Map showing the shape of Lake Benmore, with the Ahuriri arm coming from the west and the Haldon arm coming from the north
The lake has an area of about 75 km²[3][4] and a maximum depth of 90 meters.[4] The lake consists of two arms: the Haldon arm, fed mainly by the Tekapo, Pukaki and Twizel rivers, and the Ohau Canal; and the Ahuriri Arm, fed mainly by the Ahuriri River.[4] Immediately downstream is Lake Aviemore.
As of 2023, Land Air Water Aotearoa described the water quality as "very good", with a trophic level index of 1.8. It also described the quality of ecological conditions as "high", with a lake submerged plant indicators score of 72.0%.[4]
The lake is the reservoir of Benmore Dam, New Zealand's largest earth dam,[5] which was created as part of the Waitakihydroelectricity power scheme. Construction of Benmore Dam was approved in 1957[6] and the lake was filled in December 1964.[5]
After the lake was created the incidence of seismic shocks increased by a factor of three to six times.[7]
Uses
Besides being a reservoir for Benmore Dam, the lake is a fishing spot; in 2009 it was the second most-fished lake in New Zealand, with fish such as brown trout, rainbow trout, chinook salmon, and sockeye salmon. Fish in the lake include salmon that have escaped from salmon farms on nearby hydro canals.[8] The lake is also used for swimming and camping and there are walks in the area.
