ABB LGR | Application of ABB LGR water isotope analyzer on the partitioning of catchment evapotransp

Application of ABB LGR water isotope analyzer on the partitioning of catchment evapotranspiration fluxes

Evapotranspiration (ET) is an important process in the water budget of an ecosystem. Quantifying the components (E_soil and T)) of evapotranspiration is of great significance in revealing the ecohydrological process of alpine inland river basins. At present, the research on E_soil and T is mainly based on the observation site scale to calculate local evapotranspiration components, there are few reports on the changes of evapotranspiration components at the watershed scale. Hydrogen and oxygen stable isotope technology is a good tracer for the ecological hydrological cycle. It is widely used in the study of hydrological cycle Existing studies have used hydrogen and oxygen stable isotope technology to study atmospheric precipitation, water vapor sources, and runoff processes in the Qinghai Lake basin. However, there are few reports on the partitioning of catchment evapotranspiration fluxes using stable isotopes.

Based on this, to fill research gap, a group of Chinese scientists selected the Shaliu River basin (Fig.1, 37°10′55.92″-37°51′2.16″N, 99°37′10.20″-100°17′9.96″E) as the research area, they collected the monthly hydrogen and oxygen stable isotope date (ABB LGR IWA-35EP water isotope analyzer) of precipitation from June to August in 2018 and 2019, and then they studied the partitioning of catchment evapotranspiration fluxes of the northeast of the Qinghai-Tibet Plateau (QTP) by stable isotope technology and remote sensing technology. The purpose is to: (1) clarify the partitioning of catchment evapotranspiration fluxes in the Shaliu River basin of the northeast of the QTP, and (2) master the spatiotemporal characteristics of evapotranspiration flux distribution in the basin, (3) calculate E₁, E₂, E_soil and T values and ratio, and (4) quantify the percentage of composition of ET. The research results can provide data support and theoretical research for the water cycle, hydrological process research, and water resources protection and management in the alpine inland river of the QTP.

Fig.1. Location of the study area and water sampling sites.

[Results]:

Fig.2. Temporal variation in soil fractionation values (E₁) (a) and incomplete evaporation values (E₂+T) (b) in the summer of 2018 and 2019.

Fig.3. Temporal changes in soil evaporation (E_soil) (a) and plant transpiration (T) (b) values and the proportion soil fractionation in soil evaporation (E₁ : E_soil) (c) in summer of 2018 and 2019.

 Fig. 4. Temporal variation in soil fractionation ratio (E₁) (a), soil non-evaporated ratio (E₂) (b) and plant transpiration ratio (T) (c) in summer of 2018 and 2019.

[Conclusion]:

 (1) The average ratio of E₁ in the summer of 2018 and 2019 in the Shaliu River basin was 9.04% and 5.98%, respectively. The average E₁ of the watershed in the summer of 2018 and 2019 was 7.59 mm and 2.10 mm, respectively. The soil fractionation was stronger in the summer of 2018 than that in the summer of 2019.

(2) The average soil transpiration and vegetation transpiration in the summer of 2018 were 42.84 mm and 32.59 mm, the average soil transpiration and vegetation transpiration in the summer of 2019 were 35.36 mm and 26.23 mm. Therefore, both soil evaporation and plant transpiration in summer 2018 were higher than those in summer 2019, and soil evaporation was greater than plant transpiration in summer during the study period in the Shaliu River basin.

(3) Precipitation is the main climatic factor affecting the delineation of evapotranspiration flux in the Shaliu River basin of Qinghai Lake.