IRRIGATION

Grey River Argus, 13 August 1937, Page 12

IRRIGATION

In South Island DUNEDIN, August 12. The possibilities of irrigation in the South Island, and the problems that s would arise out of the present - schemes were discussed by Mr. W. C. r Stafford at the Annual Conference of 7 the. New Zealand Grassland Associa- - tion at Dunedin to-day. Mr. Stafford said that in the last - five years irrigation schemes amount- ? ing to 217,000 acres had been com- - menced. Seventeen thousand acres ? were now ready for irrigation, and for the remainder water would be ' available within the next five years. ? These, in addition to the irrigation ■ schemes of Central Otago and the i contemplated scheme of the Maniotoi to Plain, (80,000 acres) must, to a t large extent affect the farming policy, ■ and at the same time increase the productivity of the South Island. By 1 1945 the areas under irrigation would • have increased to 360,000 acres. I Developments in Central Otago 3 were taken as a matter of course. The ’ value and necessity for irrigation was i seldom, if ever, questioned; what was - questioned was the cost of the water I and the lack of a sufficient supply. Similar developments in Canterbury ! however, had led to a great deal of • controversy, and there could be no I doubt that the majority are question--1 ing the necessity for it. To this was ■ added the fact that there was a ten- • dency to enlarge on the problems that ■ would arise from the adoption of irrigation. The necessity for irrigation, provid- » ed the land was suitable was deter- . mined by the following:— '■ (1) Where the annual rainfall was > insufficient to supply the plants’ mois- ’ ture requirements. ! (2) Where there was such variation in the monthly rainfall that at cer- - tain periods there was insufficient soil ■ moisture to maintain the plants in a ■ productive state. ! (3) Where, through certain clima- ! tic conditions, there was an abnor--1 mal loss of soil moisture through ■ evaporation. (4) Where there was such variation ‘ in the annual rainfall that periodic ■ years of drought, were experienced. ! The first point provided the reason ‘ for irrigation in Central Otago, while the last three provided the reason for 1 it in Canterbury. If, therefore, wafer 1 suitable for irrigation purposes could be supplied cheaply there could be no doubt that (agriculture will benefit. In Canterbury there was available an unlimited sunnly of water suitable for irrigation. This could be taken from the rivers by means of cheap gravity intakes, in contrast to the expensive dams which had to be built in Central Otago. These rivers with their unfailing supply of water from the huge catchment areas of the Southern Alps flowed at their height during the mohths that water would be required for irrigation purposes. The nature of the ground enabled engineers to construct cheaply the necessary races. The presence of these big rivers enabled large and comprehensive schemes to be undertaken, thereby diminishing the cost per acre. The result of these advantages was reflected in the low cost of water.

The following were the irrigation ■ schemes as far as Canterbury is conI cerned:— ' (1) The Redcliff area of 5,130 acres. 1 The source of the water supply is ! the Waitaki river, and the capacity of the main race was 55 cusecs. The land, which varied from ligfit stony ! silt to heavy clay loam, was entirely flat. Water was made available here for the first time last season. The results obtained made even those farmers who were originally opposed 1o the idea, optimistic of the future. Ten per cent, of the area had been irrigated last season. (2) The Levels Plain area of 13,000 acres: The source of the water supply was the Opihi river and the capacity of the main race is 180 cusecs. The land, with the exception of 160 acres which was a clay loam, was all flat and was a light stoney silt. Water would be available f or the first time this season. (3) The Ashburton area of approximately 200,000 acres: The source of the water supply was trie Rangitata river, and the capacity of the main race was 900 cusecs. Originally the scheme had been confined to 32,000 1 acres m the Winchmore district, and 1 it ha-’ been intended to take the 1 watev f-" this from the south branch ‘ of the '-hl urton river. On the com- ' pletion of the Redcliff area in 1936 a start was made with the distributory 5 races for this scheme. It would now, I however, be linked up with the major E scheme. Water should be available s in 19‘41. g

On all the above areas farms would be supplied with eight cusecs of water whenever it is required, and there was no compulsory water-rate whatever on the land. A comparison of the charges of these and other schemes in the South Island and also in other countries was interesting: Charges for one-acre foot of water. New Zealand Scheme Cost per ac. foot. CompulsoryGalloway 8/Manuherika 8/Olrig Terrace 8/Rippon Vale (private scheme 15/Ardgour 7/6 Redcliff 2/6 Levels 3/Ashburton 3/Australia. Compulsory Bacchus Mash 12/Weeribee 12/Maffra . 10/Gouldburn ‘ 8/America. Yakima Valley I Southern California .... 72/- '

Results in otner countries had shown that where it had been possible to supply irrigation water at reasonable cost such a system of modified dry farming as practised in Canterbury had been replaced by' irrigation , farming. In Canterbury it was well-known that there are periods during which the soil moisture was insufficient to supply the plants’ requirements. These periods were mainly' confined to December, January', February and March. On account of these well-known periods, the Canterbury' farmer was unable to stock his farm to the extent that he could he be assured of a plentiful supply of feed during these months. This period of the year would cease to become a menace to him, ratner would it become a time of plenty during which he would be able to not only supply stock with sufficient food but also to conserve surplus fodder by means of hay or ensilage in a manner which had not been possible before. In order to do this, however, f it would be necessary to understand

thoroughly the principle of applying water to the soil. There could be no doubt that in the early stages of development the wide flooding methods must be the ones used. Their simplicity and low cost of land preparation made them the obvious methods in the early stages of any irrigation scheme. When the value of irrigation had been proved by these crude and inefficient methods farmers would be convinced that the expenditure of money necessary to prepare land for the efficient method of irrigation by the border dyke system was well worth while.

The development of irrigation meant a complete changeover from agricultural to grassland farming, and it meant grassland farming with the two main factors—moisture and sun-shine-—in sufficient 1 ' supply. This change-over would bring in its wake problems which would have to be solved. The would arise from improper use of water, poorutilisation of the pasture, and mismanagment of stock. The present methods of farming on the open gate system would have to be abandoned. Farmers would have again to become shepherds in the old sense of the word. To a great extent the problems arising from the application of irrigation water could and would be solved prior to any extensive irrigation taking place by farmers on these areas. Correct utilisation and management could also be demonstrated. It was with this object that co-operative demonstration farms had been established on these areas, whereby in return for the free use of the water and a certain amount of development work being carried out free of cost the farmer was prepared to irrigate along the lines suggested by the Department of Agriculture and the Public Works Department. These farms varied in size from 300 to 600 acres. By the gradual development of the properties and the establishment and maintenance of pastures under irrigation an endeavour would be made to show how the change-over from agricultural to irrigation farming was to take place. Perhaps the greatest difficulty in connection with the development of these areas would be to convince farmers that they should adopt as soon as possible the efficient method of irrigation, namely the border dyke system. Rather than incur additional outlay in the preparation of the land necessary for irrigation by the Border method there would be a tendency to continue with the free flooding methods. Farmers had been further prejudiced against the Border method by the reported heavy expenditure necessary, this being often given as many times more than the actual value of the land. This high cost per acre might have been incurred in the past, but by the use of modern implements and machinery and by the use of improved head gates the cost had been reduced to under .£2 per acre. During the past eighteen months some 200 acres had been bordered in Canterbury at this price. The land prepared was fully representative of the land which was included in the various schemes.