Application of Thermal Remote Sensing for Geothermal Mapping, Lake Naivasha, Kenya

Abstract

Remote sensing of the earth‘s surface records energy reflected or radiated by an object at different wavelengths of the electromagnetic spectrum. The wavelength region of 3-14 m is called thermal infrared region. The Landsat Thematic Mapper (TM) band 6 usually referred to as the thermal band operates in the wavelength of 10.4-12.5 m with ground resolution of 120 meters. The tone of a thermal image expresses surface radiant temperature. Radiation emitted by the ground objects is measured for temperature estimates.
Lake Naivasha, a freshwater lake, and the geothermal areas surrounding it lie on the central part of the Kenya Rift Valley (KRV). Its water is being used not only for domestic water supply and agriculture but also for the exploitation of geothermal energy. Surface manifestations, in the form of hot springs, fumaroles, solfatara, altered grounds and other volcanic-related features that are common in geothermal areas are present in Lake Naivasha and are indications of the presence of geothermal resource at depth.
A qualitative and quantitative interpretation of the thermal image south of Lake Naivasha shows that thermal manifestations and structural features in general show a relation with high heat flow. Geothermal manifestations including the wells show up on the image as scattered points with high temperature pixels with values ranging from 20-40 oC. They appear to be restricted on the west side of the main thermal divide in a NE-SW direction especially along the Olkaria Fault Zone that cuts through the geothermal area.