of our water resource infrastructure. Since 1966, with the introduction of Bulletin 13 titled ‘Methods of Flow Frequency Analysis’, the U.S. adopted uniform guidelines for performing flood flow frequency analysis to ensure and enable all federal agencies concerned with water resource design, planning, and management under flood conditions to obtain sensible, consistent, and reproducible estimators of flood flow statistics. Remarkably, over one-half century later, no uniform national U.S. guidelines for hydrologic drought streamflow frequency analysis exist, and the various assorted guidelines that do exist are not reliable because (1) they are based on methods developed for floods, which are distinctly different than low streamflows and (2) the methods do not take advantage of the myriad of advances in flood and low streamflow frequency analyses over the last 50 years. We provide a justification for the need for developing national guidelines for streamflow drought frequency analysis as an analog to the existing national guidelines for flood frequency analysis. Those guidelines should result in improved water resources design, planning, operations, and management under low streamflow conditions throughout the U.S. and could prove useful elsewhere. HIGHLIGHTS Since 1966, the U.S. has adopted uniform guidelines for performing flood flow frequency analysis.; Over one-half century later, no analogous uniform national guidelines exist for hydrologic drought streamflow frequency analysis.; Existing low streamflow frequency methods are based mostly on flood frequency analysis and do not take advantage of the myriad of advances in both areas over the last 50 years.; Numerous innovations in low flow frequency analysis are described, using analogies to recent advances in flood frequency analysis.; A justification is provided for the need to develop national guidelines for streamflow drought frequency analysis.; Such guidelines would enable agencies concerned with water resource design, planning, and management under drought conditions to obtain sensible, consistent, and reproducible estimators of low streamflow statistics.;
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