The Wainui sub-catchment is 13 kilometres north-west of Tauranga and located between Esdaile and Work Roads. It is 5058 hectares and for planning purposes includes the Apata sub-catchment. The catchment area flows from the Kaimai Ranges in the southwest to Tauranga Harbour in the northeast. The Wainui sub-catchment is part of the Tauranga ecological district. The sub-catchment is about 18 kilometres long and 5 kilometres wide. It includes 191 kilometres of stream margins and 12 kilometres of harbour margin. The Wainui River sub-catchment has four named tributary streams (Waitioka, Parapara, Pahangahanga and Kaipoko) and numerous unnamed tributaries. The Wainui River and its tributaries are classified as aquatic ecosystem streams.