Ground water recharge and flow characterization using multiple isotopes.

Area of Science:

• Hydrogeology
• Isotope Geochemistry
• Environmental Science

Background:

• Understanding groundwater recharge is crucial for managing water resources in arid regions.
• Fault-bounded alluvial aquifers present unique challenges for hydrological studies.
• Differentiating recharge sources and processes is key to effective groundwater management.

Purpose of the Study:

• To distinguish groundwater origins, recharge areas, and processes in an arid, fault-bounded alluvial aquifer.
• To investigate the role of stream channels versus mountain fronts in aquifer recharge.
• To assess the implications of recharge patterns for groundwater flow conceptualization and resource management.

Main Methods:

• Stable isotopes (delta(18)O, delta(2)H, (13)C) and radiogenic isotopes ((14)C, (3)H) were analyzed.
• Groundwater chemical compositions were determined.
• Spatial variations in isotopic signatures and water chemistry were mapped and interpreted.

Main Results:

• Recharge predominantly occurs through exposed stream channel beds, not subsurface inflow along mountain fronts.
• Groundwater near basin margins exhibits characteristics of older recharge (lower delta(18)O, (14)C, (3)H) and greater depths.
• Distinct chemical compositions differentiate basin-margin and basin-center groundwater, linked to mineralogy and recharge processes.

Conclusions:

• The study highlights stream channels as primary recharge zones in this arid, fault-bounded aquifer system.
• Recharge patterns identified have significant implications for groundwater modeling and resource management in similar geological settings.
• Sluggish groundwater movement and potential compartmentalization are suggested by isotopic and chemical data in the basin center.