Where is the water located on a 2001 old aurora 4.0 engine?

The 2001 Oldsmobile Aurora 4.0L engine (a Buick Series II 3800 engine) has its coolant located within the engine block itself, the cylinder head, and the radiator. There's also coolant in the heater core (inside the passenger compartment) and potentially some in the coolant reservoir (overflow) tank. These are the major locations. You won't find a single "water" tank or location; it's a circulating system.