Abstract
Abstract. In semi-arid regions, the annual floods of alluvial plains, wetlands and lakes provide essential services to millions of farmers, livestock holders and fishers. The scale, number and dispersion of these water bodies limit however their hydrological understanding, whose complexity is exacerbated by the mutual interactions between water and society. Rising availability of high spatial and temporal resolution remote sensing imagery provide novel opportunities to improve the understanding of the hydrology of multiple water bodies and of their ability to support local livelihoods. Multi-scalar interdisciplinary research combining remote sensing, in situ observations, hydrological modelling and farmer interviews was developed to investigate multiple socio-hydrosystems in the Senegal floodplain. Surface water monitoring with MNDWI on multi-spectral imagery (Landsat 5, 7, 8 and Sentinel-2A) is used to identify intra-annual and inter-annual variations in water availability. Validation against field monitoring (R2=0.88) and photointerpretation of drone imagery highlights the benefits of Sentinel's increased resolution to monitor floods of minor surface area and duration and improve the representation of hysteresis in floodplains. Integrated into forthcoming river basin modelling, these results can help simulate the influence of upstream changes on the hydrology and associated services of these complex socio-hydrosystems and improve watershed management.
Highlights
The annual floods of large rivers in Africa (Nile, Zambezi, Niger, Senegal, Congo) and Asia (Mekong, Ganges, Indus) support numerous ecosystem services along their alluvial floodplains
The scale, diversity and flat topography of these floodplains generate difficulties and uncertainties in the hydrological monitoring and modelling (Neal et al, 2012). These are exacerbated by the decline in observation networks, and the difficulties to apprehend and represent human influences on water resources and in turn the relationships between water resources and associated uses and services. These considerations are at the heart of the reflections developed currently in socio-hydrology (Sivapalan et al, 2012) and the 2013–2022 IAHS Panta Rhei decade (Montanari et al, 2013) devoted to increasing the understanding and representation of anthropic modifications to hydrological regimes
The opportunities in quantitative hydrology provided by the recent improvements in low cost, high spatial and temporal resolution imagery have increased significantly
Summary
The annual floods of large rivers in Africa (Nile, Zambezi, Niger, Senegal, Congo) and Asia (Mekong, Ganges, Indus) support numerous ecosystem services along their alluvial floodplains. The scale, diversity and flat topography of these floodplains generate difficulties and uncertainties in the hydrological monitoring and modelling (Neal et al, 2012) These are exacerbated by the decline in observation networks, and the difficulties to apprehend and represent human influences on water resources (withdrawals, dam management, land use changes) and in turn the relationships between water resources and associated uses and services. These considerations are at the heart of the reflections developed currently in socio-hydrology (Sivapalan et al, 2012) and the 2013–2022 IAHS Panta Rhei decade (Montanari et al, 2013) devoted to increasing the understanding and representation of anthropic modifications to hydrological regimes. Upscaled and integrated into hydrological modelling, these results will help predict climatic and human influences on flooding patterns and associated services in the Senegal floodplain sociohydrosystems
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