this is equivalent to all expenditure on basin management and flood protection plus one third of all expenditure on policy and regulation according to the user and polluterpays principles users of retail water services should pay for the full cost of urban bulk water supply services and wastewater treatment in mexico however they only pay about twothirds of the cost of urban bulk water supply since conagua collects mxn billion to provide services on which it spends mxn billion and only half of the cost of wastewater treatment following the share of user s contributions to the water supply and sanitation subsector