From piezometers to water actors and back again. A grounded sociohydrology towards the sharing of hydrological knowledge (Senegal River delta).

The Senegal River delta is characterised by two distinct features. First is the rich historical link between people and water. In this area shaped by the river flow, inhabitants developed multiple water-related activities over history and adapted to hydrological fluctuations. Fresh, salt and brackish water, from the surface and underground, are used in the daily life of riverside people, through fishing, market gardening, fluvial trade, biodiversity conservation, etc. Second is the hydraulic history of this river, commanded by periods of flood and recession. Since the 1980s, massive hydraulic development profoundly modified the river dynamics with dikes, dams and large irrigation schemes. These changes affected the functioning of the lower delta, and especially the distribution of flood waters. People adapted their practices to these changes. One of the driving forces behind these adaptations is the comprehension of the hydrological changes and their impacts on the hydrological regime, in space and time. To do this, all water actors involved in the delta (inhabitants, managers and scientists) develop a dynamic and composite body of knowledge, enabling each of them to build up a specific understanding of the river, in line with their needs for action.

Our research uses grounded sociohydrology to analyse the ways in which this knowledge is constructed. It highlights the variety of information that water actors mobilise in order to build their hydrological knowledge. Each individual produces his own indicators, data and observations. The typical distinction operated between scientific and local knowledge does not resist to this analysis. Knowledge is distinguished by the underlying logic of action and not by the kind of expertise it mobilises. For example, groundwater levels and their variations are of equal interest to hydrogeologists and farmers. Only the observation tools, wells or piezometers, may differ.

This work identifies the ways water actors share information in order to build answers to pending questions about the hydrological dynamics of the Senegal River delta. In a highly anthropised semi-arid context this information sharing enhances the level of knowledge of all groups of actors.