ABSTRACT
Jerusalem’s annual rainfall is about 600 mm, close to that of London.1 However it fallsin a brief rainy season, particularly between November and March (a quarter of the total rainfall in January alone) in heavy downfalls of short duration. The remainder of the year is almost completely dry. As the proximity of the watershed and the steep hills preclude the formation of large rivers or lakes in the vicinity (the River Jordan is 30 km away in the Jordan Rift Valley to the east) and the short duration of the rainfall makes spring water an erratic source, the best means of supplying water for the needs of the city is by collecting the rainwater in large reservoirs or in underground cisterns. Several open pools were located in the area around the city and within the city walls (Figure 18.1). Other more distant pools supplied water via aqueducts. Hundreds, perhaps thousands of cisterns, some very large, were located in the city under public buildings, houses and courtyards. The Gihon Spring to the south of the city supplemented the water supply.
