Lac McArthur
McArthur Lake
Lac McArthur Location in Quebec
Location	Val-des-Monts, Les Collines-de-l'Outaouais, Quebec, Canada
Coordinates	45°42′29″N 75°40′13″W / 45.7080555°N 75.6702778°W / 45.7080555; -75.6702778
Surface elevation	163 m (535 ft)

Lac McArthur (McArthur Lake) is a lake in the Outaouais region of Quebec, Canada, not far north of Ottawa.

Lac McArthur (EHEZQ) is in Val-des-Monts, Les Collines-de-l'Outaouais, Quebec, at 45°42′29″N 75°40′13″W / 45.7080555°N 75.6702778°W / 45.7080555; -75.6702778.^[1] It is fed by the Rivière Blanche from Lac Saint-Pierre and empties into Lac Grand to the southeast.^[2] The lake is at an elevation of 163 metres (535 ft).^[3] The lake association is a member of the Federation of Lakes of Val-Des-Monts, a voluntary organization that works to protect water quality in the region.^[4] In 1990 Air Wapus Enr. was granted a license to operate a domestic air charter service from a base at Lac McArthur between 15 May and 15 October each year, however this license ended in 2001.^[5][6]

Water quality measurements were taken in mid-June, July and August 2015.^[2] Average total phosphorus concentration was 4.4 μg/L, so the lake is classed as oligotrophic, or poor in nutrients.^[7] The average concentration of chlorophyll in the lake was 1.50 μg/L, which indicates that the biomass of microscopic algae suspended in water is low and confirms the oligotrophic classification.^[8] The average concentration of dissolved organic carbon in the lake was relatively low at 2.98 mg/L.^[9] The lake is not shown on the list of lakes affected by cyanobacteria (blue green algae) blooms between 2004 and 2014.^[10]