Proceedings of the National Academy of Sciences—Researchers dated the construction of an ancient, monumental water system in Jerusalem, Israel. Multiple elements of ancient water systems have been documented from Jerusalem’s early settlements. How the various structures may have simultaneously functioned as a single water system remains unclear, partly due to the lack of accurate dating. Elisabetta Boaretto, Johanna Regev, and colleagues report* a precise radiocarbon date—800 BCE—for the Siloam Pool’s monumental water dam, which blocked the flow of water from the Tyropoeon Valley into the Kidron Valley and onto the Dead Sea. To determine the age of the dam, the authors analyzed samples of uncharred straw and charred twigs from mortar used in between the stones of the Siloam Dam wall. The dating suggested that the Siloam Dam was built as part of a single large-scale project along with a fortified tower around the Gihon Spring and a channel directing surplus water from the spring to the dam’s reservoir, which also collected rainwater from the Tyropoeon Valley. Analysis of climate data from 850 to 800 BCE suggested that the region experienced a period of unpredictable weather, including droughts and flash floods. According to the authors, the findings suggest that the monumental Siloam Dam was built as a response to climatic changes toward the end of the 9th century BCE.
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Excavation of Siloam Dam in Jerusalem, Israel. Johanna Regev
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Article Source: PNAS news release
*“Radiocarbon dating of Jerusalem’s Siloam Dam links climate data and major waterworks,” by Johanna Regev et al., Proceedings of the National Academy of Sciences, 25-Aug-2025. https://www.pnas.org/cgi/doi/10.1073/pnas.2510396122
