The Derg catchment is located in the north west of Ireland, spanning the border between Northern Ireland (NI) and the Republic of Ireland (RoI). In the upper part of the catchment land use is predominantly coniferous plantation and bogland with low intensity farming on poor pasture land. In the lower part intensification of land use for agricultural purposes is more prevalent with improved grasslands and complex cultivation patterns.

Groundwater productivity is relatively low and only for limited individual use. Raw drinking water for a population of 1.8 million is abstracted from surface water of the River Derg.

NIWater and Northern Ireland Environmental Agency (NIEA) and the Environmental Protection Agency (EPA) implement a comprehensive monitoring program of water quality in the catchment. There are  two main threats to raw drinking water in the catchment.

• MCPA (herbicide) arising from the spraying of rushes (Juncus) on agricultural land. The need to remove rushes from agricultural land is being driven by farmers’ concerns over eligible land for the EU single farm payment. Increase in rush cover is being attributed to prolonged saturation of soil, lower stocking rates and lowered soil pH.
• Colour/turbidity arising from peaty soils and eroded sediment from both forestry and agricultural land. Chlorination reactions with dissolved organic carbon (DOC) during the drinking water treatment process results in the production of toxic trihalomethanes.

From March 2017, the Agri-Food and Bioscience Institute (AFBI) has been working on a €4.6 million INTERREG VA funded »Source to Tap project aimed at reducing the impact of land use on drinking water in the Derg and Erne Catchment. Source to Tap aims to deliver:

• a Catchment Management Plan;
• a Learning and Outreach Plan in the Derg Catchments through Source to Tap Project Catchment Officers to effect changes in attitude to protection of water quality and the water environment;
• a cross border farm Incentive Scheme in selected sub-catchments within the Derg catchment, encouraging changes in current land management practices to reduce pesticide, colour, turbidity and diffuse pollution pressures, thereby improving overall water quality;
• UK Water Industry Research (UKWIR) cost benefits assessments of the Farm Incentive Scheme.

 Related articles