MODELACIÓN DE AGUAS SUBTERRÁNEAS DEL VALLE DE COCHABAMBA UTILIZANDO MODFLOW
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Abstract
En la zona metropolitana de Cochabamba, el 65% de agua para el consumo humano proviene de las aguas subterráneas extraídas principalmente del lado oeste del Valle Central. Se ha notado una explotación intensa en la zona con un crecimiento del número de pozos en operación. Por ello el objeto de este estudio es aumentar el monitoreo de pozos y mejorar el conocimiento sobre el flujo subterráneo por medio de la configuración de un modelo hidrogeológico. El área de estudio es una zona atractiva para la explotación de aguas subterráneas por la presencia de un abanico aluvial al norte que favorece la recarga del acuífero. Se ha empleado el paquete computacional MODFLOW para la modelación utilizando datos de hidrogeología, precipitación, temperatura, evapotranspiración, perfiles estratigráficos y niveles piezométricos. Para este último se realizaron campañas de mediciones en los pozos identificados en la zona de estudio. En la calibración de parámetros, los niveles de agua simulados comparados con los observados en campo dieron un coeficiente de correlación de 0.76 y una raíz media cuadrática (RMS) de 6.2 m. El modelo fue usado en estado estacionario mostrando en equilibrio sin evidencias de sobreexplotación, con un aporte positivo de 77 m³ al sistema. La dirección principal de flujo se confirmó que es de norte a sur con cambios evidentes en la dirección por la presencia de los ríos y operación de pozos. El nivel promedio de la capa freática es de 4.9 m debajo de la superficie en la zona sur y de 130 m debajo de la superficie en la zona norte. El balance hídrico generado por el modelo presenta un aporte al sistema por la infiltración de los ríos y recarga. La salida del sistema es realizada principalmente por la evapotranspiración.
In the Cochabamba metropolitan area, 65% of water for human consumption comes from groundwater extracted from the west side of the Central Valley. There has been an intense exploitation in the area with growth of operating wells. The objective of this study is to update and extend well monitoring, and improve understanding of groundwater flow through a hydrogeological model. The study area is an attractive region for groundwater exploitation due to the presence of an alluvial fan to the north that encourages the recharge of the aquifer. The MODFLOW computer package has been used for the modeling, using hydrogeology data of precipitation, temperature, evapotranspiration, stratigraphic profiles, and piezometric levels. As for latter, measurement campaigns were carried out at identified wells within the study area. The study area is made up of unconfined aquifers with high piezometric levels. The results of the calculated heads against the observed ones in the calibration process, gave a correlation coefficient of 0.76 and a root mean square (RMS) of 6.2 m. The model was simulated at steady state, showing a balance without evidence of exploitation, with an input of 77 m³ to the system. The main flow direction is from north to south with evident changes in direction due to the presence of rivers. The average level of the water table is 4.9 m below the surface in the southern zone and 130 m below the surface in the northern zone. The water balance generated by the model presents an input to the system of river infiltration and recharge. The output of the system is mainly due to evapotranspiration.
In the Cochabamba metropolitan area, 65% of water for human consumption comes from groundwater extracted from the west side of the Central Valley. There has been an intense exploitation in the area with growth of operating wells. The objective of this study is to update and extend well monitoring, and improve understanding of groundwater flow through a hydrogeological model. The study area is an attractive region for groundwater exploitation due to the presence of an alluvial fan to the north that encourages the recharge of the aquifer. The MODFLOW computer package has been used for the modeling, using hydrogeology data of precipitation, temperature, evapotranspiration, stratigraphic profiles, and piezometric levels. As for latter, measurement campaigns were carried out at identified wells within the study area. The study area is made up of unconfined aquifers with high piezometric levels. The results of the calculated heads against the observed ones in the calibration process, gave a correlation coefficient of 0.76 and a root mean square (RMS) of 6.2 m. The model was simulated at steady state, showing a balance without evidence of exploitation, with an input of 77 m³ to the system. The main flow direction is from north to south with evident changes in direction due to the presence of rivers. The average level of the water table is 4.9 m below the surface in the southern zone and 130 m below the surface in the northern zone. The water balance generated by the model presents an input to the system of river infiltration and recharge. The output of the system is mainly due to evapotranspiration.
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Vol. 20, No. 1