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Journal of Archaeological Science (2000) 27, 645–653doi:10.1006/jasc.1999.0518, available online at http://www.idealibrary.com on

Dating the Ancient Dam of Ma’rib (Yemen)

Vincenzo M. Francaviglia

CNR-Istituto per Le Tecnologie Applicate ai Beni Culturali, C.P. 10,00016 MONTEROTONDO ST. (Roma),Italia

(Received 9 November 1998, revised manuscript accepted 11 October 1999)

It has been shown that extremely accurate absolute dates can be obtained for the silty sediments from the ancient basinof Ma’rib (Yemen) by means of AMS assay of the radiocarbon contained in detrital charcoal fragments. The resultsobtained indicate that the silty sediments relating to the final period of activity of the ancient Sabaean dam of Ma’ribare no earlier than the beginning of the Christian era and no later than the end of the 3rd century. This new evidencedisagrees with historical sources, which give the collapse of the famous Sabaean dam a much later date. The inexorablesilting up of the water storage basin and the declining importance of the locality as a caravan station are proposed asthe main causes of the decline of the entire Ma’rib hydrogeological system. 14C analysis confirms that the earliestirrigation systems in the Wadı Danah probably date from the late 4th millennium or early 3rd millennium .

� 2000 Academic Press

Keywords: YEMEN, SABAEANS, MAz ’RIB DAM, 14C DATING, SEDIMENTS, IRRIGATION, ARID LANDS,DESERT FARMING.

Introduction

T he monumental volume Archaologische Berichteaus dem Yemen (ABADY), published by theDeutsches Archaologisches Institut ¥an‘a’

(DAIS), gives an exhaustive treatment of the topic ofirrigation in the ancient Ma’rib oases (Figures 1 & 2).Nevertheless, ABADY leaves some unexplored andunsettled points. In any case, researchers of DAIS getfull credit for showing how a multidisciplinaryapproach can be used to tackle a complex problemsuch as irrigation in the ancient Ma’rib oases, of greatimportance for an understanding of the history of theSouth Arabian peoples, and above all for havinggrasped the basic mechanisms on which the Sabaeanhydraulic systems in South Arabia were based.

P. Gentelle of the French Archaeological Mission inYemen (MAFRAY) was able to uncover the mechan-ism on which the irrigation systems in the Shabwah (orS{ibwa) area were based (Figure 1).

Working independently, U.S. archaeologists arrivedat similar conclusions after analysing ancient irrigationcrops in the Timna area in the Wadı al-Jubah (Figure2) (Toplyn, 1984–1986).

The present author, a member of the ItalianArchaeological Mission in Yemen (MAIRAY), appliedand tested the same principles to the ancient irrigationsystems of Barraqish (Francaviglia, 1994, 2000),another of the ancient cities of South Arabia.

The irrigation systems in the four cases mentionedwere found to be variations of a single model that wasFax: +39-06-90-67-23-73; Email: [email protected]

6450305–4403/00/070645+09 $35.00/0

adapted to suit different environments, the origin ofwhich is, however, difficult to situate in time and space.Indeed, dressed stones of an already mature form arefound in South Arabia in archaeological contexts inwhich no traces of material culture of comparablerichness have so far been found. At the same time,there is no known civilisation in the ancient NearEast that succeeded in building hydraulic structurescomparable to those of South Arabia.

The Ma’rib DamThe ancient Sabaean dam of Ma’rib, with its basin, itssluices and its canals, is the best example of controlledirrigation in the entire Ancient World. It allowed anarea of over 9600 ha, divided into two oases, to beirrigated.

Researchers of DAIS have described a sophisticatedmethod for the relative dating of the irrigation sedi-ments produced by thousands of years of activity bythe ancient Ma’rib dams. It is based on the observationthat every annual irrigation cycle deposited a thin layerof silt (7–8 mm/year) onto the tilled fields. As theseaccumulated thin layers ultimately raised the level ofthe irrigated fields, every few decades the bottoms ofthe sluices regulating the distribution of the irrigationwater had to be raised to ensure the minimum sloperequired to reach the fields, which had now becomehigher (Wagner, 1993).

As the overall particle size distribution of thesediment layer occurring between two activity cycles

� 2000 Academic Press

646 V. M. Francaviglia

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(separated by an increase in the sluice level) displays aconstant gradual increase in particle diameter followedby a sharp decreasing size, it was possible to estimatethe duration of the entire period of activity of the greatMa’rib dam. Six periods have been identified, rangingfrom VI (the earliest, believed to have begun in themid-3rd millennium) to I (corresponding to the 6th or7th century ). Assuming a sedimentation rate of8 mm/year, and dividing the thickness of the sedimentlayer corresponding to a given period by this rate, it ispossible to estimate the activity of the period itself.The total duration of irrigation activity at Ma’rib isobtained by summing the duration of the single periods(Wagner, 1993).

This is the theory, although it is not always possibleto extrapolate as, for example, it is not possible to takeinto account periods of inactivity of the dam or periods

during which irrigation was performed exclusively orpartially with well water. Some uncertainty also sur-rounds the annual rate of sedimentation estimated inthe irrigated fields. This is believed to vary from 7 to8 mm/year, a variation that can lead to significantlong-term differences. Nevertheless, the principles ofsedimentary deposits occurring in annual cycles,their continuous variation within a single periodand of the repeatability of the periods themselvesremain valid.

The present work is aimed at seeking answers to thedoubts and unsolved questions arising out of the DAISreconstruction of the entire activity of the Ma’rib damby:

(1) testing the use of accelerating mass spectrometry(AMS) in the 14C assay performed on charcoal

Dating the Ancient Dam of Ma’rib (Yemen) 647

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and minute vegetal remains found in the upstreamand downstream sediments of the ancient Ma’ribdam;

(2) checking the dates handed down to us via historictradition of the beginning of the Ma’rib damactivity and, above all, of its end;

(3) providing an, albeit indirect, answer to thequestion of the continual increase over thecenturies of the particle diameter of the sedimentsdue to irrigation activity. Researchers of DAIStend to think in terms of geologic (neotectonic)causes while the present author favours causesinherent in the dam-sluice-canal distributionsystem.

Any artificial lake created by damming a river sooneror later ends up by silting up completely. The lakecreated by the construction of the great Ma’rib damcould not escape this fate due to the large quantities ofmineral matter transported by the wadı. The sedimentthat gradually accumulated on its bottom is easy todistinguish as it differs in diameter from that depositedin the fields downstream from the dam.

According to DAIS workers, the basin constructedby the Sabaeans at Ma’rib should be considered not asa water reservoir from which water was periodicallywithdrawn as required, but rather as a defence against

the violence of the two annual floods of the WadıDanah (the two sayls, one in spring and the other insummer).

This system had two somewhat annoying sideeffects: the gradual raising of the level of the arableland and the one of the basin bottom due to thesediment transported by the Wadı Danah. To counter-act the gradual rise in the level of the arable land, theSabaeans periodically raised the level of the dam;according to researchers of DAIS, they remedied thegradual silting up of the basin by removing the bottomsediments every 80 years or so. The silting up of theMa’rib dam, and thus the reduction of its depth,reduced its ability to curb the violence of the floods,which ended up by violently impinging upon the weirs(made of stone and wood), thus increasing the percent-age of large diameter sediment transported into theirrigated fields. This constant increase in the diameterof the sediment deposited in the arable fields ended upby increasing soil permeability and thus its waterretaining capacity.

There is some indication that the Sabaeans wouldperiodically (completely or partially?) empty the basinupstream from the Ma’rib dam. This was a titanicundertaking that had obviously to be performed in theinterval between the summer sayl and the following


one in spring. Total emptying entailed the removal of55 million m3 of silt and sand (Brunner, 1983), with thedeployment of a large number of men and beasts ofburden. Assuming that 10,000 men were employed andthat each man excavated 20 m3/day, the operationwould have taken 275 days, or 9 months! But apartfrom this, where was the excavated material taken to?In all likelihood, in the later periods the basin wasnot entirely emptied of sediment, but only the areaupstream from the sluices. The result was a reductionin the dam’s capacity and therefore in its effectivenessin curbing floods and an increase in the percentage ofcoarse sediment transported by the water onto thefields.

Even a cursory examination of the distribution ofthe sediments formed by the silting up of the Ma’ribbasin reveals the existence of extensive relic layersupstream from the dam and precisely at the sluices(north and south), on the upstream face of what is leftof the earthen dam (northern cross section), at inter-vals along both the northern and southern banks of theancient basin, as far as the modern dam (Figure 3)(Brunner, 1983). Of course, as more than 1500 yearshave elapsed since the Ma’rib dam ceased to functionthe ancient silty/sandy sediments have been strongly

eroded. Nevertheless, a number of stratigraphic dis-crepancies in the thickness of the banks indicatethat the artificial emptying was not completed (seeFigure 4).

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Figure 3. The end portion of the hydrographic basin upstream from the ancient Ma’rib dam. The irrigation and dam bottom sediments abovethe height of 1200 m, obviously, have no relation to the activity of the ancient dam (modified, after Brunner, 1983).

Sediment Upstream from the AncientMa’rib DamThe rate of sedimentation upstream from the Ma’ribdam was obviously much higher than that downstream(14 cm/year), thanks to the restraining effect on theriver due to the body of motionless water (Wagner,1993). On the basis of the theoretical curves (see Figure5), for a sedimentation rate of 14 cm/year and a basindepth of 11 m, after 200 sedimentation cycles (100years) some 1015 cm (92%) had been deposited and theresidual water depth was only 85 cm. In other words,the effective depth of the basin had exceeded the limit ofusefulness long before the 100 years were up: it hadalready halved after 40 years. Since the curve has anasymptotic trend, it follows that, in the latter years, therise in the level of the bottom of the basin was almostimperceptible. It is easy to imagine that, towards theend, the bed of the wadı must have been carved out of


Figure 4. The southern sluice (S1) of the ancient Ma’rib dam viewed from a point upstream. In the foreground: the most recent and highest(�1201 m) sediments due to silting up resting on the limestone rocks of Jabal Balaq al-Awsat. Note the disturbed stratigraphy of thesedimentary sequence in the centre of the illustration, which is possibly due to the partial emptying of the basin performed after the destructioncaused by the troops of Aelius Gallus in 24 .

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a plateau composed of coarse sediment and pebbles,almost as high as the dam itself and which forked justupstream of the dam before running towards thenorthern and southern sluices, respectively.

At the end of the active life of the Ma’rib dam, atleast as far as the southern sluice (SS) was concerned,the upstream sediment rose to within 38 cm of thehighest point of the dam itself and some 5·5 m abovethe stone bottom of the actual sluice. This means thatthe sluice was choked for many years. As far as thenorthern sluice (NS) is concerned, the highest sedimentlevel is 2·18 m from the top of the dam and 3·27 mabove the stone bottom of the dam itself (Gerig, 1982).The only certain figures are those for the depths of thebottoms and the height of the dam itself; the others,such as the (present-day) height of the sediments, areliable to vary as, by their very nature, the silty-clayeysediments are easily eroded.

The Hydraulic Works Upstream from theAncient Ma’rib DamThe construction of the modern Ma’rib dam somekilometres upstream from the ancient one will destroyall possibility of any further identification of the sandysediments from the ancient dam (Brunner, 1983).Archaeologists of DAIS managed to save the remainsof an ancient weir construction dam, the so-calledAnlage X (discovered during the 1985/86 campaignsome 1900 m upstream from the ancient dam) before itwas submerged by the water from the modern reser-voir. This hydraulic system appears to be a matureconstruction and, judging by the size of the componentelements, must have been larger than Anlage A, astructure with two sluices and four piers (period VI)built downstream from the ancient Ma’rib dam(Herberg, 1986, 1987).

The photomosaic, shown by Gerig (1982) and inUeli Brunner’s map (1983) of the silting up sedimentsof the great dam, shows that large layers of irrigationsediments were still to be found upstream, well beyondthe maximum limit reached by the ancient artificiallake of Ma’rib (1200 m contour line). Owing to theirhigher level, these ancient fields, in which the ruins ofthe water distributors are still visible, could obviouslynot be irrigated either by the great dam or by Anlage X.Evidently, there must have been many Anlagen X, Y, Zetc. located west of Rahaba or instead simple waterdiverting devices.

It is conceivable that the early hydraulic installationson the Wadı Danah were situated (in the 4th–3rdmillennium , and perhaps even earlier) well upstreamfrom the ancient Ma’rib dam, in an area in which, asthe valley was narrower, there was less arable land,although this was enough to satisfy the needs of thetime. Subsequently, as the importance of Ma’rib as acaravan stop increased, and as the demand for caravansupplies grew, the Sabaeans probably moved further

down the valley where the irrigable and arable areaswere more extensive.

In the author’s opinion, the hydraulic installations inthe Ma’rib oases are more recent than those of theBarrqish area, at least judging by the perfect dressingof the stone components (Francaviglia, 1994, 2000).

The silting up sediments lying at the foot of anddownstream from the new Ma’rib dam are character-ized by terrace work, seemingly indicating a complexgenesis: the higher parts could well be derived from theactivity of the Sabaean dam, and the lower ones couldbe related to the activity of the so-called Anlage X.

Significance and Value of Charcoal andWood Fragments Contained in the SedimentsThe author has observed that small fragments ofcharcoal and vegetal remains are to be found every-where, although not abundantly (�1/m3), in the sedi-ments upstream from the dam and in the immediatevicinity downstream.

Like any fossil contained in sediment, these charcoalfragments have conceivably been reworked and arethus significantly older than the sediments themselves.These charcoals show a rounded shape like gravel. Ascharcoal is a soft material and thus easily worn, itcannot therefore be much older than the mediumcontaining it. It has thus been postulated that thevarious horizons could be dated fairly accurately byassaying the 14C content of charcoal and woodfragments they contained.

14C Assay Method Used and ResultsObtainedIn view of the small mass (0·2–0·5 g) of the charcoaland wood samples collected, it was necessary to use theAMS technique. 14C tests were performed on eightcharcoal samples and one wood sample by A. J.Timothy Jull at the NSF—Arizona AMS Facility of theUniversity of Tucson. The samples tested (50% ofthose gathered) were found in the following locationsand gave the following calibrated ages (50 years wereadded systematically):

(1) downstream from the ancient dam, at the foot ofthose sediments found on the right side of themain feeder canal leaving the northern sluice(N1). Whatever the origin of these sediments,which occupy an unusual position downstreamfrom the dam (Gerig, 1982; Brunner, 1983;Schaloske, 1995), the 14C assay of a charcoal frag-ment contained in them gave 2245�45 years (389�204 ) (code AA27398);

(2) four charcoal samples, gathered in the gullycarved out of the sediments upstream from thenorthern sluice gave ages of 1725�45 years ( 243�396) (code AA21889), 1740�45 years


( 243�384) (code AA27394a), 1885�45 years ( 70�215) (code AA24073) and 1995�45years (45 � 68) (code AA24074);

(3) a charcoal sample gathered in the upper partof the higher sediments immediately upstreamfrom the southern sluice (Figure 6) had an ageof 1715�45 years ( 255�406) (codeAA27396);

(4) a charcoal sample from the upper sediments onthe left bank of the Wadı Danah had an ageof 1740�50 years ( 240�384) (codeAA24075);

(5) a fragment of wood from the lower sediments ofthe Wadı Danah had an age of 4460�250 years (3517�2877 ) (code AA27395);

(6) a charcoal sample, topographically situated be-neath the open space above which architectonicelements of Anlage X are located, showed an ageof 1850�45 years ( 84�239) (codeAA29397).

Although it was not possible to determine the exacttopographic level of the various samples gathered, arelationship was found between topographic level andage. None of the dated charcoal fragments are morerecent than 406 (see sample AA27396), even thoughone of them was found at the top of the last sedimen-tary series upstream from the southern sluice. It maybe thus inferred that there is a period of about 300years between the base of the sediments due to siltingup and their top: the last emptying of the basin mayhave taken place at the same time as the reconstruction

and repair work required after the destruction causedby the troops of the Roman Aelius Gallus in 24 (Schaloske, 1995).

Figure 6. The upstream part of the ancient Ma’rib dam showing: left, the northern sluice (N1) with the sediment sand banks formed duringthe more recent period of activity in the foreground; right, sedimentary layers plastered onto the dam itself.

The Roman Invasion led by Aelius GallusThere should have been abundant water at Ma’rib atthat time. However, Strabo (XVI, 782) narrates: ‘‘He(Aelius Gallus) advanced as far as the city of Mariabaof the Rammanite people and laid siege to it attackingfor six days, but then he had to move away because ofthe lack of water; and so he found himself at two days’march from the region of spices, as he had heard tell bythe prisoners of war’’ (translation by G. Franchina).

The fact that the Romans found no drinking waterat Wadı Danah is of some importance in reconstruct-ing this event and the functioning of the dam.

Wagner (1993) has estimated that 100–200 dayswould have been enough for all the water left at thebottom of the artificial lake to evaporate, at a rate of5 to 10 cm/day (which seems to be excessive). He alsoclaims that some water remained on the bottombetween the spring and summer floods. Therefore, ifAelius Gallus besieged Ma’rib during the early monthsof the year, he may well not have found any water inthe basin. But if he was there in the period between thetwo floods or immediately after the summer floodingwithout finding any water, this could mean one of threethings: that the Sabaeans opened the sluice at thebottom of the dam; or deliberately cut off the waterto deprive the Roman invaders of drinking water;


or in fact there was no water because the lake hadcompletely silted up.

According to the historical sources, Aelius Gallusand his troops wintered between 25 and 24 at LeukeKome (Figure 1). After a long and extenuating march,he reached Sabaean territory, destroyed Negrana(present-day Najrn), seized Barraqish and reached andlaid siege to Ma’rib, 6 months after leaving LeukeKome. After failing to capture the Sabaean capital, thePraefectus Aegypti was forced to withdraw. Sixty dayslater he was back in the friendly territory of theNabataeans (Enciclopedia Italiana Treccani, 1932). Itmay thus be inferred that Aelius Gallus reached Ma’ribin August or September; that is, at a time in which thedam basin, if in good condition, would still be full afterthe abundant summer sayl.

DAIS researchers claim that the Ma’rib dam ceasedto function at the end of the 6th or early 7th century, although no indirect evidence to prove this hasbeen found (charcoal, wood, etc.). It may be assumedthat, if the last emptying of the basin took place afterthe Roman invasion, the sediment accumulatingupstream from the dam would have formed a plateaucut by the two branches, northern and southern,of the Wadı Danah which extended as far as the sluicesand the dam. In such conditions of low water in thebasin, a few centimetres of sediment would representmany decades. It may be assumed that the sedimentlayers corresponding to the last few decades of thedam’s activity were easily eroded, as they were ex-tremely thin.

As a result, the carbon dating performed in this studydoes not prove that the Ma’rib dam was still in functionat the time of the definitive expulsion of the Aksumitesfrom South Arabia in 575 (Schaloske, 1995).

It is repeated that the Koran refers to the destructionof the Ma’rib dam, although it actually only says(Surah of the Saba’, 34, 16): ‘‘But they (the Sabaeans)left the Path and We sent them the flooding of the damand transformed their two gardens into two gardens ofbitter fruits and tamarisks and even then only a fewplants’’ (translation by A. Bausani). The two gardens,al-jannatayn, are the two large farmed oases of Ma’rib,separated by the Wadı Danah. The Koran evidentlymakes no mention of the period in which this misfor-tune occurred and tells of a disastrous flood, not thecollapse of the dam.

Calderoni has attempted a 14C dating of the sedi-ments plastered onto the inner face of the dam near thenorthern sluice on the basis of the humus content(Figure 6), obtaining the unlikely result of 8500 years! The humus referring to the sediment depositionperiod has clearly become contaminated with oldermaterial.

ConclusionsThe 14C datings obtained using the AMS technique onthe charcoal fragments found in the sediments of the

artificial lake created by the ancient Ma’rib dam do notprovide conclusive evidence that the activity of theentire installation ceased at the end of the 6th or at thebeginning of the 7th century . Indeed, the mostrecent of the charcoal fragments analysed, found at thehighest stratigraphic level of the sandy sedimentsimmediately upstream from the southern sluice, isdated as 255�406.

In order to explain this discrepancy, it may beadmitted that the activity of the Sabaean hydraulicsystem actually lasted as long as has so far beenbelieved but that it left very few traces owing to the factthat the basin was so heavily silted up that only a fewcentimetres of sediment could be deposited on itsbottom over the decades. All the charcoal and woodfragment contents of the last few centuries wereswept away by erosion. It must not be overlookedthat, over a basin area of some 8 km2, the reliclayers of the sedimentation inside the basin todayaccount for less than 1/25 of the total. Likewise, verylittle remains of the ancient earthen dam, the erosionof which may have begun with the floods described inthe Koran.

The almost complete emptying of the artificial lakemay well have been carried out in the course ofrepairing the hydraulic system after the damagecaused by the troops of the Roman Aelius Gallusin 24 . This hypothesis is supported by the factthat the earliest sediments on the lake bottom,with a single exception, date to the beginning of theChristian era.

It has been confirmed that it is impossible to date thesediment of the entire Sabaean irrigation system on thebasis of the age of the humus contained in it: fossilhumus was probably mixed with more recent one, thusproducing unreliable results.

14C dating using the AMS technique of the charcoalfragments frequently found in the sediments of theentire system has proved an excellent tool for making adiachronic reconstruction of the Ma’rib irrigationsystem and for the rest of Ancient Yemen.

The gradual silting up of the basin downstream fromthe ancient Ma’rib dam is the primary cause of theincrease in the diameter of the coarser fraction ofthe sediments transported by the water used to irrigatethe fields. Even though the Sabaeans managed tooffset the effects of the silting up by periodicallyemptying the artificial lake, it is unlikely that such acomplex operation could ever be performed com-pletely. The flow conditions of the Wadı Danah down-stream from the dam thus became more turbulent asthe watercourse became increasingly shallow and nar-row. A faster flow rate meant that coarser sedimentswere transported.

In the author’s opinion, of the several causesof the decline of the Ma’rib irrigation system, themost decisive is the diminished importance of thiscaravan stop along the Incense Route. The Sabaeansceased their large-scale agricultural and irrigation


activities because the decline in demand no longerjustified the heavy costs of maintaining and repairing anow outdated hydraulic system. Even the Germanresearchers are of the opinion that the smallirrigation installations situated some distance upstreamfrom the ancient Ma’rib dam date to pre-Islamictimes; that is, they are subsequent to the decline of theancient dam.

AcknowledgementsThis paper is dedicated to the memory of Prof.Gaetano Salvatore.

The present research was funded by the NationalResearch Council of Italy. The author is thus particu-larly grateful to Prof. Angelo Guarino, chairmanof the Cultural Heritage Committee, to the lateProf. Gaetano Salvatore, chairman of the MedicineCommittee, and to Dr Paolo Fiordiponti, director ofArea della Ricerca di Roma.

Warm thanks go to all those who unstintingly con-tributed to the collection of samples and the photo-graphic surveys, which took place in the hot season:Anna de Gregori, Eva Francaviglia de Gregori,Gilberto Calderoni, Luciano Cessari, Elena Gigliarellie Bartolomeo Trabassi; to the excellent German trans-lators, who had to grapple with such an unusual topicfor the first time: Elisabeth Bliersbach and PeterLussenheide; and again to the drivers of UniversalTravel & Tourism of San‘a’, who waited patientlyunder the blazing sun of Ma’rib: Nasr, ‘Alı andMuhammad.

Lastly, the author wishes to thank Prof. Alessandrode Maigret, director of the Italian ArchaeologicalMission in Yemen, for his encouragement.

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