Cavitation is one of the most prominent hydraulic phenomena facing engineers in the design and operation of pipes, water conduits, and related structures. It directly affects flow efficiency and the service life of the structure, which is why it has received wide attention in modern engineering studies as one of the most serious causes of mechanical damage in water systems. Cavitation occurs when the local pressure of the liquid inside a pipe drops below the vapor pressure of water at the prevailing temperature. Small vapor bubbles then form within the flow and collapse abruptly when they move into regions of higher pressure. This collapse produces high-energy pressure waves that act on the inner walls of the pipe. The likelihood of cavitation increases at sudden contractions, sharp bends, valves, and zones where the cross-section changes, since velocity rises and pressure drops noticeably in these locations. The effects of cavitation appear as unusual noise and vibration and reduced flow efficiency, then develop into erosion and pitting of the inner surfaces of pipes, pumps, and valves. If the phenomenon continues, the structure may suffer severe damage, leading to leakage and costly operational failures. Repeated bubble collapse at the same location also produces accumulated surface fatigue that shortens the operational life of the system. Cavitation criteria, foremost among them the cavitation number, are important tools for predicting its occurrence. This number relates the pressure at a given point to the vapor pressure of water and the kinetic energy of the flow. The lower its value, the greater the likelihood and severity of cavitation. Designers rely on this criterion to define safe limits for velocities and pressures within water systems. In light of advances in numerical modeling, it has become possible to simulate this phenomenon using computational fluid dynamics (CFD) software such as ANSYS Fluent. These programs allow the distribution of pressures and velocities to be analyzed with high accuracy and the zones most prone to vapor bubble formation to be identified, helping researchers improve designs before construction and reduce cost and risk. Methods for limiting cavitation begin with sound engineering design, such as reducing abrupt changes in cross-section, adopting gradual bends, and keeping velocities within permissible limits. They also include selecting erosion-resistant materials, aerating the flow by introducing calculated amounts of air to soften the effect of bubble collapse, as well as regular maintenance and continuous monitoring of the system. Thus, understanding and controlling cavitation is a fundamental pillar for ensuring the efficiency and sustainability of pipes and water conduits. It helps achieve a balance between hydraulic performance, structural stability, and economic feasibility in water resources management projects. Presented by: Asst. Lect. Farah Hamid Abdul Khudhair M.Sc. in Civil Engineering