Seismic activity has been induced by loading and possibly lubrication of faults in rocks underlying several artificial lakes. Such evidence of failure justifies study of incremental stress distributions produced by the filling of artificial lakes. In this paper two-dimensional lakes are considered. Equations are derived giving the incremental stress components due to a side of a water-filled trough of polygonal section in the surface of art elastic half-space. A computer program based on these equations is described. Distributions of stress parameters are shown for lakes of rectangular and isosceles triangular sections, and for a two-dimensional approximation of a section of the lake forming behind the Bennett Dam on the Peace River, British Columbia.