The map presented herewith shows the area of artesian water-bearing country in Australia as estimated by Dr. R. L. Jack, formerly Government Geologist. Since 1893 Queensland has been credited with the area of 376,832 square miles, this being equal to 56 per cent. of the estimated total. But that total has since been reduced to 569,000 square miles, and late information shows that the approximate area of the Queensland artesian basin, as ascertained by scaling off the most recent map issued by the Hydraulic Engineer, is 372,105 square miles—4,727 square miles less than the area given in his report for 1893. Yet the revised figures bring the Queensland artesian area up to 65 per cent. of the Australian total. The difference is accounted for by later information acquired in the field. Of the 372,105 square miles mentioned the area of 146,430 square miles has been tested and found to be less or more artesian or sub-artesian. Mr. Henderson says: "The flows from many of the artesian bores which at one time or another yielded artesian water have failed, but owing to the suspension of the hydraulic survey the available data are quite insufficient to admit of a trustworthy estimate being made of the area so affected."
FLOWING ARTESIAN WELLS, WESTERN QUEENSLAND
The total supply of bore water has not been ascertained by actual measurement except from Government bores. But all possible reports of reputed flows have been obtained from the owners of private bores, and the figures cut down to 47 per cent. of the furnished estimates. This reduction is not an arbitrary one, however, but is the equivalent of the difference found to exist between the average estimate and the measured flow of such bores as the Hydraulic Department has been enabled to test.
Information from the Hydraulic Engineer's office shows that up to the end of May last there were 716 flowing bores in Queensland, pouring forth an enormous supply of sparkling water estimated at slightly over 479¼ million gallons a day, equal to a discharge of 175,000 million gallons per annum.[c] This flow, if conserved in tanks and pipes, would furnish a population of nearly 12 millions with 40 gallons of water per capita a day. It would irrigate 644,366 acres of cultivated land with 12 inches of water per annum.[d] An area so irrigated, utilised solely for wheat-growing, would produce, at 20 bushels per acre, nearly 13 million bushels of grain, which is equal to 28·87 per cent. of the entire Commonwealth wheat crop for the year 1907-8. The average Commonwealth yield for the last five years, however, was 61½ million bushels. The average area under wheat for the same period was 5,864,114 acres, the average yield for the Commonwealth therefore being slightly over 10½ bushels to the acre. As much wheat is cut for fodder, and as irrigated land should produce a largely increased crop, 20 bushels per acre for such land seems a moderate estimate. Moreover, in 1902-3, the Commonwealth crop was under 12½ million bushels, or less than one-fifth of the mean average for the succeeding five years. At the same time the area of land under crop was in 1902-3 but little below the succeeding five-year average on an acre of land.[e]
The presumably perpetual daily flow of 479¼ million gallons of artesian water—the quantity named being equal to only 47 per cent. of the reputed flow in the case of unmeasured wells—has cost, so far as an estimate can be made, £1,873,515. This works out at the average of £2,616 per flowing bore, supplying 669,369 gallons a day. Calculating on the basis of 5 per cent., including interest and redemption payments, the annual charge for this money is equal to £131 per well, spread over a forty-one years' term, the average cost to each well-owner being thus £1 for 1,865,000 gallons of water a year. Thus, although much money has been lost in sinking unsuccessful bores, the investment has on the whole been amazingly profitable, even allowing that a further annual charge for maintenance must be added.
It need hardly be said, however, that in practice this enormous flow of artesian water could not be utilised solely either for human consumption or for irrigation. Under existing conditions the first claim upon it may be said to be for the sustenance of live stock, as the domestic consumption in the region of the flow is comparatively trifling. And here arises a problem of vast importance. Will this flow be perpetual, or will it gradually decline until exhaustion of the sources of supply ultimately takes place? The latter contingency there seems to be little reason to fear, for the area of the intake beds, estimated by Dr. R. L. Jack at 5,000 square miles, affords the assurance that our artesian springs will be constantly replenished by the rainfall over that large extent of country. Yet, when the existing number of artesian wells has been doubled or trebled, it seems not improbable that many of them will become sub-artesian, and only yield their fertilising streams in response to pumping-power. On this question, however, expert opinions widely differ. But, taking the experience of America and other countries in which artesian springs have been tapped, it may be said that the flow steadily decreases as the number of bores multiplies.
The Hydraulic Engineer estimates that about two-thirds of the artesian water at present tapped flows to waste. As to the definition of "waste," however, there is sharp conflict of opinion. A pastoralist who distributes a supply of a million gallons of bore water a day by replenishing dry creeks or constructing artificial channels may contend that in his case the loss by evaporation or soakage is not waste, but an expenditure of water necessary to make his artesian well serve its desired purposes. To control and distribute by means of reticulating pipes the product of all Queensland's flowing bores would involve a heavy investment of capital, and one not warranted by the existing population in the artesian area—a population mainly dependent upon sheep-raising and wool-growing for subsistence. But the time may come when it will be deemed indispensable that flowing wells should be brought under Government control, or their product be subject, as in the case of surface water, to riparian rights. The pastoralist who has spent several thousand pounds in sinking a successful bore not unnaturally claims the water issuing from it as his own property; but public policy may require that after diverting so much as may be requisite for his reasonable individual uses the remainder shall be made available for the occupiers of neighbouring lands.