Each less stringent objective and the reasons for it must be reviewed every 6 years and explained in subsequent updates of the RBMP.
Rhaid adolygu’r amcanion llai llym, ynghyd â’r rhesymau dros eu defnyddio, bob 6 blynedd a rhaid eu hesbonio yn niweddariadau dilynol y Cynllun Rheoli Basn Afon.