Evaluating the Impact of Irrigation Weirs on Vegetation using Satellite Imagery

Chad


Context and Issues

Several irrigation weirs have been constructed in Chad in order to support the local agricultural sector. Masae was asked by an International Development Agency to leverage remote sensing tools to evaluate weirs impact on submerged areas and vegetation cover.


Solution

Masae used Landsat and Sentinel-2 satellite images to measure the evolution of NDVI (Normalized Difference Vegetation Index), NDMI (Normalized Difference Moisture Index) and NDWI (Normalized Difference Water Index) levels before and after the construction of irrigation weirs between treated and control valleys.

Then, to determine the evolution of vegetation cover, the team recorded the number of pixels on treated valleys with NDVI above a fixed threshold over time. The same analysis was performed with NDWI to obtain the evolution of actual submerged areas over time.

Analysis results were provided in a written report and in a GIS data visualisation file