Water resources systems are physically complex and the solution of appropriate mathematical models is computationally demanding. This course considers physical processes in water resource systems, their mathematical representation and numerical solutions. Newton's 2nd law and the equations of mass and energy conservation are developed and applied to closed-conduit, open-channel, and groundwater flow problems. Procedures for efficient numerical solution of the governing equations are presented. Problems of non-linearity, sensitivity to data and computational complexity are introduced.