Origins of streamflow in a crystalline basement catchment in a sub-humid Sudanian zone: The Donga basin (Benin, West Africa)

Séguis, Luc; Kamagaté, Bamory; Favreau, Guillaume; Descloîtres, Marc; Seidel, Jean-Luc; Galle, Sylvie; Peugeot, Christophe; Gosset, Marielle; Barbé, Luc Le; Malinur, Fred; Exter, Sandra van; Arjounin, Marc; Boubkraoui, Stéphane; Wubda, Maxime

doi:10.1016/j.jhydrol.2011.01.054

Cited by 45 publications

(66 citation statements)

References 42 publications

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“…These results suggest that the transpiration of the riparian forest leads to the hydraulic disconnection of the permanent water table and the river. This situation was already put forward by Séguis et al (2011b) on the Donga catchment (Benin), in which our study site is included. Dye and Poulter (1995) noted that streamflow can also supply the riparian transpiration.…”

Section: Disconnection Between the Deep Groundwater Table And The Rivermentioning

confidence: 96%

“…About 50 % of the surface is or has been cultivated, while 50 % remains practically natural. The riparian forests, even if they cover only a negligible fraction of the landscape (0.9 %) are commonly found along the stream banks (Séguis et al, 2011b).…”

Section: Study Sitementioning

confidence: 99%

“…According to the World Reference Base (IUSS Working Group WRB, 2006), the soils are mainly lixisols on crests and mid-slopes, plinthosols with or without outcrops of hardpan at the slope bottom and thin sandy soils overlying a thick clayey horizon in the bas-fonds (Faure, 1977;Giertz and Diekkrüger, 2003). The French word bas-fonds denotes a tropical, seasonally waterlogged, linear depression in the headwater zones of rivers, frequently without any marked stream channel, and predominantly covered by grass species (Giertz and Diekkrüger, 2003;Séguis et al, 2011b).…”

Section: Study Sitementioning

confidence: 99%

“…Hereafter, this permanent and unconfined groundwater is called permanent groundwater. The level of the permanent groundwater table remains approximately parallel to the soil surface all year long and fluctuates between 2 and 5 m deep (Séguis et al, 2011b).…”

Section: Study Sitementioning

confidence: 99%

“…As a result, the high transpiration rates obtained in the study were considered realistic. Séguis et al (2011b) roughly estimated the riparian evapotranspiration rate for the same site between 6 and 34 mm d −1 . Despite the above-mentioned clothesline effect, the upper value was considered unrealistic by the authors themselves: according to the method they used, this large range of transpiration rates has to be considered a first approximation.…”

Section: Intra-seasonal Variability Of the Transpiration Sourcesmentioning

confidence: 99%

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

Richard

Galle

Descloîtres

et al. 2013

Hydrol. Earth Syst. Sci.

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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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Section: Disconnection Between the Deep Groundwater Table And The Rivermentioning

confidence: 96%

Section: Study Sitementioning

confidence: 99%

Section: Study Sitementioning

confidence: 99%

Section: Study Sitementioning

confidence: 99%

Section: Intra-seasonal Variability Of the Transpiration Sourcesmentioning

confidence: 99%

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

Richard

Galle

Descloîtres

et al. 2013

Hydrol. Earth Syst. Sci.

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Chemistry of groundwater discharge inferred from longitudinal river sampling

et al. 2014

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We present an approach for identifying groundwater discharge chemistry and quantifying spatially distributed groundwater discharge into rivers based on longitudinal synoptic sampling and flow gauging of a river. The method is demonstrated using a 450 km reach of a tropical river in Australia. Results obtained from sampling for environmental tracers, major ions, and selected trace element chemistry were used to calibrate a steady state one-dimensional advective transport model of tracer distribution along the river. The model closely reproduced river discharge and environmental tracer and chemistry composition along the study length. It provided a detailed longitudinal profile of groundwater inflow chemistry and discharge rates, revealing that regional fractured mudstones in the central part of the catchment contributed up to 40% of all groundwater discharge. Detailed analysis of model calibration errors and modeled/measured groundwater ion ratios elucidated that groundwater discharging in the top of the catchment is a mixture of local groundwater and bank storage return flow, making the method potentially useful to differentiate between local and regional sourced groundwater discharge. As the error in tracer concentration induced by a flow event applies equally to any conservative tracer, we show that major ion ratios can still be resolved with minimal error when river samples are collected during transient flow conditions. The ability of the method to infer groundwater inflow chemistry from longitudinal river sampling is particularly attractive in remote areas where access to groundwater is limited or not possible, and for identification of actual fluxes of salts and/or specific contaminant sources.

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Water storage changes as a marker for base flow generation processes in a tropical humid basement catchment (Benin): Insights from hybrid gravimetry

Hector

Séguis

Hinderer

et al. 2015

Water Resources Research

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In basement catchments of subhumid West Africa, base flow is the main component of annual streamflow. However, the important heterogeneity of lithology hinders the understanding of base flow generation processes. Since these processes are linked with water storage changes (WSCs) across the catchment, we propose the use of hybrid gravity data in addition to neutron probe-derived water content and water levels to monitor spatiotemporal WSC of a typical crystalline basement headwater catchment (16 ha) in Benin. WSC behaviors are shown to provide insights into hydrological processes in terms of water redistribution toward the catchment outlet. Hybrid gravimetry produces gravity change observations from time-lapse microgravity surveys coupled with gravity changes monitored at a base station using a superconducting gravimeter and/or an absolute gravimeter. A dense microgravity campaign (70 surveys of 14 stations) covering three contrasted years was set up with a rigorous protocol, leading to low uncertainties (<2.5 lGal) on station gravity determinations (with respect to the network reference station). Empirical orthogonal function analyses of both gravity changes and WSCs from neutron probe data show similar spatial patterns in the seasonal signal. Areas where storage and water table show a capping behavior (when data reach a plateau during the wet season), suggesting threshold-governed fast subsurface redistribution, are identified. This observed storage dynamics, together with geological structures investigated by electrical resistivity tomography and drill log analysis, make it possible to derive a conceptual model for the catchment hydrology.

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Origins of streamflow in a crystalline basement catchment in a sub-humid Sudanian zone: The Donga basin (Benin, West Africa)

Cited by 45 publications

References 42 publications

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

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

Chemistry of groundwater discharge inferred from longitudinal river sampling

Water storage changes as a marker for base flow generation processes in a tropical humid basement catchment (Benin): Insights from hybrid gravimetry

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