Experience has shown the important influence of rainstorm water in the arrival of pollutants to receiving water bodies. This paper presents an identification of rain gauge stations and rainstorm variables with influence over water quality parameters such as Temperature, Conductivity, pH and COD, measured in the effluent of an urban catchment. Fourteen rainfall events registered by eight rain gauge stations within or in the proximity of the studied catchment (El Salitre Basin, Bogotá, Colombia) were analysed by the use of correlation tests and Kernel Classificatory methods. Some sensitive water quality parameters to rainfall (maximum rainfall height, mean of height, total height; during a rainstorm event) were identified (pH, temperature, conductivity and settleable solids). Correlations were significant mainly for two rain gauge stations in the proximity (about 5 km) of the effluent and two others near the eastern mountains of the city (zone with high slopes).