RESUMO:Utilizou-se modelo desenvolvido em dinâmica de sistemas, especificamente para as Bacias Hidrográficas dos Rios Piracicaba, Capivari e Jundiaí (BH-PCJ), com cinco simulações para 50 anos de horizonte, como ferramenta para auxiliar na gestão dos recursos hídricos. O modelo estimou as ofertas e demandas de água, e a geração de águas residuárias dos diversos consumidores existentes nas BH-PCJ. WATER RESOURCES SITUATION AT PIRACICABA, CAPIVARI AND JUNDIAÍ WATERSHEDS USING A DYNAMIC SYSTEMS MODELABSTRACT: Using a dynamic systems model specifically developed for Piracicaba, Capivari and Jundiaí River Water Basins (BH-PCJ) as a tool to help to analyze water resources management alternatives for policy makers and decision takers, five simulations for 50 years timeframe were performed. The model estimates water supply and demand, as well as wastewater generation from the consumers at BH-PCJ. A run was performed using mean precipitation value constant, and keeping the actual water supply and demand rates, the "business as usual" scenario. Under these considerations, it is expected an increment of about ~76% on water demand, that ~39% of available water volume will come from wastewater reuse, and that waste load increases to ~91%. Falkenmark Index will change from 1,403 m 3 person -1 year -1 in 2004, to 734 m 3 P -1 year -1 by 2054, and the Sustainability Index from 0.44 to 0.20. Another four simulations were performed by affecting the annual precipitation by 90 and 110%; considering an ecological flow equal to 30% of the mean daily flow; and keeping the same rates for all other factors except for ecological flow and household water consumption. All of them showed a tendency to a water crisis in the near future at BH-PCJ.