Tasman water restrictions eased as dam opens the tap
Most of those using Tasman District Council reticulated water supplies are now free of water restrictions thanks to the release of water from the Waimea Dam.
On Saturday, water was released through the smaller of three dispersing valves.
Previously, much of the region had been under significant water restrictions, with Richmond falling under Level E.
“In the absence of releasing water, those restrictions were either going to stay in place or potentially need to be increased to a higher level,” Tasman mayor Tim King said.
While rain fell on Sunday and Monday, King said it wasn’t heavy rain by any definition.
“It wouldn’t have made a significant difference,” King said, when asked if restrictions might have been lifted without the dam releasing water.
“12mm was not going to significantly alter the situation, either in the river or ... in the district.”
The dispersing fixed cone valve that opened was “effectively like opening a tap”, but sprayed the water out in a way that dissipated its energy before it hit the river itself, he explained.
That valve was the smaller of the two pipes, which had a maximum release of 1.2 cubic metres a second, or 1200 litres.
The larger pipes that should be available for use next Monday had a capacity around five times that.
“That obviously gives Waimea Water Ltd the potential to flush the river with a more significant amount of water,” King said.
On social media, some noticed river turbidity downstream of the dam after the release of water.
King said that in an ideal world, the very first release would be done at a period of time when it was already raining or they had had the opportunity to clean out the residue of construction.
However, because it was “vitally important” in order to be able to lift the water restrictions on Monday, the water had to be released at the weekend.
Over the initial release period of a few hours, there was “some sediment that was activated from the construction site and immediately below the release point”.
King was contacted by several people about the issue, though he said the sediment was only in the river for a “short period” on Sunday.
“It wasn't ideal, but in the grand scheme of things, it’s a fairly minor inconvenience, given that meant that we could lift all the water restrictions on the Waimea Plains on Monday.”
Water restrictions for residents of Richmond, Hope, Māpua and Ruby Bay, Brightwater, Redwood 1 and 2, as well as Nelson residents whose water is supplied from the Richmond Water Supply Scheme, were lifted on Monday.
However, Wakefield and Eighty-eight Valley supplies remain at Phase A, to help maintain water levels in the Kainui Dam, while users in Dovedale remain at Phase D.
Restrictions have also been lifted for consented users in the Waimea affiliated and unaffiliated management zones.