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Publication Date
5 October 2021

Quantifying Dam-Induced Fluctuations in Streamflow Frequencies Across the Colorado River Basin

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We investigated the entire Colorado River Basin (CRB) to understand how the annual (10–14 months) and multi-annual (24–60 months) frequencies in natural flow regimes have been progressively altered by dams. Given the significant alteration over the CRB, we captured changes in streamflow frequencies between naturalized and observed monthly flows via wavelet analysis. Based on the similarity of changes in streamflow frequencies (annual and multi-annual) over the last 30 years, sections of the riverine network were classified into four groups. The annual frequency was relatively well preserved downstream of Hoover Dam while showing a systematic trend of alteration downstream of Glen Canyon Dam until Hoover Dam. Meanwhile, the multi-annual frequency component was highly altered for the entire Lower Colorado main stem (i.e., downstream of Glen Canyon). We also identified dams with significant impacts on streamflow frequency by comparing wavelet coherence estimates.


Most U.S. rivers are impacted by long-term hydroclimatic trends and dams that alter flow variability. Despite these impacts, it remains largely unexplored how dams affect the dominant frequencies of natural streamflow over a highly regulated river network. This study advances the notion that dams fundamentally alter river flow regimes across multiple frequencies and with varying amplitudes over time and space, with alteration propagating – or being dampened – by hydroclimatic fluctuations and water resource management.


This study estimated time-varying alteration in streamflow frequency in the CRB via wavelet coherence analysis between the naturalized and controlled streamflow series. Wavelet coherence loss between the naturalized and controlled flows represents the cumulative degree of alteration of the frequencies in streamflow propagated from the headwaters. Stations, where streamflow showed similar patterns in wavelet coherence loss, were grouped together, and four clusters were identified for each annual and multi-annual frequency band. At most of the stations in UCRB, the frequency component of the streamflow was relatively well preserved. Interestingly, the Colorado River after Hoover Dam showed a low degree of alteration in the annual frequency despite significant alteration induced by Glen Canyon Dam.

Point of Contact
Naresh Devineni
City College of New York (CUNY)
Funding Program Area(s)