PRZ index for identifying potential areas of recharge in alluvial aquifers and for land use planning

Abstract

An index to identify potential recharge zones (PRZs) in alluvial aquifers was developed to protect these zones during land use planning. The PRZ index was designed as an additive index through the selection of five characterization indicators. The variables were then operationalized and categorized to generate a conceptual model of the physical-geological system. The PRZ index places recharge zones into four classes according to their potential. This index was applied to the Bolo River hydrogeological area (Valle del Cauca, Colombia), and the following proportions were identified for each PRZ category with a total area greater than 426 km2: very high: 23%, high: 30%; moderate: 40% and low: 7%. The areas with a very high recharge potential were found in the upper portion of the debris cones; their potential was predominantly due to the presence of sand and gravel unconfined aquifers and to aquifer outcrop layers at depths of less than 2.5 m. These PRZs were validated with piezometry, and the hydraulic gradient for 71% of the area was greater than 1%. These areas should be declared protected areas.