Arid Zone Research ›› 2024, Vol. 41 ›› Issue (11): 1819-1830.doi: 10.13866/j.azr.2024.11.03

• Weather and Climate • Previous Articles     Next Articles

Research on the distribution and control mechanism of evapotranspiration in the Nanxiaohegou watershed based on an improved S-W model

YANG Nan1(), SONG Xiaoyu2(), DENG Jianwei1, LI Lanjun2, ZHAO Xinkai2, MENG Pengfei2, FU Chong2, WEI Wanyin2, ZHANG Yubin1, DING Lin1, LI Haolin3   

  1. 1. Gansu Academy for Water Conservancy, Lanzhou 73000, Gansu, China
    2. State Key Laboratory of Eco-Hydraulics in Northwest Arid Region of China, Xi’an University of Technology, Xi’an 710048, Shaanxi, China
    3. Beijing University of Technology, Beijing 100124, China
  • Received:2024-05-12 Revised:2024-06-26 Online:2024-11-15 Published:2024-11-29
  • Contact: SONG Xiaoyu E-mail:15379010323@163.com;songxy@xaut.edu.cn

Abstract:

In this study, we aimed to accurately quantify evapotranspiration (ET) and its components while exploring the factors that control it, which will facilitate the practical evaluation, planning, and management of regional water resources. Utilizing continuous long-term observation data and field tests conducted from 2016 to 2020 in the Nanxiaohegou watershed—a typical small watershed for water and soil conservation on the Loess Plateau—this study simulated the dynamic changes of ET and its components in typical plantation land using the improved Shuttleworth-Wallace (S-W) model. Additionally, we analyzed the coupling relationships between plant transpiration (T), soil evaporation (E), and control factors using a structural equation model. The results revealed the following: (1) The modified S-W model was effective for evaluating ET and its components in Nanxiaohe Valley. The threshold value of soil surface resistance ( r s s) was 50-2500 s·m-1, exhibiting an exponential relationship with the empirical function of soil surface water content (θ); moreover, higher sand content in the soil particles correlated with a steeper linear slope. (2) ET ranged from 276.76 mm to 402.86 mm in typical plantation land, with annual averages of T and E accounting for 51.6% and 48.4% of ET, respectively. While monthly ET, T, and E patterns were not pronounced, daily fluctuations were significant. The fluctuation trends of T and E largely reflected annual precipitation patterns but lagged behind rainfall. (3) Structural equation modeling analysis revealed that net radiation (Rn), temperature (Ta), and θ exerted the most significant effects on ET, with Rn having the largest impact on T (total impact of 0.614) and Ta having the most significant impact on E (total impact of 0.426). T was positively correlated with E, with a contribution coefficient of 0.503. Evaluating ET and its components using an improved S-W model establishes a foundation for a deeper understanding of ecological and hydrological processes in arid and semiarid regions.

Key words: evaporative components, improve the S-W model, SEM model, evaporation resistance, Nanxiaohegou watershed