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Abstract

Warm surface waters and hypoxic hypolimnion during summer stratification in eutrophic lakes, known as a temperature-oxygen squeeze, can limit available habitat for aquatic species. This study of Wood Lake, a calcareous eutrophic lake situated in the semi-arid Okanagan Valley of BC, Canada, was motivated by a decline in kokanee return spawners following a severe temperature-oxygen squeeze in 2011. Field data collected in 2015/2016, combined with DYRESM, a one-dimensional physical simulation model, was employed to investigate the factors influencing the thermal aspect of the temperature-oxygen squeeze. A relatively early and weak spring freshet in 2015 was followed by severely restricted inflows due to upstream diversions and coincident with relatively warm regional air temperatures from May through July. These factors triggered a marling event in Wood Lake and also resulted in the early onset of high epilimnetic temperatures and hypoxic hypolimnion (>20°C and