Had the work continued under the original plan it might have resulted not only in the failure of the structure itself but have been the cause of immeasurable loss to this great city of its supply of water in addition to an appalling destruction of life and property . The boroughs of Manhattan and Bronx , of an estimated population of 2,200,000 are dependent almost entirely upon the Croton River for their supply of water ; in fact , they have no other supply , except the comparatively small quantity ( 20,000,000 gallons per day ) from the Bronx and Byram Rivers , small as compared with 290,000,000 gallons , the present daily consumption of these two boroughs . The natural flow of Croton River in dry seasons was judged insufficient to supply the city as early as 1843 , now more than 60 years ago , so Croton Lake of a capac- ity of two billion gallons , was then created by building the old Croton Dam . Since then , from time to time , six other reservoirs , having an aggregate capacity of 40,000,000 , - 000 gallons , have been built on the principal tributaries of the river , above the lake , for the purpose of collecting water in wet seasons , to be discharged into the lake as re- quired for use . The city has no auxiliary supply , and no lakes or rivers that could be used as such in case of an emergency , hence an accident to a reservoir might result in so great a loss of water as to cause a water famine , truly styled one of the world's greatest disasters . The new Croton dam is located about thirty - seven miles from the Central Park reservoirs , it is on the Cro- ton River , about two and one - half miles below the old Croton dam .