This thesis presents a complete power loss model for an Archimedes screw turbine (AST), capable of predicting the mechanical power of an AST based on available energy head. This model amends a prior idealized frictionless AST performance model to include losses from inlet and outlet entrance effects, internal hydraulic friction and outlet submersion. Laboratory experiments on scale-model ASTs were conducted to determine variable relationships and validate power loss models. Gap leakage was experimentally measured in an AST, and results were compared to gap leakage models. The performance of a 7 kW grid-connected AST was measured and compared to model predictions. Finally, a delivery channel loss model is presented that predicts the needed supply reservoir head to provide an AST with a specified flow. The proposed AST power loss model improves the prior frictionless power model significantly and is generally capable of predicting the power for a real-world AST.