Ireland's State of the Environment Report 2024

193 Chapter 8: Water Figure 8.2  Surface water ecological status, 2016–2021 ˜ Less than Good ˜ High or Good 46% 54% Source: EPA, 2022 Coastal waters have the highest percentage of waters in high or good ecological status (81%) followed by lakes (69%), rivers (50%) and transitional waters (estuaries and lagoons) (36%), which have the poorest water quality (Figure 8.3). Half of the surface waters monitored in the period 2016– 2021 failed to achieve good chemical status due to the exceedance of environment quality thresholds for at least one hazardous chemical substance (Figure 8.4). However, when ubiquitous substances (chemicals widespread in the aquatic environment, such as mercury) are excluded from the assessment, 88% of water bodies are in good chemical status.