Water is a central theme in Numbers 19-20. In Numbers 19, God instructs Moses on the process on purifying someone who has come in contact with a dead body. This process includes purification in water mixed with the ashes of a red heifer. In Numbers 20, the Israelites complained to Moses about a lack of water. “Why did you bring us up out of Egypt to this terrible place? It has no grain or figs, grapevines or pomegranates. And there is no water to drink!” Moses’ act of hitting the rock to produce water instead of talking to the rock led God to punish Moses by denying him entry into the land of Canaan.
Water too was a major consideration in the establishment of Jerusalem. The City of David is the likely site of the original city of Jerusalem. Typically, a city might be built on the highest point of a hill, to take advantage of the natural defenses that a higher elevation provides. However, in Jerusalem, the original city was founded on the slope below the area of the Temple Mount. The reason was water.
A karst aquifer is an aquifer created in the space of hollowed out limestone rock. These hollowed out spaces carry water from the groundwater or other forms of precipitation. The City of David sits on a hill made of hard limestone. Water is carried from areas that feed into the limestone, through fissures in the rock. At the City of David, the waters of the Gihon Spring emerged on the eastern slope of the City of David, above the Kidron Valley.
The waters of the Gihon Spring were not constant. The flow of water at the City of David depended on the accumulation of water in the groundwater that fed into the cracks in the rock and then flowed to the surface. This feature would lead to the residents eventually devising methods to collect the waters in wetter periods for use during dry periods.
But the presence of water, so crucial for sustaining life, allowed for Jerusalem to be settled at its earliest stages.
The image above is of a pool of water that earlier would have fed into the Gihon Spring, before tunnels were built to divert the water.