groundwater is defined as all water below the surface of the ground that is in the saturation zone (that is below the water table) and in direct contact with the land or subsoil
diffinnir dŵr daear fel unrhyw ddŵr sydd islaw wyneb y tir sydd mewn parth dirlawnder (hynny yw, islaw’r lefel trwythiad) ac yn cysylltu’n uniongyrchol â’r tir neu’r isbridd