The upper Turitea Reservoir is a 12-ha reservoir that supplies water to the city of Palmerston North (Figure 1). It was constructed in 1957 and is located in the foothills of the Tararua Ranges at 40.43208°S, 175,67669°E. The 2,300 hectare catchment area is comprised mainly of native forest with a small section of pine forest bordering the northern end of the reservoir. The reservoir is contained by a 39-m high concrete gravity arch dam.