The IUH of General Hydrologic System Model

This paper describes two simple and practical forms of the general hydrologic system (GHS) model, including a 5-parameter model and a 3-parameter model, and derives and compares their instantaneous unit hydrographs (IUH) which are useful to hydrologic analysis and design. It is shown that the 3-parameter model can be derived from the 5-parameter model by modifying the assumption on the boundary conditions in solving the differential equation that represents the model. It is found that the 5-parameter model is more realistic to represent the real-world system and fit the hydrologic data consistently better than the 3-parameter model. On the other hand, the 3-parameter model is slightly simpler in form and produces IUHs always of positive ordinates.