IRRIGATION.

Ashburton Guardian, Volume V, Issue 1270, 22 June 1886, Page 2

IRRIGATION.

A special meeting of the Ashburton County Council was held at its Chambers, Baring Square, at 1.30 p.m. to-day. Present—Messrs C. J. Harper, E. GWright, J. Jackson, G. W. Leadley, and E. S. Coster. Mr Jackson was voted to the chair. The business was to consider the report of the Irrigation Committee The Chairman having explained the object of the meeting called upon the Chairman of the Irrigation Committee to submit his report. Mr Harper said he had not had an opportunity to discuss the report with the members of the Committee, He would, however, read the report he had prepared from the notes of the Committee Mr Harper was proceeding to read the report when Mr Wright rose to a point of order.

Mr Wright objected to the report being submitted as the result of tho deliberations of the Committee. It had not been approved of by the members. They should have had an opportunity ti consider it, and suggest amendments or additions.

Mr Coster saiJ, as a member of the Committee, he was quite prepared to accept the report submitted by tne Chairman. Each member of the Committee had received a copy of the report, and might have suggested any alterations. Mr Leadley said he approved of the report so far as it went; but it was not full enough. Tne Chairman suggested that the Council should adjourn to enable the members to the Committee to agree to the report. The Chairman’s suggestion was adopted, and the Committee adjourned until 3 pm-

The following are the Engineer’s report and the Engineer’s report upon the Irrigation scheme prepared for submission at to-day’s meeting of the Council - engineer’s report.

Butterick and Leadley’s drain: Having carefully examined the courses of natural depressions, and outfalls of storm water in this district, and taken levels over the same, I find that all the drainage which is at present thrown on to that portion of Butteriok’s and Leadley’s roads, extending from Dwyer’s to its junction with Wakanni Homestead road, would naturally have found its way across said road at an oblique angle into tbs Wakanni Creek, were it not for the obstructions formed by this road, and continoons lines of turf fencing along it, and also by the field fences in the district generally. What is now wanted is additional capacity in the existing artificial drains, in accordance with proposed works numbered 2,3, and 4in the petition of ratepayers to Wakanni Boad Board. After inspecting the ground, lam of opinion that the relieving channel along Stanley road proposed by the petitioners should not be undertaken. It would not be semoieable to any considerable extent and, without considerable severance of land, its junction with the creek would be awkward and expensive. The relieving channel along side of Christie’s road should be at least feet wide, but there does not seem any necessity for extending it beyond the creek near the foot of the terrace, inasmuch as the natural drainage would have fallen into this creek above this point. The channel along Wakanni Homestead road should be deepened a foot for a distance of 20 chains, and excavations properly disposed of in flood bank on field side. lam decidedly of opinion that the Wakanui Creek is the natural outlet for all the drainage now led along Bntterick’s and Leadley’s road as far down as Mr Fitzgerald’s property, and I should, by no means, recommend the closing of the drain along the Homestead road.- From that road to the Outlet on Mr P. Stewart’s property at the Beach the drain is overgrown with gorse and Vegetation, which should, I ' tUnk haVe been periodically cleared by the adjoining occupiers along the route, and which would have been a means of greatly lessening the evil complained pf. But, in order to rive adequate capacity for storm water, as well as to provide outlet for field drainage, this channel should, beside the work of clearing, be deepened from 13 to 18 inches oyep its entire length. I estimate the’cost of the necessary works as follows: . Relieving channel Christie’s road, including ford at Butteriok’s toad .. £ls Deepening drain Wakanui homestead road • • • • Deepening channel from Madden’s to outlet at Stewart’s, including concrete work at outfall £IOO

£l3O Exclusive of minorgoonneotions near Seaview. It appears to mo, however, that it is not lot the Council to maintain or enlarge these artificial drains forming part of the road lines. They have never been proclaimed public drains, and if the work should be executed in whole, or in part, the work should bo borne by tHe district immediately _interested in the irppr'oyechentß, and the district be defined under section 2ii of the pofmties Acts Athend meat Act, 1685,

eport of t ie County Engineer to tub Ch.uim vn of the Irrigation Commit.

At i ho rrquost of the Committee 1 have now the honor to autmit report on the question tor several dll'

tricts within the county, with m*p showing the various blocks, and detailed stimate of cost for each block Block No. I—Lower Bakaia and lower Wakanul, comprises an area of 82,000 acres, and would be supplied from the Rakaia river, by a main, 27 foot In formation width at its commencement and yielding 60,000 gallons a minute. Its proposed course is along line ABO, which forms the upper boundary r,f the district, and from which to the s j a, submains would be formed, the relative sizes being proportioned to the area to be served by each in a given time The existing races would a’so be enlarged and altered in some places, so as to serve as sub-mains. These sub-maics woula be

about 40 chains apart, and, toge'her are

calculated to irrigate at least 2060 acies A day to a depth of about 2 inches, Buy If inches allowing for percolation in mains and sub-mains As, probably, about one-third of each hdding would require to be watered at a time, this proportion of each (or in the aggregate 27,333 acres) would thus be served to the depth stated every fortnight, so that, if the process wore continued during the Irrigation period of, say, nine mon'ha of the year, the entire area of 82,000 acres would be covered to a depth of 10iinches

in that time. Practically, however, the entire area would not require to be watered annually, and tho irrigation period would of course vary with the nature of the season”. The estimated cost for head works, mains and sub-mains for this block is £B3BB which represents an expenditure of 2s per aore. Block No. 2—containing 66,000 acres would be supplied by main D B from North Ashburton rivet near Winohmore, and by auxiliary channel E F from South Ashburton river. The main and sub—-raai-a would be simillarly arranged as on Block, and the setvice provided wdQld be 45X00 gallons a minute. The present races would also fce enlarged to serve as sub-mains. The formation width of main at commencement would be 24 feet. The estimated expenditure for this block is £7394 the cost per acre beiog 2s 3d (nearly). Block No. 3—78,000 acres. It is proposed to enlarge tho present auxiliary channel, and existing service and also to add 30 miles of sab-mains. The jleld is calculated at 30 000 pollona per minute, but this supply, in full, might not ba available over more than seven or eight | months of the year. Daring the rest of the season there would net be much of a surplus over the ordinary supply in the existing races, but it would bo a great advantage for this block to have tho present and increased supj ly limited to an area so much smaller than

the present district- The es'imated cost for this Block is £3492 or 10|d per acre. This service would not be equal to that

on either blocks 1 or 2, bat the expense

would also be proportionately smaller. Block No. 4, Weatorfield District, 72,000 acres—After carefully examining the banks and bed of South Ashburton

river, from Valetta upwards, I have come to the conclusion that the best and

cheapest method of obtaining a supply for this district is from the present source of the races from this river at Gawlor

Downs, by enlarging mains and sub-mains. There is no other point so suitable for keeping control of the river. Lower down the course is so variable

that any headworks would readily be circumvented, and cont’nual expense would

be incurred in preserving an inlet But, besides this, the cost of enlarging the present mains would be less than that of a new main. For this block I would

propose a service of 40,000 gallons a minute. Ti is could be kept up the

greater pa-t of the year, but in a very dry season, such as the .a t, either that supply, or proposed auxiliary chcnnel BF for Wiochmore might be subject for

two or three mcnthslo some diminution. As to an outfall east of railway, I am of

opinion that, after traversing such an ex tent of dry country, the surplus water at the lower end would not he troublesome and greater part of it could be disposed of by the enlargement of Winslow and Wlllowby water race, which would, at the same time, provide the means of watering a considerable area along that route. The estimated cost of service for

No. 4 Block is £4BOO, or Is 4d per acre. Block No. 5, Rangitata, 98,000 acres— I have made a careful examination of site for proposed off-take in Rangitata river bed at G, about 24 miles north of Cracroft, and have pegged off the route, and taken sections for head race GH all

the way along the terraces —a distance of 34 miles. The formation width of this main would be 34 feet, d minish ng in size from near top of terrace to Hinds river at I, a distance of ten miles The proposed supply is 70,000 gallons a minute. You will observe from the sections and detailed estimates that heavy earthworks are necessary to surmount the terraces, the excavations for this purpose amounting to 261,330 cubic yards, but otherwise the works proposed are similar to those for blocks Nos. 1 and 2. Were this supply introduced the present service might be reserve! solely for the use of the Shepherd’s Bush District above line GHI on map. I may also state that the main HI could, at reasonable cost, be extended over the Hinds river into the Westerfield district in the direction KL, in the event of the supply from South Ashburton river ever proving inadequate for future services I estimate the expenditure for block No. 5 at £17,153, or 3s 6d per acre. I would suggest that if it were thought desirable, the Wakanui Creek might be utilised, during the greater part of the year, for irrigating the district situated Mtween it and the Ashburton river, or it might be rendered available either as an independent or auxiliary supply for watering a portion of the Seafield district, extending about 21 miles out from the creek, and embracing an area of about 10,000 acres, the greater part of which is included in block No. 1. The cost as an auxiliary supply might be set down at £7OO. I have not included the Longbeach district in the present scheme, as I am of opinion that, except for the tract alluded to along the line of Winslow-Willowby water race, irrigation is hardly required for that district to any considerable extent. The upper boundaries of Blocks 3,4, and 5 are, generally speaking, about 800 feet above sea level. For the districts higher up a system of irrigation seems hot only to be much less necessary, but the, expense of leading water for these uplands from the higher reaches of the Rakaia and RangiUta rivers would be expesgive ip proportiqa to the small benefit yrhiqh might be derived. In this connection a comparison of monthly rainfall la the different districts is interesting. I find on comparing notes of rainfall at Alford House and Ohertaey, kindly furnished by Mr Herring and Mr Wilkinson respectively, that on an average, the fall at the former place is about 40 per cent, more than at Cherlsey, vhile the record at Alford Forest is about 40 per cent in excess of that at Alford House. Very frequently too, the north west winds, which dry up the lower districts, are accompanied with rain in the upper. I believe that for the districts mapped out, the extent to which irrigation might be advantageously practised to supplement the rainfall would be that both together, the average would be at least inches per month, or 42 inches a year ; and, with water available Its tlnaeous application, in a season of drought, trould proye doubly advantageous. Withir the ffve blocks alluded to, the gravelly sub-soil is snob as to render urigatiop desirable in thp first instance, and, alter application, to prove a medium for patural drainage, free of cost.

You will observe that the total cost of the proposed scheme would be £41,227 for an area of 396,000 acres, equal to 2i Id per acre (nearly) This is exclusive of field mains (or outlets), the expense of constructing which, should, in my opian. n, 1 a defrayed by owners. Th« prime cost of these would be about fourpence per acre. The schema includes the constitution of h j-id-works, mains and suh mains, the latter being not more than 40 chains apart, and charged with a supply calculated to ever blocks 1. 2. and 5. to a depth of lOi inches during aperiod extending over 9 month of the year. The supply for Block 3, would represent a depth < f about 5 inches for the same period and No 4 about 8 inches. It is assumed, that, with the exceptions noted in the estimate the settlers would give a free right of way for these rn dns and sub mains, and provide field crossing &o. as they do for existing water races. The estimate given will represent an annual rate of about 3d, 3id, lAi, 21 end 5d for blocks Nos. 1, 2*, 3, 4~ and 5

respectively, with an aditional annual rate of a half penny per acre, i the Council shon’d defray the cost of construction of held mains The >ate would cover intreat on loan sinking fund, masntainance and supervision The question remaining, and it is a very important one, is that of distribntion. This would be by means of distributaries from the peamvnent field outlets,

oq the catch-work system. The distributing process would of course have to be undertaken by the ocoupiors, and they themselves would have to judge the value of the labor which might be necpasaay, and the extent to which they aught utilise the supply. A goed deal of the distribution might be done in connection with the ordinary cultivation of the farm, and attim-B when fieldwork is otherwise slack. Many of the existing land furrows, (generally about 18 feet apart) would serve to some extent for the reticulation, and settlers would no doubt adapt their cultivation so as gradually to extend the facilities for distribution, and reduce the cost of it to a minimum. I shon'd think about one shilling p r acre per annum would generally speaking, cover the extra coat of labor required in distribution. With water in large quantity available at such small cost, it Is difficult to conceive that a system of distribution on even the most elementary scale would not prove reproductive but the more minute the distribution the more profitable in all probability woold be the return And, while at the outset a department of irrigation might to euna extent, be considered extraneous, it would probably come to be looked upon by meet of the settlers as one of the fundamental of the farm. With reference to 'he supply which might be available from the South Ashburton river, I have gone < n what fro <a gereral observation I consider a safe basis, but it would prove uaefu to have a record of the future supplies both of the south and north branches of that river, at the different seasons of the year, and in the upper and lower districts. For the initiatiatioji of the scheme, I should say* that No 1 block, —Lower Bakala and Lower Wakanui —preaen'a the 1 most favorable conditions In any case, it would appear that an auxiliary wafer supply is wanted for the district, at-d the head works necessary for the one would to • a large extent suffice for the other. ho / water would bo obtainable in any quantity convenient to the district prop-sed to be served, anh that district which is all occupied and under cultivation is one which would be likely to be greatly benefited by such a rcbeme. '' he other blocks might follow in any order which might be decided on. With reference to No 4 block it contains a considerable area of Crown lands, and old roil way reserves, so that in the first instance it 1 might be advisable to deal with an area which would be equivalent to about half the size of the block only in which case the ontlay should not exceed £3OOO. As for No. 5 block—Rangilata—it is almost ( entirely in native grass, and to start with, I should recommend that an area of about t 20,000 acres only be dealt with towards the upper end of the block. The init'ai works would be reduced in size to sent that area and the total expenditure re quired should then not exceed £35?0, Settlement there would no doubt advance as the irrigation scheme proceeded, and as the benefit of the fertilising waters of the Dangitata river became apparent. Taking into account the growing feeling of many of the settlers throughout the county, for an increased water supply to extend to almost every paddock, it seems to me tbo time has arrived for considering a scheme either for the multiplication of water races, such ns the present, on a well defined plan, or for a scheme of irrigation proper each as is alluded to in this report.

I have now endeavoured to describe the features of tire scheme In a general way so that the committee may decide as to whether or how far they can recomend its acceptance to the settlers in the County within the various districts. I have & c. William Baa ter County Knginoer.