Run-off Has Increased By Quarter On Land In Upper Waikato Catchment

Taupo Times, Volume XIV, Issue 46, 15 June 1965, Page 2

Run-off Has Increased By Quarter On Land In Upper Waikato Catchment

An increase of 25 per cent. in the run-off volume from the upper Waikato Catchment has been recorded in the past 20 years. Accordding to the chief engineer for the Waikato Valley Authority, Mr H. C. C. Jones, rainfall in the same period has increased only five per cent.

"These figures give a clear warning that transformation of the upper catchment from native cover to grassland, with attendant consolidation of the soil, is a potent factor in increase of run-off volumetM says Mr Jones. "Step s are being taken at the present time to determine as exactly as possible, the changes in the pattern of run-off which occur locally with the change from native cover and negligible grazing to grass cover and its associated stock grazing. "The authority, in co-op-eration with the Ministry of Works, Department of Agriculture (Soil Research and Soil Conservation Division), has established a research programme covering the Otatira catchment on the northern side of Lake Taupo. "Now, other catchments are being investigated with a view to measuring the changes which occur on other pumice soil types and other forms of cover such as exotic forest. "In the meantime, however, we must continue to depend on general observation as a measure of the changes resulting from land development which most certainly includes a sharp increase in terms of peak run-off locally, and the increase in volume or run-off already referred to as reflected in the main river. "If there ig any doubt, the many cases of severe gully erosfcon arising from 100% land snrface development to grasslands

which have had the attention of the authority, give confirmation of the extra run-off load being placed on local watercourseg. This extra run-off has given rise to strespes which they are unable to take in the absence of preventative measures. "The Soil Oonservator, in his report on conservation reserves has stated that these are fc*: .... just one aspect of conservation works.' While the statement is quite correct it does not attach the importance to these which it is believed they deserve in their role as reducers of run-off and preventors of surface and water course damage. "Conservation reserves cover that class of land which the soil conservator believes to be suspect lands in that the particular soil type Lnvolved will wery likely not remain in place on such steep slopes if placed under grass and on account of resulting increase in rumoff damaging to water courses. "My condemnation goes further in that the products of erosion, as well as the increased runoff detrimentally effects the whole catchment and waterway system downstream of that point," Mr Jones continued. "With this view, great importance is attached to the setting aside of conservation reserves as Crown land with guaranteed access and their maintenence in native cover without grazing until such time as arrangments can be made to utilise and maintain them in beneficial crop cover

under afforestation. "Private ownership, except in the case of minor areas, is considered to be hazardous. If the future farmer owned the land whieh it has been decided to set aside from development, and pays rates on it, he will be tempted to try it out in grasslands an action which is not in the public interest. "The powers to govern these matters, as incorporated in the Soil Conservation and Rivers Control Act, are diffieult to enforce. Recourse to law is expensive and the outcome doubtful. It may be assumed that there will be a reluctance to take such action in the future. It does not win friends where we need friends in carrying out a soil conservation programme. "It is admitted that there are difficulties in attaining the principal object. If the area to be set aside has been burned and/or cleared, ragwort and blackberry will appear. This must either be ignored or be sprayed until such time as sufficient cover has been developed to suppress it Noxious animals will take cover there and must be controlled. To keep stock out and attain the desired object overall, permanent fences of the highest standard must be built and maintained in perpetmty. These all cost money. "Fortunately, the expenditnre lnvolved i# almost wholly intemAl, while the additional loogterm income availftbie from other land benefttting from these actipns in in terms of extra overlea* funds and hence nation** security.