Hydrological regime of Sahelian small water bodies from combined Sentinel-2 MSI and Sentinel-3 SRAL data

Aug 26, 2026

In the Sahelian semi-arid region, small water bodies such as ponds, small lakes, and rural reservoirs are crucial but remain poorly characterized due to their high number and limited in situ monitoring. This study analyzes 37 small water bodies in Mali, Niger, and Burkina Faso using a remote-sensing-only approach. Sentinel-3 SRAL water heights are combined with Sentinel-2 MSI water areas to build dense time series. Water-level variations are compared with Penman–Monteith evaporation from ERA5 reanalysis to infer dry-season regimes and quantify hydrological impacts.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages24

Reading Time1 h 0 min

AccessFree to download

Introduction

Background and need for monitoring

Remote sensing approaches for water levels

[https://doi.org/10.5194/hess-2022-367](https://doi.org/10.5194/hess-2022-367) Preprint. Discussion started: 14 November 2022 􀀍c Author(s) 2022 . CC BY 4.0 License. Hydrological regime of Sahelian small water bodies from combined Sentinel-2 MSI and Sentinel-3 SRAL data Mathilde de Fleury 1 , Laurent Kergoat 1 , and Manuela Grippa 1 1 Géosciences Environnement Toulouse (GET), UMR 5563, Université Toulouse 3, CNRS, IRD, 14 avenue Edouard Belin, OMP, 31400 Toulouse cedex 9, France Correspondence: Mathilde de Fleury (mathilde.de-fleury@get.omp.eu), Laurent Kergoat (laurent.kergoat@get.omp.eu), Manuela Grippa ([manuela.grippa@get.omp.eu](manuela.grippa@get.omp.eu)) Abstract. In the Sahelian semi-arid region, water resources, especially small water bodies such as ponds, small lakes and reservoirs in rural areas, are of vital importance. However, because of their high number and the scarce in situ monitoring networks, these resources and their spatio-temporal variability are poorly known at the regional scale. This study investigates the hydrological regime of 37 small water bodies, located in Mali, Niger and Burkina Faso, in Central Sahel. We propose a method based 5 on remote sensing data only, which consists of combining water height data from Sentinel-3 SAR Radar Altimeter (SRAL) with water area data obtained with Sentinel-2 Multispectral Instrument (MSI) to create dense water height time series. Water height variations are then compared to evaporation estimated by the Penman–Monteith method using ERA5 reanalysis by the European Centre for Medium-Range Weather Forecasts (ECMWF) to infer water regimes during the dry season. Three main regimes stand out: a net water loss, mainly resulting from anthropogenic withdrawals, a net water supply occurring after the 10 end of the rainy season through river network or water table exchange, and a balanced behaviour, where water losses during the dry season closely correspond to evaporation rates. Spatial patterns have been identified: in central Burkina Faso, most of the reservoirs show a net dry season water loss, which is explained by frequent irrigation, while reservoirs in northern Burkina Faso, generally show little water loss, indicating that water withdrawal is not significant in this area. Lakes located in the Inner Niger Delta in Mali and connected to the Niger river network generally show an important water supply, particularly at the be- 15 ginning of the dry season. Lakes in Niger tend to show a weak signal toward water inflow that could be explained by exchange processes with the groundwater. These results show that satellite data are effective in estimating hydrological regimes as well as the anthropogenic impact on water resources, at the large scale, including resources found in small water bodies. Key-words: small water bodies, hydrological regime, remote sensing, Sentinel-2, Sentinel-3, Central Sahel, Burkina Faso, 20 Mali, Niger, evaporation, water loss, water supply. 1 Introduction In the Sahel and more generally in West Africa, small water bodies are critical resources for the inhabitants, who use them on a daily basis to meet vital needs: drinking water, livestock watering, irrigation, fishing, and bathing among others (Cecchi et al., 2009; Frenken, 2005) . These water bodies are widespread all over the region and include numerous small reservoirs, for [https://doi.org/10.5194/hess-2022-367](https://doi.org/10.5194/hess-2022-367) Preprint. Discussion started: 14 November 2022 􀀍c Author(s) 2022 . CC BY 4.0 License. 25 which dams have been built, small natural lakes and ponds, and intermediate situations where existing lakes are more or less developed. Burkina Faso, for example, built many reservoirs, whose number increased from about 200 in 1974 to about 1650 in 2008 (Cecchi et al., 2009) . The aim of such actions was to address food security issues (Douxchamps, 2014) after severe droughts (Sally et al., 2011) . The central Sahelian region a

FAQs

What problem does the study address about small water bodies in the Sahel?

The study targets the limited knowledge of spatio-temporal variability of numerous small water bodies due to scarce in situ monitoring networks at the regional scale.

How are Sentinel-2 MSI and Sentinel-3 SRAL used in the proposed method?

Sentinel-3 SRAL provides water height data, while Sentinel-2 MSI provides water area data; together they generate dense water height time series using remote sensing only.

What evaporation reference is used to infer dry-season water regimes?

Evaporation is estimated with the Penman–Monteith method using ERA5 reanalysis data from the ECMWF, then compared to observed water-level variations.

Aug 26, 2026

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