Rising lakes in the Kenyan Rift Valley. Lake Nakuru flooding

Abstract

Hydrological and meteorological research are of great value to comprehend the complex Eastern Africa system, and more specifically the Kenyan Rift Valley, as impacts of climate change and indisputable changes in the hydrology of the lakes have become more apparent in recent decades. Lakes in the Kenyan Rift Valley region, spanning from the south to the north of Kenya, have been experiencing an increase in their water levels resulting in severe flooding in some cases. The flooding has been a relatively gradual but steady process throughout the 2010s. However, since 2020 the lakes have been rising more rapidly. This research aims to understand the main drivers behind the overflowing of Lake Nakuru as one of the lakes in the Kenyan Rift Valley and specifically examines the hypothesis that increased precipitation in the catchment area is the primary cause of this phenomenon. The study utilises various methodologies to analyse spatio-temporal variability in precipitation, investigate the dynamics of Lake Nakuru, and identify the origin and driving forces behind the changing precipitation patterns.

A change point analysis is performed for weather station data throughout the catchment including lake precipitation and catchment precipitation. A water balance model is built to analyse the impact of precipitation on the lake through precipitation bin analysis and different catchment interactions such as catchment runoff, lake evaporation, and sub-surface catchment storage. Multiple linear regression has been applied to identify key catchment characteristics for the variability of the lake volume. Through moisture tracking as part of this research with WAM2layers it was possible to identify changes in moisture sources and climate drivers of precipitation in the catchment.

The findings of the research reveal significant changes in precipitation patterns, with a notable increase in precipitation since 2010. Change point analysis indicates that this increase coincides with the rise in lake volume, suggesting a strong correlation between precipitation and the overflowing of the lake. The water balance model employed in the study further emphasises the impact of precipitation on the lake, highlighting the complex interactions between precipitation and the catchment. Moisture tracking and climate driver analysis provide insights into the origins of the precipitation variability. The study identifies the western Indian Ocean region, particularly east of Madagascar, as an increasingly important moisture source for the catchment area. Moreover, the study highlights a negative correlation between El Niño and September precipitation, indicating the influence of climate oscillations on the changing precipitation patterns. These findings suggest that future climate changes, including increasing sea surface temperatures and intensifying La Niña and El Niño events, may further contribute to the likelihood of flooding in the area.

Overall, the research strongly supports the hypothesis that the overflowing of Lake Nakuru is primarily caused by changes in precipitation. The study emphasises the need for further research and monitoring to better understand the complex interactions between climate, precipitation, and the lake system.