Investigating the Effect of Spatial and Temporal Variabilities of Rainfall on Catchment Response

Abstract

Abstract Rainfall, as the most important process of the hydrological cycle, has significant variabilities in time and space. Obviously, when it comes to flood management decisions, an insight on the impact of such variabilities can play a key role in reducing flood-related losses. In this study, the effects of rainfall spatiotemporal variabilities and the storm center location on the characteristics of the catchment outflow hydrograph, by using numerical experiments based on synthetic data, have been investigated. For this purpose, by introducing two different deterministic and stochastic rainfall generation models, more than 600 rainfall events with special specifications and correlation structures have been generated for Walnut Gulch catchment which is located in Arizona, the US. After calibrating the distributed MIKE-SHE rainfall-runoff model for a sub-catchment in the basin, the model is implemented over the entire catchment with synthetic rainfall of specified characteristics to answer the research questions raised. The results of the simulations indicate: 1- The location of the storm center has a significant effect on the characteristics of the outflow hydrographs. The nearer the location of the storm center to the outlet is, the higher the peak magnitude and the lower the time to peak will be. 2- Spatial and temporal resolution of the monitoring network has a considerable effect on the outflow hydrograph characteristics, especially on the peak magnitude. As spatial and temporal resolutions decrease, peak magnitude is underestimated and time to peak is overestimated. 3- The lower the correlation of rainfall events in space is, the higher the effect of spatial resolution on outlet hydrograph characteristics will be. 4- Rainfall correlation in time doesn’t seem to alter the effect of rainfall temporal resolution on the catchment response. In conclusion, it can be said that the accurate estimation of the outflow hydrograph requires access to a relatively high spatial and temporal resolution monitoring network.