Abstract

In a context of climate change and declining water resources, knowledge of low flow is essential. Present study deals with the spatial and temporal evolution of the streams low flow in Sassandra river. In the study, 12 stations of the Sassandra sub-basins (Sassandra, N’zo, Lobo, and Davo) were selected according to the availability and quality of long-term data. Annual, monthly and daily low flow data from twelve hydrological stations of the Sassandra watershed were used and cover the period from 1970 to 2015. The methodology used is concerned with extracting the low flow data and analyzing and evaluating the trends (Mann-Kendall) and change-point (cumulate sum) of low flow data. Statistical tests are applied to the mean and variance of the low-flow series. The results of the statistical tests show more trends and change points on the mean than on the variance. Significant trends show an increase in low flow waters. The significant change point detected by the cumulative sums test generally occurs between 1990-2007. In addition, tributaries are more affected by significant trends and change point detection than Sassandra river.

Highlights

  • Water resources are currently under the influence of many natural or anthropogenic phenomena

  • This study focused on the daily low water (MAM3, MAM5, MAM7, and MAM10), monthly (QMNA) and annual (Q90 and ALW) water levels

  • The index of variation shows a succession of years of low water flows from 1970 to 2004 and year of strong flow from 2004 to 2015

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Summary

Introduction

Water resources are currently under the influence of many natural or anthropogenic phenomena. Low water is defined as a natural phenomenon corresponding to a decrease in river flow, or even drying up over a period (Garcia, 2016). Depending on the field of study, different indices exist to describe low water levels (Smakhtin, 2001; Hisdal & Tallaksen, 2004; WMO, 2008; Garcia, 2016). These indices serve as thresholds for the development of different water resource management rules, leading, for example, to the limitation of withdrawals. Some studies have focused on the evaluation of the physical, chemical and bacteriological parameters of the Aghion lagoon during the low water period (Traoré et al, 2012) and the characterization of low water flows on the N’zi-Bandama River (Kouassi et al, 2018)

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