Particle circulation in irrigation reservoirs: The role of filter backwash reject on filter clogging

•We studied water and particles circulation between reservoir and its bank filters.•Returning backwash reject into the reservoir re-introduces clogging-size particles.•10% of the deep epilimnion particles >150μm are removed and re-introduced daily.•Backwash reject contains live copepods that may reproduce in the reservoir.•With a retention time of 30′ most particles of the backwash reject would sediment.