The Fault Beneath Their Feet

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Water was critical in ancient Israel (as it is today). This was especially true in time of siege because cities were usually located on higher spots (that rose higher and higher as the tell developed over time) and the springs were outside the city walls at the bottom of the hill, exposed to the enemy.

The usual ancient solution to this situation was to dig a vertical shaft (with steps to climb down) inside the city and at the bottom to dig a tunnel sloping downward to the spring outside the city wall. Still, the residents would be vulnerable if the enemy found the spring outside the city wall 066despite its protection and camouflage.^a

The water system at the mound of Hazor in northern Israel is an exception, however. The Israelite residents there dug the usual shaft, which was excavated in modern times (1968–1969) by Israel’s most illustrious archaeologist, Yigael Yadin. The shaft went down more than 60 feet and required the removal of 6,000 tons of debris and rocks. Five flights of stairs descend around the shaft’s walls. At the bottom of the shaft the ancient engineers started to dig the tunnel toward the springs outside the wall. But as Yadin excavated the tunnel, he was surprised at its direction. The tunnel did not seem to be heading to the springs. “The direction of the tunnel came as a surprise, since we expected to find it to the south, in the general direction of the springs,” Yadin wrote.

Instead, it veers westward and ends in a dug water chamber whose bottom is covered with fresh water, forming a shallow pool. The entire water system lies within the perimeter of the mound, providing the inhabitants of Hazor with a convenient approach to water during times of peace, and, more important, a secure one in times of siege.

But how did the ancient engineers know about this source of water deep underground? Yadin attributed it to their uncanny hydrological understanding:

The deliberate and planned position and direction of the tunnel indicates that the engineers possessed sound geological knowledge. It is obvious that they anticipated encountering the water-level—the same as that of the springs—even within the perimeter of the mound.

We believe that Hazor’s engineers did not know about this underground source of water when they started digging the tunnel.¹ We believe what happened was this: They began digging their shaft on the southern side of the mound, the nearest point in the city to the springs outside the city. Then they began digging the sloping tunnel. A horizontal tunnel should have been designed to connect the end of the sloping tunnel with the springs to the south. But the sloping tunnel veered westward, apparently to avoid digging too close to the outer face of the mound. It is also possible that during progressive quarrying of the sloping tunnel, groundwater began to drip from the bedrock suggesting an underground water source within the city walls. Once the groundwater level was reached, they created the water chamber for this seeping groundwater.

How did the water get here? With modern geological understanding, the answer is clear. Tel Hazor is situated over the Hula Western Border Fault, which is a major tectonic line of the Dead Sea fault system. This system has been developed over millions of years as a result of seismic activity, frequently producing major earthquakes. The underground water chamber at Hazor happens to be exactly along this fault line, using the westernmost fault plane as the edge of the water chamber. Several springs are located along this fault line, including Hazor’s springs.

But still the aquifer (where the groundwater is naturally stored) is tens of meters below the Hazor water chamber, so how did groundwater find its way up to the water chamber? Here along the fault, the bedrock is intensely fractured, forming a series of narrow vertical fissures below the water chamber down to the aquifer. At the aquifer level, the groundwater is pressurized due to the higher elevation of the water source in the Galilee mountains. As a result, water looks for preferred avenues to ascend and release the pressure. This is the source of the groundwater that flows into the water chamber.

Ironically, the Dead Sea fault, one of whose strands gave Hazor a secure source of water even when the city was under siege, also resulted in the city’s destruction. In the eighth century B.C.E. the city was destroyed by an earthquake that reached the city through one of these strands of the Dead Sea fault.

Water was critical in ancient Israel (as it is today). This was especially true in time of siege because cities were usually located on higher spots (that rose higher and higher as the tell developed over time) and the springs were outside the city walls at the bottom of the hill, exposed to the enemy. The usual ancient solution to this situation was to dig a vertical shaft (with steps to climb down) inside the city and at the bottom to dig a tunnel sloping downward to the spring outside the city wall. Still, the residents would be vulnerable […]