Abstract

Lake Naivasha is an important water resource for Kenya being a fresh-water lake in a region dominated by salty-water lakes. The lake supports several human activities around it. Its water level, though fluctuates, was gradually declining before 2010. The water level rose from March 2010 and has since remained relatively high. As a result, areas around the lake that were previously land surface are currently submerged in water. This is threatening the survival of human activities around the lake. Consequently, the study sought to establish the causes of the lake’s water level fluctuations in the period 2000-2016, focusing on the role of rainfall, temperature, human activities around the lake, and water hyacinth. Surface area of the lake covered by water and surface area of the lake covered by water hyacinth were extracted from Landsat images. The SEBAL model was used to estimate evaporation potential over the lake and differences in evaporation over areas covered by water hyacinth and open water surfaces were analysed. Water hyacinth cover was found to have significant, positive correlation with monthly average water levels (p < .05). Open water surfaces lost significantly higher water volume through evaporation than areas covered by water hyacinth (p < .05). This suggests that water hyacinth contributes to the high water levels. Rainfall received over Nyandarua slopes, which is the catchment region for in-flow rivers was also an almost statistically significant contributor to lake’s water level changes, while temperature was not. On the other hand, growing human activities around the lake seemed to contribute to water level decline through increasing abstraction from the lake. The study recommends more research on, and implementation of better and more ecologically efficient measures for controlling water hyacinth growth in Lake Naivasha.

Highlights

  • Lake Naivasha plays a very important role in the Kenyan economy being a fresh-water lake in a semi-arid region in Kenya

  • Lake surface area changes Further evidence of water level fluctuations is provided by the estimated surface of area of the lake covered by water presented in appendix A1 and figure 4 below

  • The study did not find any evidence between monthly rainfall over the lake and water level in the lake or the surface area of the lake covered by water

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Summary

Introduction

Lake Naivasha plays a very important role in the Kenyan economy being a fresh-water lake in a semi-arid region in Kenya. It supports the life of hundreds of thousands of people living within its basin. Significant agriculture occurs within the 3,376 km catchment area, including commercial floriculture and horticulture industry whose growth has increased significantly over the last two decades [1,2]. The lake provides home to a wide range of aquatic and terrestrial flora and fauna, including fish, birds, plants, etc. It supports thriving fishing and tourism industries. The underground discharge from the lake recharges the geothermal wells around the lake [3,4]

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