Thermal structure controlled by morphometry and light attenuation across subtropical reservoirs

Abstract

Thermal stratification in lakes has multiple physical, chemical, and ecological implications. Previous studies have identified the driving factors of thermal stratification in tropical and high‐latitude lakes, but their relative contributions in forming thermal structure among different deep reservoirs have received little attention. Here, the water temperature profiles, light attenuation, water substances, morphometry, and wind speed in 15 deep reservoirs in the subtropical hilly area of eastern China were measured in August 2018 (during a stable stratified period). Mixed layer depth (MLD) was positively correlated with water depth, fetch and wind speed, and negatively correlated with light attenuation. Metalimnion thickness (MT) was positively correlated with water depth, and negatively with light attenuation. The result of the multi‐linear regression analysis shows that light attenuation can better explain the variation in MLD than reservoir morphometry and wind speed. Differences in MT among these reservoirs mainly relied on water depth and light attenuation variations. Our results quantize the effect of related factors in controlling thermal stratification across deep subtropical reservoirs, suggesting that continued decrease in transparency and wind speed will strongly affect reservoir stratification.