Lake Alexandrina, New Zealand

Lake Alexandrina
A view of Lake Alexandrina from the top of nearby Mount John
Location	Mackenzie District, Canterbury Region, South Island
Coordinates	43°57′S 170°27′E / 43.950°S 170.450°E / -43.950; 170.450Coordinates: 43°57′S 170°27′E / 43.950°S 170.450°E / -43.950; 170.450
Type	Mesotrophic
Basin countries	New Zealand
Max. length	7.2 kilometres (4.5 mi)
Max. width	0.9 kilometres (0.56 mi)
Surface area	640 hectares (1,600 acres)
Max. depth	27 metres (89 ft)
Residence time	4 years
Surface elevation	732 m (2,402 ft)

Lake Alexandrina (Maori: Whakatukumoana) is a lake located in the Mackenzie Basin of New Zealand's South Island. It lies immediately to the west of the much larger Lake Tekapo and further to the east of Lake Pukaki, located to the north of Lake Tekapo township. It is a shallow lake with distinct indications of glacial origin and is spring fed with an outlet on its eastern shore mid-way down the lake. The outlet feeds into a smaller lake, Lake MacGregor before feeding into Lake Tekapo described as “Opaque and milky blue” in colour. In the desert terrain of the Mackenzie Plains, Lake Alexandrina is considered as an “oasis of life”. Lake Alexandrina is a Wildlife Refuge and a delight to a fisherman, well documented for its brown and rainbow trout and salmon.

Categorised as a Canterbury High County lake in the Mackenzie Basin, it lies a short distance from Lake Tekapo while also being connected to it. Lake Alexandrina is approached from the State Highway 8 via the Godley Peaks Road. The lake, located at an altitude of 732 metres (2,402 ft), covers an area of 640 hectares (1,600 acres) with width of 0.9 kilometres (0.56 mi) and extending to a length of 7.2 kilometres (4.5 mi). Its shores are flat. The maximum water depth in the lake is reported to be 27 metres (89 ft). The lake catchment has landscape that provides for plentiful wildlife but also has extensive cultivation which brings in a lot of nutrients, enriching the lake's with phosphorus.

The lake's annual balance is contributed by surface streams: 5.72 million m³ (27%), overland flows: 1.11 million m³ (5%), ground water sources: 10.1 million m³ (48%) and precipitation: 4.11 million m³ (20%). The storage in the lake lasts four years.

The lake has been classified as mesotrophic type. Chlorophyll levels of 0.4–3.8 mg/1 have recorded during observations carried out between November 1978 and March 1979. The total phosphorus at 1 m depth was 0.009–0.015 mg/L as measured in March 1979. The reasons attributed to high nutrient content and consequent high degree of phosphorus levels are due to nutrients entering from the lake catchment, underground sources, grazing on the periphery of the lake, human habitations around the lake, aerial spray and stocking in the trout-spawning streams.