Prolagos, an AEGEA company, provides water and sanitation services for five municipalities in the state of Rio de Janeiro, Brazil. The concession covers the famed Lakes Region (Região dos Lagos), where seasonal populations fluctuate from nearly 400,000 to more than 2 million. AEGEA prepared the Brazilian Reals (BRL) 570 million Sewerage Master Plan 2041 to expand sewerage coverage to 90 percent by 2023 and stop contamination of the region’s main attraction, Araruama Lagoon. Using SewerGEMS to model the combined sewerage and drainage systems enabled AEGEA to optimize capital expenditures (CAPEX) and operating expenditures (OPEX). Since 1998, the concessionaire has invested more than BRL 550 million, tripling the population’s access to clean water and expanding sewage collection and treatment for 76 percent of the population.