Utilization of Landsat Data for Quantifying and Predicting Land Cover Change in the Bumbuna Watershed in Sierra Leone

Abstract

Rural communities in third world countries are concerned over land use changes resulting from resource exploitation. This is the case for the Bumbuna watershed in Sierra Leone following impoundment of the Bumbuna reservoir in 2009. Farmers have increased activities along the riparian zones in protest against inundation of their farmlands. The dam operators warn this practice would threaten sustainable power supply; the farmers contend the reservoir is increasing and taking over their farms. However, it is difficult to resolve this issue without a means of quantifying the change and developing early warning systems for land cover in the watershed. This research presents a case for the use of remotely sensed Landsat data for quantification of land cover change and the development of predictive models to inform preparedness for imminent problems that may arise from land use practices. In situ water loggers, in combination with manual readings, recorded water levels in 30-minute intervals since 2009. These datasets combined with spectral values of Landsat 7 and Landsat 8 for the development of regression algorithms for predictive purposes. Digital photographs and satellite imagery illustrated the changes in land cover over time (a 33% water rise and 44% NDVI change from 2009 to 2015). These visual and spectral pictures confirm the usefulness of remotely sensed data for early warning systems in the watershed. Results of the regression analysis show Band 1 (Blue) and Band 4 (NIR) as statistically significant predictors for water level in the reservoir. The tests accounted for 84% (R 2) of the data with p-values less than α at the 0.05 confidence level. However, future trials of the model will consider reducing the 4.6 error margin to minimize deviations from the observed data.

Land Use, Microclimate, and Surface Runoff Linkages: Space-Time Modeling From Rokel-Seli River Basin, Sierra Leone

“…The amount of parameter and conceptual model uncertainty captured by the 95PPU is consistent with other studies that have been conducted in the SSA region (Schuol and Abbaspour, 2006;Schuol et al, 2008). Mansaray and Barrie (2016) where a 45.5% rise in water level was reported in the Bumbuna reservoir which would have partly triggered the flow increase. In a related study, Magilligan and Nislow (2005) observed increase in streamflow following dam construction especially during the summer months in selected reservoirs in the United States.…”

“…Rainfall drops precipitously as one moves from the western coastal lowlands to the northeastern highlands while the vegetation transition from a green lush landscape to a semi-arid savanna type cover. Major socioeconomic activities in the region include farming, cattle rearing (mostly nomadic herding), artisanal gold and industrial iron ore mining, sand quarrying, biofuel production, and fishing (Mansaray and Barrie, 2016). The 2015 population of the watershed is estimated at 730,696 (Statistics Sierra Leone, 2016) which is distributed among five relatively large cities (figure 1) and a plethora of small towns and villages.…”