Detecting Leaks from Belowground CO₂ Reservoirs Using Eddy Covariance

This chapter describes the eddy covariance method of measuring earth-atmosphere CO₂ exchange, including past applications to measurements of volcanic venting of CO₂. The technique involves continuous atmospheric measurements of both CO₂ mixing ratio and atmospheric winds from a tower platform. Equipment is robust and commercially available, and the methodology is well established. The surface area covered by the measurement is described. The area measured depends on wind speed, wind direction, surface roughness, and stability of the atmospheric surface layer. The measurement works best under well-mixed atmospheric conditions which frequently occur on a daily basis, often for a majority of the day. The ability to detect leaks from geologic CO₂ reservoirs is compared by expected leakage rates to typical ecological flux rates.