Work being carried out on the country's largest irrigation
scheme is aimed at making it more efficient.
A 1km section of the Rangitata Diversion Race has been lined
to prevent leaking.
A geo-membrane has been laid as a base for another liner with
a bentonite clay centre. Bentonite clay expands when wet to
form a seal.
This has been covered with sand and compacted topsoil about
It is hoped this will eliminate the loss of 500 litres of
water a second, operations manager Neill Stevens said.
Because a leak was in a section of the race it could not be
pinpointed, a kilometre length was lined.
The race had been closed since August 9 but was on track to
reopen on Monday,Mr Stevens said. It was generally closed
down once every three years for maintenance.
In a section near to the leak, a clay base has been added to
help with sealing and the concrete floor of the intake has
been resurfaced after it was worn away by gravel movement.
Divers cleared debris from the intake to ensure the gates
formed a good seal when closed.
Parts of the race where there was seepage were under
surveillance, Mr Stevens said, and the ongoing process of
eliminating leaks would target these areas.
''The race is becoming more efficient,'' he said.
The race travels 67km, from the Rangitata River to the Rakaia
River, feeding three irrigation schemes, two power stations,
the Ashburton District Council stock-water races and some
private water races and irrigation schemes.
It can draw 30.7 cumecs of water from the Rangitata River and
a further 7 cumecs from the Ashburton River but must not draw
more than 35.4 cumecs in total.