Irish Water says exceedances in pesticides are on the increase across Donegal.
Two exceedances were detected last year in the River Eske Public Water Supply.
Irish Water say while there is no threat to public health, it is imperative that users of pesticides are mindful of best practice when spraying their lands.
The utility, working in partnership with the National Pesticides and Drinking Water Action Group is appealing to farmers and other users of pesticides to ensure that best practice measures to protect drinking water quality are always followed.
The latest exceedances in Donegal follows on from previous exceedances noted in 2017 in the River Eske Public Water Supply and also the Killybegs Public Water Supply as well as low level detections in many other supplies.
Eight different supplies in Co Donegal (Bundoran, Fanad East, Fanad West, Frosses /Inver, Letterkenny, Milford, Fullerton Dam and Rosses) have seen low levels of the herbicide MCPA and other pesticides over the past two years.