Kirkland sources their products with regional/national producers and rebrands them. So the contents of your Kirkland water depend on which Costco you purchase it from.

Source: A friend of mine brokers deals with producers to rebrand them as Kirkland products. Perishables like 'Kirkland' Ham, 'Kirkland' Cheese, 'Kirkland' Ice Cream are packaged by different companies depending on the Costco (Costco Canada, Costco East Coast, Costco West Coast). Where as other stuff like 'Kirkland' jeans are brokered globally. Water likely falls at the national/regional level with one of the major brands, so 'Kirkland' water in Canada is likely a different kind of 'Kirkland' water sold in California.