This lecture covers the Laplace equation for groundwater flow, including the reminder of differential equations, harmonic potential, and boundary conditions. It also discusses the concept of velocity potential, harmonic potential, and the numerical resolution of Laplace's equation. The presentation emphasizes the conditions at boundaries, such as impermeable limits and equipotential surfaces, illustrated with examples like the flowerpot analogy and flow networks. The method of graphical flow networks is introduced as a tool to approximate solutions and determine flow characteristics. The lecture concludes with practical examples of groundwater flow in real-life scenarios.