Rotomairewhenua / Blue Lake

Rotomairewhenua / Blue Lake is a high alpine lake in Nelson Lakes National Park, tucked beneath steep mountain ranges at about 1,200 metres. It’s a remarkable destination, but only for a planned backcountry trip: there’s no road or day-walk access.

The shortest route starts with a water taxi across Lake Rotoroa to Sabine Hut, then about five hours on foot to West Sabine Hut and another three and a half to Blue Lake Hut. From the West Sabine swing bridge, the lake is an overnight side trip of about seven hours return. Coming from St Arnaud takes at least four days return. Book the huts you need, carry your food, and check the weather, river conditions and current track alerts before setting out. Use the cleaning stations at Coldwater, Lakehead and Sabine huts for wet or damp gear and bottles.

The shallows shift between blue-violet and green, with pale stones under the surface and forested slopes rising behind them. Measurements on six visits found visibility above 70 metres every time, reaching 81.4 metres—close to the estimated limit for pure water.

Lake Constance feeds Blue Lake through underground seepage, with springs emerging about 35 metres above the lake. Glacial gravel and landslide debris may filter out particles along the way, though the precise process is still uncertain.

Rotomairewhenua is tapu and deeply significant to Ngāti Apa ki te Rā Tō. Stay on shore: don’t touch or swim in the water, wash in it, take water from it, or put equipment into it. The same respect applies to Lake Constance. Make your overnight stop at a hut rather than camping beside either lake.

After about 1.5 hours from the West Sabine swing bridge, the valley opens through forest destroyed in a 1980 avalanche, then climbs steeply in two stages to the high basin. Avalanche paths are marked along the route, so check current track information before you go.

From the water’s edge, the clear shallows make a strong foreground against the dark beech forest and high peaks; keep cameras and tripods on land. Riflemen are regularly found in the forest around the lake, so give the bush a quiet moment as well as the view.