Seasonal Environmental-flow Demand Calculation of Reed Community (Phragmites australis var. baiyangdiasis) under Different Meteorological Conditions in Baiyangdian Lake, China

Abstract

Based on the results of existed research about environmental-flow of reed communities in Baiyangdian Lake, the Li-6400 portable photosynthesis system was used to record the transpiration rate of reed (Phragmites australis var. baiyangdiasis) leaves under different meteorological conditions. Leaf Area Index (LAI) of reed communities, evaporation rate of open water surface and meteorological conditions were also recorded. Meteorological conditions were divided into sunny, un-sunny (cloudy, overcast) and rainy days, the transpiration rate in rainy days was regarded as 0. Environmental-flow of reed community in different months was calculated according to the transpiration and evaporation. Results show that the environmental-flow differed significantly among different meteorological conditions. In particular, the environmental-flow in sunny condition was 1.58 times of un-sunny conditions on average. Under given meteorological conditions, the environmental-flows of reed communities in the Baiyangdian Lake during June to September in 2006 were 0.19×108, 0.25×108, 0.38×108, and 0.18×108m3, The actual environmental-flows of reed communities in Baiyangdian Lake from June to September were 2.25, 2.08, 3.17 and 2.57 times of the estimated values. Meteorological condition had a significant impact on the plants and wetland, when it was full considered the accuracy of environmental- flow calculation would be improved.