To help improve water quality in Lake Rotoiti, a diversion wall was completed in July 2008, to divert the water emanating from the Ohau Channel towards Okere Arm in Lake Rotoiti. The objective was that this water would be directly transported into the Kaituna River instead of entering the main basin of Lake Rotoiti. A report was produced in response to a request from the Rotorua Lakes Technical Advisory Group to determine water velocities in the region of the wall, to consider the effectiveness of the diversion. This subsequent report has been written to follow-up on the recommendation that vertically resolved measurements of water current and direction in Lake Rotoiti should be investigated. The timing of the data collection was April to May when an underflow is more likely to be present.