Recently archaeologists conducted a survey of what is known as the Biyer Aqueduct, a three-mile-long portion of the complex system used in ancient times to get water to the residents of Jerusalem. Nathan Steinmeyer explains what they found:
Throughout its long history, Jerusalem has always had a major problem securing water for its inhabitants. During the Iron Age (1200–586 BCE), the nearby Gihon spring, along with a large reservoir and cisterns, was sufficient to supply the relatively small population. Both Hezekiah’s tunnel and the Siloam Pool were built by King Hezekiah in the 8th century BCE to expand the city’s Iron Age water system.
Towards the end of the Second Temple period, the city’s population grew dramatically, and the Gihon spring was no longer able to provide enough water for the city. It was for this reason that Jerusalem’s aqueduct was built to bring in water from more distant sources. The dating of the aqueduct system, however, has been much debated.
Carbon-14 dating led the team from Hebrew University to suggest that the Biyer Aqueduct was likely constructed during the reign of the Roman governor Pontius Pilate (ca. 26–36 CE). . . . During the survey, the team documented the various methods used in its construction and took several radiocarbon samples from the plastered walls. Analysis of the samples indicates the aqueduct was likely built in the early 1st century CE and was refurbished in the 2nd century, after the destruction of the Jerusalem Temple. As such, the team suggests that the Biyer Aqueduct could be the same aqueduct attributed to Pilate by the Jewish historian Flavius Josephus.
According to Josephus, Pilate used money from the Temple’s treasury to build the aqueduct, which led to riots in the city.