Prediction of Climate Change Effects on Streamflow Regime Important to Stream Ecology

Streamflow is expected to change with climate change, but a general understanding of how climate change will affect the characteristics of streamflow important to stream ecosystems is lacking. This thesis focused on specific characteristics of streamflow, or the streamflow regime, that are important to stream ecosystems. The need to evaluate the potential impacts of climate change on stream ecosystems makes it important to study how streamflow regime may change. This work has identified 16 characteristics of daily streamflow time series that quantify the patterns and span the aspects of streamflow regimes important for stream ecosystems. Principal component analysis objectively identified five uncorrelated factors reduced from these characteristics that quantify low flow, magnitude, flashiness, timing and constancy as independent aspects of the streamflow regime. We developed a new classification of reference gauged streamflow sites across the continental US based on these factors. This classification is consistent with, and in some aspects improves upon, prior classifications in that the five factors used in classification were objectively obtained from principal component analysis and in that it retained magnitude variables that are a primary determinant of stream ecosystems. We further developed a statistical model that can extend this classification to ungauged sites based on watershed and climate attributes, and can assess the degree to which classes are projected to change with projected climate change. Our findings, presented as maps that show the streamflow regime classes and where they are projected to change, identify locations, where perennial stream classes may become intermittent and where intermittent streamflow classes may become perennial. These projected class changes provide a basis for considering the implications of these changes for stream ecosystem biodiversity and formulating approaches to protect ecosystems that may be subject to change