Palestine Exploration Quarterly 125 (1993)

THE STEPPED DAM AT WADI EL-JILAT

KONSTANTINOS D. POLITIS

The stepped dam at Wadi el-Jilat is one of the most important and certainly one of the mostimpressive hydraulic architectural structures in Jordan. The mere fact that it has not beenbreached is a tribute to its designers and builders.

The Wadi el-Jilat is a tributary of the larger Wadi Dhobai, which is part of a drainagesystem running north-east into the Qa' el-Azraq. The wadi has cut through late Cretaceous andearly Tertiary limestones, chalks and marls and at its deepest point a gorge has been formedcutting into a travertine deposit of an ancient petrified swamp. It is here that the stepped damwas constructed (Map reference BQ East 882 North, Sheet 353 II Series K737).

The dam was visited by Field in 1928, Waechter and Seton-Williams in 1937 and 1938,Glueck and Harding in 1924 and King and Rollefson in 198I. Although all gave a brief butvarying description of the dam, none were able to examine its structure carefully or excavate it.In 1987, during the second season of excavations of the prehistoric sites surrounding the gorge

Fig. I. 'Men with machine-guns' on one of the steps of the dam at Wadi el-Jilat(photo: L. A. Martin)

44 PALESTINE EXPLORATION QUARTERLY

Fig. 2. The stepped dam at Wadi el-Jilat from the east, showing the silting on the upstream side(photo: P. Elliston)

and dam at Wadi el-Jilat, Dr A. N. Garrard, the director of excavations, suggested to the authorthat he should investigate the dam more thoroughly.

In September 1988, when Dr Garrard and his team continued their excavations in Wadiel-Jilat, the author began work on the dam. The objectives were to document accurately thestructure and clarify its purpose and date. The first stage involved clearing the downstream areain the gorge and on the stepped side of the dam to the north-west in order to expose the entireface. This was originally intended for accurate photography and planning, but had the addedmerit of doing away with over-grown plants on the dam itself which had caused serioussplintering and cracking of the limestone architectural blocks, exposing the cement core toweathering, and consequently weakening the entire construction. The three buttresses hadespecially suffered from this effect, and only one is preserved to its original length. The result ofthis elementary conservation work should help maintain the dam.

A series of photographs were taken of the cleaned stepped face in separate sections,including the buttresses, corners and details of the wasm inscriptions and some pictorial scenes(Fig. I). In addition a large format camera was used to photograph the entire dam from severalangles (Fig. 2).

o 1mSection A-BSONDAGE 1988

Fig. 4. Section of the sondage on theupstream side of the dam

DAM AT \VADI EL-]ILAT

Fig. 3. Sondage on theupstream (west) side of the

dam at Wadi el-Jilat(photo: K. D. Politis)

A

I

I

II

IIL._._._._.

45

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On 29 and 30 October a one metre wide sondage was made by the author across the centralpart of the dam on the upstream south-eastern side which was silted up to the top of thestructure (Fig. 3). The objective was to reveal the method of construction used on this side of thedam. No steps were discovered at a depth of over one metre, and after three courses of well-hewnarchitectural blocks (Fig. 4), it was evident that each course slightly over-lapped the next(Fig. 5), resulting in an inverted stepped effect. Whether this was intentional or caused by earthmovements could not be established by this limited trench. No pottery was found in thissondage, although some animal bones were recovered, presumably washed down with the silts.

With much of the dam cleared of shrubbery and the first sondage completed, Franz-JosefReidel, accompanied by the author, was able to make the first top plan and section on13 November (Figs. 5 and 6). The measurements proved to be quite different from previousreports. The dam is 58 metres long, 5.5 metres wide at the east end, 5 metres wide at the westend, and 6.2 metres high where we made our section (C-D) which was the best preserved andexposed point. All three buttresses were 2.2 metres wide. Fifteen steps are also visible on thedownstream side, though it is possible that there are more hidden under the rubble. There areno sluice gates or spill-aways as such on the dam, but at either end the stone blocks have beenbuilt into the natural travertine bed-rock which could serve the purpose of releasing the tensionof excess water pressing on the central sections of the dam wall.

4

46 PALESTINE EXPLORATION QUARTERLY

o 1 2 345m

MOl JILAT - Tt£ DAM SECTlON C-D NOV 1988 REDEL

Fig. 5. The section of the stepped dam at Wadi el-Jilat

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'"o 1 2 3 4 5 10 20 30

WADI JILAT-Tt£ DAM NOV 1988 REDEL

Fig. 6. Top plan of the dam at Wadi el-Jilat

DAM AT WADI EL-]ILAT

Fig. 7. Hydraulic cement with charred remainsfrom the core of the dam at Wadi el-Jilat

(photo: K. D. Politis)

47

Fig. 8. Two types of stone-cutting from limestoneblocks at Wadi el-Jilat dam: right, long iron saw

marks; left, diagonal chisel marks(photo: K. D. Politis)

Good hydraulic-type cement (Fig. 7) was used to keep roughly packed stones tightlytogether and formed the core of the dam. This was then faced with well-hewn local limestoneblocks, some of which were shaped diagonally and horizontally by a chisel, and some cut with along iron saw (Fig. 8). Both types of blocks fit together well without any mortar in between theirjoints. The two methods of block-making may actually indicate a rebuilding or repairing of thedam. The fact that the gorge which the dam stretches across is neither very deep nor wide meansthat it would have silted up in a relatively short period of time, perhaps in only a few rainyseasons. This would indicate a very short life span for the dam, unless it was cleared outperiodically. It would therefore be perfectly possible for the upstream side of the dam to havebeen strengthened at a later period than the original construction.

The dating of dams is always precarious, especially when they are located on a populartravelling route such as is the Wadi el-Jilat (King 1987, 92). The use of pottery types found onthe surface can only testify to a presence during a certain period. Even excavated pottery fromthe silted up part of the dam proves little. Pottery retrieved from the actual construction of thedam, on the other hand, may present a stronger case for a dating method. During theinvestigation of the dam construction, several pottery sherds were noticed within the exposedcement core. When they were extracted and cleaned, they were identified as N abataeanthin-bodied, rouletted and cooking pot types (Fig. 9). Although even this is not conclusiveevidence for dating the dam, it does suggest an earlier date for the original construction than hasbeen previously proposed.

A stepped construction is not an unusual method of dam-building. But few exist whichhave such fine masonry as the one at Wadi el-Jilat. The Prosperina dam in Merida, Spain(Smith 197 I, 44, pI. 14) is the best parallel. This Roman dam has a concrete core covered by finemasonry and stepped with buttresses. The similarity of the two dams is so striking that one is

Fig. g.

PALESTINE EXPLORATION QUARTERLY

Nabataean pottery sherds extracted from the cement core of the dam at Wadi el-Jilat(photo: T. Springett)

---I!

tempted to conclude that their builders were both Roman. But it is difficult to date dams onarchitectural style alone because even later dams were built to an established formula developedby the Nabataeans, Romans and Byzantines, and continued by the Umayyads.

The use of the stepped dam at Wadi el-Jilat is not as obvious as it may seem. As mentionedabove, the gorge would have silted up quite fast when blocked. It would not have containedwater very long, and certainly could not have served as a reservoir (there is no evidence ofwaterproof plaster over the limestone blocks on either side of the dam). It may just have beenused as a seasonal water-catchment source for shepherds and travellers (Fig. 10). An alternativetheory is that it was meant to accumulate silt which was a valuable source offertile soil. But nosettlement has yet been found nearby which could have exploited this soil for agriculture.

The stepped dam at Wadi el-Jilat may originally have been a Nabataean construction thatwas rebuilt in the later Byzantine/U mayyad period, as is testified by the more abundant potteryscatters on the surface. I ts successful use as a water-catchment facility is questionable. In anycase, the dam is a masterpiece of hydraulic architecture. It is a monument in the desert no lessworthy than the castles and forts in the Azraq drainage basin. And, perhaps, it was meant to be

DAM AT WADI EL-JILAT 49

Fig. 10. Shepherds of the Shawlan bedouin tribe at Wadi el-Jilat dam (photo: K. D. Politis)

a show piece, or a gift to local desert tribes in exchange for support within a greater alliancenetwork.

BIBLIOGRAPHY

Field, H., 1960. North Arabian Desert Archaeological Survey, 1925-5° (Cambridge, Mass.), 75.Garrard, A. N., Byrd, B., and Betts, A. V. G., 1986. 'Prehistoric environment and settlement in the Azraq basin: An

interim report on the 1984 excavation season', Levant, 18, 5-24 (esp. p. 5, pi. I).Glueck, N., 1951. Explorations in Eastern Palestine IV. Part I: Text. AASOR. 25-28 (esp. pp. 49-53 and figs. 39-41, with

plate caption 'Dam in Wadi Dh6bai').Harding, G. L., no date. Unpublished notebook. Registration Centre, Department of Antiquities, Amman (on 'Wady

Dhobai').King, G. R. D., 1983. 'Byzantine and Islamic Sites in Northern and EasternJordan', Proceedings of the Seminar for Arabian

Studies, 13,79-91 (esp, p. 83).-- 1987. 'The distribution of sites and routes in the Jordanian and Syrian deserts in the early Islamic period',

Proceedings of the Seminar for Arabian Studies, 17,91-105 (esp. p. 92).King, G. R. D., Lenzen, C.]., and Rollefson, G. 0., 1983. 'Survey of Byzantine and Islamic sites in Jordan. Second

season report, 1981', ADA}, 27, 385-436 (esp. pp. 392-98 and pi. 88,2).Smith, N., 1971. A History of Dams (London).Waechter,]. d'A., Seton-Williams, V. M., and colleagues, 1938. 'The Excavations at Wadi Dhobai, 1937-1938, and the

Dhobai Industry', JPOS, 18,3/4,172-86 (esp. pp. 173-74 and plan I).