Monthly bulk deposition of SO4, NO3, NH4, P-PO4, major cations (Ca, Mg, Na, K) in kg ha-1 at the sampling station of Pallanza, in Lake Maggiore watershed. Data are volume weighted monthly average values calculated from weekly data.

The dataset contains monthly data of transparency measured as Secchi depth at the Ghiffa station (deepest point) during 1988-2018

This dataset includes Chlorophyll a concentration in μg/L. Measurements of Chl a were made on discrete water samples collected monthly in the upper 20 meters layer at sampling station Ghiffa (45°58’30’’N; 8°39’09’’E) from January 1984 to December 2018. Chl a measurements derived by spectrophotometric technique in the period from January 1984 to December 2009, while from January 2010 to December 2018 measurements derived from vertical profiling instrument (FluoroProbe).

The dataset contains monthly data, volume weighted average values for epilimnion (0-25 m) and hypolimnion (25-360 m), for the period 1988-2018 and 2019-2021 for the following variables: water temperature, pH, conductivity, Ntot, NH4N, NO3N, Ptot, PO4P, cation and anion concentrations

Lake Paione Inferiore is a high altitude Alpine lake, located at 2002 m a.s.l. in the Bognanco Valley, Province of Verbania, Piedmont Region, Italy. It has a surface area of 0.86 ha and a maximum depth of 13.5 m. It is included in the monitoring sites of the UN-ECE Program ICP WATERS (International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes) funded in Italy by Ministry of the Environment and for which the CNR Water Research Institute (CNR-IRSA) is the National Focal Centre for Italy. The lake has been studied since the late 1970s in the framework of research on the effect of acid deposition on chemistry and biology of sensitive lakes. At present meteorological data are collected continuously by an automatic weather station (AWS) located on the shore of the close lake Paione Superiore. Chemical data are available since 1978 and are still collected on a regular basis (annual or biennial frequency): pH, conductivity, alkalinity, dissolved oxygen, major anions (sulphate, nitrate, chloride) and cations (calcium, magnesium, sodium, potassium), reactive and total phosphorus, reactive silica, total nitrogen, dissolved organic carbon, main trace elements (included heavy metals). Three samples are collected on the water column at the deepest point of the lake. Winter or spring samplings are performed occasionally. Available biological data include phytoplankton, zoo plankton and benthos taxonomic composition, population dynamics of the main species and, limited to 2000-2001, bacteria, epilithic diatoms, and paleolimnological data.

Lake Paione Superiore is a high altitude Alpine lake, located at 2269 m a.s.l. in the Bognanco Valley, Province of Verbania, Piedmont Region, Italy. It has a surface area of 0.68 ha and a maximum depth of 11.5 m. It is included in the monitoring sites of the UN-ECE Program ICP WATERS (International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes) funded in Italy by Ministry of the Environment and for which the CNR Water Research Institute (CNR-IRSA) is the National Focal Centre for Italy. The lake has been studied since the late 1970s in the framework of research on the effect of acid deposition on chemistry and biology of sensitive lakes. At present meteorological data are collected continuously by an automatic weather station (AWS) located on the shore of the lake. Chemical data are available since 1978 and are still collected on a regular basis (annual or biennial frequency): pH, conductivity, alkalinity, dissolved oxygen, major anions (sulphate, nitrate, chloride) and cations (calcium, magnesium, sodium, potassium), reactive and total phosphorus, reactive silica, total nitrogen, dissolved organic carbon, main trace elements (included heavy metals). Three samples are collected on the water column at the deepest point of the lake. Winter or spring samplings are performed occasionally. Available biological data include phytoplankton, zoo plankton and benthos taxonomic composition, population dynamics of the main species and, limited to 2000-2001, bacteria, epilithic diatoms, and paleolimnological data.

Lake Maggiore was studied since the beginning of last century although not systematically. Regular research started by the foundation in 1938 of the Italian Institute of Hydrobiology "Dr. Marco De Marchi" located in Verbania Pallanza. A limnographic (level and temperature profile) and weather station came into operation in 1952. Studies on plankton and on hydrochemistry of Lake Maggiore continued between the 1950s and the 1970s, showing the progressive eutrophication of the lake. Thanks also to the research of the institute, in the 1980s effective actions to control the eutrophication were undertaken, with the large-scale activation of waste water treatment plants. In the same period a program, still active, of systematic monitoring and research sponsored by the CIPAIS (International Commission for the Protection of the Italian Swiss Waters) started: it allowed collecting an uninterrupted and long-time series, with high sampling frequency, of data related to meteorology, hydrology, physic and chemistry of the lake, organic carbon and bacterial populations, phyto-and zooplankton. The analysis of these time series highlighted an oligotrophication process leading to the current state of oligotrophy of Lake Maggiore. Recent studies also showed the effects of global warming on Lake Maggiore, which went towards the gradual warming of deep hypolimnion as well as the raising of the average temperature of the surface layers.