Lake Turkana Limnology (2024–2026): Basin-Scale Hydrographic Gradients and Seasonal Variability Following a Multi-Decadal Hiatus

Lake Turkana has experienced a prolonged hiatus in limnological monitoring exceeding four decades. Three lake-wide surveys were conducted in May/June 2024, November 2024, and March 2026, alongside hydroacoustic transects and 60–63 hydrographic stations distributed along north–south transects and west–east cross-lake gradients, As part of the WFP/UNESCO inception phase of the Netherlands-supported project “Sustainably Unlocking the Economic Potential of Lake Turkana, Kenya”. These surveys provide the first basin-wide assessment of Lake Turkana following recent hydrological changes. Results indicate that lake levels have risen by nearly 10 m over the past two decades, reaching their highest recorded level in approximately 100 years. A strong north–south limnological gradient was observed, with increasing conductivity and decreasing turbidity and temperature toward the south, reflecting the influence of low-salinity Omo River inflow in the north. Turbidity decreased from May/June 2024 to November 2024 and remained relatively low in March 2026. Significant log-linear relationships relationships were observed between Secchi disk depth and surface turbidity, as well as between Secchi depth and chlorophyll-a derived from seston filtration-retention methods. Chlorophyll-a showed a clear spatial pattern, decreasing from north to south, with mean concentrations declining from 6.8 µg L⁻¹ in May/June 2024 to 1.9 µg L⁻¹ in November 2024, before increasing to 5.24 µg L⁻¹ in March 2026. Very high chlorophyll concentrations were recorded in Ferguson’s Gulf during March 2026. Surface temperatures (26.5–31.0 °C) were comparable to historical values from the 1980s, while bottom waters were consistently 1–3 °C cooler. Conductivity (2.31–3.55 mS cm⁻¹) was generally lower than during the 1985–1988 low-water period, consistent with increased lake volume. Water column stratification occurred in May/June 2024 and March 2026, with a pycnocline between 40–50 m depth, while full mixing occurred in November 2024. River inflow zones showed consistently high turbidity, with spatial variability among delta systems. Overall, the surveys reveal strong basin-scale gradients, substantial hydrological recovery, and pronounced seasonal variability, providing an updated baseline for Lake Turkana limnology and ecosystem monitoring (≈267 words).