Using hydrologic landscape classification and climatic time series to assess hydrologic vulnerability of the western U.S. to climate.

Chas E Jones Jr,Keith A Sawicz,Laurel E Stratton,Philip E Morefield,Christopher P Weaver,Scott G Leibowitz,Randy L Comeleo

doi:10.5194/hess-25-3179-2021

Chas E Jones Jr, Keith A Sawicz + Show 5 more

Open Access

https://doi.org/10.5194/hess-25-3179-2021

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Abstract

We apply the hydrologic landscape (HL) concept to assess the hydrologic vulnerability of the western United States (U.S.) to projected climate conditions. Our goal is to understand the potential impacts of hydrologic vulnerability for stakeholder-defined interests across large geographic areas. The basic assumption of the HL approach is that catchments that share similar physical and climatic characteristics are expected to have similar hydrologic characteristics. We use the hydrologic landscape vulnerability approach (HLVA) to map the HLVA index (an assessment of climate vulnerability) by integrating hydrologic landscapes into a retrospective analysis of historical data to assess variability in future climate projections and hydrology, which includes temperature, precipitation, potential evapotranspiration, snow accumulation, climatic moisture, surplus water, and seasonality of water surplus. Projections that are beyond 2 standard deviations of the historical decadal average contribute to the HLVA index for each metric. Separating vulnerability into these seven separate metrics allows stakeholders and/or water resource managers to have a more specific understanding of the potential impacts of future conditions. We also apply this approach to examine case studies. The case studies (Mt. Hood, Willamette Valley, and Napa–Sonoma Valley) are important to the ski and wine industries and illustrate how our approach might be used by specific stakeholders. The resulting vulnerability maps show that temperature and potential evapotranspiration are consistently projected to have high vulnerability indices for the western U.S. Precipitation vulnerability is not as spatially uniform as temperature. The highest-elevation areas with snow are projected to experience significant changes in snow accumulation. The seasonality vulnerability map shows that specific mountainous areas in the west are most prone to changes in seasonality, whereas many transitional terrains are moderately susceptible. This paper illustrates how HL and the HLVA can help assess climatic and hydrologic vulnerability across large spatial scales. By combining the HL concept and HLVA, resource managers could consider future climate conditions in their decisions about managing important economic and conservation resources.

Highlights

A stable and predictable water supply is imperative for food security, ecosystem sustainability, economic stability, and even national security (National Intelligence Council, 2012) and is related to the threats of increased flooding, droughts, wildfire, and more extreme temperatures (Mancosu et al, 2015; Mekonnen and Hoekstra, 2016)
hydrologic landscape (HL) maps for the remainder of the conterminous U.S are available and are included in the Supplement (Fig. S6; subsurface permeability maps are not available for all of the lower 48 states)
The hydrologic landscape (HL) concept is useful for gaining a better understanding of hydrologic behavior at the assessment unit and watershed scales across large geographic regions

Summary

Introduction

A stable and predictable water supply is imperative for food security, ecosystem sustainability, economic stability, and even national security (National Intelligence Council, 2012) and is related to the threats of increased flooding, droughts, wildfire, and more extreme temperatures (Mancosu et al, 2015; Mekonnen and Hoekstra, 2016). The hydrologic landscape vulnerability assessment described provides a relatively simple approach for assessing hydrologic vulnerability based upon inferences of hydrologic behavior (using hydrologic landscapes) in response to climatic impacts This approach can be applied across large geographic regions and can potentially benefit numerous sectors, including environmental, economic, and other ecosystem services. A study by Cook et al (2015) found a growing risk of unprecedented drought in the western U.S based on temperature projections and no clear pattern in future precipitation. This sampling of the existing research highlights the cross-cutting hydrological changes that are occurring across the nation and illustrates how different sectors and geographies are experiencing different impacts

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