The sources of water in South-Eastern Egypt, as in the Egyptian deserts generally, may be divided into three main classes:—
[(1)] Springs;
[(2)] Wells;
[(3)] Rock basins.
Springs.
As springs are classified those water sources where water issues naturally from the rocks, either above or near ground level, without the aid of artificial excavation. As will be seen on looking through the list of water sources on [pp. 244] to 250, springs are less common than wells and rock basins, but some of the best known water sources, such as those of Abraq, Abu Saafa, Abu Hodeid, and Meneiga, belong to this class. The Arabic word for spring is Ain, but the Bedouin seldom use this word, calling springs and wells alike Bir, which properly signifies a well. Small springs are called Megal by the Ababda, and Megwel by the Bisharin tribes.
Springs may occur in any kind of rock, but the rock must be either of a porous nature or must contain fissures. Thus the springs of Abu Saafa and Abraq occur in sandstone, which is itself porous and permits the passage of water through the body of the rock, while the springs of Meneiga occur in a crushed serpentine, which, though not itself a porous rock, is full of fissures and crush-planes, and thus is capable of holding and giving passage to underground waters. It is in consequence of the non-porosity and the comparative fewness of fissures in granitic rocks that springs are seldom seen to issue from rocks of this class.
The collecting areas of the Eastern Desert springs are mostly in the immediate neighbourhood of the springs themselves. Thus, for instance, the springs of Abu Saafa and Abraq are fed by the rainfall on the great sandstone plateaux which surround them, while those of Meneiga are supplied by the rainfall on the mountain mass of Gebel Gerf. In consequence of the fact that the waters do not travel very far underground before they issue from the springs, the water is generally cool. The yield of the springs is usually small, rarely exceeding ten litres a minute from any individual spring, but it is wonderfully constant; the rocks of the collecting area form a huge reservoir which only parts slowly with its water contents, and thus springs may go on yielding supplies when, after a succession of three or four nearly rainless years, many of the wells and rock basins are quite dry.
As a rule, spring waters are very clear and potable. The purest are those which pass through siliceous rocks such as sandstone; where the rocks are rich in lime and magnesia, as serpentines and gabbros, the salt-content of the spring may be fairly considerable, but there is no known spring in this part of Egypt of which the water is so salt as to be disagreable to the taste.[114] It is their constancy combined with the purity of their water that makes the springs the most highly prized of desert water sources.
Springs are mostly on or near the main camel roads, for the roads are naturally selected so as to utilise these constant water supplies. Frequently, however, the spring is situated up a lateral valley some little distance from the main track, and is more or less difficult of access. The springs of Abu Saafa are on a main road, where the Wadi Hodein cuts cleanly through the sandstone plateau; but those of Meneiga, being at the head of a cul-de-sac, are only approachable by a branch track. At large springs the Arabs generally dig out a series of basins into which the water flows, so that these are always full of water ready for the camels of a caravan to drink. At megals there is usually no pool, or only a very small one, in sand or detritus; this sand is scooped out and the water is baled from the hole with a tin can. The absence of a pool is probably due to a desire to check evaporation. The flow at a megal is frequently so small that only a few litres per hour can be obtained; the small trickling spring of Sikait, for instance, was yielding only twenty gallons of water per diem in 1906, but even this small supply was highly prized by the miners working there, on account of its purity as a drinking water.