Ikawhenua Ranges cross the Waiohau Plains to join the Rangitaiki. The river travels for across the Waiohau Plains before it enters a gorge housing the man-made Lake Matahina the waters of which power the Matahina Power Station. No major tributaries enter the river downstream of the Lake Matahina. Below Matahina the Rangitaiki passes the village of Te Mahoe and through a well-defined valley before crossing the 29,000 ha Rangitaiki Plains and passing the settlements of Te Teko, Edgecumbe and Thornton. At Edgecumbe a large dairy factory owned by Fonterra discharges waste products into the river. The river finally enters the sea at Thornton through a man made long channel. Watershed Prior to the completion of the Matahina Dam annual discharge figures for suspended and bed load sediment near the river mouth were about 201,000 and 188,000 tonne respectively, Since then the Matahina dam has acted as an effective barrier to the seaward movement of sediment by the Rangitaiki River, with equivalent post-dam values have dropped to 65,000 and 10,000 tonne. This trapping of sediment has halted or substantially reduced the downstream historical rising river bed and coastal progradation of the Rangitaiki plains. Since the completion of the upstream Aniwhenua dam in 1982, it had become the principal sediment capture point though an increasing amount of sediment is being deposited in the deep portion of Lake Matahina. The river's condition is monitored at Murupara, Aniwhenua and Te Teko. River modifications The arrival of Europeans in the area lead to draining of wetland and low-lying areas along the river to create usable agricultural and horticultural lands. To support these activities the Rangitaiki Land Drainage Act was passed in 1910. One the Rangitaiki plains approximately 40,000 hectares of wetland was drained and converted to farmland. At the same time the existing dual discharges of the river towards the Whakatane River to the east and the Tarawera River estuary to the west were replaced by the cutting of a channel near Thornton to provide a new direct outlet for the Rangitaiki to the sea. Within a day of the new outlet being opened in May 1914 the level of the Rangitaiki in the lower sections of the Rangitaiki Plains area dropped by approximately. This fall of the river level encouraged further agricultural and horticultural development in this area following the end of World War I. The hydro-electric potential of the river has been utilized