Vertical CTD profiles and salinity data from the Volturno River mouth SAL.WE project – July 2025 and January 2026 campaigns

Description This dataset provides multiparametric Conductivity–Temperature–Depth (CTD) probe measurements collected along the terminal reach of the Volturno River and the adjacent coastal sector (Campania region, southern Italy) within the framework of the SAL.WE project. The dataset documents the vertical and longitudinal structure of salinity and associated physico-chemical parameters during two contrasting seasonal monitoring campaigns: July 2025 (summer, low-flow conditions) and January 2026 (winter, higher-discharge conditions). The Volturno River coastal plain is a low-gradient fluvial–coastal system vulnerable to saltwater intrusion and salinisation processes. The data were collected to characterise the spatial evolution of the salt wedge from the river mouth towards the upstream fluvial sector and to support subsequent statistical and hydrogeological analyses of salinity variability under different hydrological conditions. Sampling activity At each station, vertical profiles were acquired along the water column using a multiparametric CTD probe. The probe measured salinity and a set of associated physico-chemical variables, including water temperature, electrical conductivity, dissolved oxygen, pH, total dissolved solids and fluorescence-related parameters. Measurements were acquired within a limited temporal window during each field campaign and should therefore be interpreted as synoptic spatial characterisations of the respective observation periods. Files included in the dataset File name Sheet name Campaign Content SALWE project - July 2025.xlsx 02-09.07.2025 July 2025 summer campaign 446 individual CTD readings from 20 stations, distributed from the Volturno River mouth to the upstream fluvial sector near Capua. The surveyed axis extends from 0 to 44 km from the river mouth. SALWE project - January 2026.xlsx 16.01.2026 January 2026 winter campaign 537 individual CTD readings from 13 stations, including offshore/coastal stations, the river mouth and the lower estuarine reach. Distances range from -3 to 5 km from the river mouth. Data structure and variables Both Excel files contain the same column structure. Each row corresponds to one CTD measurement at a given station, depth and time. Column name Description Unit / format ID Sampling station identifier text X (Longitude)_E Longitude of the sampling station decimal degrees, WGS84 Y (Latitude)_N Latitude of the sampling station decimal degrees, WGS84 date Date of acquisition Excel date format time Time of acquisition Excel time format Depth (m) Measurement depth below water surface m temperature (C°) Water temperature °C Conductivity Electrical conductivity recorded by the CTD probe instrument output Salinity(‰) Salinity ‰ / practical salinity as reported by the probe Oxygen (%) Dissolved oxygen saturation % Oxygen (mg/Kg) Dissolved oxygen concentration mg kg⁻¹ pH Hydrogen ion activity expressed as pH pH units Trx-chl(a) Chlorophyll-a fluorescence-related parameter instrument output Phycocyanin Phycocyanin fluorescence-related parameter instrument output Phycoerythrin Phycoerythrin fluorescence-related parameter instrument output TDS Total dissolved solids instrument output Distance from the mouth river (km) Distance of each station from the Volturno River mouth; negative values identify offshore/coastal stations seaward of the mouth km Campaign-specific notes July 2025 campaign: the file includes 20 stations from the river mouth and lower estuarine reach to the inner fluvial sector near Capua. Station IDs include FV - Foce Volturno, FV - 01 to FV - 16, FV - CeA, FV - Grazzanise and FV - Capua. January 2026 campaign: the file includes 13 stations: FV-C01, FV-C0, FV-Foce Volturno and FV - 01 to FV - 10. FV-C01 and FV-C0 are located seaward of the river mouth and provide coastal/marine reference conditions for the January survey. Potential reuse The dataset can be used to reconstruct vertical salinity profiles, longitudinal salinity sections and freshwater–brackish–marine transitions along the Volturno River mouth. It is suitable for hydrogeological and hydrochemical interpretation, comparison between seasonal saltwater intrusion configurations, statistical modelling of salinity variability and integration into monitoring or digital-twin workflows for coastal water-resource management. Acknowledgements The field campaigns were conducted as part of the SAL.WE. project by a Collaboration Agreement pursuant to Art. 15 of Law 241/90 between the Autorità di Bacino Distrettuale dell’Appennino Meridionale and the Institute of Marine Sciences of the National Research Council (CNR-ISMAR), providing technical and scientific support for planning activities aimed at rebalancing natural processes, Action A.5.8, Line 5 of the Development and Cohesion Fund 2014–2020 – PED Acque (SAL.WE. Project, CUP F52G16000010001; Scientific Coordinator: Dr. Fabio Matano).