We performed ground-based measurements (downwind, site-wide characterization) of methane emissions from older light oil and natural gas production sites in Alberta, Canada (Red Deer region, 60 measured sites). We developed a distribution of site-based methane emissions and as previously found in production regions in the United States, a small fraction of the sites account for the majority of methane emissions: 20% of the sites emit three quarters of the methane from oil and gas production. Using empirically derived emission factors, we compared an estimate of regional methane emissions, to a top-down airborne-based measurement of the same region. The airborne measurement was 35% lower, though not statistically different (4,800 ± 3,200 vs. 3,100 ± 2,200 kg CH 4 h –1 ). In Alberta, the majority of these oil and gas emissions go unreported under current reporting requirements. Effective mitigation will most likely require frequent monitoring to identify high-emitting sites as well as leaky components that we hypothesize are also a major contributor to emissions.