LOWERING THE WAIKATO.

Pukekohe & Waiuku Times, Volume 2, Issue 129, 19 September 1913, Page 3

LOWERING THE WAIKATO.

Engineers at Issue. Mr Thompson's Unfavourable Report. Mr Kennedy Stiil Firm.

At a general meeting of the Waikato Kiver Board on Monday the progress report from fcr J. a. Thompson, land drainage engineer, on th? surveying of the Waikati River from the heads to Mercer, was read. The report, dsted sth August and addressed lo tha Under-Sec, elary lor Lands, waa as follows: "I hsve now to place before you the results so far obtained by cur levelling of the Waikato river from the heads to Mercer wharf. "I regret to inform you that serious differences have b.en disclosed in the survey made for the Waikato [River Association in the year ' 1911, and to illustrate the matter I herewith attach a tracing which shows the position pretty clearly. The longitudinal section has been eo plotted that the levels of the Waikato River Association survey cnuld be readily compared with the points fixed by Mr Morpeth, assistant engineer of this Department. The initial datum of the 1911 survey was used to base our survey en. It is impossible to reconcile the levels taken by us of low water spring tides at the tar and Port Waikato wharf with tfose of the 1911 survey, and considerable differences are show". Continuing the levels to Tauranganui the old bench mark was re-ievell d and an error of 0.45 feet found Again Rt Lapwood's mill a difference 388 feet was found; this bench mark also marks the level of the 1907 floor'. At Tuakau bridge an error of 3.38 feet wa9 disclosed, and at Mercer wharf an error of 2.54 feet was tourd in the value thereof. "From the foregoing it will be seen that the levels obtained by the Waikato River Association in 1911 ate fairly good from Port Waikato wharf to Tauranganui, but from that point of view to Lapwood's mill a considerable error has crept in which, however, becomes romewhat reduced as it reaches Mercer wharf. Considerable pains have been taken to fix the usual spring and ordinary tides at the "bar" ar.d Port Waikato wharf. As a matter cf fact several years is usually required to fix very eccurately these values, but time did nut permit of this, and I am satisfied that our results are near the mark. "The Waikato River Association's survey shows the summer level of river at Mercer wharf is 19.? feet, above low water jpring tides at "bar," but the new survey makes it to be only 11.97 feet, ar.d again if a similar comparison is made at Port Waikato wharf it is found tbat the survey of 1911 gives a fall from Mercer whsrf of 16.7 feet, whereas the new survey shows it to be only 11.87 feet, thus showing a loss of 483 feet which represents the margin the Waikaw River Board expected to lower the summer level of the river at Mercer. It should, however, be noted that the summer level of two surveys at Mercer differ by 0.86 feet as we recorded a lower water level in 1913 than the survey cf 19J1 did.

"All levels have been thoroughly checked either by making complete circuits or by a system ol check levelling, *nd wherever errors were disclosed in connection with the 1911 survey the matter receive special attention. As a final check on our levels they were connected to the system of new results run by the Railway Department from Auckland, as ths result of the closes are as follows:—Based on mean sea levels, 0.87 feet; Based on ordinary high water spring tides, 0.84 feet; Based on high water mark, 0.09 feet; Based on highest spring tide, 0.27. This gives a general mean close cf 0.52 feet.

"The result is satisfactory and is as close as could possibly be exrected considering that the total length of levelling involved over 70 miles. We have a record of the lowest summer level of river at Mercer in 1911 (the lowest for 25 years) and this level is only 1.87 feet above the highest spring tide at "bar" recorded by us during our late investigations. Another very important matter to note is that on February 22nd of this year tidal action amounting to one inch was observed on the gauge at Mercer wharf. Great care had been shorn in fixing gauges between Mercer and the bar. Some 15 gauges having been established between those points. ... As you are aware until now the levels obtained by the Waikato River Association hsd not heen suspected of being in error anu upon them the Board's engineer based his assumptions of possible imprcvements as also did the Board itself. The errors disclosed by cur survey show how needful such survey was end has been the means of saving the ratepayers' money. Mr A. Morpeth, assistant engineer, has under my instructions carried the work out very carefully and 1 am satisfied of its correctness. As a result of our new survey ard investigations I arrive at the following conclusions:-

"1. That in the interests of the ratepayers the departmental survey authorised by the Hon. Minister l'or Lands haa proved indispecaible. "2. That owing to the unexpected errors now disclosed in the 1911 survey obtained by the Waikato River Association, it is q;-ite impracticable for the summer level of the river at Mercer to be lowered four feet as represented by the Waikato Kiver Boatd. "3. That owing to die incorrect data supplied to Mr C. L>. Kennedy, C E , he will have great difficulty in securing a lowering of summer water level at Mercer by two fett, such being only possible by great expenditure ar.d constant dredging of such a nature as to make the proposed scheme of the Waikato River Beard far from financial.

"4. That any lowering of summer level will only result in tidal action being thareafter experienced at Mercer. "5. That the :rijoinii.g swamp lands will be extremely difficult to drain in the ordinary wny, but this point will be dealt with upon the levels, etc., of the Whanagmarino and Maramaiua lai.ds being obtained later on. "6. That within certain limitations it ia posaibfc to improve the Waikato river from Mercer to the heads for navigation, but the headworks would have to extend considerably loiithof Merctt'* ..

MR KENNEDY'S REI LY. Fon C. D. Kennedy, consulting eieiret? Napier, to the chairmr.n i t the ft ail-: :h Kiver Board, Meicn : - "I iisvj tu acknowledge recent of a cupy of tLe recently-pretared eeetions of the Waikat? river from the Heeds to Mercer, showing variations between tfe levels oi which I based my report and (hose taken hy tie Lands Drainage Department, and copy of Mr Thompson's letter to the Urder-Secretery for J. ands of August,

''3 he tiscrepancies shown are serious, the or e affecting the question most being that the new survey shows the mean sea level at 44.27 ttlo.v the assume 1 datum, whilst that on which 1 baeed my calculations was 41.40, a ditt';rence of about 2 te c t 10 inches.

"Though these corrected levels, fre m Mr Thompson's point of view, justify him in making the summary set cut at the end ct his report, there is ample evidence by inspection of the river and its cor.elition that its water can be materially lowered. The l-.vel at Kaitangata can assuredly be reduced considerably if the river is confined below and the very extensive sard-banks removed. There is evidence that many years ago the Lv.l of the bed was five feet or fix feet lowir than it is at present at Mercer, and that even wit'r.in the last five and twenty years the ordinary water Uv.l has risen from two feet to three feet.

"In the face of Mr Thompson's letter you will no doubt have great difficulty in carrying cut the improvements recommended in rcy first report, and I advise your Board to carry Out, or to irduee the Go vernment to carry out, the training walls from Kaitangata to Paksu ss suggested by me. I am of opinion that thiese will lower the river at Kaitangata several feet and render the river navigable for vessel of si;; feet or seven teet draft. If the result, after the works are carried out, is not to lower the river materially at that poi :>t, then it would be inedvisabla to proceed with the works cn the higher reaches." ENGINEERING COMMISSION ASKED FOR.

After the reoprts were read. Mr Glass stated that Mr Breakall, the original surveyor, now admitted that tnere was an error cf 2 ie;t 6 inches in the Morctr level, but that errur had rectifiel itself. It apceared that Mr Morpeth had takea the lowest summer level and the highest spring tides. Mr Breakall stated that ha had aiiowed 2 feet for any discrepancies*, and he still maiu'ained that the river could be lowered 4 feet. Mr Dean: Is that official?

Mr Glass: No, but Mr Breakall says ha will Etick to it. He moveJ, "That a copy of Mr Kennedy's report be sent to the Prime Minister, and that he be requested to now appoint a commission (as promised by the Prime Minister) composed of the l»:st engineers outside thb Government service that can obtained, and that in the meantime the levels and hfoimation obtained by Mr Morpeth be rhecked off by an engineer outside the Government department for the benefit of the engineering commission when appointed." This resolution wa3 carried.