USE OF CONTINUOUS SIMULATION VERSUS THE DESIGN STORM CONCEPT FOR WATER QUALITY.
The validity of the design storm concept has been challenged by several investigators since the development of computer simulation models. Of particular interest are the studies that compare system performance. Continuous simulation involves the generation of surface runoff quantity and quality time series with a physically-based catchment model, from long-term historical precipitation data. The simulated response of the system is described statistically, and the proposed design is adjusted until an acceptable risk of violation is obtained in terms of frequency or return period of the variable of interest. The large number of factors that affect the quality of surface runoff prevents the use of any single event for proper analysis and design. It is the frequency response of the system which is significant, and also duration. Thus, long-term historical rainfall data are required.
