Underneath the parched lands of Australia lies a great subterranean reservoir, extending below one-fifth of the whole continent. By drilling numerous artesian wells, engineers have brought the waters to the surface in their efforts to combat the menace of drought
ON THE SHEEP FARMS of Queensland and New South Wales water for livestock and for human consumption is obtained by drilling artesian wells to tap the waters of the Great Artesian Basin. The depth of the bores varies and sometimes, as in the well illustrated, pumping is necessary to bring the subterranean water to the surface.
VAST areas of the interior of Australia are wholly without permanent surface waters. Rivers disappear as though by magic, and fail long before they reach the sea. Much of the land is nothing more than desert; other regions depend on an erratic water supply and are subjected to long periods of drought. The would-be stock-raiser travelling inland would strike vast tracks covered with rich lush grasses six feet in height, clearly having splendid stock-fattening qualities. Here he would settle and for a time do well. Then, suddenly, there would come a period of great drought and the whole land would be devastated. Sheep would die in thousands. These droughts were once the scourge of the country and the ruin of hundreds of the most skilful and resourceful stock-farmers the world has known. Yet the coveted water was not far away. It was often under the stockmen’s own feet. The engineer pointed out the existence of this water and showed how it could be tapped. He had tackled the problem in a scientific way. He first calculated the rainfall and the flow of the rivers to ascertain how much water was “missing”. Billions of gallons were unaccounted for, and it was soon clear that the water which the land needed so badly had percolated into the ground and was being held some distance below the surface.
Exhaustive research revealed the presence of artesian basins, one of which is the largest in the world. The Great Artesian Basin, as it is called, covers about one-fifth of the continent, and is situated chiefly in a region of low rainfall. Queensland has the lion’s share, about three-fifths of the total area of about 600,000 square miles. New South Wales has rather less than one-fifth, and South Australia rather more than one-fifth of the whole. A still smaller area overlaps the southeastern corner of the Northern Territory.
It was the terrible drought of 1880 that led to the successful tapping of this mammoth underground storage basin. A small, keenly anxious group of engineers, scientists and stockmen met at the Killara sheep station between Bourke and Wilcannia, in New South Wales, to watch the sinking of the first artesian bore in Australia. The sun shone from a cloudless sky, but the shadow of death fell on the whole scene. Gaunt, greyhound-like sheep, dying or dead, were scattered at intervals, interspersed with countless rabbits, which had been killed by eating the bark of the stunted and leafless shrubs. Old wheel ruts, hard as iron, marking the course followed by panting horses from the surrounding country, led away across the yellowish-brown expanses of the parched plain.
The engineers were supremely confident, having been taught by previous, almost unerring inferences from geological research. Most of the others were doubtful, evincing that suspicion of the man of calculation and theory which is found so often among so-called practical men. Slowly, with the rough appliances of that time, now ancient from an engineering standpoint, did the process go on. The boring tools were gradually driven with successive blows, until, at the unexpectedly small depth of 140 feet, there was a roar and a column of water shot nearly twenty feet into the air, to the satisfaction of the believers and to the surprise of the stockmen.
The water thus won was an insignificant drop in the giant wilderness of the west, but its great importance was at once recognized. It indicated the presence of a vast underground supply, which would at least cause numerous wells to flourish in the desert. The Government took up the matter instantly and artesian bores were sunk all over the land, with amazing results. In two decades the territory of New South Wales alone had been tapped in 119 places, with an aggregate of 216,089 feet of piping. This brought up from the depths more than 50,000,000 gallons of water every twenty-four hours. By 1914 the number of bores in New South Wales totalled 381, yielding in the aggregate about 100,000,000 gallons of water daily. In Queensland there were at that time 985 bores, yielding a total of about 500,000,000 gallons daily.
5,045 Feet Below the Surface
One of the wonders of these bores is the enormous depth to which some of them are sunk. The deepest is the famous Whitewood bore, on the great Bimereah sheep station in Queensland. It goes down 5,045 feet, or nearly a mile into the ground, and has a flow of 70,000 gallons a day. The Dolgelly bore, New South Wales, has a depth of 4,086 feet, with a yield of 682,000 gallons a day.
This great quantity of water, however, is nearly trebled by that given by the Milchomi bore, round which a veritable city has sprung up in what was once desert land. The thriving township of Barcaldine, in Queensland, is another instance of bores giving birth to cities. Here were once glistening salt flats without a blade of grass. Now the whole district spouts with water and wheat yields forty bushels to the acre as a result of this artesian irrigation.
The quantity and quality of water brought up by these spouting bores vary considerably. The well which gives the greatest flow is that at Charleville, in South Central Queensland. The flow averages over 3,000,000 gallons a day. It is stated that a flow of one million gallons is sufficient for the stock on 80,000 acres, but for agricultural purposes about 400 acres only can be served by this quantity of water.
IN NEW SOUTH WALES the Florida artesian bore was sunk in 1905 and at first yielded 1,232,550 gallons of water a day. In 1912 the pressure was 45 lb. per square inch. By 1928 the flow had diminished to 346,527 gallons and the pressure was only 23£ lb. per square inch.
Sometimes the water is heavily impregnated with soda and other minerals. In many instances it has to be treated even before the cattle can drink it, or else allowed to flow down channels in which its impurities are lost. On the other hand, however, it may be water of a delicious quality. Then the temperature of the water ranges from icy coldness to far above boiling point. At the Moree bore in New South Wales, 2,793 feet deep, the temperature of the water at emission from the earth is 110° Fahrenheit. The water in another bore not far off has a temperature of 148° F. Round some of these bores, where the water emerges at high temperature and where it also has medicinal qualities, numerous spas and sanatoria have sprung up.
Bore sinking in the wilds of Australia is not an easy task. The country has first to be surveyed and a likely spot selected. To this place the apparatus, machinery and stores have to be conveyed. For this work camels are often used because of their ability to go for long periods without water. Here in the desert the engineer and his men have to camp, entirely cut off from civilization, and patiently bore for water. Should their mission fail, which rarely happens, there follows a hasty rush back to avoid starvation.
Briefly, the method of boring is as follows. A steel derrick, 60 feet high, with a timber platform at the ground level, is erected over the site of the projected well. By means of an up-and-down movement of a heavy beam, operated by a steam engine, the various kinds of steel tools cut through the rock by successive blows dealt at the rate of thirty to fifty a minute. As it goes down, the bore is lined with wrought-iron tubes with a diameter of about 10 in. at the top, diminishing to about 5 in. in the deepest levels. This lining keeps a way clear for the upward passage of the water when the bore is complete. In rock the rate of penetration varies from 3 in. to 12 in. an hour.
The percussion system has in some instances been superseded by the diamond drill, whose action is quite different, the tool being constantly turned and doing its work by abrasion. The diamonds, set in steel crowns, are generally of the black variety called carbonado (see the chapter “Diamonds and the Engineer”). A drill using chilled shot has been used also. The cost has been in Australia from 15s. to 40s. per foot of depth, the deeper wells being the more expensive per foot.
From some of the deeper bores the water springs up with great violence. For instance, at Boomi, in New South Wales, the pressure at the surface of the ground is 150 lb. per sq. in., and if the casing were carried up sufficiently high, the water would rise 350 feet above the ground level. In many of the wells this characteristic might be made a source of power. In other wells, which are called subartesian, the water, through rising from a great depth, fails to reach the surface, and has to be assisted to that level by pumping.
Generally speaking, water obtained from a great depth has to be cooled off considerably before it can be drunk by sheep and cattle. For this reason, and also for irrigation purposes, the artificial fountains are carried along in channels for forty or fifty miles over the sheep runs for which Australia is famous. On the way big lakes are formed, in which luxuriant rushes and sedges flourish, and the kangaroo and waterfowl love to dwell.
Natural Heat for Incubators
Pipes and flumes carry supplies far and near, for the water is also largely used for wool-scouring. In many instances the soda and similar substances in the water make it specially fitted for laundry work. But one of the queerest uses to which ingenious farmers put the natural heat of the artesian fountains is to form incubators by means of lined boxes full of eggs. The hot water just out of the tube flows all round these boxes, and hatches out the chickens.
By 1914 some 1,500 bores had been sunk in various parts of Australia. Stockmen generally seemed to be under the impression that the supply was inexhaustible and they allowed the water to run to waste without any control. Then, gradually, a diminution in the flow was noticed and this began to create anxiety as to the permanence of the supply. Extensive investigations were accordingly undertaken by all the States concerned, to ascertain the bounds and limitations of the Great Artesian Basin.
SPOUTING HIGH IN THE AIR, water from an artesian bore at Charleville, in South Central Queensland, flows at the rate of about 3,000,000 gallons a day. One million gallons are sufficient for the stock on 80,000 acres of land, but for agricultural purposes this quantity will serve only about 400 acres.
Legislation was passed to stop the waste of water by insisting that each bore should be controlled by a valve, to shut off the flow of water when it was not being used. Measurements made from time to time of the flow of many bores disclosed the startling fact that in spite of all precautions, the flow continued to decrease, and at the end of the decade ending in 1924 this decrease had averaged about 3½ per cent per annum in the bores of New South Wales.
A similar state of affairs was found also in Queensland, where the total artesian flow diminished from about 500,000,000 gallons daily in 1914 to 308,000,000 gallons a day in 1928, in spite of the fact that the number of bores had increased from 985 to 1,372 in that period.
The result of many observations showed that there are at least three reasons for these losses. The first is loss of efficiency, due to corrosion of the steel pipes which form the lining of the bores. The bore water is under considerable pressure and when the pipe has been perforated by corrosion the water is forced into certain dry and porous rocks which occur in the levels above the water-bearing stratum. An attempt was made to overcome this loss by using two steel pipes, one within the other, and by filling the space between the pipes with cement. When the inner pipe in contact with the water became dissolved further corrosion was thus prevented by the cement lining provided for the outer pipe.
A second cause of leakage is undoubtedly due to water finding its way up round the outside of ill-fitting casings into dry porous beds above, but this is probably a minor cause of loss. The third and chief cause of the serious diminution of flow is undoubtedly that water is being taken out of the Great Artesian Basin at a rate which exceeds the supply.
Fresh Water from the Sea
The chief supply of the artesian water is rainfall, which, falling upon great belts of porous rock along the eastern highlands, soaks through certain porous beds to feed the underground water supplies. The porous strata lie upon non-porous rocks, which prevent its further downward passage. In addition a great mass of non-porous rock overlies the porous zone, preventing the escape of the water to the surface. It is by drilling through the cover rock that the saturated porous bed is reached, and then the water under pressure is forced through the bore to the surface.
The water which sinks into the porous stratum, after having travelled for hundreds of miles underground, finds certain natural outlets. It is because this free circulation is maintained that the artesian water can be used, for if it were merely stored underground in a stagnant condition it would dissolve such quantities of mineral matter as to make it too saline for use.
The chief outlet for the artesian water at the surface of the ground is in the great zone of mound springs which lies to the south-west of Lake Eyre in South Australia. Here the water reaching the surface is lost by evaporation, which is great in this arid climate. The great bulk of the artesian water, however, finds its way into the sea on the floor of the Gulf of Carpentaria. In certain spots in this gulf the flow is so strong that mariners have recorded bailing fresh water from the sea.
The water that is taken from the Great Artesian Basin by bores is probably only a small fraction of that which finds its way into the sea. But the steady diminution of the flow of the bores is a warning that too much water is being taken from the basin. Some concerted policy of rationing this supply is now necessary. Hence the engineer is being consulted. His task calls for lengthy surveys and practical control over wide areas.
BORE SINKING in New South Wales. When a likely site for an artesian well has been surveyed and selected, engineers establish a camp, all their food and materials having to be transported across rough country. Generally a steam engine provides the power for the drilling.
