A water delivery system (18) for delivering water for injection into gas turbine engine combustor (4) includes a centrifugal pump (19) and a metering valve (23). The centrifugal pump (19) has an inlet (20) connected to a water source and a discharge (21) connected to a water supply line (22). The metering valve (23) is connected to the water supply line (22) downstream of the discharge (21) of the centrifugal pump (19). The water supply line (22) is connected to an injector nozzle (14) downstream of the metering valve (23). The metering valve (23) is operable to regulate a flow rate of water in the water supply line (22), to thereby meter an amount of water supplied to the injector nozzle (14).