Stochastic Streamflow Simulation at Interdecadal Times Scales and Implications for Water Resources Management in the Colorado River Basin

Nowak, Kenneth C.

Graduate Thesis Or Dissertation

Stochastic Streamflow Simulation at Interdecadal Times Scales and Implications for Water Resources Management in the Colorado River Basin Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/sn009x95s

Abstract

The severe and sustained nature of the recent drought in the southwestern United States, coupled with a growing collection of scientific literature indicating that anthropogenic climate change will further dry the region, have raised considerable concern about the reliability of its water resources. Undoubtedly, climate change poses a significant threat to water supplies in the Southwest. However, relative to this long-term shift in basin yield, natural variability is likely to be the key driver of supply risk over, say, a 20 year horizon. Hence, the focus of this work is on the development of tools and strategies to address streamflow variability, at the decadal time scale, with application for improved water management in the Colorado River Basin.Streamflow simulation and disaggregation methods are first presented. These novel techniques offer the ability to simulate multi-site data at a variety of time scales--including daily, while also preserving non-stationary spectral properties seen in historic data. An analysis of Colorado River flow variability follows. Here, physical mechanisms are established for significant variability modes, and subsequently, links with large scale climate phenomena are proposed. Based on insight gained from the aforementioned work, a technique for decadal flow regime projections in the Colorado River Basin was established. The approach is demonstrated on paleo reconstructed data and then used to make actual future projections. Last, the Bureau of Reclamation Colorado River long-term planning model (CRSS) is used to assess adaptive operational policies. The objective is to improve Basin-wide supply reliability under various potential future hydrologic conditions, including climate change scenarios derived from downscaled general circulation model output. These policies were developed to reduce system losses and capitalize on information provided by flow regime projections. Results show that under the variety of hydrologic conditions notable savings are seen, which help to reduce overall system risk of shortage conditions.

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