Trend analysis of rainfall variability and its impacts on water resources in the Lake Naivasha Basin, Kenya
Paper Details
Trend analysis of rainfall variability and its impacts on water resources in the Lake Naivasha Basin, Kenya
Abstract
Rainfall variability is a key climatic factor influencing hydrological processes, water resource availability, ecosystem functioning, and socio-economic development. In recent decades, climate change has intensified rainfall variability, increasing the frequency and severity of floods and droughts across many regions. This study investigates long-term rainfall variability and its hydrological and environmental impacts within the Lake Naivasha Basin, Kenya, over a 35-year period. The basin supports one of Kenya’s most important freshwater ecosystems and sustains floriculture, horticulture, fisheries, tourism, and wetlands of high ecological value. Rainfall data from the Kenya Meteorological Department, streamflow records from the Water Resources Authority, lake-level observations, remote sensing products, land-use datasets, and water quality records were analysed using the Mann–Kendall trend test, Sen’s slope estimator, and time-series analysis to detect temporal trends and assess hydrological responses. The results indicate increasing rainfall variability, particularly in the upper catchments, with noticeable changes in the timing and magnitude of seasonal rainfall. Streamflow exhibited significant seasonal fluctuations, characterized by declining dry-season flows and shifting peak discharge periods. Lake Naivasha experienced increased water-level variability, with more frequent flooding events interspersed with periods of below-average water levels. Water quality analysis revealed increasing nutrient enrichment and sediment loading associated with agricultural runoff and shoreline development, accelerating eutrophication across several parts of the lake. These hydro-climatic changes have contributed to the degradation of riparian vegetation, wetland inundation, declining fish productivity, and increasing competition for water among agricultural, industrial, environmental, and domestic users. The study highlights the combined influence of climate variability and anthropogenic pressures on the basin’s hydrological regime and emphasizes the need for integrated water resources management, strengthened hydro-meteorological monitoring, catchment restoration, sustainable abstraction practices, and climate-resilient planning to enhance the long-term sustainability of the Lake Naivasha Basin.
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