This PredictPedia entry covers the Polymarket event "How low will Lake Powell drop?", which is grouped under the Climate category. The event is built around the lowest daily elevation recorded at Lake Powell, the reservoir behind Glen Canyon Dam. According to the provider's rules, the market resolves on the lowest daily elevation recorded between market creation and March 31, 2027, as published by the U.S. Bureau of Reclamation [1]. Because a lower reading can occur at any point in that window, every outcome is settled after the window closes, based on the lowest daily reading recorded during it [1]. The event is split into separate brackets rather than a single question. The four markets in this sample ask whether the minimum elevation stays above 3,510 ft, falls between 3,500 and 3,510 ft, falls between 3,490 and 3,500 ft, or falls below 3,490 ft [1]. Each bracket is its own Yes or No contract, so the brackets describe different ranges of the same underlying measurement. The reservoir itself is described in historical sources. Glen Canyon Dam is a concrete arch-gravity dam on the Colorado River in northern Arizona, near the city of Page. It was built by the Bureau of Reclamation from 1956 to 1966 and forms Lake Powell, one of the largest man-made reservoirs in the United States [3]. Glen Canyon and Lake Powell are managed by the Department of the Interior within Glen Canyon National Recreation Area [3]. The provider's rules also address data problems. If the resolution source publishes clearly erroneous data caused by technical or operational error, or by unauthorized interference, the market may remain open for up to seven calendar days so a corrected value can be published. If no correction appears in that period, the provider may issue a clarification [1]. The rules also state that Bureau of Reclamation data is provisional and subject to revision, and that the lowest value reflected in that data as of April 15, 2027 governs the outcome [1]. A separate Lake Powell elevation website may be referenced, but if it disagrees with the Bureau of Reclamation value, the Bureau's value governs [1].

Historical Context

Lake Powell was formed when Glen Canyon Dam was built on the Colorado River between 1956 and 1966 [3]. The reservoir is named for John Wesley Powell, who in 1869 led the first expedition to traverse the Colorado River's Grand Canyon by boat [3]. The dam's reservoir flooded a series of deep sandstone gorges now known as Glen Canyon [3]. A different Colorado River reservoir, Lake Mead, is described in a separate source as having fallen to its lowest level since its original filling on 7 August 2026, reaching an elevation of only 1037.31 feet as of 17 October 2026 [2]. That observation concerns Lake Mead, which is formed by Hoover Dam, and does not measure the Lake Powell elevation used to settle this contract [2].

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