Umm Daraj : The rehabilitation of an ancient dam
This project was financed by Aqaba Special Economic Zone Autority (ASEZA).
This is a reproduction of an article published in 2013, the article reference can be found at the bottom of the page.
To see the pictures of the construction site click here
The name of this dam refers to a staircase dug into the rock, which gives access to the interior of the basin (Figure 41). These steps were hidden by the sand fill. They only appeared after the dam had been excavated. Six steps, carved into the rock, are located on the left bank wall. They lead to the bottom of the reservoir and allowed for easier maintenance (cleaning, repairing of the plaster, monitoring of the building) and also, probably, access to the water when the level of the reservoir decreased.
In 2010, we began excavation work on the Umm Daraj dam. This dam is located 5 km from the village of Ramm, in the interior of the desert. We assigned the study of the filling process to Nicolas Jacob, MCF in geography at the University of Lyon 2. Patrick Ferrera, INRAP, was in charge of drawing the facings and the cuts. The objective of this operation was to take datable material to know the chronological succession of the filling, and to provide the current population with an additional dam, on the other hand. Since recent dams are now private property, reserved for those who have the resources to sustain and build them, the poorest people are dependent on those who are willing to take them in with their livestock. Given that the filled dams (Figures 42 and 43), which have been abandoned, are nobody’s property, one Bedouin asked us to excavate the dam so that it could benefit the community of those who do not own a dam.
The filling of the ancient reservoir consisted of sand (Figure 43), brought mainly by the erosion of the rocks by the flood waters. Eroded North-Arabic graffiti are engraved on the wall at the bottom of the basin. These graffiti, which are unreadable, are at a height of about 2 m from the filling. The reservoir measures approximately 35 m at its longest point, with an average width of about ten metres and a depth of about 4 m.
Before starting the total removal of the sandy fill, a stratigraphic borehole was drilled in the central part of the old reservoir to study the sedimentary fill.
The sounding revealed stratigraphic units and provided sedimentary information (granulometry, organic material content, presence of carbonates) that could provide clues to answer questions relating to the filling chronology and the nature of the sediments.
A total of 17 stratigraphic units were identified (Figures 44, 45 and 46). Fine sand alternates with layers of more or less compact consistency. The last layer, that of the bottom of the reservoir (US 17), is 1.5 to 2 cm thick. Its dark colour suggests an organic composition (tank bottom silt or algae brought by rainfall).
It is a very simple construction technique. The building consists of two block walls about 30 cm wide (Figure 42). These two walls contain a filling of rubble, abundantly cemented with mortar, and small sandstone chips, which provide the whole with resistance to water pressure and infiltration. On the left bank, the slope of the sandstone wall decreases at the level of the fourth foundation of the wall and the upper foundations overflow onto the rock in place, forming an angle directed towards the inside of the reservoir. The structure, which is very narrow at the base, is approximately 1.20 m wide and has a developed length of 4.00 m at the crowning level.
The lower part of the facings is wedged by slabs to ensure watertightness and block infiltration of the structure. The thickness is approximately 1m (Figures 47 and 48).
Both facing walls are made of well squared, quadrangular sandstone blocks with a coarse but generally fairly well preserved bossing, especially on the outer wall (Figs. 49 and 50). The stone modulus is irregular in length, ranging from 25 cm. to more than 60 cm. and more regular in thickness (close to 27 cm.). The blocks are jointed using hydraulic mortar; small sandstone chips are sometimes used to ensure a constant level of the blocks in the same bed.
Some blocks show traces of quarry peaks at the base of the dam; but there are no traces of erosion on the building. On the crowning, a corner stone shows striations that could be marks or inscriptions – in this case, the stone would constitute a reuse, which remains to be checked by a specialist.
There is currently no facing or paving at the top of the dam; some cut stones present in the reservoir, at the foot of the inner wall, suggest that the original height of the building was higher. Other observations reinforce this hypothesis: quadrangular notches (abutments) are in fact visible in the rock on the left bank, in the alignment of the dam’s facings. These notches are located at a height equivalent to the thickness of two additional rows of blocks in relation to the current crown of the dam. Their size corresponds to the modulus of the facing stones. The plaster which serves as hydraulic mortar in the joints of the dam is present at the corners of these notches. Finally, there are traces of staking between the end of the inner wall and the edge of one of these abutments. It is possible that these small asperities served to reinforce the adhesion of the mortar in contact with the ashlars and the rock in place. These observations seem to confirm the hypothesis that the dam spilled over more on the left bank wall and that it was higher than the current level.
On the right bank wall, a white crust is present up to about 20 cm above the crowning blocks. It consists of a very smooth outer layer with a chalky appearance and an inner layer with a sandy appearance. This crust is also found on the reservoir walls, at a height equivalent to that of the sandy filling. On the other hand, it is absent at the same height on the downstream side of the dam. Near the site, this white crust is present in some diaclases and at the foot of some walls. This material was taken for analysis but, after a first observation, it evokes a carbonate precipitate – probably born in not very cold waters – which could have penetrated through a thin thickness of the weathered sandstone on the surface, which would explain the presence of the two layers of different appearance. Outside the dam, the formation of this deposit could be linked to the concentration of runoff in the diaclases or to seasonal stagnation of water in depressions.
In the vicinity of the staircase mentioned above, there are still a few indentations in the left bank wall to the right of a diaclase. These marks are very blunt but appear very similar to the abutments we have just described. Squared blocks lie at the foot of this diaclase in the bottom of the tank.
In view of these elements, it is quite tempting to think that a small wall had been built in front of this diaclase in order to obstruct it and make the tank watertight. As the crack is not very wide and the wall is sloping, it is possible that the blocks did not have a sufficient base and that the whole thing was unsealed when the dam was no longer maintained.
These elements argue in favour of a slightly higher retention structure than at present, i.e. one row of stones on the right bank and two rows in the lower part on the left bank. This would correspond fairly well to the level of the white crusting. It was probably completed by a small secondary dam to prevent water loss by a diaclase.
Once the reservoir has been cleared, the total capacity can be measured. With a length of 35 m., an average width of 11 m. and an average depth of 3.5 m. (4 m. under the waterfall upstream, 3 m. against the dam, taking into account the foundations that are currently missing), the reservoir could hold approximately 1350 m3 of water (Figure 52).
The C14 analysis of six samples gave a range of dates from the 5th to the 17th century. These dates correspond to a time when the basin began to fill with sand, i.e. when it was no longer active. Its cleaning, which required great resources, had to be abandoned by the local population, who turned to the construction of smaller and more easily cleaned dams.
|US 27||Calibrated age : 407 to 542 BC|
|US 16||Calibrated age : 653 to 767 BC|
|US 8||Calibrated age : 596 to 658 AD|
|US 6||Calibrated age : 610 to 690 AD|
|US 3A||Calibrated age : 658 to 772 AD|
|US 1||Calibrated age : 1490 to 1654 AD|
Very eroded Nordarabic inscriptions are engraved on the wall of this dam (Figure 53). Access to the place where they are engraved is very difficult, unless it can be assumed that they were engraved at a time when the dam began to be filled in, i.e. after the 5th century. (US 27). Apart from these inscriptions, we did not find any ceramics or inscriptions in the immediate vicinity of the dam, as is the case at al-Kharaza.
The rainwater retention techniques observed at Wādī Ramm are similar to those found in Petra or elsewhere in Jordan. Expertise carried out at Tal Remah, carried out within restoration of the traditional hydraulic system, shows similarities in the techniques used at Titin (Oun, et al., 2011). Another study, this time in Titin, highlights the ecological disaster affecting the region and the need for a plan to rehabilitate traditional hydraulic systems (Farajat, et al., 2005)..
A rehabilitation programme for this type of remains could help the local population who are struggling to find water. This type of study could therefore serve not only to learn about ancient hydraulic systems, since Al-Kharaza and Umm Daraj were carried out by the Nabateans to provide water for the caravans that crossed the region (Eadie, et al., 1986). This type of operation is important to know about climate change and to provide the local community with an additional reservoir for water supply.
The excavation of the Umm Daraj dam required the mobilisation of fourteen workers, four people for material management, two drivers and a team of five people seconded from Aqaba Special Economic Zone Autority (ASEZA) for the project. The remoteness of the site made it difficult to transport the team and equipment. Without the full assistance and support of the Commissionner for the Environment, Dr Salim al-Moughrabi (ASEZA), this project would not have been possible. I would like to thank Patrick Ferreira and Nicolas Jacob for agreeing to participate in this project.
Caro, R. et Eagleson, P. 1981. Estimating aquifer recharge due to rainfall. Journal of Hydrology. 1981, Vol. 53, pp. 185–211.
Eadie, J. W. et Oleson, J. P. 1986. The water-supply systems of nabatean and roman Humayma. Bulletin of the American Schools of Oriental Research. 1986, Vol. 262, pp. 49-76.
Farajat, M., Amoush, H. et Abou Salah, R. 2005. Hydroge-ophysical exploration for groundwater potentials titin basin, south jordan. Hydrogeologie und Umwelt. 2005, Vol. 8, pp. 1-13.
Farès-Drappeau, Saba et Zayadine, Fawzi. 2001. A priliminary report on the forth season of the Wâdi Iram Epigraphical, Geographical and Archaeological survey. Annual of Department of Antiquities of Jordan. 2001, Vol. 45, pp. 205-216.
Ministry of Water and Irrigation. 2004. Environmental and Social Assessment Disi-Mudawarra to Amman Water Conveyance System. Amman, Jordan : s.n., 2004.
Oun, Mohammad et Tabin, Raed. 2011. Ecosystem restora-tion to secure water and food in the arid areas in jordan: tal remah case study. 2011.
Qudah, Khaldoun, A. et Smadi, Abdullah A. 2011. Trends in maximum daily rainfall in marginal desert environment: signs of climate change. American Journal of Environmental Sciences. 2011, Vol. 7 (4), pp. 331-337.
 It required 14 workers and one month of work to remove 2500 m3 of sands.
 This study was carried out as part of a development programme for the rehabilitation of translational techniques for water supply.
To quote the article : Saba Farès, “Umm Daraj et al-Kharaza : les barrages antiques au service des nomades d’aujourd’hui “, Saba Farès (édit), Des déserts et des hommes : Wādi Ramm, Jordanie : histoire économique, religieuse, sociale et environnementale : actes du colloque international à Wādī Ramm, les 11,12 et 13 novembre 2011, 52, A.D.R.A.; De Boccard, pp. 227-260, 2013, Études anciennes, 978-2-913667-36-5.