 General distrust of tap water quality has led to much of the population purchasing drinking water; Mexico was ranked the third largest consumer of bottled water in 2009.Greater Mexico City is served by a singled combined sewer system, collecting municipal wastewater, industrial wastewater and storm water.It includes of pipes, 68 pumping stations, numerous dams, lagoons, and regulatory tanks for flow control, 111 km of open canals, 42 km of rivers (rio) used primarily for drainage, and 118 km of underground collectors (interceptor and emisor) and tunnels.