Indirect and direct recharges in a tropical forested watershed: Mule Hole, India

• Published in: Journal of hydrology (Amsterdam) Vol. 364; no. 3; pp. 272 - 284
• Main Authors: Maréchal, Jean-Christophe, Varma, Murari R.R., Riotte, Jean, Vouillamoz, Jean-Michel, Kumar, M.S. Mohan, Ruiz, Laurent, Sekhar, M., Braun, Jean-Jacques
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 30.01.2009; [Amsterdam; New York]: Elsevier; Elsevier
• Subjects: Analytical solution; Chloride mass balance; direct recharge; Earth Sciences; Earth, ocean, space; Environmental Sciences; Evapotranspiration; Exact sciences and technology; Forest; forested watersheds; Geochemistry; Global Changes; groundwater; groundwater flow; groundwater recharge; hydrochemistry; Hydrogeology; Hydrology; Hydrology. Hydrogeology; indirect recharge; Mineralogy; Natural recharge; rain; runoff; Sciences of the Universe; Silicates; tropical forests; Water geochemistry; water table; Water table fluctuation; watershed hydrology; India; Asia; Karnataka India; Forest; Water table fluctuation; Natural recharge; Analytical solution; Chloride mass balance; Evapotranspiration; floods; mass balance; joints; ground water; ground-water recharge; evapotranspiration; natural recharge; drainage basins; aquifers; hydrochemistry; fluctuations; flow; chlorides; rainfall; streams; water table; runoff; hydrodynamics; halides; forests; infiltration; hydrologic cycle; electrical conductivity
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2008.11.006

It is commonly accepted that forest plays role to modify the water cycle at the watershed scale. However, the impact of forest on aquifer recharge is still discussed: some studies indicate that infiltration is facilitated under forest while other studies suggest a decrease of recharge. This paper presents an estimate of recharge rates to groundwater in a humid forested watershed of India. Recharge estimates are based on the joint use of several methods: chloride mass balance, water table fluctuation, geophysics, groundwater chemistry and flow analysis. Two components of the recharge (direct and indirect) are estimated over 3 years of monitoring (2003–2006). The direct and localized recharges resulting from rainfall over the entire watershed surface area is estimated to 45 mm/yr while the indirect recharge occurring from the stream during flood events is estimated to 30 mm/yr for a 2 km-long stream. Calculated recharge rates, rainfall and runoff measurements are then combined in a water budget to estimate yearly evapotranspiration which ranges from 80% to 90% of the rainfall, i.e. 1050 mm/y as an average. This unexpected high value for a deciduous forest is nevertheless in agreement with the forest worldwide relationship between rainfall and evapotranspiration. The large evapotranspiration from the forest cover contributes to decrease the recharge rate which leads to a lowering of the water table. This is the reason why the stream is highly ephemeral.