3.—(1) Before the beginning of each year in which it intends to supply water for human consumption purposes, Scottish Water must designate and name the areas within its area of supply that are to be water supply zones for that year.
(2) A water supply zone may not comprise an area whose population immediately before the beginning of the year in question is estimated by Scottish Water to exceed 100,000.
(3) A water supply zone may not comprise an area with significant variations in water quality.
(4) Scottish Water may not vary a designation under paragraph (1) after the beginning of the year in relation to which the designation has effect.