Citation:

Sawicz, K., S. Leibowitz, R. Comeleo, AND C. Jones. Simultaneous Semi-Distributed Model Calibration Guided by Hydrologic Landscapes in the Pacific Northwest, USA. American Geophysical Union Fall Meeting, San Francisco, CA, December 12 - 16, 2016.

Impact/Purpose:

EPA’s Western Ecology Division has published and is refining a framework for defining landscapes hypothesized to have similar hydrologic response to precipitation events. These hydrologic landscapes (HL) were developed to help characterize the change in hydrologic response of watersheds under climate change at a variety of different scales. The HL framework was created for the Pacific Northwest (PNW) states of Washington, Oregon and Idaho. The HLs were developed using the National Hydrography Dataset Plus (NHD+) catchments. Classification components describing climate, seasonality of water availability, aquifer permeability, terrain, and soil permeability are then applied. This approach has the potential to assist in management of water quality and quantity and ecosystem status because HLs represent hydrologic response across a variety of spatial scales. One hypothesis set forward from this study is that hydrologic response, as inferred from the aggregation of HL assessment units, will improve the accuracy of hydrologic model predictions and calibration. This work specifically tests the ability or inability for HL-codes to inform and share model parameters across watersheds in the Pacific Northwest. It also contributes to deliverables under ACE CIVA-2.3.

Description:

Modelling approaches to transfer hydrologically-relevant information from locations with streamflow measurements to locations without such measurements continues to be an active field of research for hydrologists. The Pacific Northwest Hydrologic Landscapes (PNW HL) provide a solid conceptual classification framework based on our understanding of dominant processes. A Hydrologic Landscape code (5 letter descriptor based on physical and climatic properties) describes each assessment unit area, and these units average area 60km2. The core function of these HL codes is to relate and transfer hydrologically meaningful information between watersheds without the need for streamflow time series. We present a novel approach based on the HL framework to answer the question “How can we calibrate models across separate watersheds simultaneously, guided by our understanding of dominant processes?“. We should be able to apply the same parameterizations to assessment units of common HL codes if 1) the Hydrologic Landscapes contain hydrologic information transferable between watersheds at a sub-watershed-scale and 2) we use a conceptual hydrologic model and parameters that reflect the hydrologic behavior of a watershed. In this study, This work specifically tests the ability or inability to use HL-codes to inform and share model parameters across watersheds in the Pacific Northwest.

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