Reflections in Perspective
From DT Online
Reflections, of a building in water for example, can be constructed in perspective using the same Vanishing Points.
Reflections, of a water-side building for example, are drawn simply by creating an upside down version.. Vertical lines are continued downwards and lines going into the picture connect to the same Vanishing Points as the real view.
Look carefully at the green lines - these are drawn in perspective by connecting them to the same Vanishing Points as were used for the original drawing. Vertical lines are continued downwards and distances equal to the height above water marked along them.