A multi-tracer approach to delineate groundwater dynamics in the Rio Actopan Basin, Veracruz State, Mexico

• Published in: Hydrogeology journal 2016-12, Vol.24 (8), p.1953-1966
• Main Authors: Pérez Quezadas, Juan, Heilweil, Victor M., Cortés Silva, Alejandra, Araguas, Luis, Salas Ortega, María del Rocío
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Basins; Chlorofluorocarbons; Coastal environments; Earth and Environmental Science; Earth Sciences; Elevation; Environmental tracers; Evapotranspiration; Geochemistry; Geology; Geophysics/Geodesy; Groundwater; Groundwater flow; Groundwater recharge; Highlands; Holocene; Hydrogeology; Hydrology; Hydrology/Water Resources; Isotopic enrichment; Recharging; Saline water; Saline water intrusion; Stable isotopes; Total dissolved solids; Tracers; Urban areas; Waste Water Technology; Water Management; Water Pollution Control; Water Quality/Water Pollution; Water resources; Water springs
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-016-1445-4

Geochemistry and environmental tracers were used to understand groundwater resources, recharge processes, and potential sources of contamination in the Rio Actopan Basin, Veracruz State, Mexico. Total dissolved solids are lower in wells and springs located in the basin uplands compared with those closer to the coast, likely associated with rock/water interaction. Geochemical results also indicate some saltwater intrusion near the coast and increased nitrate near urban centers. Stable isotopes show that precipitation is the source of recharge to the groundwater system. Interestingly, some high-elevation springs are more isotopically enriched than average annual precipitation at higher elevations, indicating preferential recharge during the drier but cooler winter months when evapotranspiration is reduced. In contrast, groundwater below 1,200 m elevation is more isotopically depleted than average precipitation, indicating recharge occurring at much higher elevation than the sampling site. Relatively cool recharge temperatures, derived from noble gas measurements at four sites (11–20 °C), also suggest higher elevation recharge. Environmental tracers indicate that groundwater residence time in the basin ranges from 12,000 years to modern. While this large range shows varying groundwater flowpaths and travel times, ages using different tracer methods ( 14 C, 3 H/ 3 He, CFCs) were generally consistent. Comparing multiple tracers such as CFC-12 with CFC-113 indicates piston-flow to some discharge points, yet binary mixing of young and older groundwater at other points. In summary, groundwater within the Rio Actopan Basin watershed is relatively young (Holocene) and the majority of recharge occurs in the basin uplands and moves towards the coast.