The extent of flooding on low-lying farmland next to the Waitaki River has surprised Environment Canterbury, but it can do little about it until the river level drops.
On Tuesday, Environment Canterbury (ECan) staff flew over the lower river, between its mouth and Kurow, to see what damage had occurred since heavy rain on May 16 and 17 forced Meridian Energy Ltd to release flood flows; the highest, at 1554cumecs, since 1995.
The flow yesterday ranged between 711 and just over 800cumecs - more than double its average - as Meridian continued to release water while its storage Lakes Pukaki and Tekapo remained above their maximum operating levels as a result of heavy rain.
ECan flood controller Philip Lees said yesterday said there was "quite a bit of water" outside the riverbed, resulting from the high flows.
"In fact, we were quite surprised how much was out of the river," he said.
High flows, which occurred from the end of April when there was also heavy rain, had caused some big changes in the river, with braids shifting, and erosion.
That was feared as the river dropped, releasing shingle it had collected and changing course.
In some areas where farmers had developed land close to the river's edge, water had found its way into old channels, particularly around Ikawai and Duntroon.
There had also been erosion along the river.
Mr Lees said nothing could be done until the river dropped back to normal levels.
Then, it would be known how permanent some of the outbreaks were.
Once the river fell, ECan staff could better evaluate the damage and look at how it could be repaired.
"Until it does, it is very difficult to determine what is happening, and whether water will move away when the river falls."
Mr Lees said a report, along with costs, would be prepared for the lower Waitaki River rating district committee.
The committee oversees the rating district which pays for flood control and repairs on the river.
Rates are collected from property owners and Meridian.
The report would go to a meeting with the committee, which would then make recommendations on work and how it would be paid for, Mr Lees said.
Yesterday, Meridian was spilling 100cumecs from Lake Pukaki and 75cumecs from Lake Tekapo, which was being released down its Waitaki system.
Meridian's external relations manager, Claire Shaw, said yesterday if there was no further heavy rain, spilling could cease at Pukaki at the end of this weekend, with other releases reducing next week.
Yesterday Pukaki and Tekapo were still above their maximum levels, and inflows were still above average for this time of the year.
Lakes Benmore and Aviemore were within their operating range, while Waitaki remained above.
