Partitioning of vertical water loss in reed swamp wetlands: theory, research and application

This paper proposes an on-site monitoring system for evaporation (E (w)) and evapotranspiration (ET) in wetlands called the Compensation Evapotranspiration Observation System. Considering the characteristics of wetlands environment and emergent plants, the vertical flux of water loss in wetlands can be separated using the system based on compensation principle. A comparison research on water loss through ET in reed (Phragmites australis) stands between Zhalong wetland and Baiyangdian wetland was carried out in 2004-2009. In Baiyangdian wetland, the ET rates from three reed stands with different leaf area indexes were measured. The results show that annual ET in Zhalong wetland was 739-886 mm during study period. Comparatively, annual ET of the three reed stands in Baiyangdian wetland was 970-1117 mm, 1261-1452 mm and 1759-2035 mm, respectively. The ET rates in Baiyangdian were stronger than in Zhalong because of the effects of geography and climate characteristics. Moreover, seasonal dynamic changes and influence factors of transpiration-acting factor from the two wetlands were also analyzed. It is indicated that the transpiration-acting factor can be affected by geographic location, aboveground biomass, plant growth and climate conditions.