This is a very important issue for Forest and Bird and we must do everything possible to stop this dam.
The 85 metre Mokihinui Dam proposed to completely block the mighty Mokihinui River would be an environmental tragedy unprecedented in recent years in New Zealand.
The damming of a vast pristine river system in a wlderness is something that today only really happens in third world wilderness areas where it is forced on those communities such as in the Amazon, Congo or Indonesia.
Construction of such a dam in a pristine river system would today be unprecedented in first world countries where there isn't much wilderness left and people are more enlightened about the impact on river ecology. In parts of the western USA they are actually now removing hydro dams to try to reverse the terrible destruction of river ecology caused by these dams.
The vast catchment of the Mokihinui river system above the proposed dam site is one of the most pristine wild and beautiful parts of our country. The whole hydrology of this largely natural river system will be destroyed by a concrete dam that blocks the river.
Native eel species, lampreys, galaxiids (whitebait) torrent fish and many other species all require passage to and from the ocean to complete their life cycles. Fish passes are often quoted as the solution but on high dams the evidence is that they generally don't work.
It is worth reflecting that once the first dams went in on the Clutha, the Waitaki and the Waikato rivers many decades ago, they blocked the passage by fish up and down those rivers. Susequent dams, although controversial (eg Clyde Dam on the Clutha, )couldn't make fish passage to the ocean worse because this had already been blocked by the Roxborough Dam. The same with Aviemore/Benmore Dams where the old Waitaki Dam had already blocked fish passage in the Waitaki River system downstream of Aviemore and Benmore.
From a river hydrology/fish ecology viewpoint is what is so terrible and final about a dam on the Mokihinui. It destroys the whole nature character of the entire Mokihinui River system, one of New Zealand's great wild rivers.
To me, this is actually by far the most significant and irreversible impact of the dam rather than the hectares of native forest that the dam lake will destroy.
It is ironic that a private hydro generator has received planning consent for their proposed scheme on the nearby Stockton Plateau. Trustpower have approval to proceed with their Arnold River Scheme and they are re-activating their Amethyst scheme at Hari Hari. So at the very time that the claim is made that the West Coast needs more electricity from a Mokihinui Dam to meet its power needs, there are at least 3 other new West Coast hydro schemes already approved or underway.
Declaration of Interest: I own and operate a small 25 KW run of the river hydro scheme on the Moeraki River, South Westland. This is 35 years old. Consented by the West Coast Regional Council, this takes about 25% of the normal Moeraki River flow and puts it back into the river 500 metres downstream of the hydro turbine through a tail race. We note the eels, the whitebait and the lampreys that swim around the power station and keep to the main channel of the river. We also operate a fish trap to lift any other fish that do come up the tail race to place them back into the river above the hydro.
So it is possible to extract hydro electric power from a river without completely damming that river and wrecking its ecology. The little town of Haast also has a "run of the river" hydro scheme on the Turnbull River.