Regionalización de Sequía Hidrológica en la Cuenca del Río Bogotá a partir del Método de L-Momentos

Abstract

The present work is aimed at estimating the magnitude of hydrological droughts in the Bogotá River Basin through the application of the L-Moments Method. The unit of analysis is composed of 32 hydrological time series based on the datasets of minimum monthly flows with a record length of 24 years (1991-2014), obtained from IDEAM, CAR and EAAB’s hydrometeorological stations. The methodology according to the Regional Frequency Analysis (ARF) based on L-moments and the specific objectives of this work are divided into 5 stages: review and quality control of the data; identification of homogeneous regions; selection of probability distributions and quantiles estimation; characterization of hydrological drought and Mapping. As a result, 4 homogeneous regions were obtained, defined by the stations sharing the same frequency distribution. The best fit probability distribution function (FDP) for Region 1, 2 and 4 is the Generalized Logistics, while for Region 3, it is the Generalized Pareto. From the regional L-moments the parameters of each PDF were calculated, and then proceed to the estimation of the regional and quantile at the site level. Regional quantile indicate the magnitude of hydrological drought in terms of water deficit (%), when compared by a threshold or level of truncation given by the average of the regional quantile () function. According to the % of deficit, drought was classified as: Light (<60%), Moderate (60% to 70%), Severe (70% to 80%) and Extreme (> 80%). Finally, the quantiles or runoff values (mm) obtained per station were used for the application of the IDW interpolation method for the generation of quantile maps to different return periods (5, 10, 20, 50 and 100 years). In relation to the 5 maps: the upper basin, the western sector and the municipalities of San Antonio del Tequendama, Tena, Soacha and Sibaté present the lowest flows compared to the remaining area of the basin. On the other hand, the deficits of all regions are above 50%, with Region 3 being the most vulnerable. In addition, the runoff gradually decreases over time to more critical scenarios and extreme droughts. Finally, the results of this study are significant for planning contributions and management holistically water resources by determining the areas with greatest magnitude of drought events. The association of maps of vulnerability to drought allows obtaining maps of drought risk, which are useful in decision making in risk management plans.