Lake Turkana after four decades: Limnological gradients and changing hydrographic conditions in a highly dynamic desert lake

Lake Turkana is the world’s largest permanent desert lake, yet detailed limnological observations have been scarce for nearly four decades. We present results from three lake-wide surveys conducted in May/June 2024, November 2024 and March 2026 alongside hydroacoustic surveys, providing a contemporary baseline for assessing hydrographic and ecological dynamics. Sixty to 63 hydrographic stations were sampled across nine north–south transects using a calibrated CTD profiler, complemented by Secchi depth and surface chlorophyll-a measurements. A pronounced north–south gradient was evident, with conductivity increasing and turbidity and temperature generally decreasing southward, reflecting the strong influence of the low-salinity Omo River inflow. Conductivity ranged from 2.31 to 3.55 mmhos cm⁻¹ and was slightly lower than measurements from the 1980s, consistent with substantial increases in lake level. Temporary stratification occurred at approximately 40–50 m in May/June 2024 and March 2026, but no persistent anoxic layer was observed and the lake was largely mixed in November. Mean surface temperatures (26.5–30.0°C) were comparable with observations from the 1980s. Chlorophyll-a declined from 6.8 µg L⁻¹ in May/June 2024 to 1.9 µg L⁻¹ in November before increasing to 5.24 µg L⁻¹ in March 2026, with substantially higher concentrations in Ferguson’s Gulf. The surveys establish a renewed lake-wide limnological baseline and demonstrate the importance of sustained monitoring to understand hydrological variability, ecosystem dynamics and fisheries productivity.