Paleohydrology of the Lower Colorado River Basin and implications for water supply availability
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Date
2012-10
Authors
Lukas, Jeffrey J., author
Wade, Lisa, author
Rajagopalan, Balaji, author
Colorado Water Institute, publisher
Journal Title
Journal ISSN
Volume Title
Abstract
As the annual demand on the Colorado River system approaches the annual supply, the contribution from the Lower Colorado River Basin (LCRB)--on average about 15 percent of total system flows--becomes more critical. In order for these flows to be incorporated into planning frameworks, it is important to understand their long-term variability and develop robust simulation methods that can capture the variability. The main objectives of this project were to develop new paleo-reconstructions of LCRB hydrologic variability from tree rings and incorporate them into a more complete assessment of the risk for the entire Colorado River Basin. We first worked to develop or refine naturalized flow records for the Gila and non-Gila subbasins of the LCRB. We found that while the historic Gila River naturalized flows near the mouth could be estimated with high confidence, the non-Gila LCRB flows carry more uncertainty. We then used several different statistical methods, including two new methods, to calibrate a regional network of tree-ring data against these naturalized flow records. The resulting flow reconstructions extend back about 400 years, and are more robust for the Gila River than the non-Gila portion of the LCRB. The reconstructions show that the 20th century has been unrepresentative of the longer period of hydrologic variability in several key respects. We then incorporated the variability in these new tree-ring reconstructions into a more complete water-balance model simulating the managed Colorado River system, which was run under multiple future scenarios representing different levels of climate change impact and increasing demands. We found that the periodic large inflows from the Gila River have a small but measurable effect in reducing overall system risk (of depleting) storage under all scenarios.
Description
October 2012.
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Subject
Gila River
tree-ring reconstruction
water shortage
reservoir levels
streamflows
Streamflow
Paleohydrology
Tree-rings -- Reconstruction
Colorado River (Colo.-Mexico)
Water-supply