Monitoring <i>Eichhornia crassipes</i> and <i>Myriophyllum aquaticum</i> in Irrigation Systems Using High-Resolution Satellite Imagery: Impacts on Water Quality and Management Strategies
2025
Susana Ferreira | Juan Manuel Sánchez | José Manuel Gonçalves | Rui Eugénio | Henrique Damásio
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 <i>Eichhornia crassipes</i> (water hyacinth—WH) and <i>Myriophyllum aquaticum</i> (parrot’s feather—PF). All three vegetation indices exhibited significant linear regressions with pH, with the EVI showing the highest coefficient of determination (R<sup>2</sup> = 0.761), followed by the NDVI (R<sup>2</sup> = 0.726) and GCI (R<sup>2</sup> = 0.663), with <i>p</i>-values and ANOVA <i>p</i>-values below 0.05. Dissolved Oxygen (DO) also showed strong correlations, particularly with the GCI (R<sup>2</sup> = 0.886 for both DO concentration and saturation). The NDVI and EVI demonstrated significant regressions for these parameters, with R<sup>2</sup> 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.
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