NEW-ZEALAND BASED MERIDIAN Energy’s $1.2B Project Aqua proposal would divert 70% of the annual flow from the Waitaki river to a 60km long power canal system, leaving just a third of the 360m3/sec flow in the existing river channel.

The diverted water will feed six hydro power stations sited up to 10km apart. The upper catchment’s low rainfall and storage could mean the power stations would cease operating to maintain minimum flows in the river, but this was expected to be very rare.

The Kurow intake would include ‘breach embankments’ that would progressively wash away during a flood, increasing flow down the natural riverbed. Meridian would also release four flushing flows down the natural riverbed in summer/autumn and winter. These 400-500m3/sec flows would run for one or two days, with the first three flushes at intervals of every several weeks from January until April, then once in July or August.

The first construction would be the intake and diversion structure at Kurow, 68km northwest of Oamaru, plus the upper three power stations and infrastructure connecting them and a river outfall at Black Point. This would take three years and make it possible to have the three stations generating while construction of the lower three power stations and canals continued over another three years with completion due in 2011.

Downstream, the canal would progressively rise out of the ground to be carried as an aqueduct within embankments, reaching a height of 20m at power stations, where the water would fall around 30m to be discharged into another deep cut, and so on down the canal.

The first power station would be 10.8km downstream from the intake structure at Kurow, with the other five power stations at intervals of between 4.6km and 10km. Each station would have a single 90MW Kaplan turbine.