Determining long-term effective groundwater recharge by analyzing vertical soil temperature profiles at meteorological stations

• Published in: Water resources research Vol. 41; no. 9; pp. W09501 - n/a
• Main Authors: Cheviron, B, Guerin, R, Tabbagh, A, Bendjoudi, H
• Format: Journal Article
• Language: English
• Published: American Geophysical Union 01-09-2005; Blackwell Publishing Ltd
• Subjects: amplitude damping; convection; Groundwater hydrology; groundwater recharge; Groundwater transport; heat transfer; heat transport; Hydrology; infiltration (hydrology); Instruments and techniques; long-term recharge; methodology; modeling; new methods; phase lag; seepage; soil depth; soil profiles; soil temperature; soil thermal properties; Somme River; spatial variation; temperature; temporal variation; velocity; France; temperature; phase lag; Somme River; heat transport; long-term recharge; amplitude damping
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2005WR004174

Vertical water seepage in soils results in convective heat transport that modifies the temperature profiles and their variations with time; consequently, there is a relationship between temperature profile variations with time and the vertical Darcy velocity associated with the seepage. Considering the annual sinusoidal time variation of the temperature at the soil surface, it can be shown that convective heat transport has a significant effect on the amplitude damping with depth and a negligible effect on the phase lag with depth of the temperature time signal. Standard meteorological stations constitute a relatively dense network, and we show that their routinely collected data can be used to determine an average value of the vertical Darcy velocity, u(z), representing the effective annual recharge over long time periods (several years). A new procedure for determining u(z) from these temperature records is presented. First, the layering of the medium is determined by an electrical sounding. Then the thermal properties of each layer are inferred from the phase lag with depth. Finally, u(z) is calculated from the amplitude damping. After having tested this approach with synthetic data, we used the 1984-2001 Abbeville (Somme, France) data to determine the average recharge over six 3-year periods. The results are in good agreement with classical meteorological recharge estimates and show a significant increase in the recharge during the last 3-year period, consistent with the observed phreatic 2001 flood event. Specific temperature measurements at appropriate depths and time steps could drastically improve the sensitivity of the method.