How does lake water clarity affect lake thermal processes?

Area of Science:

• Environmental Science
• Hydrology
• Climate Science

Background:

• Lake Poyang, China's largest freshwater lake, experiences significant water clarity variations.
• Understanding how these clarity changes affect thermal processes is crucial for ecosystem management.

Purpose of the Study:

• To investigate the impact of altered water clarity on thermal dynamics in Lake Poyang.
• To assess the influence of radiation penetration changes on lake water surface temperature and internal temperature profiles.

Main Methods:

• Utilized a physically based lake model integrated within the Community Land Model.
• Conducted controlled simulations using varying water extinction coefficients (K) to represent different water clarity levels.
• Compared simulation results (DEFAULT, CTL, DARK) against observed data from 2000 to 2015.

Main Results:

• Simulations with more accurate water extinction coefficients (CTL and DARK) showed improved temperature predictions compared to the DEFAULT simulation.
• Decreased water clarity (DARK simulation) led to increased radiation absorption in the upper water layer and reduced absorption at depth.
• Higher lake water surface temperatures and stronger lake-air interactions were observed from February to July, while lower temperatures and fluxes occurred from August to January.

Conclusions:

• Altered water clarity significantly modifies thermal stratification and heat distribution within Lake Poyang.
• A marked decline in water temperature, exceeding 5°C during June-August, was noted with decreased clarity.
• Findings offer valuable insights for managing inland freshwater systems affected by water clarity changes.