Occurrence of THM and NDMA precursors in a watershed: Effect of seasons and anthropogenic pollution

► Precursors of THM and NDMA were evaluated in a watershed. ► High concentrations of THMFP and NDMAFP were detected. ► Pollution (point or diffuse) in addition to NOM may act as DBP precursors. ► No relationship between DBP precursors and water quality parameters was detected. ► Spatial effects are more important than the effect of the seasons.