Monitoring Eichhornia crassipes and Myriophyllum aquaticum in Irrigation Systems Using High-Resolution Satellite Imagery: Impacts on Water Quality and Management Strategies

This study presents a remote sensing (RS) approach for monitoring invasive aquatic species and assessing their impact on water quality in the Lis Valley Irrigation District (LVID), Portugal. Using high-resolution PlanetScope imagery (3.7 m resolution), this method overcomes spatial limitations in narrow irrigation canals. Representative sub-zones were selected to analyze spatial and temporal trends, and vegetation indices (Normalized Difference Vegetation Index—NDVI, Enhanced Vegetation Index—EVI, Green Chlorophyll Index—GCI) were calculated to map the spread of Eichhornia crassipes (water hyacinth—WH) and Myriophyllum aquaticum (parrot’s feather—PF). All three vegetation indices exhibited significant linear regressions with pH, with the EVI showing the highest coefficient of determination (R2 = 0.761), followed by the NDVI (R2 = 0.726) and GCI (R2 = 0.663), with p-values and ANOVA p-values below 0.05. Dissolved Oxygen (DO) also showed strong correlations, particularly with the GCI (R2 = 0.886 for both DO concentration and saturation). The NDVI and EVI demonstrated significant regressions for these parameters, with R2 values between 0.661 and 0.862. The results demonstrate the potential of RS to detect invasive species and assess their ecological impact, providing a cost-effective tool for management strategies in irrigation systems. Future research should integrate more field data and extend the study period to enhance classification accuracy.