IRRIGATION.

Dominion, Volume 1, Issue 46, 18 November 1907, Page 6

IRRIGATION.

Few readers will feel inclined' to quarrel -with the placing upon the Estimates of a sum of money for the investigation and prosecution of schemes of irrigation. The subject already has a bibliography of its own which can be consulted by those desirous of going fully into matters, and it is unnecessary for us to do more than mention one instance of the benefits derived. Egypt, for example, without irrigation would be a desert.. With her ancient system of irrigation she grew one crop a year and was bankrupt. Last year, after three vears' enjoyment of a modern irrigation scheme, she exported agricultural produce to the value of twenty millions sterling. Striking results also have been obtained in France, Spain, Italy, India, California, etc., while in New Zealand itself a few agriculturists have repaired and pressed into service disused mining races, sometimes on a necessarily small scale, but at others with an amount of pecuniary benefit truly astonishing. As regards the scientific aspect of the question, it may be said briefly that, given a suitable soil, or at least the means of enriching that soil with the constituents which it lacks, the crops it is possible to win will only be limited by the quantity of sunlight available and of tile water supplied by Nature or man. Now, many parts of Now Zealand possess a sufficient rainfall, but insufficient sunshine; others an adequate amount of sunshine, but a very scanty local precipitation. Husbandry under the latter conditions, though pleasant' enough, is unremunerative, but the artificial provision of the water requisite would render the agriculturist's existence simply idyllic. The grant of £3000 for the present year will hot, -of course, do all this, but it will pave the way by completing surveys and by effecting small alterations and repairs in races already existing. At the least it will serve as an earnest of the sincerity of the promises! of the Government, and leads us to hope that it is really intended to spend the £100,000 spoken of by the Minister. .Much has been publicly said and written on the question of irrigation; but the present grant is the first tangible proof of interest that has been given officially, although the Lands and Survey Department has already done a considerable amount of sound unobtrusive work in the matter. We are not in posr-lission of the plans of the Minister, bu: are probably safe in assuming that particular attention will be paid to the Plains of Central Otago, these containing, roughly, half a.million acres of land of glacial formation, with a rainfall of, say, sixteen inches per annum. Space wil not permit of our going deeply* into figures, but it is clear that the £100,000 mentioned will not suffice for the simultaneous prosecution of all the practicable schemes. . The expenditure of this sum might, however, effect the irrigation of the Maniototo and Idaburn Valleys, for example, and these will serve for the purposes of illustration. For the former the cutting of a long race would be necessary to bring the water from the Upper Taieri. For the latter certain existing mining races could be utilised, and a storage dam might be constructed. The net result would be the bringing under close cultivation, at an annjial oharge for interest and upkeep of £6000 or £7000, of an area of from 100,000 to 200,000 acres now carrying on the average one sheep to every three acres. Taking the mean of these figures, then, a few years should see 150,000 acres irrigated at an annual charge of IOJd. per acre. Now, in Egypt, according to "Hazell's Annual," the increase in rental after irrigation is £1 per acre per annum, while expert witnesses before a New South Wales Parliamentary Committee - last year stated that farmers—in this particular case they were pastoralists— : could well afford to pay from 6s. to 9s. per acre per annum for irrigation. Taking the lowest sum as reasonable, it will be seen that in the case of the Maniototo and Idaburn the cost of construction would bo repaid in two years and a half, and the capital thus released could be applied to the prosecution of further schemes.

The sequestration of streams for irrigation 'purposes may, however, be viewed with displeasure by the more ardent advocates of schemes for the hydro-electric generation of power. We cannot enter here into a discussion of the merits of the rival objectifs, but will merely say in passing that the same remarks apply to generation of power as to illumination, and, just as it is unfair to compare the electric light of the present day with )h.e jgas of twenty years back, so. it is.

to place a modern electrical plant side by side with a prime mover so obsolete thermodynamically as a steam engine. While it is true that even a modern steam plant such as that of the Wellington City Council shows high power costs, the very qualified success of the Waipori Falls scheme, on the other hand, .indicates pretty clearly that in such matters engineers have not reached finality, and that "Festina lente" will be a safe motto to adopt, since a considerable period will probably elapse before heat engines are altogether out of running. Moreover, there will be plenty of water-power available even after all the ■ irrigable land in the Dominion has been satisfied, more especially as a great hydrostatic head is not required for the distribution of the water over tlie areas likely to be considered. O , point worthy of note is that the im- £.' gineer, however highly skilk his profession and experienced in Jr.igation matters, must necessarily oe inferior to his confrere with local knowledge. Fortunately, there are in New Zealand a number of capable officials who know their particular districts from end to end, who have already gone deeply into the subject of irrigation, and who will bring the matured thought of years to the matter.