ASSESSMENT OF SMALL WATER BODIES IN IRELAND

First and second order streams comprise 77% of the 74,000km of river channel in Ireland but monitoring stations are typically on third or higher order rivers. Ireland has over 12,200 lakes: 745 of these have been defined as water bodies for the Water Framework Directive and 222 lakes are included in the monitoring programme. The ecological status of unmonitored water bodies is extrapolated from the monitored network. Some 30% of the main-stem monitored river channel length fails to achieve good ecological status. Of this, half is impacted by diffuse pollution and half by point source pollution. Pollution from diffuse sources such as agriculture or scattered rural dwellings is more difficult to pinpoint than that from point sources such as wastewater treatment plants. A simple 'pathways' hypothesis suggests that the risk of diffuse pollution is proportional to the length of river bank and thus, small stream channels comprising 77% of the total river network pose a challenge. The Small Stream Risk Score (SSRS), designed to pinpoint sources of diffuse pollution, is a simplified macroinvertebrate risk score for non-specialists. By comparing SSRS values for small streams immediately upstream of a polluted main-stem monitoring station the source can be narrowed down and pinpointed more accurately.