Monday paper: Interplay of riparian forest and groundwater in the hillslope hydrology of Sudanian West Africa (northern Benin)


Richard, A., Galle, S., Descloitres, M., Cohard, J.-M., Vandervaere, J.-P., Séguis, L., and Peugeot, C. 2013. Interplay of riparian forest and groundwater in the hillslope hydrology of Sudanian West Africa (northern Benin), Hydrology and Earth System Sciences 17, 5079-5096. DOI: 10.5194/hess-17-5079-2013.

Abstract

Forests are thought to play an important role in the regional dynamics of the West African monsoon, through their capacity to extract water from a permanent and deep groundwater table to the atmosphere even during the dry season. It should be the case for riparian forests too, as these streambank forests are key landscape elements in Sudanian West Africa. The interplay of riparian forest and groundwater in the local hydrodynamics was investigated, by quantifying their contribution to the water balance. Field observations from a comprehensively instrumented hillslope in northern Benin were used. Particular attention was paid to measurements of actual evapotranspiration, soil water and deep groundwater levels. A vertical 2-D hydrological modelling approach using the Hydrus software was used as a testing tool to understand the interactions between the riparian area and the groundwater. The model was calibrated and evaluated using a multi-criteria approach (reference simulation). A virtual experiment, including three other simulations, was designed (no forest, no groundwater, neither forest nor groundwater).

The model correctly simulated the hydrodynamics of the hillslope regarding vadose zone dynamics, deep groundwater fluctuation and actual evapotranspiration dynamics. The virtual experiment showed that the riparian forest transpiration depleted the deep groundwater table level and disconnected it from the river, which is consistent with the observations. The riparian forest and the deep groundwater table actually form an interacting transpiration system: the high transpiration rate in the riparian area was shown to be due to the existence of the water table, supplied by downslope lateral water flows within the hillslope soil layer. The simulated riparian transpiration rate was practically steady all year long, around 7.6 mm d−1. This rate lies within high-end values of similar study results. The riparian forest as simulated here contributes to 37% of the annual hillslope transpiration, and reaches 57% in the dry season, whereas it only covers 5% of the hillslope area.

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Hydrology and Earth System Sciences (HESS) is an international two-stage open access journal for the publication of original research in hydrology, placed within a holistic Earth System Science context. The discussion and peer-review of submitted papers are handled in the open access discussion journal HESSD. Final papers, upon acceptance, appear in HESS (see Review Process under the heading Review).

HESS encourages and supports fundamental and applied research that seeks to understand the interactions between water, earth, ecosystems and man. A multi-disciplinary approach is encouraged that enables a broadening of the hydrologic perspective and the advancement of hydrologic science through the integration with other cognate sciences, and the cross-fertilization across disciplinary boundaries. HESS, therefore, has the ambition to serve not only the community of hydrologists, but all earth and life scientists, water engineers and water managers, who wish to publish original findings on the interactions between hydrological processes and other physical, chemical, biological and societal processes within the earth system, and the utilization of this holistic understanding towards sustainable management of water resources, water quality and water-related natural hazards.

The scope of HESS therefore encompasses:

  1. The role of physical, chemical and biological processes in the cycling of continental water in all its phases, including dissolved and particulate matter, at all scales, from the micro-scale processes of soil water to the global-scale processes underpinning hydro-climatology.
  2. The study of the spatial and temporal characteristics of the global water resources (solid, liquid and vapour) and related budgets, in all compartments of the Earth System (atmosphere, oceans, estuaries, rivers, lakes and land masses), including water stocks, residence times, interfacial fluxes, and the pathways between various compartments.
  3. The study of the interactions with human activity of all the processes, budgets, fluxes and pathways as outlined above, and the options for influencing them in a sustainable manner, particularly in relation to floods, droughts, desertification, land degradation, eutrophication, and other aspects of global change.

The journal will publish research articles, research and technical notes, opinion papers, book reviews, brief communications, and comments on papers published previously in HESS. Papers can address different techniques and approaches, including: theory, modelling, experiments or instrumentation. The journal covers the following Subject Areas and Techniques/Approaches, which are used to categorise papers:

Subject Areas:

  • Hillslope Hydrology;
  • Catchment Hydrology;
  • Global Hydrology;
  • Rivers and Lakes;
  • Coasts and Estuaries;
  • Hydrometeorology;
  • Vadose Zone Hydrology;
  • Groundwater Hydrology;
  • Ecohydrology;
  • Biogeochemical Processes;
  • Urban Hydrology;
  • Engineering Hydrology;
  • Water Resources Management.

Techniques and Approaches:

  • Theory Development;
  • Modelling Approaches;
  • Instruments and Observation Techniques;
  • Remote Sensing and GIS;
  • Mathematical Applications;
  • Stochastic Approaches;
  • Uncertainty Analysis.

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