A system includes an emissions control system. The emissions control system includes a processor programmed to receive one or more selective catalytic reduction (SCR) operating conditions for an SCR system. The SCR system is included in an aftertreatment system for an exhaust stream. The processor is also programmed to receive one or more gas turbine operating conditions for a gas turbine engine. The gas turbine engine is configured to direct the exhaust stream into the aftertreatment system. The processor is further programmed to derive a NH3 flow to the SCR system based on an SCR model and the one or more SCR operating conditions, to derive a NO/NOx ratio, and to derive a fuel split for the gas turbine engine based on the NH3 flow, the NO/NOx ratio, or a combination thereof.