A Study of the Fosu Lagoon Watershed in Ghana: A Remote Sensing Approach

Abstract

This work explored a remote sensing research approach for the study of the Fosu lagoon and its watershed. Land-Use/Land-Cover (LU/LC) and estimation of water quality parameters from the watershed and lagoon respectively was undertaken together with confirmatory social data. Landsat satellite data for the years 1991, 2007 and 2018 were used for LU/LC of the Fosu lagoon watershed with net changes for the classes built-up (90.4%), dense vegetation (-32.1%), sparse vegetation (37.7%), bare land (-6.4%) and water (-41%) over the period. Overtime, changes of the LU/LC had effects on the Fosu lagoon and contributed in diverse ways to its degradation. Regression analysis between the water quality parameters and reflectance values of the WorldView-2 satellite at nine sampling points revealed R2 values and corresponding linear equations. The band ratio B2/B4 had the highest R2 (0.512) for DO, B4/B3 for pH (R2 = 0.8209), B2/B5 for Turbidity (R2 = 0.648), single band B6 for TDS (R2 = 0.019), B2 for conductivity (R2 = 0.047) and band ratio B1/B3 for depth (R2 = 0.321) and were selected as such. Results however could not be used for interpolation and possible creation of maps. Social investigation explored existent conditions about the lagoon on the ground. Filth, vegetation and siltation reflected as the highest trend of change with frequency 34.7%. Fishermen also confirmed lagoon depth reduction. Algal blooms had the highest mean statistic of (4.32 ± 0.086) as a single threat. Other significant threats were improper refuse disposal (4.13 ± 0.095), and erosion & siltation (4.29 ± 0.107). The combination, Dredging, Desilting & General Cleaning had the highest frequency (25%) by way of restoration. Fishermen, Policy Makers & Traditional Council (43.7%) were mostly suggested to drive the restoration process.