Estuaries are coastal indentations where freshwater mixes with seawater (Pritchard 1967), and are found everywhere in the world. Moreover, the estuarine ecosystems are usually characterized by high biological productivity and great biodiversity. However, these characteristics are very sensitive to the climate regime, the geological environment and the hydrological quality. In metropolitan environments with high social, urban and economic complexity, river fows usually play an important role in the regulation of estuary biochemistry, and therefore their control is essential. Such estuary, is the one generated by the Besós river, located in the north of Barcelona, where the management of the water cycle of its riverbed and its mouth is a shared strategy for the development of the territory between the municipality of Sant Adriá del Besòs, the town hall of Badalona, the Consorci del Besòs, the Polytechnic University of Catalonia and the b_TEC Foundation. These institutions share the Territorial Specialization and Territorial Competitiveness Project (PECT) of the Besòs Sustainable Territory coast, where one of its objectives is the improvement and use of water and coastal resources in the Besòs environment. In this framework, it is intended to reduce the impact of heavy rain scenarios and frequent sewer overfows, which involve poor water quality scenarios on the beaches near the river mouth, through the use of surplus groundwater to improve the water quality of the riverbed, instead of being sent to the sewer. To evaluate the degree of improvement provided by this solution, in the Besòs estuary it has been deployed and installed a new integrated biogeochemistry observatory that includes (a) a costal buoy with a multi-sensor system and (b) a riverbed platform with a multi-sensor system as shown in Figure 1, that provide long series of real-time data.
