The catalyst behind the formation of Ngamanawa Incorporation was the 1968 Notice of Intention to Take Land For Electricity Works. The original intention was to take 5000 acres however after much protest by the owners, and the appointment of an engineer from the Ministry of Works, 120 acres was assessed as necessary for the hydro project.
1970 saw the amalgamation of titles of various Te Papa Paengaroa, Tauwharawhara and Kaimai Blocks into the Ngamanawa Block. Ngamanawa Incorporation set up by order of Maori Land Court on 6 May 1971 with the first meeting of the Incorporation being held on Monday 12 July 1971 at the Maori Land Court in Tauranga. Victor Carlos Smith was appointed as Chairman and H C Waterhouse was appointed Secretary. The Committee comprised Mary Te Amo Lucas, Eugene Denis Morgan, Louis Desmond Smith, David Haumaha, Ivan Williams. Mr Waterhouse was later replaced by John Menneer as Secretary.
Kaimai No 3 was included in the Incorporation on 24 February 1977 and part of Whaiti Kuranui 5D2 was amalgamated with the Incorporation early in 1983.
After 6 years of negotiations between five different forestry companies a lease agreement between Ngamanawa Incorporation and New Zealand Forest Products was signed at the Annual General Meeting of the Incorporation on 28 May 1977, the term of lease being for 99 years.