Bathymetric survey of lake Naivasha and its satellite lake Oloiden in Kenya; using acoustic profiling system

Abstract

Lakes and reservoirs play important roles as freshwater sources for domestic, indus-trial, agricultural, fisheries and recreational purposes. However, for the lakes to be sustainably exploited, there is need to understand their bathymetric characteristics by conducting bathymetric surveys. This aids in generating information that can guide lakes stakeholders and managers in establishing the volume of available water. It is recommended, therefore, that bathymetric surveys be conducted at ten-year intervals. Such continuous bathymetric information is lacking in many lakes, espe-cially in developing countries. One example is Lake Naivasha in Kenya, which is largely exploited for various socio-economic purposes. Despite its importance, its most recent published bathymetric data were collected in 1991. The goal of the pre-sent study, therefore, was to conduct a bathymetric survey of Lake Naivasha and its satellite Lake Oloiden, using an Acoustic Profiling System (APS) to generate Depth–Area–Volume relationships for the lakes. The survey results indicate the in the year 2016 mean depth, volume and surface area of the lake were 4.68 m, 722 × 106 m3and 154.17 × 106 m2, respectively. Because of limited information from the 1991 sur-vey, the 2016 survey results were comparable with those of 1983. The difference in the lakes mean, and maximum depth for the 1983 and 2016 survey was less by 0.23 and 2 m, respectively. This could be an indicator the lake is being affected by anthro-pogenic activities or environmental changes. The established Depth–Area–Volume relationships are crucial since they provide invaluable information to lake and water resources managers for making informed decisions regarding management of the lake’s water resources.