Flow Modification in the Nation's Streams and Rivers

Circular 1461
National Water-Quality Program
National Water-Quality Assessment Project
By: , and 



This report summarizes a national assessment of flowing waters conducted by the U.S. Geological Survey’s (USGS) National Water-Quality Assessment (NAWQA) Project and addresses several pressing questions about the modification of natural flows in streams and rivers. The assessment is based on the integration, modeling, and synthesis of monitoring data collected by the USGS and the U.S. Environmental Protection Agency at more than 7,000 streams and rivers across the conterminous United States from 1980 to 2014. Key findings include the following. First, flow in many of the Nation’s streams and rivers is different from what it would be under natural conditions. In particular, low flows are more frequent, are of shorter duration, and vary less from one year to the next than they would naturally. In addition, high flows have been reduced in magnitude, are of shorter duration, are less frequent, and vary less from one year to the next than they would naturally. Other characteristics of natural flows also have been modified. Second, over the last 60 years (1955–2014), climatic trends have caused a change of 50 percent or more in one or more streamflow attributes at two-thirds of climate-sensitive streamgaging sites. However, these climate-induced changes have been less influential on streamflow modification than have land and water-management practices. Third, in every region assessed, streamflow modification was associated with reduced ecological health, as indicated by two biological communities—invertebrates and fish. Biological communities were increasingly likely to be impaired (defined as having lost a statistically significant number of species) in streams with flows most different from natural conditions. Finally, several case studies are presented that illustrate viable management strategies for balancing the water needs of people and ecosystems.

Suggested Citation

Carlisle, D.M., Wolock, D.M., Konrad, C.P., McCabe, G.J., Eng, K., Grantham, T.E., and Mahler, B., 2019, Flow modification in the Nation’s streams and rivers: U.S. Geological Survey Circular 1461, 75 p., https://doi.org/10.3133/cir1461.

ISSN: 2330-5703 (online)

ISSN: 1067-084X (print)

Study Area

Table of Contents

  • Foreword
  • Acknowledgments
  • Chapter A. Overview
  • Chapter B. National Assessment of Streamflow Modification
  • Chapter C. Streamflow Modification Associated with Land and Water Management
  • Chapter D. Streamflow Modification and Climate
  • Chapter E. Ecological Consequences of Streamflow Modification
  • Chapter F. Managing Modified Streamflows
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Flow modification in the Nation’s streams and rivers
Series title Circular
Series number 1461
DOI 10.3133/cir1461
Year Published 2019
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) WMA - Earth System Processes Division
Description ix, 75 p.
Country United States
Online Only (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details