Greenhouse gas (GHG) concentrations, physio-chemical water properties, metal concentrations and carbon radiogenic and stable isotope data of the GHG were measured to investigate the properties of mine water from legacy coal mines across the Midland Valley, Scotland between June 2022 to September 2022. Sixteen identified outflows from abandoned coal mines were selected for measurement. The locations are distributed from Lathallan Mill in the northeast to Kames in the southwest and included mine water outflows from the Fife, Central (Lanarkshire), Lothian and Ayrshire coal fields. Some of the outflows had treatment systems and others discharged directly into rivers or streams. Full details about this dataset can be found at https://doi.org/10.5285/49daf07b-cfbe-48d1-8889-1adafe410a2e
