Hydroclimatic Analysis of Rising Water Levels in the Great Rift Valley Lakes of Kenya

The Central Rift Valley lakes of Kenya have recently experienced significant increases in their water levels, negatively impacting the local communities. This has provoked renewed concerns about the causations, with various geological, anthropogenic and hydro-climatic influences hypothesized as potential causes of the water level rises. This study systematically analyses and documents water level fluctuations in Lakes Baringo, Bogoria, Nakuru, Solai, Elementaita and Naivasha. Long-term hydrometeorological analyses are undertaken to understand potential causes. Satellite-based lake volume variation data is used to derive the “Integrated Catchment Response” (ICR), a magnitude which allows to relate the changes in water balance components to the signal observed in the lake volume changes. Compared to 1984-2009, the increases in lake areas range from 21% for Lake Naivasha to an extraordinary 123% for Lake Solai. Fluctuation between minimum and maximum water level range between 8.53 m and 2.38 m. Mean annual rainfall for 2010-2020 increased by up to 30%. Actual evapotranspiration also increased, but to lesser extent compared to rainfall. The results clearly show the connection between changes in (effective) rainfall and observed lake level rises and that changes in catchment properties due to anthropogenic influences or changes in underground permeability are not necessary to explain the lake level rises. The ICR highlights that only small changes in the water balance are necessary to explain the increases in the lake level rises.