State Water Resources Research Institute Program

Project ID: 2008WY45B
Title: Multi-Century Droughts in Wyoming's Past: Evidence of Prolonged Lake Drawdown
Project Type: Research
Start Date: 3/01/2008
End Date: 2/28/2009
Congressional District: 1
Focus Categories: Drought, Water Supply, Sediments
Keywords: Drought, Lakes, Water Volumes, Long-Term Climate Change
Principal Investigators: Shuman, Bryan N ; Minckley, Thomas A ; Shinker, Jacqueline J
Federal Funds: $ 21,523
Non-Federal Matching Funds: $ 49,224
Abstract: Wyoming has historically experienced extended periods of drought, which have had significant economic and social impacts. Tree-ring records and archeological evidence indicate that past centuries have contained multi-decadal "megadroughts" far more severe than any drought of the past 150 years. However, the potential for extreme drought is poorly known. Here, we propose to study the extent and controls on past dry periods in Wyoming that exceeded even the severity of multi-decadal "megadroughts." Preliminary direct measurements of the prehistoric shoreline elevations of lakes in the North Platte watershed indicate that these natural reservoirs experienced prolonged draw downs of 30% or more of their volumes for periods of centuries to multiple millennia during the past 4500 years. The average volume of water flowing through these lakes indicates persistent dry conditions that were similar to conditions that have only been experienced in six years since 1948 (1954, 1956, 1962, 1964, 1966, and 2002). Indeed, lakes that experienced only minor draw down in 2002 were desiccated during prehistoric dry periods. These centennial-to-millennial variations in the availability of water are important because they occurred when the world's climate was similar to today. In other words, these fluctuations were not part of the end of the last ice age, but part of the natural climate variability that preceded historic time. Therefore, such persistent drought may well represent an analogy for periods in Wyoming's future, and should be studied. Proposed work would include 1) an extensive survey of lakes in the North Platte drainage basin, using sub-surface radar, to determine the extensiveness of past periods of low lake levels, 2) sediment core analysis, including radiocarbon dating and fossil analyses, of a few representative lakes to date and quantify past climate conditions, and 3) hydroclimatic analysis, comparing paleoclimate estimates with modern climatic data and climate model output, to examine the factors that contributed to the periods of prolonged drought. Improved data would provide direct measurements of regional water levels during extremely dry periods and, thus, could provide important data for considering future drought vulnerability and impacts, which are useful in the development of associated contingency plans.

Progress/Completion Report, PDF

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