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Assessment of Long-Term Trends in Streamflow Statistics Within and Near the Mobile Bay and Perdido Bay Watersheds, United States, 1950–2022

Scientific Investigations Report 2026-5142
Prepared in cooperation with the Gulf Coast Ecosystem Restoration Council
By: , , and 
https://doi.org/10.3133/sir20265142

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Abstract

The U.S. Geological Survey, in cooperation with the Gulf Coast Ecosystem Restoration Council, assessed monotonic trends for a variety of streamflow statistics for 69 long-term U.S. Geological Survey streamgages within either the Mobile Bay or Perdido Bay watersheds that were active through at least at the end of calendar year 2019. Long-term data were defined for this investigation as having at least 50 years of cumulative record within the period since January 1, 1950, with a requirement for a complete record of streamflow during the 2010s (2010–19). The 69 streamgages have at least 54 years and as many as 73 years of daily mean streamflow data; the median period of record is 72 years; and 15 of the streamgages are identified as “major nodes” on the basis of the criteria described. The occurrence of statistically monotonic significant trends for the 69 streamgages at the 0.05 significance level is spatially shown for six statistics. For the major node streamgages, the study depicts (1) time-series graphics of annual mean, annual harmonic mean, decadal 10th, 50th, and 90th-percentile streamflows, and (2) a variation on Quantile-Kendall plots of Kendall’s tau and streamflow nonexceedance probabilities for each of the 365 days of a year. Trend assessment synthesis shows that, except for a few streamgages with relatively greater counts of statistically significant trends than others, the majority (about 93 percent) of individual trend tests indicate no trend in the streamflow and ecological metrics considered.

Suggested Citation

Asquith, W.H., Crowley-Ornelas, E.R., and Whaling, A.R., 2026, Assessment of long-term trends in streamflow statistics within and near the Mobile Bay and Perdido Bay watersheds, United States, 1950–2022: U.S. Geological Survey Scientific Investigations Report 2026–5142, 35 p., https://doi.org/10.3133/sir20265142.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Streamflow Statistics, Major Node Streamgage Identification, and Approaches for Trend Assessment
  • Assessment of Long-Term Trends of Streamflow Statistics Within and Near the Mobile Bay and Perdido Bay Watersheds
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Assessment of long-term trends in streamflow statistics within and near the Mobile Bay and Perdido Bay watersheds, United States, 1950–2022
Series title Scientific Investigations Report
Series number 2026-5142
DOI 10.3133/sir20265142
Publication Date April 30, 2026
Year Published 2026
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Lower Mississippi-Gulf Water Science Center, Oklahoma-Texas Water Science Center
Description Report: viii, 35 p.; Data Release
Country United States
State Alabama, Florida, Georgia, Louisiana, Mississippi, Tennessee
Other Geospatial Mobile Bay and Perdido Bay watersheds
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Additional publication details