MONOWAI STATION

Southland Times, Issue 22042, 15 June 1933, Page 5

MONOWAI STATION

RISE IN THE LAKE. CHIEF ENGINEER’S REPORT. The recent rise in the lake surface near the headworks at Monowai received brief reference in the monthly report of the chief engineer (Mr L. B. Hutton), which was presented at Tuesday’s meeting of the Southland Electric Power Board. The report stated:—“lt will be remembered that at the beginning of April we had a quick rise in the lake, and that the river discharge was increased in proportion over a period of three days. From April sto 12, matters were stationary, but on the 13th heavy rains caused another rise in the lake up to the lift 6in level, and this again had to be met by increased river run-off for more than a week. However, on April 30 the lake had been brought down to the 10ft 9in. level, and had held there for five days. The discharge over the month averaged 1440 cusecs, whereas the powerhouse consumption was only 320 cusec; so that we used one part, and wasted four parts of the whole. For the first week in May, the lake level remained round about 10ft 9in. but then, owing to rain, it rose to lift, and the discharge was consequently increased between 7th and 14th. On the 14th, the lake had been brought back to 10ft 9in., but heavy, warm rain commenced to fall on the 14th, which was a Sunday. All possible stop logs were removed from the control gates and the river rose from a normal discharge of about 400 cusec, to the unprecedented figure of nearly 5000 cusec, which corresponds to four feet above its normal level. At this point, it was overflowing its banks at the island, breaking across the flat for half a mile, and flowing across the lake road toward the Peat Bog, being returned to the river at the Pondage after crossing the road again two and a-half miles further down. Despite this discharge, the lake continued to rise, and in 36 hours had reached 12ft 9in., with variations due to lake surges, and funneling, up to 12ft lOlin. This, as members will realize, was only one and a-half inches below the two concrete wing walls placed on the control gates in 1928. The lake remained round about the 12ft 9in.—l2ft lOin. mark until noon on Thursday, 18th, after which it showed a falling tendency; but it was not until the 22nd that it had dropped to the lift mark, which is the true top of the control gates. Since then, the level has been brought slowly down to 10ft Bin.

“The average discharge of the river over the whole month was 2067 cusec. In order to cope with the threat to the top of the earth dam at the lake, work was commenced on Monday, the 15th, with the limited personnel available; and two men with sacks were despatched from town in the evening, arriving about 10.30 p.m. We were also lucky in being able to arrange with the manager and three men of the Motu sawmill, to proceed to Monowai; so that by 1 a.m. on the 16th 10 men were at work, filling sacks with spoil, and laying along the crest of the earth dam. This work continued all Monday night, Tuesday and Wednesday, and as an extra precaution a row of bags was placed on the control gate wing walls. When an attempt was made to reach the village from the lake just after daybreak on Tuesday, the 16th, it was discovered that the bank of the Monowai River at the south end of the bridge, had been washed away. The end of the bridge had subsided, and a gap of 40 feet lay between. As the motor lorry and five motor cars were on the north side, the problem of transporting supplies, etc., was rather a problem, especially as men could not

be spared just’then to put a light bridge across the gap. We were lucky in being able to use a fallen tree over the gorge down towards the powerhouse, though this necessitated a long detour over rough country. On Thursday, a light bridge was put across the gap, but this is only of a temporary nature, and there is, of course, no question of its carrying much traffic. In view of this unprecedented rise in the lake level, it has been deemed advisable, while the labour was available, to raise the crest of the earth dam a further height of 18in. This has now been done, and the wet of the winter will assist in consolidating it. The lake side surface has been napped with boulders to resist wave action. The experiences of the month, the observations made, and the records secured, will be of great value, both educationally and historically, to the board. I wish to express my appreciation of the way the board’s staff, and also those who so willingly came to our assistance, worked so earnestly under most trying conditions.” The chairman (Mr W. Hinchey) stated that the Wallace County Council had refused to spend any money in repairing the bridge and the work was not the board’s responsibility. As the matter was urgent, the Public Works Department had been communicated with, but nothing further had been heard.

After hearing the report, the board carried a vote of thanks to the chief engineer and the-staff for their efforts.