Mapping Ireland’s Surface Water from Space: Comparison of three remote sensing platforms

Water plays a vital role in Earth’s ecosystems, hence, the management and monitoring of water resources are significantly important. Ireland has more than 12200 lakes, 3,192 river water bodies including rivers, streams, and tributaries that exceed in total 70,000 km. However, few of them are currently monitored (2% of lake and 1.8% of river). Earth observation (EO) has shown promise in understanding and monitoring water resources. However, the sizes of Ireland’s water bodies have remained a challenge for EO monitoring.

In this research, three different platforms (Landsat 8-OLI, Sentinel-2A and PlanetScope Ortho Scene 3B product) are used to calculate their individual spatial coverage of water bodies across Ireland and quantity their usefulness for water quality monitoring. To explore if water extraction methods impact the results, four different water extract methods (NDWI, NDVI, MNDWI, and AWE have been used to create water masks for Ireland. These water masks created for each platform were then compared with existing map of river network, lakes, and water monitoring stations. The results indicated that AWE’s water mask is the best performing extraction method compared to the existing maps, while the high-resolution platforms (Planetscope and Sentinel-2) clearly outperforms Landsat, Landsat is still able to detect at least 51.90% and 1.63% of rivers. This shows that even the coarser resolution Landsat imagery is useful in monitoring water quality across Ireland.