This research concerns to study the quantity of seepage running downward from triangular open channel with lining and unlining using computer program SEEP/W (which is a sub-program of Geo-Studio).
Using SEEP/W experiments two groups were carried out with three different downstream slopes of triangular open channel, three different upstream slopes, three variable free board, three different height of triangular open channel, for first group using three different permeability for soil around the triangular open channel and for second group using three different permeability for lining layer and for soil around triangular open channel. For each run the quantity of seepage were determined. Dimensional analysis was used with helping of the theoretical results to develop empirical equations in order to determine the quantity of seepage running downward the triangular open channel for lining and unlining. Also, Verify the SEEP/W results with analytical method ofVedernikov’s equation. Results show good agreement for triangular open channel unlining layer.