Henley Lake, during a period of low inflow. PHOTO/FILE

Henley Lake faces crisis
Doing nothing not an option to fix consent issue

PAM GRAHAM
pam.graham@age.co.nz

Henley Lake may have to become “more like a wetland” in summer if big money is not spent on an alternative water supply.

That was the gist of a report to yesterday’s Masterton District Council meeting, which came after a working group mulled the issues behind closed doors.

Councillor Gary Caffell is on the working group and said the report to council danced around what was one of the most difficult issues he had faced in his time on council.

He said it was time to make people aware that a lot of money had to be spent to keep water flowing to the lake or let it “become more of a wetland”.

“It is certainly the most difficult thing I have been involved with on council in trying to find an answer.

“Everywhere you go it is big money. It will just come down to whether the council is prepared to spend big money.”

The council’s assets and operations manager David Hopman said he wouldn’t use the word “wetland” but every summer the lake would drop in level and look quite different.

He said Greater Wellington Regional Council’s new Natural Resources Plan, and the Whaitua process, were going to limit Masterton’s ability to take water from the Ruamahanga River.

He said the working group had been working on options to make the lake more tolerant to limited water inflows.

It could be planted to be more able to have varying levels, and in the middle of summer it would be very low.

“We have a lot of work to do to explain what a drought-tolerant lake will look like. Every summer this lake will drop. It has to be tolerant to low inflows,” Hopman said.

The report recommends the council engage with the community about future options and then report back.

Henley Lake was conceived as a recreational area in the 1960s and was constructed in the 1980s.

As many as 500 people walk there each day and many water activities happen on the lake, which does have a problem with toxic algal blooms during the late summer, when water flows are low and temperatures are high.

This has limited the availability of the lake for on-water recreation.

The lake is primarily fed through a water race from the Ruamahanga River, which runs next to the park. Three small streams also enter the lake and provide supplementary flows, but the primary water source is necessary in order to maintain lake health.

The main intake is subject to the requirements of the Resource Management Act and provided for by way of a resource consent issued by Greater Wellington Regional Council.

This consent has now expired, and changes to regional plan rules have made getting a new one more complex.

Flows from the lake are discharged to a constructed wetland area. When there is heavy rain, water runs back to the Ruamahanga River through a discharge channel.

A degrading river bed is making it harder to maintain good, consistent flows into the lake and during the summer months, the lake levels drop exposing the bed edge.

Council has proposed to install a pump station to help maintain the flow of water into Henley Lake during low river flows, and funding for this was included in the Long Term Plan. But the proposed Natural Resources Plan will prohibit taking water from the river when the flows drop below a minimum level.

This would prevent the pump station operating at the time it would be required.

Potentially, the Whaitua recommendations may provide for a low-flow take for the lake but not for at least 12 months.

The working party had decided it was time to consult stakeholders about finding an alternative source of water for use at times of low water flows.

This could either be stored water or deep ground water bores.

The other option was to adapt the lake itself to buffer against period of low inflows.

Doing nothing is not an option because the resource consent renewal needs to be resolved.

Either approach – modification of the lake or pursuing an alternative supply – will incur significant costs which will need to be consulted on.

Modification of the lake would result in a significant change in its appearance.

The proposed engagement is separate to a formal consultation which will be required once options are refined as a result of the engagement process.

The same issues facing Henley Lake will also apply to the Lake of Remembrance in Queen Elizabeth Park but there, the council has a consent to take water for five more years.