Prepared by the Task Committee to Revise Guidelines for Dam Instrumentation of the Committee on Water Power of the Energy Division of ASCE. Monitoring Dam Performance: Instrumentation and Measurements presents the fundamentals and current state of practice of instrumented measurements for monitoring dam performance. Dam performance monitoring is a balance of visual surveillance and instrumental measurements to accurately understand how well a dam is performing. Mechanical, electromechanical, and electronic instruments are used to measure geotechnical, structural, hydraulic, or geohydrologic dam performance indicators that are not observable by visual surveillance. Performance monitoring as part of a comprehensive dam safety program is a powerful tool for identifying and managing the risk of failure associated with a dam. Instrumented monitoring produces quantitative data regarding foundation, reservoir, tailwater, and precipitation conditions surrounding and within the dam. Instrumented monitoring can provide long-term records of data, allowing for detection of time or load-dependent trends in a dam's performance. MOP 135 delves into embankment, concrete, and other types of dams. It also examines their possible vulnerabilities, as well as explores how their potential modes of failure lead to asking performance questions that instrumented measurements can help monitor. This manual of practice covers<: recognizing vulnerabilities affecting dam performance; identifying performance indicators; understanding means and methods of measuring performance indicators; planning and implementing a monitoring program; acquiring, managing, evaluating, and presenting data; and making decisions and taking action on the basis of monitoring results. MOP 135 is a valuable resource for members of the global dam community, including dam owners, engineers, and regulators.