Gas turbine performance enhancement technologies such as inlet fogging, combustor water/steam injection and overspray are being employed by users in recent years without fully evaluating their effect on gas turbine performance and operability. The water injection techniques can significantly affect the engine operating point thus a careful analysis should precede the application of performance enhancement devices, especially when the devices are retrofitted to old engines or engines operating at extreme conditions. The present paper, examines the most widespread techniques that implement water injection by using in-house models that can reproduce the effects of water injection on the gas turbine and compressor off-design operation. The results are analyzed with respect to both performance augmentation and engine operability in order to give further insight on gas turbine operation with water injection. The behaviour of the gas turbine is interpreted while the risks on engine integrity due to water injection are identified. (C) 2009 Elsevier Ltd. All rights reserved.