Worship in the Temple of Jerusalem was based on the need of constant purification so as to respect the Covenant, requiring the High Priest be immersed in the running spring waters borne to the heart of the Temple.
The Temple was therefore organised around a continuous supply of running spring waters, however the only springs having a suitable and constant flow rate were the Etam Springs, a collection of springs at an altitude higher than that of Jerusalem, situated in a region to the south of Bethlehem.
The waters of these springs supplied a storage and collection area called Solomon’s Pools situated at approximately 785 metres above sea level, whilst the average elevation of the cisterns was at approximately 725 meters above sea level. The water was therefore carried by gravity to the Temple of Jerusalem by aqueducts, either in the form of channels and tunnels cut into the rock, or bridges crossing valleys and ravines.
However during certain months of the year the flow rate was insufficient for the needs of the Temple. Therefore cisterns were cut into bedrock of the Temple Mount. These subterranean cisterns could store up to fifty million litres of water.
According to Jewish law the purification power ceased once the water became and water contained in the cisterns could have been declared impure according to the Torah.
Therefore it was necessary to conceive a system that ensured a continuous flow of the water stored in the cisterns, this was ensured by a system of cascades so that the water was in continuous movement.
Without the exploration by the archaeologists of the engineers of the Palestinian Survey Fund the water system would have never been discovered. De Lussac considered this water system to have been conceived and designed uniquely for the needs of the Temple and its purification rights. By extension this system was the only surviving structure of the Temple destroyed by the Romans in 70AD.
Up until the 19th century it had been relatively feasible for Westerners to explore and study, with the necessary approval, the surrounding area of Jerusalem and the aqueducts that carried water to the presumed site of the Temple. However, any investigation into the Haram underground was totally forbidden to infidels by the Muslim authorities.
Popular legends told that the underground was haunted by djinns, good or evil genies, but who had been the first creatures outside of Mecca to have recognised Mohammed as the Prophet and were converted to Islam.
In the 19th century the sanitary conditions in the Old City had reached such a disastrous state that the city authorities were forced to call on the help of foreign specialists to help modernise the water and drainage system.
Thus British officers of the Royal Engineers were given the task of carrying out a survey, which was extended to a detailed topographical and geographical survey of the whole of the Holy Land and in which Jerusalem and the principal holy sites were studied from their historical, religious and archaeological aspects.
The men who carried out the work included three officers of the Royal Engineers assigned to the Palestine Exploration Fund: Charles Wilson, Charles Warren and Claude Reignier Conder, and in addition Conrad Schick, a German architect and researcher who became a representative of the Palestine Exploration Fund and its equivalent German organisation.
These men located a large number of underground cisterns taking dimensions and determining levels, as well as describing the nature of their construction and investigating the vestiges of channels and conduits connected to the water storage network with as much rigour as the circumstances permitted.
Exploration of the Haram’s underground was carried out over twenty five years, between approximately 1850 and 1875, during a period of relative tolerance of the Muslim authorities.
The official reason for this topographical survey was for the planning of a water supply system for Jerusalem and an efficient system for the evacuation of waste water. But in spite of this official reasoning the resistance of certain Muslim religious leaders did not weaken and provoked in a recurring fashion many difficulties for the exploration of the Haram underground.
The surveyors used many different ruses to achieve their goals, especially the intrepid Warren whose determination often reached the limit of Muslim tolerance when he dug shafts outside of the Haram and tunnelled under the ramparts into the Haram’s underground itself.
Exploration was made difficult at times as it was forbidden to dig shafts or carry out the least excavation work inside the Muslim Haram. In the same manner scaffolding was totally excluded which meant the archaeologists had to improvise as best they could.
This dangerous work was undertaken solely by candlelight or burning torches, at a time before the invention of magnesium lamps with little protection against the dangers of their rough tunnels collapsing.
Whenever the Muslims were alerted by suspicious noises and threatened Warren with reprisals, it was necessary to pay baksheesh and cease the excavations in progress.
These engineers gave little thought to the possible link between the underground water storage and distribution and the Temple of the Jews.
De Lussac concluded that the Temple would have been situated downstream of this elaborate water storage and distribution with its spouts supplying water for purification for the evacuation of the offal and dejections from the animals sacrificed by the Temple priests.
The detailed knowledge of the hydraulic system as it stands today is due to the extensive work of these engineers and archaeologists who codified and explored the cisterns, as well as the different tunnels and conduits that carried water and waste.
The descriptions, surveys and elevations recorded relative to the cistern-reservoirs, conduits and channels in the bedrock were principally made by Pierotti, Barclay, Wilson, Warren and Schick.
Certain measurements were checked by Conder, in particular the precise elevation above sea level for each cistern and the surface level of the Haram vertically above each respective cistern.
The results of the surveys with the related maps and drawings were published by the Fund in the 1884 book that included two parts for Jerusalem, composed of descriptions and plans.
O’Connelly read one of Wilson’s accounts of the first exploration campaign:
The cisterns were explored in December and January before the last rains. The measures were carried out with a yard stick when I was alone and with a surveyor’s chain when we were several persons. The elevations were measured with a prismatic altimeter or with a compass.
But none of these measurements could be considered as perfectly exact because it is not easy to work holding a candle in one hand and with your feet in water. On certain occasions it was very difficult to determine the exact nature of the vault of the cistern or to be entirely sure of the presence or absence of a conduits outlets or inlets. In addition the candles gave off a very weak light for such immense cavities, and before the arrival of the magnesium from England the winter rains had started and we were obliged to halt the explorations.
Three men were employed for the exploration of the cisterns, an interpreter and two labourers. The most part of the descents into the cisterns ere made with a ladder and rope. But in certain cases for the smaller cisterns their inlets were too narrow and this method could not be used, then a knotted rope was tied around the waist and lifting our arms as high as possible we tried to squeeze into the access holes on the surface.
The interpreter watched everything that happened and sent down candles by a cord for this purpose. Certain of these descents were carried out by Doctor Chaplin, who was always ready to join in these explorations, others were made by myself alone.
It was a big problem to come back up, because the ladder and rope often hanging 12 metres swung and twisted in every direction in a very disagreeable way, whilst our clothes were soaked and hindered our legs….
Wilson established the topographical contours of the subterranean rock as well as inventorying the system with reference numbers and all their corresponding measurements with the greatest precision possible.
Warren, Wilson
’s successor, however remarked that there remained an immense amount of exploration work to be undertaken in the Sanctuary, all the surface drains be examined, and the probability of new cisterns being discovered, however in 1875 the exploration work came to a sudden end.