EPA - Ireland's Environment, An Integrated Assessment - 2020

Ireland’s Environment – An Integrated Assessment 2020 Significant agricultural pressures include run-off of nutrients and sediment from agricultural land and farmyards and the contamination of surface waters with pesticides. Drainage of agricultural land can also damage the physical integrity of streams and rivers and increase the loss of sediment to larger downstream rivers. More generally, work done to protect river banks, to prevent flooding or to maintain navigation channels in rivers and estuaries may damage sensitive water habitats if the hydrology and morphology of these waters are substantially changed in character. Discharges from wastewater treatment plants can lead to organic and nutrient enrichment with consequent effects on dissolved oxygen levels and biological communities. Poorly treated sewage can also pose a risk to public health by potentially contaminating the source of drinking water supplies with harmful bacteria and viruses. Over half (56%) of the combined sewage loading that arises in large urban areas in Ireland is discharged from plants that are not meeting the required European standard (EPA, 2020a). Furthermore, raw sewage from the equivalent of 78,000 people in 35 towns and villages is still released into the environment every day. The majority of this (from 31 of the towns and villages) is discharged directly into estuaries and coastal areas. In relation to forestry, inappropriately sited forests and poorly managed forest operations can negatively affect water quality and aquatic habitats and species. The most common water quality problems arising from forestry in Ireland are the release of sediment and nutrients to the aquatic environment and impacts from acidification. Forestry may also give rise to modified stream flow regimes caused by associated land drainage. Impacts of Nutrients (Nitrogen and Phosphorus) on Water Quality in Ireland One-third of rivers and lakes and one-quarter of estuaries already have too much nutrient in their waters, and nutrient concentrations in our rivers and nutrient inputs to our marine environment are increasing. One of the main problems damaging the quality of surface waters is nutrient pollution caused by too much nitrogen and phosphorus (see Topic Box 7.2). Nitrogen pollution in the south and south-east of the country is damaging the ecological health of many of our estuaries and nearshore coastal waters. In these areas, which have freely draining soils, nitrate seeps rapidly into groundwater, and losses are closely correlated with the intensiveness of farming: the higher the rate of application of nitrogen, the higher the nitrate concentrations in waters. Since 2013, nitrogen emissions have increased as both cattle numbers and fertiliser use have increased. In freshwaters and in some of our more river-dominated estuaries, phosphorus is often the nutrient of most concern. Phosphorus concentrations are elevated in various parts of the country, particularly along the east coast and in parts of the south (see Figure 7.9b). Phosphorus losses come primarily from wastewater discharges and run-off from agricultural land on poorly draining soils. Diffuse phosphorus losses from agriculture are difficult to tackle, as the sources do not occur uniformly in the landscape but in ‘hot spots’ or critical source areas. 172