Date set for the manuscript: The Role of Sediment Gas Storage in the Methane Dynamics of a Shallow Freshwater Reservoir

The dataset supports the findings of the manuscript entitled: Linking Sediment Gas Storage to the Methane Dynamics in a Shallow Freshwater Reservoir. The manuscript presents results based on in-situ monitoring at the main pre-dam of the Wupper reservoir. The reservoir is located in Germany and the monitoring was conducted from March 2020 to November 2021. The main goal of the monitoring was to measure the spatial variability of methane fluxes and its dynamics in the reservoir. The methane budget of the reservoir was then analysed in combination with estimates of the amount of free gas stored in the sediment matrix, which were derived from acoustic observations. The findings are discussed in the manuscript.

Therefore, the dataset provided as an xlsx file includes separate sheets for:

• Sediment measurements of potential methane production (PMP), loss on ignition (LOI), dissolved methane (CH₄) in porewater, carbon and nitrogen content.
• Gas content in the sediment estimated from maximum acoustic backscatter for 2020 and 2021 for the reservoir spatial grid.
• Monthly time-series of methane fluxes (oxidation, diffusion, ebullition, and potential flux at the sediment water interface - PSWI) for each monitoring location and for the reservoir (average of all monitoring locations) with the inclusion of degassing at the dam overflow and advective methane transport (Net-export) by inflow and outflow.
• Time series of daily mean values of ebullition and environmental parameters monitored in the reservoir.

Explanations and units are provided in column labels. NaN refers to missing data.

In this version (Version 2), the calculation of the PSWI has been corrected. It is now calculated as the vertically integrated potential methane production over the top 30 cm layer of the sediment.