THE RODING SCHEME

Nelson Evening Mail, Volume LXXII, 14 April 1939, Page 4

THE RODING SCHEME

ORIGINAL ESTIMATES CONFIRMED RECENT GAUGINGS UNDER DROUGHT CONDITIONS Continuing, the Mayor said there had been quite a lot said about the possible supply in drought conditions from the Roding river from which the new supply (now in progress of construction) would be provided for the city and adjoining areas. The council had received from the Nelson office of the Public Works Department reports on the gauging of the flow of the Roding on the 17th and 23rd March, which showed that 3,100.000 gallons of water per day was available at the present time in the Roding, and with the addition of 200.000 gallons per day from Long Gully, made the total of 3.330.000 gallons per day available from the new supply scheme. The City Engineer (Mr J G. Littlejohn) in his estimate of 3.250.000 gallons per day in drought conditions, had been very near to the mark. That figure had been based on gaugings taken in the drought period in 1928. PUBLIC WORKS REPORT The Public Works report stated: “Independent gaugings of the Roding river at the site of the Nelson City Council’s proposed new water scheme have been carried out by Mr Jamieson on the 17th March, and by Mr J. Ford, assistant engineer, on the 23rd March.

“Both gaugings run out at very much the same figure—s. 63 cusecs (Mr Jamieson’s result) and 5.16 cusecs (Mr Ford’s result). Mr Jamieson had marked the water level with spikes driven into the rock, and on Mr Ford’s visit a week later there had been no appreciable change in the water level. It would be quite safe to take the flow as 5.57 cusecs, or 3,100,000 gallons in 24 hours.”

The letter stated that on the way up the Roding to the waterworks site, all j the springs were running. There were no dried up springs to be seen, contrary to what was to have been expected after such a long period of dry weather. | Inquiries made indicated that springs 1 generally in the district were still j running well, and would indicate that the ground water supplies had been increased to an unusual degree by ex- , ceptionally heavy rainfall experienced 1 up to the end of 1938. The flow of the Brook stream had also been investigated above the high level weir. That was 1.3 cusecs. or over 700,000 gallons in 24 hours. The catchment area above the point of gauging was three square miles which gave a dry weather run-off of .43 cusecs per square mile. The Roding gauging was about .41 cusecs per square mile. That confirmed the Departmental official’s original report on the Roding scheme, namely that the dry weather run-off of the larger streams and rivers whose catchments were on country composed of rocks classed geologicall\ as Maitai series in this district was about .41 of a cusec per square mile. Another interesting feature of the high level weir was the amount of water escaping underneath it through the fissure.*? in the rocks and running into the main dam. The metered discharge from the weir 'was 400,000 gallons per 24 hours, the balance running into the main dam. The Mayor added that Mr Climie, the engineer in charge of the tunnel for the Roding scheme, had reported that be could notice no fall in the stream in the past month. Councillor F. Sharland said that the small springs and streams were now more inclined to make than to fall on account of the heavy dews being experienced. Councillor L. C. Pettit said he had been on the site of the Roding scheme at the week-end. and the men engaged on the work had kept a close watch on the stream during the past month, and they assured him that no falling off Lad taken place. Mr Pago commented that very pleasing progress was being made with the tunnel, the rate of the tunnelling now being about 500 feet per month.