Ireland's State of the Environment Report 2024

198 Chapter 8: Water Topic Box 8.1  Examples of damage to river hydromorphology (continued) Barriers impede the movement of water, sediment and fish, such as salmon, and alter the natural flow of a river. Hard engineering works on rivers permanently damage the habitat, reduce shade, and can give invasive species an advantage. Healthy riverine hydromorphology means rich and mature riparian zones, no barriers, a clean riverbed with a natural flow, and a healthy ecology. 2 Different terms, such as phosphate and nitrate, can be used for phosphorus and nitrogen depending on analysis and reporting requirements. Nutrient pollution The most significant issue affecting water bodies at risk of not meeting their environmental objective is nutrient pollution. When phosphorus or nitrogen 2 enter waterways they can cause excessive growth of plants and algae. This overgrowth can clog up those waterways and lead to oxygen loss from the water, which harms the ecology. Monitoring data show that recovery can occur relatively quickly when the nutrient sources are removed and when there are good water quality areas upstream for restoring the aquatic wildlife. Nitrogen pollution is caused mainly by agricultural activities. Phosphorous pollution comes from both agricultural losses and urban waste water. While increased concentrations of both phosphorus and nitrogen can lead to eutrophication, the presence of excess phosphorus is of particular concern for the ecological health of our rivers and lakes. Elevated levels of nitrogen are more of a concern for our estuaries. High nitrate concentrations in some drinking water supplies can pose a risk to human health.