Low Streamflow Trends in the United States

Abstract

This research considered low streamflow features which are an important indicator of droughts and suggests significant information for water-resources decision making. Consecutive low flow conditions in a river can create chronic water scarcity. Water scarcity is one of the main drivers of a social and economic conflicts. This research has observed not only locations where suitable adaptive management measures are needed but also locations where low flow regime changes due to natural / climate effects or anthropogenic impacts. Trends in low flows in the United States were evaluated using Mann-Kendall and the Sen-Slope trend tests. 5% significance level is used and an evidence of mostly upward trends in low flows in the United States was found. Trends in referenced (not exposed to anthropogenic impacts) and non-referenced stations (exposed to anthropogenic impacts) were also investigated separately, and then compared. Results illustrate that the percentage of significant low flow trends in non-referenced stations are higher than referenced stations. Furthermore, wavelet, PCA and clustering analysis were also performed. Wavelet analysis was used to determine the amplitude and timing of such low streamflow discontinuities for specific wavebands. Clustering analysis helped to determine a grouping low streamflow patterns with similar annual flow behaviors.