An access permit must be held by those using the lake for fishing and similar activities.

[1][2] Extensive engineering works were carried out between 1964 and 1971 diverting a number of streams (including Whanganui River) into Rotoaira via Lake Otamangakau and construction of a tunnel through Pihanga to the Tokaanu Power Station.

[5] Motuopihi was the hiding place of Te Rauparaha and where he composed the Ka Mate haka.

[5] Opōtaka, a traditional site of Māori occupation, is situated on the northern shore of the lake.

Of significance to iwi Ngāti Tūwharetoa and Ngāti Hikairo it was excavated during archaeological investigations on the Tongariro Power Scheme and was found to have been occupied in the 19th century.