H.—29

3

know that such a large quantity of water is met with at the outflow; and, in order to trace the source from which it comes, I would suggest that the upper basin and the reservoir be emptied during the dry season, leaving only the pool; and that a staging be erected over this pool, and the water pumped from it and passed through the scour-pipe, which could be quickly done by using a small engine. Measurements of the flow should be taken previously to and during the pumping operations. This would conclusively prove whether there is any connection between the reservoir and the outflow. If such a connection exists—and assuming that the old bed of creek intersected by the puddle-wall is thoroughly sealed by the puddle being taken 4ft. into the solid rock, and the pipe-track cut through solid rock, also in the bed of the creek, and thoroughly puddled—l would feel disposed to seek for the leak by sinking a shaft through the embankment where shown by X to a depth exceeding that of the bottom of the pool, driving under the bye-wash; and if the flow were found here would cut a trench right up to the surface, and under the bye-wash to a short distance beyond the storm-water channel into the solid ground, filling it up with the best clay puddle procurable, thus forming a continuation of the puddle-wall. At the same time, if the bulk of the water were not found after having sunk the shaft at x , I would recommend extending the drive put in by Mr. Hay towards the puddle-waj], which doubtless would prove whether or not the water is coming through the embankment. During heavy floods the upper basin has become filled to such an extent that the water overflowed its embankment into the reservoir, which caused the storm-water channel to be so strained that it was unable to carry off the flood-waters. This, to my mind, is a decided element of danger, and should not be allowed to exist. Provision should at once be made to carry off this surplus water by either constructing a new storm-water channel on the western side of reservoir or enlarging the existing one. I would favour the enlarging and strengthening the existing one, selecting from the excavation the best of the clay, to be tipped into the pool to act as puddle,-and generally seal over the pool, so that all the water in the reservoir would find its way to the scour-pipe, and thus allow the reservoir to be emptied and cleaned out at any time. I am of opinion that if these recommendations are given effect to the reservoir would be per±eCtiy Sate' E. E. Usshee, M.lnst.C.B., The Engineer-in-Chief, Wellington, District Engineer.

Enclosure No. 1. Table A. Memorandum of Gaugings at alleged Leak, Ross Creek Reservoir.

• Firßt recorded.

Gallons discharged per 24 Hours. Depth of Water in Eeservoir. Date. Gallons discharged per 24 Hours. Depth of Water in Beservoir. Date. .870—April 8 882—March 15 „ 18 „ 20 » 22 „ 28 April 1 „ 4 5 7 Sept. 18 20 Oct. 4 11 18 25 Nov. 1 8 10 15 22 29 Dec. 5 6 11 13 20 23 25 .883—Jan. 25 30 Feb. 7 14 Oct. 24 Nov. 7 Dec. 20 884—April 28 . May 6 Xg 8,020 0,480 5,232 4,800 4,320 3,456 3,698 4,700 3,456 2,736 5,760 5,568 5,760 4,536 4,320 4,656 3,600 3,456 3,312 3,456 2,784 2,618 2,880 2,544 2,064 2,616 2,784 2,328 ■4,616 8,208 8,640 11,520 13,296 7,968 8,640 11,400 8,208 7,200 0,912 Ft. in. 25 8* 30 4 27 10 28 9 27 8 24 7 21 7 19 9 18 5 16 3 41 8 41 1 37 0 34 6 31 9 29 3 26 5 21 4 19 3 18 4 1G 5 13 6 10 5 11 0 9 2 9 2 14 (i 14 (1 14 6 45 0 43 7 42 5 40 8 44 0 40 4 46 0 45 0 42 10 4.1 7 1884—May 20 June 3 10 July 8 » 15 22 1886—Feb. 22 23 24 25 26 27 „ 28 March 1 2 3 4 5 6 7 8 9 1889—June 26 July 5 6 8 10 15 16 17 18 19 20 22 23 24 25 2G 6,648 7,200 6,648 6,168 5,064 4,320 4,200 4,050 4,056 3,926 3,840 3,716 3,551 9,600 4,670 3,638 3,797 3,756 3,563 3,456 3,388 3,229 7,0566,696 6,384 7,704 7,488 6,888 12,552 ll,2S0 9,144 7,632 6,528 5,808 4,584 4,320 4,084 3,850 3,650 Ft. in. 40 9 39 2 37 C 39 5 38 9 38 2 15 0 16 10 17 8 17 1 16 6 15 11 15 4 14 9 15 10 17 1 16 6 15 10 15 3 14 7 13 11 13 2 23 3 27 2 27 1 27 1 27 10 28 4 29 9 29 9 30 0 30 2 30 11 31 7 31 10 31 5 31 2 31 10 32 4