Flow-through pCO2, O2 and some CH4 measurements throughout the Danube River Delta in spring (17.05.2017 - 26.05.2017). Surface water flow-through system set up on a houseboat (see Canning et al., 2020). All running on the same water at almost the same time (within seconds), therefore all joined together into each data set. Gaps from sensors depend on when they were logging. For the pCO2, some gaps will be due to periods of zeroing and flushing. Depth of pumps: approx. 75cm Flow rate: ~ 5-6 L/min flow readings logged for Aug and Oct. May data was manually logged and recorded, therefore potential discrepancies. All data was processed following Canning et al., 2020 (In Review). Seasonal sensor data are in separate files. Sensors: pCO2: CONTROS HydroC CO2 FT pCH4: CONTROS HydroC CH4 FT - formerly Kongsberg Maritime Contros GmbH, Kiel, Germany; now -4H-JENA engineering GmbH, Jena, Germany O2: CONTROS HydroFlash O2 - formerly Kongsberg Maritime Contros GmbH, Kiel, Germany SBE 45 Micro Thermosalinograph - Sea-Bird Electronics, Bellevue, USA Gorgova climate station data used for climate data. Flags from internal questionable data are noted. Flags from notes in the field (such as plant coverage) are stated in meta data. During Aug, there was a high load of plant coverage and this has a separate flag column. Data split into rivers, channels and lakes through coding (RCL), with a description of each area in RCL comment. pCH4 and pCO2 converted into concentration using temperature, salinity, Wiesenburg and Guinasso 1979, and Weiss, 1974 respectively. Day-night codes in which the houseboat was stationary are marked in Day Night Code (numbering which for each cruise).