Deep Cove is an arm of Doubtful Sound

Doubtful Sound

Doubtful Sound is a very large and naturally imposing fjord in Fiordland, in the far south west of New Zealand. It is located in the same region as the smaller but more famous and accessible Milford Sound...

, a deep indentation in the southwest coast of New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

's South Island

South Island

The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...

. Along with the Hall Arm, which lies to the southwest of Deep Cove, it forms one of the two most remote parts of the sound from the Tasman Sea

Tasman Sea

The Tasman Sea is the large body of water between Australia and New Zealand, approximately across. It extends 2,800 km from north to south. It is a south-western segment of the South Pacific Ocean. The sea was named after the Dutch explorer Abel Janszoon Tasman, the first recorded European...

, with its mouth being 32 kilometres (19.9 mi) from the mouth of Doubtful Sound. Elizabeth Island lies close to the junction of Deep Cove and the Hall Arm. The cove is home to several notable waterfalls, notably Helena Falls and Lady Alice Falls.

Until the 1960s, Deep Cove was only accessible from the sea or via the Wilmot Pass

Wilmot Pass

The Wilmot Pass is a high pass on the main divide of New Zealand's South Island. It connects Doubtful Sound, a deep indentation in the coast of Fiordland, to the valley of the West Arm of Lake Manapouri. The pass is named after E. H. Wilmot, a former surveyor-general of New Zealand, who had noted...

 walking track. In 1964, however, the cove saw the start of considerable activity as it became an important part of the Manapouri Hydroelectricity Project

Manapouri Power Station

Manapouri Power Station is an underground hydroelectric power station on the western arm of Lake Manapouri in Fiordland National Park, in the South Island of New Zealand...

 as the site of the tailrace tunnel from Lake Manapouri

Lake Manapouri

Lake Manapouri is a lake in the South Island of New Zealand. Its name is Maori for "sorrowful heart", though this name is misapplied due to an early cartographical error...

. A 10 kilometres (6.2 mi) tunnel connects the cove with the lake. The tunnel was completed in late 1969, with the power station became operational the following year. A second tunnel was started in 1997 and became operational in 2002.

The discharge of clear fresh water has had an impact on fauna

Fauna

Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...

 and flora

Flora

Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...

 by letting light into the lower layers of the sound. Nevertheless, this is an area naturally high in fresh water inflows (7.6 metres of rain falls annually). In the 1980s an application was made to extract and ship the water overseas but the project did not proceed.

Vegetation and wildlife

The wildlife in this area include dolphins and birds. Introduced species include mice, rats and hare. The Deep Cove watershed is heavily forested with Nothofagus

Nothofagus

Nothofagus, also known as the southern beeches, is a genus of 35 species of trees and shrubs native to the temperate oceanic to tropical Southern Hemisphere in southern South America and Australasia...

(beech) trees, a large variety of understory shrubs and ferns being present.