Lake Rotoiti

There are numerous geothermal inputs to the lake, with the largest coming from the Tikitere geothermal field. Several small streams discharge to the lake in the eastern basin and a few warm streams discharge into the western basin, but the main input is from Lake Rotorua via the Ohau Channel into the western basin. Water passes through the channel at an average rate of 15cu m per second. Prior to the construction of the Ohau Channel diversion wall this water sometimes plunged into the eastern basin of Lake Rotoiti as an underflow. The flow is now effectively diverted directly to the outlet at Okere and on to the Kaituna River. The Ohau Channel diversion wall was completed in July 2008 and results in nutrient reduction to Lake Rotoiti (76 percent for phosphorus and up to 73 percent for nitrogen). The reticulation of sewage from the Okawa Bay community was completed in 2008 and may be one of the reasons for the water clarity improvements seen at Okawa Bay. Land management options continue to be developed around the lake with riparian plantings and fencing off of waterways from stock. Oxygenation and capping of the lake bed sediments could also result in improvements to the lake. Lake Rotoiti has three water quality monitoring sites - in the deep eastern basin, in the narrows between the two western basins and in Okawa Bay. An electronic cyano-bacteria health warning sign at Gisborne Point continues to provide lake users with up-to-date health warning information.