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Characterization of Suspended Sediment Flux and Streamflow Trends in the Fountain Creek Watershed, Colorado, 1998 Through 2022

Scientific Investigations Report 2025-5089
Prepared in cooperation with Colorado Springs Stormwater Enterprise
By: , , and 
https://doi.org/10.3133/sir20255089

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Abstract

The U.S. Geological Survey evaluated long-term suspended sediment flux and streamflow datasets for temporal trends (monotonic and step trends) at 10 streamgage sites within the Fountain Creek watershed in central Colorado using the Mann-Kendall test (monotonic trend) and the Wilcoxon signed-rank test (step trend). Data were collected in cooperation with Colorado Springs Stormwater Enterprise. In this study, 10 sites with long-term suspended sediment records were evaluated during their operational periods, which ranged from 1998 through 2022. To assess how stream behavior might relate to shifts in suspended sediment transport, the Richards-Baker flashiness index, a measure of flashiness, was evaluated for each site. The Richards-Baker flashiness index was calculated for the same months as streamflow and suspended sediment (April through September) using all available streamflow data for a given site. Additionally, cumulative double-mass curves were developed to define temporal variation in the relation between streamflow and suspended sediment loads. This was completed by assessing differences in slopes before and after an observed break in the double-mass curve plots.

Five streamgage sites showed statistically significant (p<0.05) negative trends for suspended sediment flux, and nonsignificant decreases were indicated at the other five sites. The statistically significant negative trends are distributed across the watershed and include smaller tributaries and the main stem of Fountain Creek closer to its confluence with the Arkansas River. Such a broad distribution of negative trends is most likely an indication of improved water quality in the watershed with regards to suspended sediment. Assessing causes for the decreases in suspended sediment loads is beyond the scope of this report; however, spatially distributed bank erosion control projects, stormflow retention projects in the watershed, and changes in climate and storm patterns could be some of the potential drivers of the suspended sediment load trends in this watershed. The flashiness of the streamflow was assessed and can be dismissed on the basis of this study as a potential driver of trends in suspended sediment flux because the magnitude of changes was found to be negligible at all sites.

Suggested Citation

Downhour, M.S., Hennessy, E.K., and Bern, C.R., 2025, Characterization of suspended sediment flux and streamflow trends in the Fountain Creek watershed, Colorado, 1998 through 2022: U.S. Geological Survey Scientific Investigations Report 2025–5089, 30 p., https://doi.org/10.3133/sir20255089.

ISSN: 2328-0328 (online)

ISSN: 2328-031X (print)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Purpose and Scope
  • Study Background
  • Study Methods
  • Suspended Sediment Flux and Streamflow Trends
  • Characterization of Suspended Sediment Flux and Streamflow Trends
  • Summary
  • References Cited
  • Appendix 1. Plots of Monthly Mean Suspended Sediment Flux and Monthly Mean Streamflow Through Time with Thiel-Sen Robust Linear Regression Line for Each Site
  • Appendix 2. Double Mass Plots of Cumulative Monthly Suspended Sediment Loads and Cumulative Monthly Streamflow Through Time with LOESS Smooth Line
Publication type Report
Publication Subtype USGS Numbered Series
Title Characterization of suspended sediment flux and streamflow trends in the Fountain Creek watershed, Colorado, 1998 through 2022
Series title Scientific Investigations Report
Series number 2025-5089
DOI 10.3133/sir20255089
Publication Date September 22, 2025
Year Published 2025
Language English
Publisher U.S. Geological Survey
Publisher location Reston VA
Contributing office(s) Colorado Water Science Center
Description Report: v, 30 p.; Data Release: Database
Country United States
State Colorado
Other Geospatial Fountain Creek watershed
Online Only (Y/N) N
Additional publication details