Effects of space-time dynamics of precipitation on timing and shape characteristics of runoff events

The observed variability in shape and timing characteristics of event hydrographs emerges from the variability in the types and structure of the corresponding hydrometeorological events and their interaction with the variable catchment states. The increasing temporal resolution of available hydrometeorological data provide a possibility for deciphering the effect of space-time dynamics of precipitation on the characteristics of event hydrographs and might provide useful insights into the differences on the controls of small and large runoff events. In this study, we comprehensively analysed the effects of the spatio-temporal dynamics of precipitation on the characteristics of hourly event hydrographs using the analytical framework of Viglione et al. (2010). We examined eight properties reflecting the shape and timing characteristics of 2026 hourly event hydrographs and 20 indicators describing the spatio-temporal structure of precipitation and pre-event wetness states in seven contrasting catchments in the Bode River basin, located in central Germany, using random forests and Accumulated Local Effects (ALE) techniques.

We found that the steepness of the rising limbs of event hydrographs is controlled by the intensity of precipitation, its temporal dispersion, and the catchment-averaged storm velocity. The contribution of these indicators is even more apparent for large runoff events (i.e., events with larger peak discharges). Instead, the event time scale of the hydrographs is rather affected by the volume of precipitation and antecedent base flow in combination with the spatial properties of precipitation (its spatial spread and proximity to the catchment outlet). Moreover, we found that the duration of precipitation events plays a major role in defining the response time of catchments. Finally, our results demonstrate that the effects of spatio-temporal structure of precipitation for the shape and timing characteristics of hydrographs are especially prominent for larger events, indicating the potential importance of these features for accurate flood forecasting and constructing of design synthetic hydrographs. The future effort will focus on examining the validity of identified controls for a larger and more diverse set of catchments in Germany.

References

Viglione, A., Chirico, G. B., Komma, J., Woods, R., Borga, M., and Blöschl, G. (2010). Quantifying space-time dynamics of flood event types. Journal of Hydrology, 394 (1-2):213–229.