Evapotranspiration Partitioning and Response to Abnormally Low Water Levels in a Floodplain Wetland in China

Xiaosong Zhao,Yuanbo Liu

doi:10.1155/2016/3695427

Abstract

Evapotranspiration (ET) is an important component of the wetland water budget. Water level declines in Poyang Lake, the largest freshwater lake in China, have caused concerns, especially during low water levels. However, how wetland ET and its partitioning respond to abnormally low water levels is unclear. In this study, wetland ET was estimated with MODIS data and meteorological data. The wetland ET partitioning and its relationship with abnormally low water levels were analyzed for 2000–2013. The results showed that the water evaporation rate (Ewater) was larger than the land ET rate (ETland); theETland/Ewaterranged from 0.77 to 0.99. When the water level was below 12.8 m, the ET partition ratio was larger than 1, which indicates that wetland ET comes from land surface ET more than water evaporation. The negative standardized water level index (SWI) was used to represent an abnormally low water level in the wetland. Although the monthly wetland ET decreased as the negative SWI decreased,ETlandwas higher than the average under negative SWI conditions from September to December, when the water level decreased. The abnormally low water level induced more water loss from the land surface, especially when the water level decreased, which reduced the available water resources along the wetland shore.

Highlights

Evapotranspiration (ET) is the major factor that controls water balance in most wetlands
Though evaporation that was estimated by the modified Priestley-Taylor equation was lower than the measurements at high value, which is an obviously improved estimation accuracy compared with the evaporation from the Priestley-Taylor equation, Φ = 1.26 (R2 of 0.23 and RMSE of 31.4 mm d−1)
Wetland ET was separated into land ET and water evaporation in Poyang Lake wetland

Summary

Introduction

Evapotranspiration (ET) is the major factor that controls water balance in most wetlands. Changes in the proportion of water lost via ET from land surfaces versus evaporation (E) from water bodies relative to the total wetland ET affect ecological, biogeochemical, and hydrological cycles at multiple temporal and spatial scales in floodplain wetlands [3]. Many studies have highlighted the linkage between ET partitioning versus water level and vegetation cover in wetlands [4,5,6,7,8]. Vegetation cover and soil conditions are important factors that affect the rate of water loss [11]. Huxman et al [12] identified the partitioning of ET as one of the most important ecohydrological challenges in understanding vegetation dynamics and succession in floodplain wetlands

Results

Discussion

Conclusion