Robustness of hydroclimate metrics for climate change impact research

Abstract

Metrics based on streamflow and/or climate variables are used in water management for monitoring and evaluating available resources. To reflect future change in the hydrological regime, metrics are estimated using climate change information from Global Climate Models or from stochastic time series representing future climates. Whilst often simple to calculate, many metrics implicitly represent complex physical process. We evaluate the scientific validity of metrics used in a climate change context, demonstrating their use to reflect aspects of timing, magnitude, extreme values, variability, duration, state, system services, and performance. We raise awareness about the following generic issues (a) formulation: metrics often assume stationarity of the input data, which is invalid under climate change; and do not always consider potential changes to seasonality and the relevance of the temporal window used for analysis; (b) climate change input data: how well are the physical processes relevant to the metric represented in the climate change input data; what is the impact of bias correction on relevant spatial and temporal scale dependencies and relevant intervariable dependencies; how realistic are the data in representing sequencing of events and natural variability in large‐scale ocean–atmosphere systems; and (c) decision‐making context: are rules and values that frame the decision‐making process likely to remain constant or change in a future world. If critical climate or hydrological processes are not well represented by the metric constituents, these indices can be misleading about plausible future change. However, knowledge of how to construct a robust metric can safeguard against misleading interpretations about future change. This article is categorized under: Science of Water > Methods Science of Water > Water and Environmental Change Science of Water > Water Extremes

Using a Scenario‐Neutral Framework to Avoid Potential Maladaptation to Future Flood Risk

“…Management plans can thus be updated using successive generations of model projections without undertaking additional impact modeling. Brown et al () and Ekström et al () emphasize that indicator(s) and/or threshold(s) used to assess system performance under climate stress should be specified with local stakeholders. Risk assessment can then be tailored to meet community/management needs.…”

Improving hydrological projection performance under contrasting climatic conditions using spatial coherence through a hierarchical Bayesian regression framework

“…The model has been used successfully across a wide range of hydro-climatic conditions across the world, including the crash testing of model performance under contrasting climatic conditions (Coron et al, 2012), and the simulation of runoff for revisiting the deficiency in insufficient model calibration (Fowler et al, 2016). For example , Fowler et al (2016) verified that conceptual rainfall-runoff models were more capable under changing climatic conditions than previously thought. These characteristics make the GR4J particularly suitable as a starting point for implementing modifications and/or improving predictive ability under changing climatic conditions.…”

“…In the second step, the wet years were defined as the complement of the dry years in the historical records. A similar approach to define the dry and wet years was used by Fowler et al (2016).…”

Concurrent Hydroclimatic Hazards from Catchment to Global Scales

“…The use of metrics, for both (multi)hazard/risk quantification, is nowadays common practice (e.g. Cutter et al, 2008;De Luca et al, 2019b;Ekström et al, 2018;Forzieri et al, 2016;Hao et al, 2018;Russo et al, 2015). One of the main advantages of metrics is that they can be useful for translating observed or projected impacts of one or more natural hazards to the wider community, nonexperts included.…”

“…This chapter therefore introduces a pragmatic approach for detecting and quantifying the characteristics of extreme MBF episodes and their links with ETCs. It also uses new and established metrics that could be relevant for assessing hydroclimatic impacts (Ekström et al, 2018). GB has been used as a pilot area, but the techniques deployed are applicable wherever there are gauged river flow data.…”