Lake Mapourika is located on the West Coast

West Coast, New Zealand

The West Coast is one of the administrative regions of New Zealand, located on the west coast of the South Island, and is one of the more remote and most sparsely populated areas of the country. It is made up of three districts: Buller, Grey and Westland...

 of New Zealand's

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...

 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...

. It lies north of Franz Josef Glacier

Franz Josef Glacier

The Franz Josef is a long glacier located in Westland Tai Poutini National Park on the West Coast of New Zealand's South Island...

, and drains into the Okarito Lagoon

Okarito Lagoon

Okarito Lagoon is a coastal lagoon on the West Coast of New Zealand's South Island. It is located 130 kilometres south of Hokitika, and covers an area of about 12 km², making it the largest unmodified wetland in New Zealand....

. It is the largest of the West Coast lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

s, a glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 formation from the last ice age

Wisconsin glaciation

The last glacial period was the most recent glacial period within the current ice age occurring during the last years of the Pleistocene, from approximately 110,000 to 10,000 years ago....

. Since the water from glacial melts no longer drains into the lake, it is filled with fresh rain water which runs though the surrounding forest floor, collecting tannins, giving it its dark colour. As the winds of the region sweep high above the mountains of the Southern Alps

Southern Alps

The Southern Alps is a mountain range extending along much of the length of New Zealand's South Island, reaching its greatest elevations near the island's western side...

, the water is left unruffled and quite reflective of the forest on the lake fringes.