The data consist of physico-chemical parameters of river water in Nivelle and its tributaries, collected since 2009. The parameters are water temperature (°C), hydrogen potential (pH), conductivity, turbidity, nitrates (NO3-), ammonium (NH4+) and ortophosphates (PO4 ---). This data is collected as part of the French Environmental Research Observatory (ERO) on Diadromous Fish in Coastal rivers (DiaPFC). ORE DiaPFC is a research infrastructure dedicated to the study of diadromous fish populations under the influence of anthropic pressure (e.g. agriculture) and environmental changes (e.g. climate). The Nivelle is a 39 km long coastal stream of Pays Basque. It has its source in Spain and flows into the Bay of Biscay at Saint-Jean-de-Luz. Its drainage basin has a surface area of 238 km2, and is dominated by marly-calcareous formations. It is essentially agro-pastoral with more than 50% of the land area made of moors (Dumas, 2003). The oceanic climate, mild and wet (1700 mm year-1 in St-Pée-sur-Nivelle), provides a mean annual discharge of 5.4m3/s downstream from the confluence of the main tributary, the Lurgorrieta, and 9m3/s at the mouth.