Computer study plan for Rakaia River

Press, Volume CXIV, Issue 33706, 2 December 1974, Page 16

Computer study plan for Rakaia River

A computer simulation of the Rakaia watershed will be set up by Lincoln College if it gets a research grant to enable a study to be made of the inter-relationship between the water used in the Lake Coleridge hydro-electric power station and demands for irrigation water and other uses.

The college scheme was outlined in a letter received by the water committee of the North Canterbury Catchment Board from Professor J. B. Dent and Mr G. Frengley, of the college’s valuation and farm management department. “Water is required from the Rakaia River for power generation, irrigation, recreation, domestic, and stock needs,” they said. “Predicted developments will impose demands for water which will exceed the river flow on occasions in the summer.

“Lake Coleridge holds the key to maintaining the flow during these critical periods. Below the power station, the flow can be modified by releases of water determined by the power-generation schedule.”

They said that while the prime purpose of the proposed research was to see if power-house water releases could be arranged to maintain river flows when they were most neded, it could show a need for extending storage in Lake Coleridge. “It is certainly true that the amount of water frequently given to crops today is excessive for an effective response to water,” they said. “This extravagance is encouraged by the present costing method for irrigation water. A full study of irrigated farming systems, their profitability, and their likely adoption under different water allocations is a basic component of the proposed study.” The timing of releases of water through the power station would greatly influence the seasonal supply of water for farming and the production systems developed, and their profitability. It was proposed to show how recreational uses of the river could be accommodated. The growth of population in Christchurch, including Rolleston, would need more water. These demands would affect longterm w'ater use, and the lake could be a factor if underground water was insufficient. The committee recom-

mended the board’s acceptance of the proposal, and asked it to arrange talks as to a research grant, estimated by the college to amount to $32,175 for a two-year period ending in March, 1957.