Fish & Game says TrustPower data shrinks wetland

BY PENNY WARDLE

Ecologist Vaughan Keesing yesterday told the Environment Court in Blenheim that little vegetation of value would be lost if TrustPower built its hydroelectric power scheme on the Wairau River.

TrustPower expert witness Dr Keesing based this conclusion on walking along the affected stretch of river, surveying riparian vegetation by air and on-the-ground transects.

The court is considering whether TrustPower should be granted resource consent to build its scheme, after a Marlborough District Council-appointed panel's decision to approve the application was appealed.

Dr Keesing's survey tallied 40 hectares of wet willow or native riparian wetland – a figure challenged by Fish & Game lawyer Maree Baker, who suggested that it was understated.

She quoted evidence from expert witness Neil Deans that a number of sites classified as "willow dry" included areas of water, based on observation of Google aerial photographs.

Dr Keesing conceded that his maps were not 100 per cent accurate. "Little slithers" of water, which ran through some surveyed areas, were excluded because "they were not sufficiently large or undifferent to warrant their own area of map", he told TrustPower lawyer Christian Whata.

Even if Mr Deans was right on all counts, Dr Keesing said any omissions were insignificant when considered against the total river habitat available to species including ducks and geese.

Vegetation growing on the river margins was mostly introduced species, including willow, sycamore, hawthorn, pine, poplar, broom and gorse, Dr Keesing said.

These species were very tolerant and would adapt rather than die if water was diverted into TrustPower's hydro scheme.

He based this conclusion on TrustPower's latest drawdown prediction of 0.3 metres, half the company's previous estimate, Ms Baker said. She noted that standing water in native wetlands alongside the Wairau was typically 0.2m to 0.3m deep.

If the water table dropped 0.3m, plants would be left high and dry. Dr Keesing said this was not an issue for plants. These species "are used to ephemeral `upping and downing' of the system. A little additional `upping and downing' will be highly tolerated".

He said remaining native shrublands were on terraces and hill slopes above the zone that would be affected by drawdown caused by TrustPower's proposed scheme.

Ms Baker suggested that Dr Keesing's wetland assessment was "not very thorough" and "a lot of discretion was used" in deciding which wetland areas to include.

Told that it was better than any previous Wairau wetland survey, she emphasised that this was what caused her concern.

Dr Keesing admitted that he had failed to find some significant wetland sites previously surveyed by contract ecologist Philip Simpson for TrustPower.

Given the time, he would have checked the locations with Dr Simpson, he said.

Marlborough's wetlands were in decline, Dr Keesing admitted.

Given this scenario, he agreed with Ms Baker that careful analysis was important. This was achieved for native plants on the terraces.

Dr Keesing noted that all 16 named south-bank tributaries of the Wairau "are heavily modified, degraded and of intermittent flow". There were no significant conservation or fisheries values in these small tributaries, he said.

The degradation of fish habitat was mainly a result of sedimentation and nutrification resulting from "increasing dairying in the upper valley moving down, which I expect to add even more nutrients".

Dr Keesing investigated whether or not the connectivity of north-bank tributaries to the Wairau would be threatened.

Questioned by Ms Baker, he admitted that low flows could threaten connectivity and agreed that a condition of consent should be written that required TrustPower either allow more water down the channel if it became a problem or to dig a connection.

- The Marlborough Express