BIBLE HISTORY DAILY

Monumental Dam from Time of Biblical Kings Uncovered

Discovery reshapes understandings of ancient Jerusalem

The 2,800-year-old dam wall discovered in the City of David, from the time of the biblical Kings. Courtesy Emil Aladjem, IAA.

Archaeologists in Jerusalem have uncovered the largest dam ever constructed in ancient Israel. Dated to the reigns of kings Joash and Amaziah of Judah (late ninth century BCE), the dam would have drastically reshaped the city’s water system and topography, creating what is today known as the Pool of Siloam. But how exactly does this dam relate to other parts of the city’s ancient water system, and how much does it change the way we think about the development of biblical Jerusalem?

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Damming the Flood Waters

Archaeologists with the Israel Antiquities Authority uncovered the dam during their excavation work at the proposed site of the Siloam Pool in the City of David Archaeological Park. “This is the largest dam ever discovered in Israel and the earliest one ever found in Jerusalem,” said excavation directors Nahshon Szanton, Itamar Berko, and Filip Vukosavović in a press release. “Its dimensions are remarkable: about 40 feet high, over 26 feet wide, and the uncovered length reaches 69 feet—continuing beyond the limits of the current excavation.”

Built near the southern end of ancient Jerusalem’s southeastern ridge, the dam created an artificial reservoir, blocking water that flowed down the Tyropoeon Valley towards the Dead Sea. With additional water diverted from the Gihon Spring by the Siloam Channel (and later by Hezekiah’s Tunnel), the reservoir would have stored a tremendous amount of water, creating the massive pool usually identified as the Siloam Pool (although some of the excavators disagree with that designation).

Close up of the dam wall. Courtesy Emil Aladjem, IAA.

However, since the Siloam Pool was used well into the Roman period, the dam’s initial date of construction remained a mystery. Using high-precision radiocarbon dating techniques, a team of scientists from the Weizmann Institute reached a surprising conclusion: The dam’s construction dates to the late ninth century BCE, during the reigns of kings Joash and Amaziah of Judah.

A view inside Hezekiah’s Tunnel. Courtesy Nathan Steinmeyer, BAS.

Comparing the date of the dam with climatic data, the team suggests that the dam was likely constructed to help the city overcome short-term fluctuations in rainfall. These fluctuations would have included several years of low precipitation, together with short episodes of heavy rainfall that resulted in flash floods. The dam served to mitigate both water shortages and damage caused by flash flooding.

This dam formed just one part of Jerusalem’s multilayered water system during the Iron Age II (c. 1000–586 BCE), joining the Spring Tower (which some identify with the biblical Millo), Hezekiah’s Tunnel, and the Siloam Channel. According to the researchers, who published their findings in the journal Proceedings of the National Academy of Sciences, the dating of the dam may challenge existing views about the dating of these other structures. While both the Spring Tower and the Siloam Channel have often been attributed to the Middle Bronze Age (2000–1550 BCE), some scholars have instead placed their construction in the tenth or ninth centuries BCE. If the latter dating is accepted, that could mean that the dam, Spring Tower, and Siloam Channel were all part of a single monumental construction project aimed at drastically altering the city’s water system.

But not all scholars are convinced by this hypothesis. As Chris McKinny, Associate Professor of biblical archaeology at Lipscomb University, told Bible History Daily, “I still think that it makes the most sense that the Spring Tower and the Siloam Channel were initially built in the Middle Bronze Age and continued to be in use until the late eighth century BCE.”

The benches of the Siloam pool with the excavation tent on the left. Courtesy Nathan Steinmeyer, BAS.

Nevertheless, McKinny and other archaeologists were impressed by the discovery. “The dating of the new dam to the late ninth and early eighth centuries is incredibly important for our understanding of several important topics related to Jerusalem. The number of major discoveries in the City of David over the last decade or so is staggering—it is the greatest leap in our understanding of Judah’s earliest capital since the explorations of Charles Warren in the 1860s.”

McKinny was especially quick to highlight that the recent discoveries in the City of David have demonstrated that ancient Jerusalem began to expand and increase in power and influence much earlier than scholars had previously thought.

Related reading in Bible History Daily

Rethinking the Pool of Siloam

Where Is the Original Siloam Pool from the Bible?

All-Access members, read more in the BAS Library

Siloam Inscription Memorializes Engineering Achievement

The Siloam Pool

The Siloam Inscription Ain’t Hasmonean