Tracking reservoir warming in a changing climate: A 31-year study from Czechia

Area of Science:

• Environmental Science
• Climate Science
• Hydrology

Background:

• Freshwater reservoirs are vital for water management but are increasingly impacted by climate change.
• Rising surface water temperatures in temperate regions exceed air temperature increases due to warming, hydrology, and reservoir shape.
• Long-term data on reservoir thermal responses and short-term variability are limited.

Purpose of the Study:

• To investigate long-term warming trends and daily thermal fluctuations in Czech reservoirs.
• To identify environmental drivers influencing both mean temperatures and short-term variability.
• To understand the relationship between warming rates and day-to-day temperature variability.

Main Methods:

• Analyzed 31 years (1991-2021) of surface water temperature data from 35 Czech reservoirs.
• Utilized statistical modeling to identify predictors of mean temperature and short-term variability.
• Developed a novel corrected metric for day-to-day variability (DTDV) to assess thermal fluctuations.

Main Results:

• Reservoir surface temperatures increased by an average of 0.59 °C per decade.
• Air temperature, altitude, and retention time predicted mean temperatures.
• Inflow rate, depth, and retention time influenced short-term fluctuations (DTDV).
• DTDV trends positively correlated with warming rates, indicating linked thermal reorganization.
• Strongest warming occurred in April, with minimal change in May, linked to regional climate shifts.

Conclusions:

• Climate change and local factors interact to drive thermal dynamics in reservoirs.
• Warming trends and increased short-term variability are linked phenomena.
• Findings inform adaptive strategies for water quality, stratification, and biodiversity management.