Lake Surface Temperatures: Influencing Factors and Their Effects on Columbia River Basin Reservoirs

Lake surface temperature (LST) is one of the key indicators required for ecological and hydrological studies and for water quality management. Satellite remote sensing of LST has high spatial and temporal coverage and can be a cost-effective method to monitor lakes. This study explores geophysical and meteorological factors that control LST by studying LST for 115 reservoirs in the Columbia River basin from 2000–2022. We found that climatic factors such as air temperature, vapor pressure deficit, and surface specific humidity explained up to 80% of the variability observed in LST. Precipitation, wind speed, wind direction, lake characteristics, and lake elevation appeared to have negligible influence on the temporal variability of LST for these Columbia basin reservoirs. Our study revealed that there is an overall increasing trend in LST between 2000 and 2022. In 66% of reservoirs, surfaces warmed annually at a mean rate of 0.25 °C per decade, while the remaining reservoirs cooled annually at a mean rate of 0.16 °C per decade. Low elevation reservoirs with small surface areas warmed the fastest, whereas surfaces of high elevation reservoirs had a cooling trend, especially for reservoirs with large surface areas. LST trends were insensitive to reservoir depth. Using the vantage of space and multi-decadal observations, this study presents a thorough overview of the thermal behavior of reservoir water surfaces in the Columbia River basin. The findings can build clear pathways to improving hydro-ecological studies and water management of the region that is drought-prone and impacted by climate change. Key Points: According to multi-decadal remote sensing data of surface temperature, 76 out of the 115 reservoirs studied in the Columbia River basin warmed annually at a mean rate of 0.25 °C per decade, while the remaining reservoirs cooled annually at a mean rate of 0.16 °C per decade. Low elevation reservoirs with small surface areas warmed at high rates while many high elevation reservoirs with large surface areas were cooling. Climatic factors such as minimum and maximum air temperature and vapor pressure deficit have a larger influence on lake surface temperature compared to reservoir parameters such as depth, surface area, and elevation.