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Scientific Investigations Report 2013–5013

Prepared in cooperation with the U.S. Fish and Wildlife Service

A National Streamflow Network Gap Analysis

By Julie E. Kiang, David W. Stewart, Stacey A. Archfield, Emily B. Osborne, and Ken Eng

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Abstract

The U.S. Geological Survey (USGS) conducted a gap analysis to evaluate how well the USGS streamgage network meets a variety of needs, focusing on the ability to calculate various statistics at locations that have streamgages (gaged) and that do not have streamgages (ungaged). This report presents the results of analysis to determine where there are gaps in the network of gaged locations, how accurately desired statistics can be calculated with a given length of record, and whether the current network allows for estimation of these statistics at ungaged locations.

The analysis indicated that there is variability across the Nation’s streamflow data-collection network in terms of the spatial and temporal coverage of streamgages. In general, the Eastern United States has better coverage than the Western United States. The arid Southwestern United States, Alaska, and Hawaii were observed to have the poorest spatial coverage, using the dataset assembled for this study. Except in Hawaii, these areas also tended to have short streamflow records. Differences in hydrology lead to differences in the uncertainty of statistics calculated in different regions of the country. Arid and semiarid areas of the Central and Southwestern United States generally exhibited the highest levels of interannual variability in flow, leading to larger uncertainty in flow statistics.

At ungaged locations, information can be transferred from nearby streamgages if there is sufficient similarity between the gaged watersheds and the ungaged watersheds of interest. Areas where streamgages exhibit high correlation are most likely to be suitable for this type of information transfer. The areas with the most highly correlated streamgages appear to coincide with mountainous areas of the United States. Lower correlations are found in the Central United States and coastal areas of the Southeastern United States. Information transfer from gaged basins to ungaged basins is also most likely to be successful when basin attributes show high similarity. At the scale of the analysis completed in this study, the attributes of basins upstream of USGS streamgages cover the full range of basin attributes observed at potential locations of interest fairly well. Some exceptions included very high or very low elevation areas and very arid areas.

First posted June 10, 2013

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Suggested citation:

Kiang, J.E., Stewart, D.W., Archfield, S.A., Osborne, E.B., and Eng, Ken, 2013, A national streamflow network gap analysis: U.S. Geological Survey Scientific Investigations Report 2013–5013, 79 p. plus one appendix as a separate file, http://pubs.usgs.gov/sir/2013/5013/.



Contents

Acknowledgements

Abstract

Introduction

Objectives of the Streamgage Gap Analysis

Study Area and Data

Streamgage Gap Analysis for Gaged Locations

Streamgage Gap Analysis for Ungaged Locations

Summary and Conclusions

Further Work

References Cited

Appendix 1. Gages Used in the Reference-Quality Streamgage Dataset

Appendix 2. Basin Attributes at Gageable Watersheds and Gaged Basins for Each Hydrologic Unit Code Region


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