Floods in winter, droughts in summer under proposed management plans
Total bans on watering gardens could alternate with potentially dangerous floods if rules proposed by Ruamahanga whaitua committee are put in place.
Masterton District Council has warned in its submission to the whaitua implementation plan that the combination of reduced water takes at times of low river flow, and an inability to clear streams and rivers to facilitate stormwater flow, will make managing water difficult.
A “surprise” increase in the minimum flow level for the Waingawa, not signalled previously, would see restricted take days increase from 20 to 50 days a year – doubling the cost of the council’s proposed $5 million storage plan.
“This was not raised in earlier discussions with the whaitua and therefore comes as a surprise,” acting chief executive David Hopman wrote in the council’s submission.
The council has included $5 million for increased raw water storage in year six of its long-term plan.
“We would have to double the size of that, to enable us to keep supplying water to businesses, and that could increase the cost to $10 million.
“We’ve got some time to think about it, but that is a big number.”
Carterton and South Wairarapa district councils have made submissions on the whaitua plans, both highlighting questions over the future of water races.
All three councils want a clear cost-benefit analysis spelt out.
“We hold the strong view that the draft WIP recommendations are aspirational, which is good, but they need to be realistic as well,” Carterton Mayor John Booth wrote.
The whaitua, a community-led group charged with overseeing freshwater and land resources for the Greater Wellington Regional Council, is required to implement the government’s national policy statement for freshwater management.
Part of this is a push for riparian planting alongside rivers as a way of reducing nutrient content, but Hopman said this could create flooding issues at times of high flow.
“As these trees get older, they fall into the river and block culverts and bridges.
“Riparian planting has to be well-managed to mitigate the risks.”
The whaitua also recommends action to restore and manage native fish habitats in all waterways, including urban streams – but these are an integral part of Masterton’s stormwater management system.
Clearing of the Kuripuni stream to stop flooding of residential properties required a resource consent.
“That was an onerous process … we struggled to get that consent.
“We have to be able to co-manage these streams to prevent flooding . . . [and] there are a whole lot of streams that we are going to have to manage in that way.”
Hopman said clearing the streams was a key part of controlling flooding.
“We rely on natural waterways that run through Masterton for the management of stormwater for the urban area.
“The whaitua want to go even further to increase the ecological value of streams.
“That will come at a cost associated with flooding.”
The council’s submission raises serious concerns on the issue.
“In addition to the impact on property, there is an increased risk to individuals’ personal safety.”
Separate to the whaitua proposals, the regional council is calling for submissions on its new floodplain management plan which also has serious flooding implications for landowners, including the council.
Erosion in buffer areas is likely “due to the greater opportunity rivers will be given to meander and behave more naturally”.
But Hopman said while “benefits will come through the diverse and ecologically healthy river systems . . . there would be a loss of property”.
In the council’s case, that would require work to be done to protect vulnerable infrastructure, including the landfill and the Homebush wastewater treatment plant.
The whaitua will present its final implementation plan to the regional council on August 16.
MDC discussed the issues at its infrastructural services meeting yesterday.