Cobb Reservoir, lake in New Zealand

Cobb Reservoir is a 2.34 km² hydro storage lake in the Tasman District, 27 km west of Motueka, lying between the Wharepapa/Arthur, Peel and Lockett ranges. It is 6.34 km long, up to 460 m wide, and entirely surrounded by Kahurangi National Park, though the reservoir, dam, penstock and powerhouse are excluded from the park. The earth dam is 32 m high and 221 m long.

The Cobb River feeds the reservoir, and the dam was built between 1949 and 1954, replacing a smaller structure from about ten years earlier. It is an earth dam 32 m high and 221 m long, chosen because the area's geology ruled out a concrete dam. Water drops about 595 m to the power station 4.2 km northeast, where six Pelton turbines produce up to 32 MW.

The reservoir takes its name from the Cobb River and Cobb Ridge, and the surrounding valley lies within Kahurangi National Park, New Zealand's second-largest national park. The unsealed access road built in the 1940s is the only road into the park's interior, and trampers use it to reach tracks around the valley and nearby mountain lakes.

The access road is unsealed and may close during heavy rain or snow, so check weather conditions before visiting. Bring warm clothing, adequate supplies, and tell someone where you are going for safety.

The reservoir, dam, penstock and powerhouse are excluded from Kahurangi National Park, even though the lake is entirely surrounded by it. The access road over Cobb Ridge is the only road into the park's interior, and it stays unsealed from Cobb Power Station onwards.