Inland waters are usually not well restrained in terms of greenhouse gas measurements. One of these regions is the Danube Delta, Romania. Therefore, we measured continuously with sensors to collect high-resolution data for CH₄ and O₂ throughout the Delta. We found significant variation for all concentrations over the day and night and between regions, as well as large spatial variation throughout all regions, with large CH₄ concentrations flowing in from the reed beds to the lakes.