Understanding complex volcanic hydrosystems using a multi-tracer approach

Area of Science:

• Hydrogeology
• Environmental Science
• Volcanic Hydrology

Background:

• Climate change is reducing groundwater recharge and altering residence times in exploited aquifers.
• Understanding aquifer characteristics is crucial for defining sustainable yields, especially in volcanic regions like Volvic, France.
• Decreased groundwater recharge in the Volvic volcanic aquifer raises concerns about water use sustainability.

Purpose of the Study:

• To investigate the decrease in groundwater recharge in the Volvic volcanic aquifer.
• To characterize the origin and environmental impact of this resource decrease using a multi-tracer approach.
• To improve the understanding of volcanic aquifer systems' response to climate change.

Main Methods:

• Hydrogeological monitoring of the Volvic volcanic aquifer.
• Estimation of groundwater ages using multiple tracers.
• Analysis of major elements chemistry and water stable isotopes.

Main Results:

• Estimated relative fractions of ancient and modern water contributions (up to 20%) to the aquifer.
• Determined apparent groundwater ages of approximately 34 years.
• Highlighted the complementarity of tracers for defining recharge sources and groundwater transit times.

Conclusions:

• A hydrogeological conceptual model revealed a bi-modal recharge system: a long-term component (approx. 30 years) and a recent component (approx. 1 year) from precipitation.
• The multi-tracer approach effectively characterized groundwater circulation and the impact of climate change on volcanic aquifers.
• Results provide a basis for developing hydrological models to assess global change impacts on volcanic water resources.