A RIPARIAN PROBLEM

Nelson Evening Mail, Volume LXIV, 5 August 1931, Page 2

A RIPARIAN PROBLEM

LACK OF WATER IN THE OPAWA i INTERESTING POSITION IN MARLBOROUGH THE SETTLERS’ CASE Something like 80 settlers who have farms on one side or the other of the Omaka River, from Renwick down to Thomson’s Ford, have signed a petition that is to be submitted to the next meeting of the YVairau River Board praying that a proportion of water be allowed to flow from the Wairau River down the Opawa, reports the “Express,” The petitioners consider that the productivity of their properties has been adversely affected by the confinement of the whole of the Wairau in its own bed; and they express the opinion that the safest and cheapest method of diverting some cf Ihe water from the big river into 'he Opawa would be by means of a culvert at Conder’s groyne. It is some months now since a representative meeting of farmers at Rapaura, after comparing notes regarding the effect of the shortage of water in the Opawa, arranged to make representations to the River Board on the matter. The Board was duly approached, but after giving the matter a certain amount of consideration and obtaining an engineering opinion on the best means of granting the settlers’ request, it deferred making a final decision. There was no intention on the part of those most directly concerned to let the scheme drop, however, and they have been working quietly ever since preparing the petition, which they regard as a representative expression of opinion which the Board cannot justly ignore. Weight is added to the petition by the fact that its signatories are confined exclusively to those owners and occupiers of land directly and detrimentally affected by the existing conditions.

It is generally agreed amongst farmers contiguous to the Opawa River that the complete cutting off of Wairau water has reduced production by anything from 20 to 40 per cent., and this is regarded as a quite conjgrvative and reasonable estimate. In the past much of the land could have been classed as some of the richest in the province, but on account of its nature it requires a plentiful water supply. There is also a big proportion of light land to which water is an _ absolute essential. While the term “irrigation” has been used in connection with the proposal there is, as far as is known, no intention on the part of anyone to undertake a scheme of artificial watering of the farms. All that is desired is to simply return enough water to the Opawa to restore the springs and creeks to their previous flow by means of the natural soakage and percolation. This is especially desirable in the sum-mer-time when there is a deficiency of rain; and that being so it has been suggested that there is no reason, in the event of some scheme being adopted, why provision should not be made to control the inlet so that in the wet season when there is a likelihood of floods the culvert could be closed altogether. Wihle a definite means of giving effect to the petitioners’ wishes has yet to be adopted, it is understood that a tentative recommendation is that a low-level concrete culvert 12ft. wide by 4ft. high should be constructed at the end of Conder’s groyne, and that the groyne be then extended some.)distance beyond to reinforce the position, It is realised that the culvert —or some form of fluming—would need to be carried a distance down the bed of the Opawa in order to take the outlet sufficiently far from the groyne to obviate any danger of a scour running back and undermining the stone work. From a flood prevention point of view ?? is argued by the supporters of the scheme that the extension of the groyne beyond the culvert "would have material advantages, as the Wairau has shown a tendency to work round the present extremity of the groyne, thus creating the danger of an unlimited quantity of flood-water getting into the Opawa which, now that the Fairhall will empty into it, might create a serious menace to the Blenheim district. Another aspect of the scheme in the light of flood protection is that many of the willow trees planted in the Opawa for protective purposes are dying through lack of water, and their loss might be serious if the Wairau at any time did burst into the Opawa. It is fairly apaprent that the intake of any culvert installed would always be liable to blockage by the formation of sand or shingle bars as the Wairau changes its course along the face of the groyne, but certain settlers, it is stated, are prepared to give an undertaking to attend to the clearing of the intake whenever necessary.