Aquifer vulnerability mapping in the Turbio river valley, Mexico: A validation study

Abstract

Aquifer vulnerability assessments can be made using quantitative methods such as DRASTIC and AVI. Their typical output maps are generally not validated or verified with field data. This paper proposes validation alternatives for aquifer vulnerability mapping. The DRASTIC mapping of the Turbio river valley, in Guanajuato State, Mexico comprises an area of 1300 km2. Comparing it with another aquifer vulnerability map generated by the AVI method, it could be validated. DRASTIC parameter comparison was also applied. A rescaling of the original DRASTIC rating range is proposed and justified based on the analysis of its effective weight. The vulnerability tendencies obtained were correlated with observed hydrogeochemical information. The observed values for chloride and TDS agree with the vulnerable areas defined by DRASTIC and AVI. Those areas correspond to the riverbed of the León-Turbio fluvial system. Some potential pollution sources are located in the vulnerable zones. The results demonstrate the importance of validation alternatives. They also show how in the most vulnerable areas, solutes coming from pollution sources are affecting the groundwater quality.