Landsat : water quality surveillance of Roodeplaat Dam

Master Thesis


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University of Cape Town

The need for accurate, synoptic, up to date information, concerning the quality of South African impoundments, prompted a study into the relationship between Landsat reflectance data and chlorophyll ~ and turbidity in Roodeplaat Dam. Surface and integrated chlorophyll a as well as surface and integrated turbidity were collected simultaneously with the satellite's overpass, from 32 sampling sites on the impoundment. Six days, between 81.10 .14 and 82 .11.16, were cloud free and the data were analysed in order to establish the relationship between the specific water quality conditions and the satellite reflectance data. Prior to the analysis certain factors required attention. Firstly, it was important to accurately align the sampling sites with their corresponding Landsat pixels. Secondly, the satellite reflectance data were corrected for influences of haze and the angle of the sun. Thirdly, the requirement that the water quality surface reference data be representative of the range of conditions in the impoundment was recognised. Lastly, the interrelationship between chlorophyll a and turbidity and the multicollinearity evident between the four reflectance bands, demanded that a multi-variate statistical technique be implemented, in order to adequately analyse the available data.

Bibliography: pages 104-118.