Original Correspondence

Akaroa Mail and Banks Peninsula Advertiser, Volume VI, Issue 591, 14 March 1882, Page 2

Original Correspondence

We are at all times ready to give expression to every shade of opinion, but in no case do we hold ourselves responsible for the views advocated by our correspondents.

PROPOSED DRAINAGE OF LAKH ELLESMERE.

To the Editor. Sir, —I have read the report of the committee appointed by the Akaroa County Council; and also the evidence given by settlers and others, which all goes to show that tho source of the water supply into Lake EUesmere is almost entirely from the sea, and that the lake repeatedly rises from 18in to 2ft in the 24 hours from the action of the sea alone. I also see that the inference drawn is, that if the sea could he prevented from coining in, the evaporation would be more than sufficient, to keep the fresh water running into the lake, down ; and that the land could therefore be sold and occupied, and all danger to the railway avoided. Further, that if the embankment and flood gates, proposed by Mr Watkins be erected (although not originally as the same plan was pretty well analysed 15 or 16 years ago) that this end may be gained. Now, no doubt, this or any other plan that the gentlemen forming the committee may arrive at compatible with safety, and cost, is worthy of being looked into, with a view to assist at getting at the pros and cons of the matter. I beg to say, I do not think that the lake is effected by the sea much above high tide, or that thelaka is in the habit of rising all over from 18in to 2ft in 24 hours, or that evaporation will absorb all the fresh water running into the lake, or that the proposed embankment and Hood gates will answer. First, I say from my own knowledge, that after the lake has been let out and every thing drained to a normal level, and working with the tide, Lake EUesmere is not affected all over the lake by the high tide, but only a few inches. This has been learned from experience, with rafting timber. The water does back up in and around Harts creek a little more, but subsides to the height of high tide over the lake when high tide is reached. As to the rise of 18in spoken of, it is caused by the wind alone, and whenever this occurs it subsides on the opposite side of the lake, so that I maintain the sea exerts no power over the lake beyond forming the bank which closes the mouth at a little over high tide level. In the formation of this bank by the action of the sea, the shingle is thrown up in layers at an angle, with a fall to about half tide, and so builds the bank up until it is completed, when the lake, commences to drain through the shingle, and follows that course to half tide. All seas and surfs thrown up and broken upon the beach, and often running over the top, and appirently into the lake, simply subside through the shingle without affecting the lake and join the other streams running underneath to the sea without interruption from the surf above, and find their level to the tide, no matter how high the sea is, as there is comparatively no connection between each succeeding wave. Any one conversant with the place will know that the lake is higher than the highest tide after the bank is finally formed, and is always running through the shingle into the sea, and taking ail with it that has been thrown over by the surf. The Maories make use of these currents by forming channels, in which they catch eels, and they will tell you that once the bank is formed the two waters never meet —on the surface of the bank. Assuming that I am correct in the above statement, where does the water come from but the watershed of the lake, which at a fair calculation including the lake itself covers an area of between 600 and 700 square miles, which water has no other outlet. Besides, independant of rainfall, there are springs forming themselves into rivers and creeks all round the lake, that would form one river of considerable magnitude. Further, there is the Selwyn, which in accordance with Mr Lunn's evidence runs a mile wide and 3ft deep. I have seen the river myself under similar circumstances. Who can say what quantity of water may come off 700 square miles of country ? in the number of heavy rainfalls we have, independant of the above springs. Any one during last winter passing along from Birdling's to Ahuriri, a distance of 12 miles, will know that there was one sheet of water coming off the hill alone, forming no river at all, but backed up by the railway embankment 18in above the level of the lake before it

could find its way into the lake by the railway bridges. These are the sources from which the lake is filled principallyabove high tide of the sea. Now, allowing that the proposed embankment is all

complete and in working order, with flood gates, etc., what size would the gates require to be, and how many of them ? If the lake takes 6 days to run out, which it does to a normal level, through this neck of the lake some 20 chains wide where the embankment is proposed to be erected, with all the fore ; of the lake behind it : how long would it take to run out the confined waters of the lake through three flood gates 23t't each opening (a workable size), or say a chain of the whole width

and under the same circumstances? Would

it not be 120 days in discharging the same amount of water without allowing for friction in passing through the gates, and would it not also have to discharge all the accumulations during the extra tim« it was running, checked by every tide, with which it would subside without much

current? What would the sea be doing with the shingle bank with nothing to

resist its action ? It would reform the

bank in a very sho/t time and the lake could not be let out again until it was in flood as before, and unless a head of water

could he got from Hart's creek and the Leeston district, and conducted into the bason ar Tamutu in sufficient quantity to be able to fill it to the high level of the lake, over and above what was coming in

every turn of the tide, there would not be

mujh chance of the success of the pro-' posed scheme. I might bring under notice the action of

the sea on Lake Forsyth, where the 8 and Burf in south-west weather is backed up much higher than at; Tntnutu, through the confinement of the sea in that bight by the Peninsula. Now, it is well known that hefore Lake Forsyth is let out it usually rises some three or four feet above the road, and at that height it soon begins to scour (as the shingle is much lighter than at Tamutu, where the formation of the bottom is principally heavy boulders, and very bad to scour), and cuts its way against a strong sea and surf and forms 8 fresh-water current eight or nine miles out to sea, leaving a breach in the bank some four chains wide, the lake subsiding in a day to tide level, thus giving the sea and tide free access, and usually closing in a day or two the bank formed, leaving the lake at tide level, and remaining at that level, although the surf is dashing up the bank high above the level of the lake, and subsiding, as at Tamutu, through the shingle to the sea, without affecting the lake. When the sea has had every opportunity of filling the lafte, if it could, above tide level—l mean since last let out, about eight months ago—the lake has remained at what is known as a low level, rising and falling a little, according to the rainfall; but when there is no rainfall, the lake is always lowering through the shingle, no matter what the seas are outside.

In conclusion, I am of opinion that the sea ie the power exerted over the shingle bank and lake up to high tide, and until the bank is finally formed, and remains the main power, by retaining the banks until the watershed of both lakes fills them up sufficiently high to enable them to be let out. I have had a good many years' experience, as a member of the Little Biver Road Board, in accepting contracts for letting out the lake, and in using the lakes at lower levels from year to year myself, at all times and levels, with punts, and rafts without punts. I would often have been glad, for months after the lake had been let out, to have seen a general rise of even 3in, to say nothing of 18in or 2ft, but have not seen it.

I would suggest that, until some defined plan has been arrived at, the lakes be let out as heretofore, and at 2ft lower level than last year, and not let the matter be undecided as to how much it would cost, and who is to pay for it, so that tho first opportunity may be taken, say in June or July next, to employ experienced contractors (with horses and scoops), who have had to do with it before. In my opinion there will then not be nnxh fear of its affecting the railway.—Yours, etc.,

W. COOP.

Little River, March tlth, 1882,