One of the objects of the invention is to provide a water-saving type advanced humid air gas turbine system (AHAT) that can decrease the amount of makeup water to be supplied from the outside, by reducing the amount of water consumed when the gas turbine system is starting up, shut down, or subjected to load rejection. The gas turbine system includes a compressor, the compressed air header for generating humidified combustion air, a combustor for generating combustion gas, and the turbine. When the gas turbine system is starting up, shut down or subjected to load rejection, steam coming from the heat recovery steam generator is recovered by blocking the first steam system and making the second steam system communicate with the heat recovery steam generator.

An apparatus, system, and method for a gas turbine engine may include a sectioned heat exchanger. A heat exchanger may include an inlet manifold configured to receive a working fluid. A plurality of circuits including at least first and second circuits configured to transfer heat with respect to the working fluid. Each of the circuits may have a circuit inlet valve, a circuit heat exchange channel, and a circuit outlet valve. The heat exchanger may further include an outlet manifold configured to pass the working fluid to an outlet. The heat exchanger may include a first sensor configured to measure of first parameter of the first circuit and a second sensor configured to measure a second parameter of at least one of the outlet and the second circuit. A controller may be configured to selectively isolate at least one of the plurality of circuits based on a pressure difference between the first and second parameters.