One of the prerequisites for the existence of towns, settlements, and even military installations such as fortresses is the guarantee of a secure water supply. It is essential for the survival of the inhabitants. The water for daily consumption must be supplied mostly from the surrounding geographical area. Difficulties arise most frequently from the fact that supply and demand are regulated by completely different factors and so only rarely coincide. The demand for water is influenced by the prevailing customs of the inhabitants, while available water supply is ruled by climate, precipitation, and the topographic conditions of the site.
The conditions at fortresses in arid areas are extremely unfavorable. Precipitation is minimal and very unevenly distributed throughout the year; and fortresses are situated on isolated hills or rocky peaks for strategic purposes. Securing the water supply under these circumstances calls for much ingenuity and technical expertise on the part of the engineer. Nevertheless, the second-first century BCE Hasmonean builders were able to solve these problems in the desert fortresses around the Jordan Valley.