Two of New Zealand's leading deer farms in the Hakataramea Valley want to increase the area they irrigate by building a dam up to 28m high to form a lake 2.2km long.
Foveran Station and Winterberg Farm, both owned by Bob Robertson, have applied to Environment Canterbury (ECan) for five resource consents for new irrigation of up to 740ha.
They are being considered by an ECan panel of three commissioners sitting in Oamaru to hear a total of 56 applications for new and existing takes of water in the Hakataramea Valley and on the lower Waitaki River below the Waitaki dam.
Mr Robertson's two properties, predominantly deer farms, total about 2000ha.
"We are recognised as one of the leading deer studs in New Zealand and are proud of that reputation," farms manager Barry Gard told the hearing yesterday.
Legal counsel Robert Makgill said four of the applications were for Winterberg Farm and a neighbouring property to use water from Homestead Stream, which enters the Hakataramea River just upstream from Wrights Crossing, for new irrigation of up to 690ha.
The fifth was to increase the irrigated area on Foveran using water from the Hakataramea River, increasing the amount taken under an existing consent.
The Homestead Stream proposal is an earth fill dam in a natural gorge to store up to 5.5 million cubic metres of water, harvested during snow melt and high flows.
That would irrigate 401ha on Winterberg Farm and 289ha on the neighbouring RPNZ Properties Ltd farm.
The environmental effects, with appropriate mitigation and consent conditions, would be minor.
Some effects, including creation of the new lake, could be positive, Mr Makgill said.
Mr Gard said the two farms relied on irrigation to sustain high-quality pasture production during dry summer months. More irrigation was needed to increase the area of high-quality pasture and winter feed for the deer stud operations.
Water harvested from Homestead Stream during high flows would otherwise flow straight into the Waitaki River and out to sea.
"There is tremendous scope to transform these dry areas into irrigated pasture and winter feed supplements would give us the options of increasing our deer fenced area and also guarantee winter feed for our merino sheep," Mr Gard said.
Hydrology consultant Dave Stewart said the Winterberg dam abstractions would have very little impact on existing flows in the Hakataramea River.
For most of the year there was no flow in the stream where it joined the river and the contribution to the Hakataramea River when it was low was insignificant.
Engineer Bob Hall said the dam could be built and operated safely, provided appropriate procedures were followed.
In the unlikely effect of a dam failure, the effects would be minor.
The height of the dam, yet to be finalised, provided a buffer for years when there were insufficient flows to fill it between irrigation seasons - a wise move given the nature of the catchment, Mr Hall said.
Environmental consultant Tom Heller said current nitrogen levels in the Hakataramea River were from in-stream and riparian activities, not irrigation practices. Any discharges from the Winterberg dam would reduce nutrient concentrations.
Water quality in the river and its tributaries was extremely variable and dependent on seasonal conditions with, at times, higher than normal nutrients.
The Winterberg and Foveran applications would have minimal impact, he said.
Freshwater ecology consultant Wayne Donovan said the Hakataramea River supported a variety of fish and bird species, some nationally endangered.
It was a spawning river for trout and salmon from the nationally important Waitaki River fishery.
The proposal would not significantly alter the water quality in the Hakataramea River and not have a significant adverse effect on its ecology, Dr Donovan said.
