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Exploring the Impact of Vegetation Type and Plant Growth Cycle on the Evapotranspiration Storage Selection Function Using Particle Tracking Approach

Bayat Afshary, Nooshdokht | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52803 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Danesh Yazdi, Mohammad
  7. Abstract:
  8. StorAge selection (SAS) functions describe the mechanism by which water particles with different ages exit a hydrological system through outfluxes such as streamflow and evapotranspiration (ET). The shape of the ET SAS functions affects the storage residence time distributions, ET travel time distributions, and discharge travel time distributions that control the hydrochemical dynamics of water. They also carry fundamental information to understand the response behavior of the system, and are affected by processes such as precipitation, outflow, ET, as well as the physical properties of the system. To better understand the shape of these functions, other important factors such as the type of vegetation and the effect of different phases of plant growth should also be investigated. Since the ET SAS functions are a combination of evaporation (E) and transpiration (T) SAS functions, and E and T follow independent mechanisms, the ET SAS functions cannot solely describe the particles removal by E and T in the root zone. The purpose of this study is to explore the impact of vegetation type and plant growth cycle on the shape of the ET SAS function using a Lagrangian particle-tracking model, EcoSLIM. For the purposes of this study, we modified the particle allocation scheme with respect to their source, and partitioned ET using the mass balance approach. We then investigate the dynamics of SAS functions in a hypothetical hillslope under three vegetation types (winter barley, soybean, and tree). The results showed that the growing season and the root depth are the dominant factors in particle removal with different sources through T.Plants growing in summer removed the water that has entered the system through the summer precipitation, and plants growing in spring removed mostly the spring snowmelt water. The shape of ET SAS functions in different plant growth phases was almost the same (invariant in time), whereas in the cold season, their shape was quite different. Therefore, seasonal calibration of the E and T SAS functions is required during the growing and cold seasons. Although the E and T SAS functions are almost constant over time in the growing season, they show alarger degree of variability over time by the longer plant growth period.Therefore, the parameters of the ET SAS functions should should also be calibrated in the growing and cold seasons, separately
  9. Keywords:
  10. Vegetation ; Plant Evapotranspiration ; Plants Growth ; Particles Tracking ; Evapotranspiration Partitioning ; StorAge Selection Function

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