DETERMINACIÓN Y ANÁLISIS DE LOS CAUDALES DE EVENTO EXTREMO MEDIANTE TORMENTAS ESTOCÁSTICAS EN LA CUENCA DE MISICUNI-COCHABAMBA, BOLIVIA
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Abstract
El cálculo de los caudales máximos por medio de la generación estocástica de tormentas elípticas dentro de la cuenca Misicuni se realizó con los softwares especializados IT-LluviaNH y IT-Inundación del Banco Interamericano de Desarrollo desarrollados por la plataforma CAPRA, obteniendo las curvas PADF características y 300 escenarios de tormentas estocásticas evaluados en los modelos hidrológicos e hidrodinámicos resultando en hidrogramas a nivel de presa y de subcuencas para diferentes periodos de retorno. Se determinaron también caudales máximos por medio de metodologías convencionales relacionando las curvas IDF y tormentas de diseño. La comparación gráfica y numérica de los hidrogramas a la salida de la cuenca permitió verificar la variación entre las metodologías aplicadas y el impacto en el aliviadero de la presa a través del tránsito de avenidas sobre el embalse. Los caudales máximos estocásticos resultaron inferiores a los determinados por las metodologías convencionales. Esto se debe a la no uniformidad de las intensidades de precipitación sobre el área de la cuenca. Sin embargo, contemplando la simultaneidad de escenarios de evento extremo independientes en cada subcuenca (aplicando porcentajes muy bajos a la probabilidad de excedencia) se tienen caudales máximos similares entre las metodologías. Asimismo, se calculó la proyección de los caudales con periodo de retorno de 2, 5, 10, 20, 50 y 100 años a periodos de retorno de 1000 y 10000 años para ambas metodologías. El impacto de los caudales estocásticos máximos laminados no representa un riesgo para el aliviadero de la presa al ser menores al caudal de diseño.
The calculation of peak flows by means of stochastic generation of elliptical storms within the Misicuni basin was performed with the specialized software IT-LluviaNH and IT-Flood of the Inter-American Development Bank developed by the CAPRA platform, obtaining the characteristic PADF curves and 300 stochastic storm scenarios evaluated in the hydrological and hydrodynamic models resulting in hydrographs at the dam and sub-basin levels for different return periods. Peak flows were also determined by conventional methodologies relating to IDF curves and design storms. The graphical and numerical comparison of the hydrographs at the basin outlet made it possible to verify the variation between the methodologies applied and the impact on the dam spillway through the transit of floods over the reservoir. The stochastic peak flows were lower than those determined by conventional methodologies. This is due to the non-uniformity of precipitation intensities over the basin area. However, considering the simultaneity of independent extreme event scenarios in each sub-basin (applying very low percentages to the probability of exceedance), the maximum flows are similar between methodologies. Likewise, the projection of flows with return periods of 2, 5, 10, 20, 20, 50 and 100 years to return periods of 1000 and 10000 years was calculated for both methodologies. The impact of the maximum stochastic flows does not represent a risk for the dam spillway since they are lower than the design flow.
The calculation of peak flows by means of stochastic generation of elliptical storms within the Misicuni basin was performed with the specialized software IT-LluviaNH and IT-Flood of the Inter-American Development Bank developed by the CAPRA platform, obtaining the characteristic PADF curves and 300 stochastic storm scenarios evaluated in the hydrological and hydrodynamic models resulting in hydrographs at the dam and sub-basin levels for different return periods. Peak flows were also determined by conventional methodologies relating to IDF curves and design storms. The graphical and numerical comparison of the hydrographs at the basin outlet made it possible to verify the variation between the methodologies applied and the impact on the dam spillway through the transit of floods over the reservoir. The stochastic peak flows were lower than those determined by conventional methodologies. This is due to the non-uniformity of precipitation intensities over the basin area. However, considering the simultaneity of independent extreme event scenarios in each sub-basin (applying very low percentages to the probability of exceedance), the maximum flows are similar between methodologies. Likewise, the projection of flows with return periods of 2, 5, 10, 20, 20, 50 and 100 years to return periods of 1000 and 10000 years was calculated for both methodologies. The impact of the maximum stochastic flows does not represent a risk for the dam spillway since they are lower than the design flow.
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Vol. 24, No. 2