sentences:  The La Mesa Watershed Reservation which hosts the dam and reservoir is jointly administered, supervised, and controlled by the Department of Environment and Natural Resources of the Philippine national government and the is under the joint administration, supervision and control of the (DENR) and the Metropolitan Waterworks and Sewerage System (MWSS).The La Mesa Dam is part of the Angat-Ipo-La Mesa water system which supplies water to the population of Metro Manila and surrounding provinces.The water collected in the reservoir is treated at the La Mesa and Balara Treatment Plants.