Characterization of Spatial Variability of Precipitation by Spatial Moments of Catchment Rainfall in a Tropical Environment

The spatial rainfall distribution influences the shape of the basin hydrograph response. Understanding and characterizing the relationship between the spatial rainfall organization and the flood shape response allows hydrological simulation models improve its performance in modelling extreme rain events. Therefore, it improves management of reservoirs operation in rainy seasons or systems for early alert for risk management. This paper describes the spatial rainfall organization in terms of Spatial Moments indexes of catchment rainfall into the Suarez river basin, one of the basins with a big contribution within the chain for hydropower generation in Colombia. Spatial Moments indexes make it possible to quantifying the dependence existing between the spatial organization of rainfall and basin morphology. Moreover, they describe the concentration and dispersion as a function of the distance measured along the drainage network. In tropical regions, there have been fewer studies than attempts to characterize the spatial distribution of precipitation and its relation to the drainage network and the flow path. We calculate the spatial moments of catchment rainfall for thirty rainfall events and related it with basin morphology and the drainage network. Results shown that majority of extreme rainfall events in this tropical basin have a unimodal distribution along the flow distance, and that the rainfall field centroid is located downstream of the catchment centroid, between catchment centroid and the basin outlet. Confidence interval for indexes was calculated by Bootstrapping methodology. Same indexes reported in scientific literature for other regions located at higher latitudes, are greater than the indexes calculated in this paper, indicating interesting differences in tropical rainfall distribution. Results of the study can be used in an improvement of the rain monitoring network in the basin and in prioritizing the maintenance of the gauge stations located in strategic places according to the characteristic distribution of rainfall in this basin.