# Mechanisms affecting stormflow generation and solute behaviour in a Sahelian headwater catchment

Ribolzi, Olivier and Karambiri, Harouna and Bariac, Thierry and Benedetti, Marc and Caquineaux, Sandrine and Descloitres, Marc and Aventurier, Alain (2007) Mechanisms affecting stormflow generation and solute behaviour in a Sahelian headwater catchment. In: Journal of Hydrology, 337 (1-2). pp. 104-116.

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## Abstract

Summary The aim of this study was to analyse stormflow processes and the behaviour of solutes therein $(Ca^{2+}, Mg^{2+}, Na^+, K^+$, alkalinity, $NO^-_3 , SO^{2-}_4, Cl^-, Si)$, during flood events in tropical semi-arid conditions. The study site was a small Sahelian catchment (1.4 ha) located in northern Burkina Faso. Runoff and rain water was sampled over a 2-year period (1999 and 2000). In addition to dissolved load, suspended load was measured in the stream water collected at the outlet of the catchment. Isotopic tracing using $\delta^{18}O$ was also conducted during two very different flood events. The results indicated that: (i) event water was by far the major contributor to the stream stormflow, with Hortonian overland flow being the main stormflow process at work; (ii) a small fraction of pre-event soil water may have contributed during the recession of heavy flood with wet antecedent conditions; (iii) solute concentrations were higher in runoff compared to rainwater. With the exception of $NO^-_3$ and $Cl^-$, the highest concentrations were measured at the onset of floods, and almost always decreased during the rising stage of the hydrographs; (iv) a good correlation was found between sus-pended load and the concentrations of $Ca^{2+}, Mg^{2+}$, alkalinity and Si. It was concluded that fast physico-chemical interactions between event water and reactive suspended phases may explain most of the chemical changes between rainwater and floodwater.

Item Type: Journal Article Copyright of this article belongs to Elsevier. Division of Mechanical Sciences > Civil Engineering 14 Aug 2007 19 Sep 2010 04:39 http://eprints.iisc.ernet.in/id/eprint/11713