Regionalization of precipitation, its aggressiveness and concentration in the Guayas river basin, Ecuador

Abstract

The aggressiveness of rain contributes to the erosion of the soil in high mountain regions, and therefore to the sedimentation in the lower part of the watershed. To know about the aggressiveness of rain in coastal and Andean regions contributes to the formulation of mitigation measures that help to the reduction of erosion and loss of nutrients. Fournier indices, Modified Fournier and precipitation concentration provide the ability to estimate the spatial and temporal distribution of the aggressiveness of the rain. This study presents a spatial and temporal analysis of climatic aggressiveness in the Guayas river watershed located on the coast and the equatorial Andes. Registered monthly data of 30 rainfall stations for the period 1968-2014 was selected. Homogeneous precipitation zones were determined by the k-means method. The results indicated two predominant homogenous regions, the first located to the west in the coastal and Andean zone (85;2% of the area of the Watershed), with a high and very high aggressiveness index, while the distribution of precipitation in the second region (High mountain) resulted from very low to low aggressiveness. The greater potential aggressiveness of rain corresponds to a greater accumulation of average annual rainfall, which indicates a high seasonal influence of rainfall, i.e., a greater amount of rainfall can precipitate in a reduced number of consecutive months. The concentration values reveal a regional gradient in the east-west direction, which goes from moderately to strongly seasonal. The trend analysis of the monthly rainfall concentration shows no significant changes in the study period. However, these findings explain why the western and southern region of the Guayas river watershed is exposed to sedimentation problems in the lower part, due to the erosive capacity of rain in the higher and middle part of the watershed.