In the arid climate of the ancient Near East, the need for water was always fundamental and its proximity dictated the location of early settlement sites. Eventually, surface waters along rivers and lakes were manipulated into complex irrigation systems, rainwater was husbanded in storage reservoirs and cisterns, and underground sources, marked by oases and springs, were tapped by wells.
Water sources for agrarian use—crop irrigation and animal husbandry—were normally on the outskirts of a settlement site. However, as large population centers developed, their walled defenses made external access not only inconvenient, but a fatal weakness when under siege. Access via closed tunnel systems became an adaptation to the need for an intramural water supply.
Since the late nineteenth century, archaeologists working in Palestine have identified and explored such systems, most notably at Jerusalem, Gibeon, Megiddo, Gezer, and Hazor. At the first three, the systems exploited natural springs located on the slopes of their lower tell. These springs were created by natural karst-forming processes: the migration of groundwater through joints and bedding planes dissolves and forms channels in the limestone bedrock. Interruptions in the bedding planes at fault lines or erosion at valley locations produces exposures at which water flows freely or settles into pools, or catchments. The caves and pools at the Giḥon Spring at the foot of Mt. Ophel in Jerusalem are classic expressions of this process.
The various initiatives taken to secure springs and to access their waters from within a city are best illustrated at Megiddo, where three historical stages are evident. The first, prior to the tenth century BCE, involved only protecting the spring chamber by covering it and constructing a stairway access that could be blocked and masked under siege. A more ambitious second stage, constructed during the reign of King Solomon in the tenth century BCE, included a camouflaged gallery running through and below the city wall, connected to a long, covered stairway that lead downslope to meet the earlier entry to the spring chamber. In the ninth century BCE, a third-stage adaptation was engineered: a wide shaft, 35 m (115 ft.) deep, was sunk inside the city; from its base, a lateral tunnel 61 m (200 ft.) long was hewn to the spring chamber. The tunnel was pitched slightly downward, so that the water from the spring flowed to a storage sump at the base of the shaft. Water could be drawn from there by descending a long staircase that spiraled down the outer walls of the shaft opening.
A slightly earlier (twelfth century BCE) example of the second-stage, covered-stairway type is found at Tell es-Sa῾idiyeh (biblical Zarethan), and intramural shafts and tunnels similar to the Megiddo stage-three constructions are found at Gezer and Hazor. However, at the latter two sites, the systems lead to internal subterranean pools, not to external springs. Their builders tapped waters deep in bedrock, a significant innovation. The ambitious scale of these shaft-and- tunnel excavations suggests that the engineers did not proceed by chance. A key to their confidence in finding subterranean water may be seen at Gibeon (Ar., el-Jib).
Gibeon's systems offer additional parallels to each of the three Megiddo stages, but with a significant difference in the third stage. Although, as at Megiddo, a tunnel was cut from the spring some 33.5 m (110 ft.) in the direction of the internal shaft, it ended some 4.6 m (15 ft.) away from the shaft base. The connection most likely was not completed because a feeding aquifer had already been tapped at the bottom of the shaft. If Gibeon's third-stage shaft system is indeed the “Pool of Gibeon” in 2 Samuel 13–17, it would have been built before about 990 BCE and would thus be the earliest of the known and datable open-shaft/tunnel structures.
The most elaborate and complex of these early systems is on ancient Jerusalem's southeastern hill below the City of David. Its main elements were identified by explorers in the nineteenth century. In 1838 Edward Robinson discovered the 533 m (1,750 ft) long Siloam Tunnel (Hezekiah's Tunnel) that carries water from the Giḥon Spring on the east to the Siloam Pool on the southwest; in 1867 Sir Charles Warren investigated a vertical shaft (Warren's Shaft) leading up from one of the lower spring and tunnel chambers to a more horizontal ramp tunnel that enters the city; and in 1886 Conrad Schick explored an irrigation tunnel in the bedrock (the Siloam Channel) that leads south from the spring and has windowlike openings all along the eastern ridge.
In the 1980s, the geological study carried out by Yigal Shiloh and his team showed that the development of each of these systems involved exploitation of natural karst features in the bedrock. Thus, the vertical shaft and the ramp tunnel above it were originally parts of a natural dissolution channel that was further shaped and expanded to provide access to the Giḥon's waters from within the city walls. Based on its identification with the ṣinnor (“gutter” or “pipe”) mentioned the story of David's conquest of the city in 2 Samuel 5:6–10, early explorers referred to it as the Jebusite Shaft. It was accordingly dated pre-Davidic, before 1000 BCE. Although it is reasonable to assume that elements of the natural shaft and channel were present in David's time, the construction date for the more developed system cannot be ascertained on present evidence. However, the paleography of an inscription found in the Siloam Tunnel dates its construction securely to about 705 BCE, in the reign of Hezekiah. [See Siloam Tunnel Inscriptions.] Moreover, if the Siloam Channel is the “upper outlet of the waters of Giḥon” that Hezekiah closed to direct waters west, as recorded in 2 Chronicles 32:30, a pro quem date for the construction and use of that feature is also established.
- Cole, Dan P. “How Water Tunnels Worked.” Biblical Archaeology Review 6.2 (March-April 1980): 8–29.
- Gill, Dan. “Subterranean Waterworks of Biblical Jerusalem: Adaptation of a Karst System.” Science 254 (1991): 1467–1471.
- Issar, Arie. “The Evolution of the Ancient Water Supply System in the Region of Jerusalem.” Israel Exploration Journal 26.2–3 (1976): 130–136.
- Lamon, Robert S. The Megiddo Water System. Chicago, 1935.
- Pritchard, James B. The Water System of Gibeon. Philadelphia, 1961.
- Shiloh, Yigal. “The Rediscovery of Warren's Shaft.” Biblical Archaeology Review 7.4 (July–August 1981): 24–39.
- Wilkinson, John. “Ancient Jerusalem: Its Water Supply and Population.” Palestine Exploration Quarterly 106 (January–June 1974): 33–51.
Joe D. Seger