A new method called the Complementary Hydrograph method can convert known unit hydrographs into different durations. This method is similar to the S-Hydrograph method but involves decomposing the unit hydrograph into two "complementary" hydrographs associated with sequential rainfalls. The Complementary Hydrograph method produces the same results as the S-Hydrograph method and sometimes requires fewer computational steps. Both methods are based on the principles of superposition and linearity. The Complementary Hydrograph method is more versatile and can handle various types of unit-hydrograph conversion problems, including deriving unit hydrographs from varied intensity rainfall.