Irrigation scheme on target

00:53, Feb 11 2013
rangitata south irrigation
LARGE SCALE: Rangitata South Irrigation on track for March 2013.

The first of the giant ponds at the Rangitata South Irrigation scheme could be filled by the end of the month, as construction of the project continues.

Workers were one third of the way through lining the surface of the first of the ponds, Rooney Earth Moving general manager Colin Dixon said.

The plastic lining came in large rolls that were unwrapped and the edges were then joined together.

"It's like a sewing machine, it runs up the seam really slowly and melts them together," Mr Dixon said.

He estimated it would take four to six weeks to line each pond. The ponds were lined one after the other, rather than all at the same time. As soon as one pond is lined, it can be filled with water.

"The way the system works here is that the ring race fills up with water and it connects into the ponds that you let it exit into.


"We block off all of the ponds except for the ones that are lined and allow them to be filled."

The water can run into the pond and out again into the races. Once completed those farms closest to the ponds could get ready to receive water.

That would depend on how long the commissioning process took, he said. This is when dirty water is fed through the races that connect the pond to the farms and the silt from the water settles on the the porous soil on the bottom of the race, sealing it naturally.

The $82 million Arundel-based scheme will irrigate 16,000 hectares of land between the Rangitata and Orari rivers.

Seven storage ponds will harvest floodwater from the Rangitata when flows exceed 110 cubic metres per second and the ponds' capacity will be 16.5 million cubic metres of water.

He said the high flows in the Rangitata River had delayed construction for four weeks. Construction was also under way on the intake structure at the Rangitata River and farmer shareholders were working on building their own storage ponds.

The Timaru Herald