Caracterización hidrogeológica del acuífero semiconfinado subsuperficial de la comuna de Ninhue, Región de Ñuble, Chile
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Fecha
2020
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es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
Se determinó la composición litológica del sector sur del acuífero de Ninhue mediante Sondaje
Eléctrico Vertical SEV, clasificando la formación geológica como un acuífero semiconfinado
compuesto por gravas arenosas, limitada superiormente por una capa semipermeable de arena
arcillosa definida como acuitardo e inferiormente por roca intrusiva de edad Carbonífero-Pérmico
representada por el Batolito Costero del Sur que actúa como acuifugo, todo lo anterior cubierto por
suelo orgánico-arcilloso. Los SEV son analizados en conjunto a datos geofísicos recopilados de
manera bibliográfica, con métodos de Transiente Electromagnética TEM. Además, se determinan
distintos parámetros hidráulicos para las capas saturadas, de tal forma, se estima una capacidad de
infiltración para los suelos predominantes, que varían entre 20 a 290 mm/h para suelos agrícolas y
entre 10 a 30 mm/h para suelos generados por bosques. En cuanto al acuitardo que subyace los
suelos, se estimó una conductividad hidráulica de 0.1 m/d, con transmisividades entre 0 y 3.5 m2
/d.
Respecto al acuífero, este presenta variaciones significativas en las potencias estimadas, con valores
de 3 metros principalmente en sector Cerro Ninhue, hasta 77 metros en sectores suroestes de la
comuna, con capacidad de almacenamiento total de agua de 128 a 288 Hm3
y volumen eficaz
extraíble de 93 a 181 Hm3
. Las transmisividades varían en tres rangos, 0-10 m2
/d, 10-100 m2
/d y
100-350 m2
/d con conductividad hidráulica promedio de 4.8 m/d. Los parámetros obtenidos son
incorporados en un Inventario de Puntos de Agua IPA que posee 64 puntos georreferenciados,
siendo posible obtener diversos modelos conceptuales de tipo mapas en conjunto a metadatos de
sitios web. Finalmente, se integra la información en un modelo hidrogeológico generalizado de fácil
comprensión que identifica zona de recarga, descarga y dinamismo hidráulico de las capas del
subsuelo.
The lithological composition of the southern sector of the Ninhue aquifer was determined by SEV Vertical Electric Sounding, classifying the geological formation as a semi-confined aquifer composed of sandy gravels, limited superiorly by a semipermeable layer of clay sand defined as aquitard and inferiorly by intrusive old rock. Carboniferous-Permian represented by the Southern Coastal Batholith that acts as an aquifuge, all of the above covered by organic-clay soil. The SEVs are analyzed together with geophysical data collected in a bibliographic way, with TEM Electromagnetic Transient methods. In addition, different hydraulic parameters are determined for the saturated layers, in this way, an infiltration capacity is estimated for the predominant soils, which vary between 20 to 290 mm/h for agricultural soils and between 10 to 30 mm/h for generated soils. through forests. As for the aquitard that underlies the soils, a hydraulic conductivity of 0.1 m/d was estimated, with transmissivities between 0 and 3.5 m2 /d. Regarding the aquifer, it presents significant variations in the estimated powers, with values of 3 meters mainly in the Cerro Ninhue sector, up to 77 meters in the south-eastern sectors of the commune, with a total water storage capacity of 128 to 288 Hm3 and effective removable volume 93 to 181 Hm3 . The transmissivities vary in three ranges, 0-10 m2 /d, 10-100 m2 /d and 100-350 m2 /d with an average hydraulic conductivity of 4.8 m/d. The parameters obtained are incorporated into an IPA Water Points Inventory that has 64 georeferenced points, making it possible to obtain various conceptual maps-type models in conjunction with website metadata. Finally, the information is integrated into a generalized hydrogeological model that is easy to understand, identifying the recharge, discharge and hydraulic dynamism zone of the subsoil layers.
The lithological composition of the southern sector of the Ninhue aquifer was determined by SEV Vertical Electric Sounding, classifying the geological formation as a semi-confined aquifer composed of sandy gravels, limited superiorly by a semipermeable layer of clay sand defined as aquitard and inferiorly by intrusive old rock. Carboniferous-Permian represented by the Southern Coastal Batholith that acts as an aquifuge, all of the above covered by organic-clay soil. The SEVs are analyzed together with geophysical data collected in a bibliographic way, with TEM Electromagnetic Transient methods. In addition, different hydraulic parameters are determined for the saturated layers, in this way, an infiltration capacity is estimated for the predominant soils, which vary between 20 to 290 mm/h for agricultural soils and between 10 to 30 mm/h for generated soils. through forests. As for the aquitard that underlies the soils, a hydraulic conductivity of 0.1 m/d was estimated, with transmissivities between 0 and 3.5 m2 /d. Regarding the aquifer, it presents significant variations in the estimated powers, with values of 3 meters mainly in the Cerro Ninhue sector, up to 77 meters in the south-eastern sectors of the commune, with a total water storage capacity of 128 to 288 Hm3 and effective removable volume 93 to 181 Hm3 . The transmissivities vary in three ranges, 0-10 m2 /d, 10-100 m2 /d and 100-350 m2 /d with an average hydraulic conductivity of 4.8 m/d. The parameters obtained are incorporated into an IPA Water Points Inventory that has 64 georeferenced points, making it possible to obtain various conceptual maps-type models in conjunction with website metadata. Finally, the information is integrated into a generalized hydrogeological model that is easy to understand, identifying the recharge, discharge and hydraulic dynamism zone of the subsoil layers.
Notas
Tesis (Geólogo)
Palabras clave
Acuíferos, Hidrogeología, Chile, Ninhue