Analysis of the recharge processes and surface-groundwater interactions in the Bolo catchment of the Cauca river, Colombia

Abstract

We have carried out a detailed analysis of the recharge processes and surface water -roundwater flow interactions in the Bolo catchment of the Cauca River (Colombia), one of the areas with highest groundwater demand in the region. This research is focused on the study of groundwater recharge in the aquifer and its interactions with the Bolo River. Estimated recharge varies with the geology, with a higher recharge in the alluvial fans mostly underlain by loam sandy soils, and lower values in the alluvial plains, where loam clay soils are redominant. Estimation of average annual recharge by the soil water balance method varies from 162 mm/year (11% of P) in the alluvial plains and up to 522 mm/year (35% of P) in the alluvial fans. Estimated recharge values are lower with the chloride mass balance method, with an average of 102 mm/year (7% of P) in the alluvial plains and 385 mm/ year (26% of P) in the fans. Surface water - groundwater interactions were studied through the analysis of groundwater hydraulic heads and hydrochemical analysis. Our results confirm that the Bolo River and the shallow aquifer have different interactions throughout the catchment, producing recharge and discharge areas.