Opportunity Title:

Using Water Isotopes to Determine Flow Sources and Test How Landscape Characteristics Inform the Hydrologic Behavior of the Columbia River

Research Area:

Water

EPA Lab/Center/Office:

National Health and Environmental Effects Research Laboratory (NHEERL)

Location:

Corvallis, OR

Duration:

6 - 12 months

Brief Summary:

We propose to use stable isotopes of surface water to explore how well hydrologic characteristics of landscape units reflect their contribution to flow within the Columbia River Basin.

Opportunity Description:

Stable isotopes of surface water vary spatially, reflecting an integration of precipitation inputs and evaporation. These spatial isotopic patterns are called Isoscapes, which can be useful for determining how and when spatially distributed water sources contribute to flow within major water bodies (Brooks et al. 2012). Additionally, hydrologic classification based on watershed characteristics is an approach that has been applied towards understanding hydrologic behavior and watershed influences on freshwater resources (Wolock et al. 2004, Wigington et al. 2012). This is based on the concept that hydrologic function (e.g., streamflow response) is the result of hydrologic form (e.g., climate and geology) which have been described in the context of hydrologic landscapes (HL) that have been mapped for the Pacific Northwest by scientists at the Western Ecology Division (WED) with plans for the entire U.S. While HLs use morphological characteristics to classify watersheds, it remains unclear as to how well HLs will accurately reflect hydrology inputs in downstream systems without independent verification. We propose to use variation in the stable isotopes of water to assess how various parts of a basin contribute to surface flow over time. Additionally we wish to test how well HLs characterize those flow contribution since the HL concept is being proposed as a management tool to describe hydrologic behavior of watersheds across the country. We will use an extensive isotope data set from the Columbia River Basin to test our hypotheses.

We are seeking a student to use a 3-year time-series of water isotopes collected within the Columbia River and spatially distributed sample collected within the Columbia Basin to explore if HLs can help understand variation in landscape contributions to flow within the River. Specific research actions will include 1) developing a surface water isoscape for the Columbia Basin and 2) evaluating the integration of hydrologic landscape units into larger basins by using stable isotopes as spatial integrators of flow.

Develop a Columbia Basin Isoscape: Precipitation isotopes vary dramatically across the Columbia Basin because of strong rainout processes as storms originating from the Pacific Ocean move inland across the basin. This variation in precipitation isotopes creates a strong spatial pattern in water isotopes from headwater that feed the Columbia River. We have surface water isotopes collected within the U.S. portion of the Basin that can be used to construct a model that describes how surface water isotopes vary across the basin.

Testing methods for integrating hydrologic landscape units within larger basins: HLs are based on the underlying hydrologic characteristics of landscape units such as geology and climate, and are being developed at the national scale as a tool for managers. However, we need to understand how these hydrologic properties integrate across basins to reflect hydrologic behavior for larger water bodies such as the Columbia River. Water stable isotopes are conservative tracers of hydrologic fluxes that contain spatial information on water sources, and can be used to test how well HLs predict the dominant sources and timing of water within larger watersheds. Using the regional isoscape developed above, and our water isotopes time-series measured within the Columbia River, we will test how well HLs indicate the dominant sources and timing of water within watersheds.

Brooks, J. R., P. J. Wigington, D. L. Phillips, R. Comeleo, and R. Coulombe. 2012. Willamette River Basin surface water isoscape (d18O and d2H): temporal changes of source water within the river. Ecosphere 3:39 http://dx.doi.org/10.1890/ES11-00338.1. Hill, R. A., M. H. Weber, S. G. Leibowitz, A. R. Olsen, and D. A. Thornburgh. 2016. The stream-catchment (STREAMCAT) dataset: a database of watershed metrics for the contermious United States. Journal of the American Water Resources Association 52:120-128. Wigington, P. J., S. G. Leibowitz, R. Comeleo, and J. L. Ebersole. 2012. Oregon hydrologic landscapes: a classification framework. Journal of the American Water Resources Association. Wolock, D. M., T. C. WInter, and G. McMahon. 2004. Delineation and evaluation of hydrologic-landscape regions in the United States using geographic information system tools and multivariate statistical analyses. Environmental Management 34:S71-S88.

Opportunities for Professional Development:

The student will learn about applying stable isotope techniques to characterizing landscapes, water flow, climate change, and environmental changes. Student will employ a Hydrologic Landscape classification system as part of their internship at the Western Ecology Division (WED). The student will have the opportunity to work with scientists in a multidisciplinary laboratory internationally recognized for analyzing and interpreting stable isotopes, and with the EPA scientists responsible for developing HLs and other spatial databases on surface water attributes (StreamCat and LakeCat (Hill et al. 2016)).

Point of Contact or Mentor:

J. Renee Brooks, brooks.reneej@epa.gov