THE IMPACT OF CLIMATE CHANGES ON THE ANCIENT WATER WORKSWATER WORKS

Three main factors have dictated the nature of the water works in Jerusalem from its earliest history until today.

(a) The short term climatic factor, namely the dry summer months and occasional years of drought.

(b) The long term climatic factor of the past periods of wet and dry climates.

Figure 7.3 Hydro-geological columnar section (according to Gavrieliet al.2002)

(c) The need for security which dictated the building of the often fortified settlements on the peaks of hills and thus creating the need for a secure access to the nearest water resource in the valleys.

The short term climatic factor, of rains during winter and dry summer months, dictated, in the first place, the need for collecting the rainwater. This called for the excavating of cisterns either by private people in their yards collecting the water from the roofs of their houses, or by the authorities creating reservoirs or pools as public projects. This device of water supply, known since ancient times was not, however, always practical in Jerusalem due to the fact that the oldest part of city (variously known as the Eastern Hill, Ophel, Jebusite City, City of David, Siloam and Silwan) was built on the rather permeable Bina limestone. Thus the construction of cisterns had to wait until the invention of impermeable plaster sealing the bottom and the walls of these structures. The production of plaster involved the smelting of limestone to produce lime, slaking it with water and producing some kind of paste. William F. Albright suggested in 1940 in his monumental work From the Stone Age to Christianity that it was the appearance of iron tools for digging water cisterns in bedrock and the invention of impermeable plaster which enabled the early Israelites to settle in the hills. Zertal (1990) suggested that during the early occupation of the Iron Age/Israelite period, of the 13th to the 11th century BC, water was stored primarily in large earthen jars (pithoi), a working solution for a limited population. The excavations carried out in Jerusalem have shown that already the pre-Israelite inhabitants during the Middle Bronze Age were able to hew and cut horizontal and vertical passages through the bedrock in order to reach the springs below their city.

However, as they seem to have lacked the knowledge to produce plaster to stop the leakage, there is, so far, no example of pre-Israelite cisterns or tanks, although such cisterns may have existed but were re-excavated or have not yet been found.

The other method to guarantee water supply during the summer months was to locate the fortified city above a natural perennial spring and construct sheltered access passages to reach the spring in the valley, particularly in times of siege. This solution became practicable after the introduction of bronze technology around 2000 BC as well as of iron tools by 1000 BC. It would involve searching for a passage to approach the spring itself or to draw or divert water from it to the site where it was needed.

Such passages existed as natural solution channels, the work needed was to enlarge them and build openings, staircases and tunnels to allow access to the spring.

7.5.1 Impact of climate changes during prehistory

The climate during the Pleistocene, the time of the arrival of the Hominins stone tool makers, was a function of the changes between glacial and inter-glacial periods. Glacial periods, as evidenced by the Mediterranean Sea regressions, were cold and humid, while inter-glacial and post glacial periods, evidenced by transgressions, were warm and dry. During glacial periods in the region of Jerusalem terra-rosa type soils developed, while during inter-glacial periods erosion took place. The climate during the last glacial period (ca. 70,000 to 15,000 BP) was not different, namely, generally cold and humid. During the last glacial period the palaeo Dead Sea extended over most of the Jordan Valley (Bookman et al. 2004;

2006). At the end of this glacial period atca. 15,000 BP, warmer conditions prevailed over the Middle East.

Tools of Palaeolithic hunters and gatherers have been discovered and dated most probably to glacial periods in the north and thus humid periods in the Middle East, as these tools were found in heavy red loams characteristic of these periods. A site of the Middle Palaeolithic age (ca. 200,000–50,000 BP) was excavated at Ramat Rachel, on the southern outskirts of Jerusalem. Two other sites of the Palaeolithic period were found in its southern part (Emeq Rephaim Street) and in the vicinity of Mount Scopus.

So far no remains of the Neolithic periods,ca. 9000 to 5000 BC, have been found around Jerusalem.

Neolithic settlements seem to have been concentrated in the valleys and in the coastal plain of the

Mediterranean Sea. Small amounts from the Chalcolithic period,ca. fifth and early fourth millennia BC, were found throughout most of the excavations of the area of ancient Jerusalem on the eastern hill, particularly around the Gihon Spring (Shiloh, 1978–1984).

Remains of the Early Bronze Age, dated to the third millennium BC, were reported by the archaeologist Yigal Shiloh as well as Reich and Shukron (2002a) on the eastern hill. The cemetery explored by de Vaux on the central section of the upper slope of the Ophel was dated to the second phase of the Early Bronze Age I period (de Vaux, 1971). The size of the cemetery indicates a modest village. The evidence for the subsequent Early Bronze Age II and III period, in general the first urban phase characterised by monumental architecture in the Levant, is extremely thin on the ground, again pointing to a village or small but possibly fortified town.

The water supply of a settlement this size during the short term dry season in an overall cold and humid climate of the Early Bronze could easily be solved by storing water in jars or basins, sherds of which were found at the lowest levels of the excavations and in crevices of the rock. Whatever the case, the massive construction work of the following periods eliminated any archaeological evidence of these early periods. During this period a karstic gallery, enlarged to a tunnel may have been excavated from the small walled city on the Eastern Hill to reach a small perched spring. This spring dried up during the Intermediate Bronze Period and the gallery was abandoned. This project will be discussed in detail below.

The Early Bronze Age ended around the middle of the third millennium BC followed by the Intermediate Bronze Age (IBA), which was a dry period, the desiccation reaching its maximum aroundca.2200 BC. The cities were abandoned or destroyed and the economy of the entire region shifted accordingly to a more pastoral subsistence economy. There are no remains of this period on the eastern hill due to the massive reworking of the area during the following periods, as mentioned above. However, rock-cut tombs, common during this period and regarded as a sign for a dominantly transhumant way of life, are found scattered throughout the hill country indicating that some sort of settlement did exist.

7.5.2. Impact of climate changes during history 7.5.2.1 Middle to Late Bronze Age period

During the Middle Bronze Age from 2000 to 1550 BC the climate became relatively humid again, which enabled a cultural and material renaissance. During this period the introduction of bronze and other technological innovations took place. The excavations on the Eastern Hill revealed that the most impressive visible remains were of a fortress-city of the Middle Bronze Age dated to around 1900 to 1800 BC. Most probably Jerusalem and its territory had then become an independent city-state ruled by a king similar to her neighbours such as Shechem (Tell Balata) to the north, Hebron (Tel Rumeida) to the south and Gezer to the west. During that period different variations of the city name “Jerusalem” were found in the Tell el-’Amarna letters in Egypt (ca. 13th century BC) and the Sennacherib inscriptions (ca.7th century BC). The meaning of the name is not clear, but it possibly originates from the Sumerian word for town or cityuru, or the rootyrwto found, establish, combined with the name of a West Semitic deitySalimu, the god of sunrise.

Now we come to the question of why the low topographical extension of the Eastern Hill (Figure 7.4a) was chosen for a settlement throughout history rather than the higher level of the Temple Mount (Moriah), or any of the other neighbouring hills such as Western Hill across the Tyropean Valley (Mount Zion) or the Mount of Olives to the east (Figures 7.4a and b).

The conventional answer to this question is that ancient Jerusalem was nearer to the perennial Gihon spring. As mentioned before, we suggest that there existed a small perched spring high up flowing from a karstic channel at the bottom of the porous Meleke crystalline limestone on top of the Mizi Ahmar denser dolomite (Issar, 1976). We suggest that the most probable reason for deciding to settle at this site for the

first time, as well as for the location of the Middle Bronze walled city, was the presence of this spring which, flowed during the Early Bronze Age, dried up during the Intermediate Bronze Age and may have started to flow again during the more humid Middle Bronze Age period. It dried up again during the dry Late Bronze Age period. Moreover, about 1000 years later the existence and development of the karstic horizontal channel leading to this spring helped the discovery and development of the system known today as Warren’s Shaft which enabled the people of the city to reach the spring of Gihon from inside the city.

Figure 7.4 (a) Relief map of Ancient Jerusalem. (b) Geological cross-section through City of David. (c) Water supply system of Jebusite City and City of David. (d) The City of David, the Gihon outlet and the“Niqba”

The existence of such a spring was suggested by Issar (1976) and the excavations of Reich and Shukron confirmed, in our opinion, Issar’s suggestion. In their report of 2002(a) they ask why the roof of the tunnel of approach to Warren’s Shaft is 6.5 m high. When standing at the upper opening of that shaft looking south, an opening about 3 m higher than the floor of the tunnel can be seen. Reich and Shukron cleaned this opening and discovered that the tunnel turns east and leads to the top section of a rock-cut pool. By accident they found remains of the expedition of Vincent and Parker of 80 years before. This tunnel follows the contact line of the Meleke crystalline permeable limestone and the dense dolomitic Mizi Ahmar rock.

We suggest that the natural spring, then still flowing, was fed by the karst passage, which was followed by the tunnel diggers of the Middle Bronze period, who may have widened a more ancient tunnel. This perched spring received its water from the permeable Meleke layer. Shukron and Reich maintain that when this tunnel, the height of which was about 2.5–3 m, was cut during the Middle Bronze Age, the workmen were unaware of Warren’s Shaft, a natural sink hole just below their feet (Figure 7.4c).

As the climate during the second millennium BC was less humid and more varied than that of the preceding period, the supply of the upper perched spring may have diminished or even dried up in summers of aridity. Consequently, collecting pools on the slope below the outlet of the small spring as well as surface water flow from the near environment had to be constructed. In addition, the entrances to the upper spring and the pools which collected its water, as well as that of the lower lying spring Gihon, were protected by massive towers discovered by Reich and Shukron in the late 1990’s (2002a). They measured 13.7×16.8 m with a wall thickness close to 4 m and were appropriately called by the discoverers“Pool Towers”.

The spring of Gihon (from g-y-h to burst-out) is a typical pulsating karstic spring issuing from the dolomitic rocks of the lower part of the Bina Formation and the upper part of the Veradim Formation.

The karstic system has developed, most probably, on the semi-permeable layer of the Kefar Shaul chalky-marl layer. The pulsation is due to a siphon structure in one of the karstic channels: when the level of the water table reaches above the“knee”of the siphon, the water emerges with a throb, adding to the basic flow of the spring coming from the other sub-channels. The duration of each pulse used to be about 30–40 minutes, occurring each 4–6 hours during winter and about 8–10 hours in the dry summer. The storage capacity of the spring varies due to its limited local recharge basin. Accordingly, after years with high precipitation such as, for instance, winter 1983 the daily output reached about 5000 m³/d, whereas in autumn 1979, a relatively dry year, it reached only 700 m³/d. We assume that during humid periods the spring reached the surface and overflowed into the Kidron Valley. The farmers living down the valley utilised the water by digging channels and diverting it to irrigate their terraced fields.

When the spring disappeared in dry years, attempts were made to enlarge the outlet. Eventually, a curved stepped slope was cut to facilitate fetching water by jars or skins. When the yield of the spring fell to a minimum, or even dried up during extremely dry years, attempts were made to renovate its yield by driving tunnels into the fissures wherefrom the water used to come out.

Fromca. 1500 to 1300 BC namely over the Late Bronze period (1500–1200 BC) a phase of warming and aridity took place. The result was a marked negative impact on the water resources of the Near East causing political and socio-economical changes in its wake.

Towards the end of the period, a phase of severe desiccation most probably caused the pastoralists east of the Jordan and in the southern deserts to invade Canaan. Unable to sustain their herds they were forced to settle in the more humid parts of the country. (In the letters found at Tell el Amarna in Egypt the kings of Canaan complain about the threat of the“piru/Habiru”pastoral nomads who were gaining a hold in the region.) Whether these are the forerunners of the“Children of Israel”is a question still under debate. Parallel to this invasion from the east and south, and again probably linked by similar environmental changes, a series of sea-borne invasions of the so-called Sea Peoples, among them the Philistines, arrived from the west.

In Jerusalem the arid climate caused the small upper perched spring discussed above to dry up. The level of the Gihon subsided and put the former Middle/Late Bronze Age water works out of use. Whether this fact brought about the desertion of the city by its former inhabitants and its occupation by other tribes, such as the Jebusites from Anatolia, can only be surmised. And so, Reich and Shukron’s (2002a) claim that the famous Warren’s Shaft was a post-Middle Bronze Age. Project appears to be substantiated but with the question of its date remaining open.

As the main effort of the new people occupying the city was to ensure their supply from the Gihon spring, especially in times of siege, it brought them to develop the karst channels leading to the outlet of the now dry small perched intermittent spring mentioned above and utilise a karst shaft to arrive at the level of the main spring. This feature is the famous Warren’s Shaft, a 40 m long vertical sink-hole. At the bottom of the shaft is a small solution hole where containers lowered by a rope could be filled (Figure 7.4c). Whether this shaft is the Zinnor which helped Joab to conquer Jebus (II Samuel V:8) is outside the subject matter of the present work. While enlarging the cave from which the Gihon emerged, a solution channel was found connecting the Gihon to another karstic spring known as Siloam. The connection between the two springs could be observed either by the similar pulsation or simply by throwing straw into water at the Gihon and seeing it appearance at Siloam. This gave the idea for a unique project which will be discussed later (Figure 7.4d).

Two other sophisticated water works were found in the Biblical city of Gibeon (present village al-Jib), which is situated about 10 km north of Jerusalem, and its water works also show the impact of the dry period of the Late Bronze period. (The root of Gibeon is“gev”, namely water-hole and in ArabicJib). These water works comprise two independent systems (Pritchard, 1961): (a) a large pool with its spiral stairway (Figure 7.5) and (b) an inclined gallery leading to the spring outside the walls and horizontal galleries feeding the spring (Figure 7.6).

Figure 7.5 Gibeon, large pool with spiral stairway (After J. Pritchard: The Water System of Gibeon, 1961)

The first system consists of a pool and stairway to the bottom of the pool and another steep passage from the bottom of the pool to a small cavern with a dripping spring. Issar (1976) suggested that the general evolution of this system was like that of Jerusalem, namely that in the first stage a passage to a small perched spring was developed. This passage was enlarged and widened to a shaft with a staircase so that water could be carried with less effort. It is now suggested that the flow of the small perched spring dried out as a result of the dry climate of the Intermediate Bronze period. (In 1976 Issar was not aware on the severity of climate change and he thus suggested that the spring dwindled‘due to the covering of the drainage basin’. The new data on the warm and dry climate of the Intermediate and Late Bronze Age (Issar and Zohar op.cit.) led him to change his explanation). The shaft was then excavated during the Middle Bronze Age to look for water. When water was found the staircase of the shaft was developed to enable the carrying of water from the bottom of the shaft. (It seems probable that this system, after the second system leading to the spring was developed, did not serve for daily supply but as a ritual place connected with water, though a discussion of this aspect is beyond our scope here). When the climate dried up again during the Late Bronze Age, the inhabitants extended the shaft downwards into a lower karstic cave containing a dripping spring (Figure 7.5).

The second system is like that of the Jebusite system of Jerusalem, which was built to reach the perennial spring emerging at the foot of the hill on which the walled city was situated. Also in the case of Gibeon the changes due to the climate changes can be seen. The whole system leading to the spring is composed of four units (Figure 7.6):

Figure 7.6 The gallery water system of Gibeon (After J. Pritchard: The Water System of Gibeon, 1961)

(a) A gallery, moderately inclined, from the inside of the wall reaching a small blind alley. It is suggested that this gallery led to a small perched spring, which dried up during the Intermediate Bronze Age.

(b) A steep gallery deviating from the lower end of“unit a”and opening into“unit c”. This gallery may have been constructed during the Middle Bronze Period.

(b) A steep gallery deviating from the lower end of“unit a”and opening into“unit c”. This gallery may have been constructed during the Middle Bronze Period.