A new synthetic unit hydrograph computation method based on the mass conservation principle

Abstract

Synthetic unit hydrograph (SUH) methods are popular and play an important role in many water resources analyses of un-ganged watersheds. These methods are simple, requiring only an easy determination of watershed characteristics, such as catchment area and river length. In some cases, they may also include landuse characteristics and serve as useful tools to simulate runoff from watersheds undergoing land-use change. To develop a synthetic unit hydrograph, several synthetic unit hydrograph models such as HEC-HMS, Nakayasu, SnyderAlexeyev, SCS, and GAMA-1 are commonly used in Indonesia. In this paper, a new method for computing the synthetic unit hydrograph based on mass conservation principles is presented. This mass conserving synthetic unit hydrograph calculation procedure, called the ITB SUH calculation method, has been implemented in the development of ITB-1 and ITB-2 SUH. The unit hydrographs are synthesized by using either a simple single function (ITB-1) or using two simple functions (ITB-2) combined with automatic adjustable peak discharge factors. Some applications of the method in computing design floods of smalland medium-size catchment are presented. The results show that, although input requirements for the ITB SUH calculation method are simple and the calculation is easy, the final results agree well with other methods developed previously.