Section 165(1) in The Punjab Panchayati Raj Act, 1994
(1)Seats shall be reserved for -(a)the Scheduled Castes; and(b)Backward Classes;in every Zila Parishad and the number of seats so reserved for Scheduled Castes shall bear, as nearly as may be, the same proportion to the total number of seats to be filled by direct election in that Zila Parishad as the population of the Scheduled Castes in that Zila Parishad area bears to the total population of that area and such seats may be allotted by rotation to different constituencies in a Zila Parishad.