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Estimation of Irrigation Volume by Assimilating Soil Moisture Satellite Data into a Soil Water Model

Khamseh, Fatemeh | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58377 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Danesh Yazdi, Mohammad
  7. Abstract:
  8. Agriculture accounts for 70% of global freshwater consumption. However, precise data on irrigation water use (IWU) at the regional scale is often lacking, which hampers the development of effective water management plans. This study aims to estimate irrigation water use (IWU) by integrating remote sensing soil moisture (SM) and actual evapotranspiration (ET) data into a root-zone soil water model. Since irrigation influences both SM and actual ET, increases in SM and ET following irrigation events can be leveraged to frequently retrieve IWU from remotely sensed data. In this regard, we first developed an irrigation-free soil water model simulating root-zone SM dynamics during non-growing periods. To estimate IWU, we calculated residuals between modeled SM and 9 km root-zone SM retrieved from SMAP L3, as well as residuals between modeled ET and retrieved ET from the 30-m OpenET product. We used annual IWU data from Arizona State, USA, in 2017 to examine model performance. The simulated SM by our soil water model showed strong agreement with SMAP, evidenced by RMSE = 0.014 mm3/mm3 and R2 = 0.74. The estimated IWU using OpenET closely aligned with benchmark data, showing a bias of -17 %. We further found that over 97 % of the estimated IWU was attributed to ET rather than SM residuals. Uncertainty analysis indicated a coefficient of variation of 0.25 in IWU estimates, primarily due to biases in meteorological and remote sensing inputs
  9. Keywords:
  10. Irrigation ; Soil Moisture ; Remote Sensing ; Agriculture ; Water Resources Management ; Soil Moisture Active Passive (SMAP)Calibration ; Actual Evapotranspiration

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