We observed that the levels of natural organic matter (NOM) were variable
during different seasons, with maxima in the fall for both provinces. In the regions under study, the highest trihalomethane (THM) and haloacetic acid (HAA) levels were achieved in warmer seasons (summer, fall), as observed in previous studies involving large systems.Observed THM and HAA levels were three times higher in systems in the province of Newfoundland & Labrador than in the province of Quebec.