Mule Hole forest watershed (India)

Vegetation controls water availability → the regolith stores and delays water → groundwater flows through the crystalline aquifer → groundwater exports the products of weathering.

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Location: Bandipur Forest, South of Bangalore, Karnataka state, India

Elevation: 820 - 910 m a.s.l.

Geology: Crystalline rock basement (gneiss, granite)

Aquifer type: fractured crystalline-rock aquifer

Scientific question: "How does the forest influence weathering and water cycle under tropical conditions?"

The Mule Hole watershed is part of M-TROPICS Observatory and the OZCAR research infrastructure

Location map

Key findings

Forest evapotranspiration strongly limits groundwater recharge, with deep roots extracting water from the regolith.
The thick weathered mantle acts as a major water reservoir, buffering and delaying groundwater recharge.
Groundwater and surface water are largely disconnected, with significant recharge occurring indirectly from the stream.
Deep groundwater flow dominates the chemical export from the watershed, accounting for more than 90% of the dissolved chemical flux.

Hydrogeological model

(a) Cross section of the experimental site with water table fluctuations (LF: pre-monsoon low flow in June 2006; HF: post-monsoon high flow in December 2005) . (b) Recharge estimated using CMB method. (c) Water content from geophysical measurements (MRS)

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MULE HOLE – FIELDWORK: SOMETIMES HYDROGEOLOGY IS NOT THE BIGGEST CHALLENGE!

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Groundwater monitoring: 100% successful. Elephant avoidance: also successful.

Picture Gallery

Scientific collaborations

Indian Institute of Science team: M. Sekhar, M. Kumar, M. Varma, S. Subramanian
IRD & GET teams: JJ. Braun, J. Riotte, JM. Vouillamoz, S. Audry, C. Lagane

The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset III: Hydro-geochemical monitoring of the Mule Hole catchment, south India

Jean Riotte, Laurent Ruiz, Stephane Audry, Jean-Pierre Bedimo Bedimo, Jean-Jacques Braun, Bernard Dupre, Christelle Lagane, Jean-Christophe Maréchal, Hemanth Moger, Mandalagiri Subbarayappa Mohan Kumar, Murari Varma, Muddu Sekhar

Hydrological Processes, vol. 35, 2021

Vegetation impact on stream chemical fluxes: Mule Hole watershed (South India)

Jean Riotte, Jean-Christophe Maréchal, Stéphane Audry, C. Kumar, J.P. Bedimo Bedimo, Laurent Ruiz, Muddu Sekhar, M. Cisel, , M.R.R. Varma, C. Lagane, P. Reddy, Jean-Jacques Braun

Geochimica et Cosmochimica Acta, vol. 145, 2014, pp. 116-138