Large bottomless lysimeters were used to study water balances in treeless and tree-covered areas on a raised mire. These lysimeters, big enough to hold a mature tree, measured liquid discharge from enclosed peat. By analyzing discharge along with other water balance components, researchers estimated evapotranspiration rates and compared treeless and tree-covered areas. Results showed that discharge measurements were reliable for short periods with moderate rainfall, but leakage could occur in extreme weather conditions due to water exchange across the lysimeter walls. Suggestions for improving the lysimeter system were made.