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A Method for Characterizing Late-season Low-flow Regime in the Upper Grande Ronde River Basin, Oregon

May 16, 2016


This report describes a method for estimating ecologically relevant low-flow metrics that quantify late‑season streamflow regime for ungaged sites in the upper Grande Ronde River Basin, Oregon. The analysis presented here focuses on sites sampled by the Columbia River Inter‑Tribal Fish Commission as part of their efforts to monitor habitat restoration to benefit spring Chinook Salmon recovery in the basin. Streamflow data were provided by the U.S. Geological Survey and the Oregon Water Resources Department. Specific guidance was provided for selection of stream gages, development of probabilistic frequency distributions for annual 7-day low-flow events, and regionalization of the frequency curves based on multivariate analysis of watershed characteristics. Evaluation of the uncertainty associated with the various components of this protocol indicates that the results are reliable for the intended purpose of hydrologic classification to support ecological analysis of factors contributing to juvenile salmon success. They should not be considered suitable for more standard water-resource evaluations that require greater precision, especially those focused on management and forecasting of extreme low-flow conditions.


Valerie Kelly and Seth White


Kelly, V.J. and S.M White. 2016. A method for characterizing late-season low-flow regime in the upper Grand Ronde River Basin, Oregon. U.S. Geological Survey Scientific Investigations, Report 2016–5041 for Columbia River Inter-Tribal Fish Commission. 41p. Online at



Report No.


Media Type

Inter-Agency Report