In order to protect his crops from the fierce onslaught of wind-borne sand the native is compelled to erect fences and barricades along the northern boundaries of his fields. These serve his purpose for the time being, the sand which would otherwise have cut and beaten down the growing crops being deposited on either side of the fence, where the velocity of the wind is checked. The arrested sand accumulates with increasing rapidity as the size of the obstruction becomes greater, a veritable dune, constituting a really efficient protection to the cultivated lands, being formed over the site of the original small and insignificant hedge. Unfortunately, this sand continues to collect, and although the cultivator may have satisfactorily insured himself against the frequent damage caused to his crops by their exposure to wind-driven sand, he is now confronted with the still more serious prospect of having his lands overwhelmed by the ever-increasing dunes, which have grown to considerable proportions as the result of his efforts to protect himself.
Fortunately for the occupiers of these outlying settlements, the progress of such dunes, formed more or less artificially on the northerly sides of the cultivated tracts, is not at the same rate as that of isolated dunes moving across the open desert plain. Owing to the presence of a certain amount of moisture in the superficial layers of the ground in the neighbourhood of the wells and the cultivated lands, plants of various kinds are enabled to thrive, with the result that the dunes become to some extent ‘fixed’ by wild vegetation. The most valuable plant in this connection is the tamarisk, which by means of immensely long roots continues to thrive and keep its head above growing dunes with remarkable facility. To a certain extent, moreover, the moisture from the soil itself rises by capillarity into the base of the sand, and assists the vegetation in binding it into a compact mass, which is not liable to movement in the same degree as dry sand. The rate of progress of such dunes may therefore be reduced to a considerable extent, but the movement can never be altogether stopped. As we have seen in the case of the hamlet of Meheriq, the sand eventually gets the upper hand, blotting out the arable lands, burying the palm-groves, and forcing man to abandon his habitations.
In the neighbourhood of the Corporation’s Headquarters a considerable area of the floor of the depression has been brought under cultivation during the last three years. This tract is exposed on every side, there being no protection whatever in the shape of natural features. Although occasional sandstorms are experienced from the south, and even from the east and west sides, practically the whole of the trouble encountered comes from northerly sandstorms and sand-laden winds. It was found quite impossible to raise crops unless the fields were protected by storm-walls or fences, the young plants being cut down as if by a scythe. So long as the reclamation of land proceeded from south to north at a fairly rapid rate, the accumulation of sand against these fences was of little moment, being, indeed, rather welcome than otherwise, as the sand was found to be of considerable value when spread out and ploughed into the heavy clay soil with which this area is superficially covered. When, however, a storm-wall remains for several consecutive months exposed to the open desert to the north, the accumulation of sand becomes a more serious matter, and care has to be taken to avoid the formation of dunes, which it might be afterwards difficult to get rid of. A fairly satisfactory mode of procedure is the planting of narrow belts of ‘sesban,’ or other quickly-growing shrub, along the northern limits of the newly reclaimed lands; a hedge of this description forms an efficient shelter to the fields, while at the same time it allows a good deal of the sand to filter through and become absorbed by the soil.
THE CORPORATION’S HOMESTEAD (HEADQUARTERS).
Most of the dunes in the Gennâh district are more or less covered with tamarisk and other wild vegetation, but that their progression southwards has only been retarded, and not prevented, is evident from an examination of the country. Large areas of land have been abandoned owing to the invasion of the dunes, and the magnificent wells of Gennâh are threatened with destruction within a very short term of years, unless special measures are adopted to cope with the advance of the sand. The available land in the vicinity of the village has long been insufficient to utilize the water discharged by these wells, which has in consequence to be led by a channel of several kilometres in length to lower ground south-east of the Gorn el Gennâh. This channel is being constantly pushed to the south, and as the ground rises in that direction, it may eventually become impossible to maintain the conduit at a sufficiently low level to carry the water of the wells to this outlying district.
The southern portion of the oasis is the only area where sand and wind can be said to be of any actual benefit to the inhabitants, but in this area, owing to the broad plains of alluvial clay, the suspended material consists to a very great extent of fine argillaceous particles. At many of the wells in the Dakhakhin and Beris districts the cultivators encourage the gradual deposition on their fields of the sand and clay-dust borne by the northerly winds. The mixture forms an excellent loam, and an annual dressing of the material is regarded as desirable, and even necessary, on account of its value as a fertilizer. The result of this gradual deposition of wind-borne material has been that the cultivated terraces have in many cases attained to such elevations that the discharges of the wells have suffered very considerable diminution, owing to the increased height of the outlets.
To the west of the villages of Maks and Beris the great belt of sand has already enveloped a number of wells, and appears to be still encroaching—as the individual dunes follow their normal course in a direction slightly east of south—on the area occupied by the existing cultivated lands. Fortunately there are still extensive tracts of cultivable land comparatively free from accumulations of drift sand, and doubtless the inhabitants, when driven by the irresistible forces of Nature from the localities they now occupy, will again, as they have so frequently been compelled to do in the past, migrate to pastures new.
CHAPTER XV
SOME ECONOMICAL ASPECTS OF THE OASIS
The Staple Crops of the Oasis — Rice the Summer Crop in Northern Kharga — The Value of Rice in the Reclamation of Land — The Date Harvest — Conditions under which the Date-Palm flourishes — Varieties — Propagation — The Doum-Palm — Lucerne — Its Value in Land-Reclamation — The Vine — Oranges and Other Fruits — The Wadi Molûk — Earthy Minerals — The Ancient Alum Mines — The Phosphatic Deposits.