Description: A number of studies expect an increase of carbon export by rivers to the Arctic Ocean due to rapidly changing climate in the Arctic One possible reason for the increase of carbon export is thawing permafrost, which can lead to a mobilization of previously frozen dissolved organic matter (DOM). Scarce measurements of DOC and the coloured fraction of DOM (CDOM) (〈 8 samples/year) were previously used to estimate fluxes to the Arctic Ocean for the whole year. Here, we present a new high frequency sampling program and its viability to monitor export fluxes of DOM and its biogeochemistry in the Lena River. This dataset includes measurements of several water parameters, such as temperature, electric conductivity, dissolved organic carbon (DOC), spectral CDOM absorption (aCDOM), stable water isotopes and major ions. The high sampling frequency throughout the whole year facilitats the identification of the main drivers behind the seasonality of DOM concentration and biogeochemistry of the Lena River. The high number of samples throughout the whole year allows flux calculations that are independently from load models that likely lead to a large variation of earlier studies. Optical indices reveal changing composition and sources of DOM throughout the year. This dataset represents the first year (April 2018 to April 2019) of a planned long-term monitoring program at the Research Station Samoylov Island and provides a baseline data set against which future change of this large integrative system may be measured. A continuous sampling of Arctic River water will facilitate to identify intra and inter-annual trends with ongoing climate change.