Section Iv.—Wadi Rayan and Neighbourhood.

This part of the Fayûm is of special interest in consequence of its possible future as a reservoir. Although the area has not yet been examined in detail by the Geological Survey it will be useful to bring together all the information that is at present available.

In 1882, as a counter-project to other irrigation schemes, Cope Whitehouse suggested utilising as a reservoir the Wadi Rayan, a depression which had been referred to by Linant de Bellefonds. At the request of Sir Colin Scott Moncrieff the Government deputed Colonel Western to make plans of the Wadi Rayan and surrounding country and to ascertain the capacity of the depression and its capability of being used as a reservoir. Liernur Bey under his direction prepared a contoured map, and Colonel Western’s report, plans, and estimates were published. Some general details of the wadi and surrounding hills are given and the detailed survey showed that the 30 metre contour line (above sea-level) enclosed an area of 706 square kilometres (170,000 feddans). The lowest points of the depression were found at 42 metres below sea-level. The sand, scrub and springs are briefly referred to and the discharge of the latter is given as equal to that of a very slow-going four inch hand pipe, the water running out at about + 20 m. and disappearing in the sand. Wadi Muêla was found to be separated from the Rayan depression by sandhills and rock at a mean level of + 50 metres, the lowest point in Muêla being at + 25 metres. A line of levels was run from Rayan through Muêla to the Nile Valley, the highest point crossed being at + 105 metres; for fifteen kilometres the level was not below + 75 metres. In order to find the most suitable passage for a canal to connect the Nile with the Wadi Rayan two lines of level were made after a reconnaissance of the hills near Sidmant el Jebel: the southern, from Ezba Menesi Ali, near the Gharaq canal, to Mazana on the Bahr Yusef, being considered the best. Along this line the highest point was only at + 44·7 metres and the average + 35 metres along four kilometres. Borings were not made here but judging from the surface excavation would be mostly in soft limestone, sand, and conglomerate. A much shorter route is from Deshasleh on the Bahr Yusef over the hills about 5 kilometres to the south of Mazana or Sidmant into the Wadi Gharaq, a distance of 30 kilometres. This route was not however levelled but is fairly straight and apparently not much higher than the Mazana passage.

The survey of the + 30 metre contour line of the Wadi Rayan proved that there were only two outlets into the Fayûm, both on the northern side: these two openings are only from 400-500 metres wide and their lowest points are not below + 25 or + 26 metres.

In 1889 Sir C. Scott Moncrieff published a further note, in which he briefly discussed the probable cost and benefits to be derived from the suggested reservoir, concluding that at least the project was one worthy of being thoroughly examined.

In 1894 the plans and designs in connection with the Wadi Rayan were published and the possibility of utilizing the Wadi Rayan was examined by Sir William Willcocks, then Director General of Reservoirs, from an engineering point of view, and the questions of its probable cost and future utility were discussed. In this report it is stated that the routes proposed by Colonel Western in 1888 pass through salty marls and clays unsuitable for holding canals. Another route is suggested, which after leaving the Nile Valley crosses the high desert ridge in a straight line, passing through the so-called Wadi Liernur (Wadi Lulu of Cope Whitehouse); this depression is 12 kilometres long and has its bed some 24 metres below the general level of the desert. Plate 15 of the report shows the Wadi Rayan, the deserts between it and the Nile Valley and the cultivated land. The map was begun by Col. Western and completed by Willcocks. The lowest point of Wadi Rayan is shown as − 42 metres and the depression is separated from the Fayûm by a limestone ridge generally from + 34 to + 60 metres, except at two places where it falls to + 26 metres above sea level on a length of 600 metres. Within the + 27 metre contour line the wadi has an area of 673 square kilometres and a capacity of 18,743,000,000 cubic metres. Between it and the Nile Valley lie 30 kilometres of desert, of which 11 are occupied by a marked depression discovered by Liernur Bey in 1887. At the extreme western edge of the Nile Valley (here 20 kilometres wide) runs the Bahr Yusef. Comparing the proposed Wadi Rayan reservoir and the ancient Mœris and allowing for a difference of 4·5 metres between the levels of the Nile Valley in B.C. 2,000 and to-day, Willcocks assumes that the high water mark of Lake Mœris was at + 22·5 metres and its area 2,500 square kilometres, against 673 square kilometres of the Wadi Rayan at + 27 metres. It is pointed out that the ancient lake had the great advantage that in those days the Bahr Yusef was an important branch of the Nile, if not the main river itself, and the reservoir was connected with the Nile by a natural ravine of great length and short breadth, across which a massive embankment was thrown and destroyed annually, the surplus water of high floods being stored for the deficiency of low floods.

The published sections along the lines of borings put down show the different strata cut through by the proposed canal. The Nile Valley, along the line of the inlet canal, consists of hard clay 6 to 10 metres thick, lying on coarse sand. Along the outlet canal sandy clays and clays alternate to a depth of 10 metres. On entering the desert sands and sandy conglomerate, with gypsum and salt, are met with below the surface, then a yellow marl with salts, and finally a plastic black clay overlying the Parisian limestone. These beds are most extensive in the narrow neck of land between the Nile Valley and the Fayûm and to some 10 kilometres to the south of it. They rise to + 70 metres. There are some other marls inside the Wadi Rayan or in the adjacent depressions and as they have to be traversed by the canals form a serious factor, being easily dissolved in water; in consequence Willcocks chose the alignment of the inlet canal along the Bahr Belama where the extent of these beds would only be 2·5 kilometres against 9 kilometres on the alternative route marked on the plan. A narrow neck of land, some 15 kilometres in length, runs between the Fayûm and the depressions traversed by the proposed Wadi Rayan canal; this neck is the continuation of the salty marls and clays, but the limestone is near the surface and is overlain by a thin deposit of sand and pebbles, with freshwater shells on its northern slope at + 22·50 metres; the southern slope is entirely devoid of them. Willcocks points out that it is evident the ancient Mœris rose to + 22·50 metres but its water never penetrated into the Wadi Rayan. The report goes into details of inlet and outlet canals, discharge, necessary masonry works, cost, and compares the different reservoir schemes.

After a careful review of the whole question, the scheme, while considered perfectly feasible as far as available data went, was abandoned by Sir William Garstin in favour of the less costly and more useful Nubian reservoir.

EL WADI, RAVINE NEAR QASR GEBALI.]

In an appendix to the above report Schweinfurth discusses the question as to how salt the water of such a reservoir would become. He points out that the exact valuation of the salt which would be contained in this reservoir when the water had risen to + 27 metres cannot be accurately determined, owing to the absence of information on certain points. The maximum quantity of salt in the desert soil is estimated at 2% and this figure is used in his calculation, which includes the amount of salt which would be brought into the reservoir, (1) from the Nile during filling and in the extra water entering to replace that lost by evaporation in the lake and canals; (2) from the ground forming the bed of the lake (far the largest item); (3) from the bed and banks of the inlet canal, both in the desert and in the Nile Valley; and (4) from infiltration. The figure obtained is 7,500 million kilogrammes, equal to 0·04 per cent, or almost one twenty-fifth per cent of salt. This amount is only equivalent to half the salt existing in many of the well waters used in the country for irrigation. As Schweinfurth is careful to point out his calculation is based on maximum and assumed data.

The question of the utilisation of the Wadi Rayan as a reservoir has recently been again brought to the front, notably by Sir William Willcocks in a paper read before the Khedivial Geographical Society, Cairo. The author, after pointing out the value of such a lake, working in connection with the Assuan reservoir, discusses at length the position, dimensions, and functions of the ancient Lake Moeris. It is suggested that the main canal should be cut through the desert opposite Mazana and crossing the so-called wadis Liernur and Masaigega enter the Wadi Rayan at its easternmost point. These wadis would in time become covered with alluvium and be converted into valuable cultivated land. After examining the big ravines of the Fayûm, where similar beds are exposed, the author comes to the conclusion that the maintenance of canals in the saliferous marls, which form part of the desert through which the inlet canal would pass, would offer no particular difficulties.

With regard to the questions of leakage into the Fayûm and of the water of the lake eventually becoming salted, Sir William Willcocks says, “When the old Lake Moeris, or the present Fayûm, was full of water and 63 metres higher than the bottom of the Wadi Rayan and remained so for thousands of years, there was no question of the waters having become salted or having escaped into the Wadi. The Wadi was as dry as it is to-day and the great inland sea was always fresh.” As to the question of leakage into Gharaq the author considers that if water found its way into that depression it would be a distinct advantage, as such water could be pumped into the Nezleh canal and utilized elsewhere; he maintains at the same time that no leakage will take place. Incidentally it is mentioned that the Wadi Rayan is separated from the Fayûm by a limestone ridge, a statement which, as will be shown later, requires modification.

Until a detailed geological examination of the Wadi Rayan and neighbourhood has been carried out it will not be possible to form reliable opinions on many of the questions raised in connection with the prospective reservoir. The writer’s acquaintance with the area is limited to a traverse in 1899 from the Nile Valley through Wadi Muêla to Rayan and thence to Gharaq, and subsequently to a stay of a few days duration in the neighbourhood of the Rayan springs, after mapping the extreme south-west of the Fayûm depression. While the accompanying maps may be taken as representing fairly accurately the bolder topography of the region, they do not replace the older contoured maps of the floor of the depression and the country between it and the Nile Valley to the east, accompanying the report on “Perennial Irrigation and Flood Protection in Egypt.”

The following description of this part of the district is based on a traverse from the Nile Valley through the wadis Muêla and Rayan to Gharaq; the detailed geological sections measured and examined along the line of route will be given later.

Between the village of El Gayat and the mouth of the Wadi Muêla (16 kilometres to the north-west) stretches a gradually rising undulating gypseous plain, superficially covered with loose sand and rounded pebbles of quartz and flint. In occasional small hills the white limestone which forms the underlying rock is visible. Near the entrance to the wadi stands a somewhat prominent conical hill composed of hard whitish fossiliferous limestone passing down into more sandy and clayey beds. The bottom of the wadi is cut out in soft green and brown clays, its surface being covered with blown sand, fragments of limestone, flints and gypsum. From the mouth of the wadi the Nile Valley cliffs run north and south in a winding irregular manner. On entering the valley several outstanding flat-topped limestone capped hills are passed on the right hand; they are in part joined to the regular bounding cliff beyond; the eastern cliff is steep and well-marked, while that on the west only outcrops here and there, buried as it is in immense accumulations of blown sand, rising in places into definite dune-ridges. Wadi Muêla has a length of some 18 kilometres and lies nearly N.W. and S.E. The central part of its floor is a sandy scrub-covered area, the lowest points lying at about + 25 metres; just at the southern edge of the scrub stands a small hill composed of hard shaly clays capped by white limestone, surrounded by a saline, superficially dry. Holes dug in this are at once filled with excessively salt water, and by evaporation of the brine in shallow troughs supplies of white fairly pure salt can be obtained. The area is known as Warshat el Melh. Banks of reeds were found growing on the north side of the saline, the surface of the latter being here composed of a soft brown sandy salty deposit, caking here and there into a hard earthy impure salt.

In the lowest spots the saline frequently consists of soft wet sludge; its area is about half a square kilometre but the depth of the deposit is unknown. In the middle of the scrub-covered area to the north lies Ain Warshat el Melh, a pool of water, fairly fresh and drinkable, although ferruginous, measuring 10 by 5 metres in size and from 2 to 2½ metres deep. The water evidently rises from a spring on the west side, round which are fifty square metres of green rushes, with some larger bushes. The ground around and above is very saliferous; between the spring and the ruins to the north the ground is sandy, with many bushes and much scrub. This ground extends two kilometres to the west, whence it gradually passes up into great masses of drift sand; an occasional small outcrop of the top of the plateau above the sand is all that serves to locate the position of the buried cliff. On the east side the sandy ground with scrub extends about a kilometre, beyond which the plain gradually rises for another kilometre to the base of the cliff beyond, which is fairly steep and well-marked, though with an entire absence of indentations of any kind.

Close to the north end of the valley, and about 33 kilometres from El Gayat, lie the ruins known as Der el Galamûn bil Muêla. At the time of our visit a new square stone building was in course of erection and five or six persons were inhabiting the place. There are several small palms scattered about to the south of the monastery and an excellent running spring of clear water five hundred paces to the south-west. A new well is being sunk within the premises. To the north of the monastery the eastern cliff takes a marked trend to the west for some three kilometres, whence it resumes a northerly direction, always maintaining its character of a steep well-marked escarpment rising some 100 metres above the floor of the wadi. At the corner of the cliffs the lowest bed exposed is a white limestone; this is overlain by gypseous clays passing up into sandy beds, the latter being surmounted by the white limestone capping the escarpment.

We are here on the summit of the divide between Wadi Muêla and Wadi Rayan, the height of the floor being about + 105 metres; to the north stretches a gradually widening bay descending to the lowest ground of the Rayan depression. Immense accumulations of sand almost block the defile and stretch away to the east, and the hitherto well-marked cliff on that side bends back and is lost to view. On the other side however, the bounding wall gradually emerges from the dunes, getting more distinct as it is followed northwards until it becomes quite clear of the sand. The first glimpse of this cliff is seen a couple of kilometres west of the pass in an outcropping headland, the next point visible being some five kilometres further west. Between these portions of the cliff are one or two outliers, surrounded by quantities of blown sand. A depression known as Wadi Korif is reported to lie to the west, and much scrub and some water is said to exist there; such a wadi is marked on Schweinfurth’s map but apparently has not been examined.

Continuing in a N.N.W. direction high rather steep dunes occur on either flank, running N.N.W. and S.S.E. Between the dunes is a fairly hard undulating sand-flat affording an easy route; further on a narrow defile between the dunes leads down to the centre of the depression. The main areas occupied by blown sand are shown in the accompanying maps. The most interesting part of the depression is the bay lying to the south of the narrow well-marked promontory jutting out from the southern plateau, a huge pointer, as it were, in the direction of Gharaq; this is the Cape Rayan of Schweinfurth.

The bay is on three sides completely enclosed by cliffs and its floor is thickly covered by a luxurious growth of wild scrub—chiefly tamarisk and ghardag; numerous isolated palm trees occur, especially in the neighbourhood of the water which exists at several points. There are three particularly good springs, the positions of which are shown on the accompanying maps. According to Colonel Western’s survey the water emerges at about + 20 metres. In 1899 the water of the northern spring was found to have a temperature of 26°C. On our last visit we found an artificially constructed pool of two metres diameter and a depth of 30 centimetres; on the west side of this were two springs, marked by the motion of the grey sand rising and falling in the vents, down which a stick could be easily pushed to a depth of two metres. The output of these springs together amounted to six litres a minute; the water was quite clear and although soft and rather ferruginous not by any means unpalatable (see analyses below). The pool lies on an open bare sandy spot and is surrounded by scattered bushes, none of which however are within fifteen metres; a sand dune lies 150 metres to the south-west, with bushes and seven or eight young palms. The southerly spring has an output of 21 litres a minute, and its water does not differ essentially from that of the northern spring. Rising at the foot of a palm tree it forms pools on either side; thence it flows a distance of 20 metres into an artificially constructed shallow basin 2 to 3 metres across, from which it runs away down the slope and disappears after five or six metres. The east spring, which is situated on the east side of the dunes bounding the mouth of the bay, consists of a small hole cut out in soft sand. The water seemed good, although analysis shows the salts content to be high; this spring does not run, but if emptied the hole soon refills. The remains of old buildings occur near the well, in the shape of loose roughly squared limestone blocks, broken pottery, and remains of old walls; the latter are nearly level with the ground and very thickly and solidly built.

To the south of the promontory lies the so-called Little Rayan. Here there is a good deal of scrub, and water can be obtained on the lowest ground at a few metres depth, although there do not appear to be any surface springs.

The geological succession of beds exposed in the cliffs of the promontory is given later. Broadly speaking it consists of two thirty-metre bands of hard limestone separated by 68 metres of softer sandy and clayey beds. The lower of the limestone bands in places forms the floor of the depression but more frequently the latter is composed of the overlying sandy or clayey beds. The depression is bounded on the north side by the same succession, and, as far as could be judged from observations made on the traverse, the bed of limestone capping the ridge, and forming the plain stretching away to the Birket el Qurûn and to Gar el Gehannem, is identical with that capping the cliffs to the south, i.e. is the uppermost of the two thick limestone bands. At the two points more particularly noticed, namely, the spurs projecting southwards into the depression, 23 kilometres west and 18 kilometres W.S.W. of Gharaq basin, the sequence seemed to be the same as in the southern cliffs, although, owing to the northerly dip, the upper bed of limestone lies at a much lower level and the basal beds are not exposed at all. In both these localities, however, some of the underlying clays were exposed, as well as on the lowest spots crossed between the most easterly spur (18 kilom. W.S.W. of Gharaq) and the extensive dunes lying immediately west of Gharaq cultivation. These dunes, though of no height, have remarkably steep sides. In crossing Gharaq to the Fayûm cultivation occasional beds of yellow sandy limestone were noticed, but their horizon was not determined. Numerous bored blocks, probably belonging to the marine Pliocene, were observed scattered about. Apparently the uppermost thirty-metre band of limestone passes continuously northwards under the cultivated lands of Gharaq and the Fayûm; in the ravines of the latter this limestone is not observed, the soft limestones exposed below the alluvial deposits almost certainly belonging to the overlying Ravine beds. The country to the east of Gharaq has not been geologically examined and the exact locality in which the thick bed of limestone dips underground and is overlain by the succeeding beds is doubtful. Further north, in the desert ridge east of Qalamsha, we have observed the Birket el Qurûn beds and a section measured at this point is given later.

As it appears to have been freely assumed that the ridge separating the Rayan depression from the cultivated lands of Gharaq and the Fayûm is formed throughout of solid limestone, it is important to point out that, on our assumption of the identity of the beds of limestone capping the cliffs to the south and the plain to the north of the Wadi Rayan, the dividing ridge would in part be formed of the underlying arenaceous and argillaceous beds.

The absence of Nile deposit and freshwater shells in the Wadi Rayan will, when confirmed after a thorough examination of the area, afford the strongest evidence that the depression was never directly flooded by Nile water. The fact that the dividing ridge is probably everywhere above the highest level attained by Lake Mœris, and by the still more ancient prehistoric lake, is almost sufficient in itself as a proof of this. It does not however follow that there was not leakage through the ridge into the Rayan basin, as such leakage might conceivably have taken place to a considerable extent without the water ever having collected in sufficient quantities to form even moderate sized pools within the depression. The bottom of the depression is for the most part covered with soft porous sandy deposits overlying the Eocene bed-rock below, and at the present time the water of the Rayan springs, though continually running, at once disappears from sight, drains down to the lowest parts of the depression and is then gradually lost by evaporation or underground leakage. In the lowest parts of the depression this water is, as already mentioned, met with on digging to a very moderate depth.

A careful examination of the flanks of the ridge separating the Fayûm and Gharaq cultivated areas from Rayan might prove if such leakage ever took place. If such was the case the seepage was probably along the line of junction of the limestone and underlying clayey or sandy beds. Even if it were proved that there never was leakage from Lake Mœris into Wadi Rayan, it would not be safe to assume that the converse would not happen, as the dip of the beds is from south to north and this fact is one to be reckoned with. Judging from the nature of the Eocene beds forming the Wadi Rayan, my opinion is that leakage on a large scale would not take place, and that owing to the northerly dip any water that escaped from the reservoir would pass indefinitely northwards and would not find its way through the overlying limestone to the surface either in Gharaq or the Fayûm cultivation. A detailed examination of the local geology would, however, be necessary to prove or disprove this. As to the question whether the Wadi Rayan as a whole would hold water, as far as is known there are no faults or other fissures of any magnitude through which the water could escape. No doubt a good deal of water would be lost before the smaller joints and passages, which exist in all rocks, were silted up. Schweinfurth supposes that the freshness of the Birket el Qurûn is due to the existence of subterranean outlets, and such might also be found to exist in the Wadi Rayan. In any case the argillaceous deposits from such a lake would very soon form a bed to all intents and purposes impermeable.

With regard to the extent of salinity of such a lake Dr. Schweinfurth’s figures are of considerable interest and value, although based wholly on assumed data. The greater part of the salt would be derived from the rocks and soil forming the bed of the reservoir and only by extensive sample collecting and analysis can reliable figures be obtained. We believe that in the lowest parts of the basin the salt content of the ground would be found considerably in excess of the two per cent used by Schweinfurth in his calculation, although his total estimate would probably be found well within the mark.