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Estimating Spatially Explicit Irrigation Water Use Based on Remotely Sensed Evapotranspiration and Modeled Root Zone Soil Moisture

Zhang, Caijin ; Long, Di

Water resources research, 2021-12, Vol.57 (12), p.n/a [Periódico revisado por pares]

Washington: John Wiley & Sons, Inc

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  • Título:
    Estimating Spatially Explicit Irrigation Water Use Based on Remotely Sensed Evapotranspiration and Modeled Root Zone Soil Moisture
  • Autor: Zhang, Caijin ; Long, Di
  • Assuntos: Accuracy ; Agricultural management ; Agriculture ; Climate variability ; Components ; Crop water ; Crops ; Energy balance ; Estimates ; Estimation ; Evapotranspiration ; Groundwater ; Groundwater irrigation ; Groundwater recharge ; Irrigation ; Irrigation efficiency ; Irrigation practices ; Irrigation scheduling ; Irrigation systems ; Irrigation water ; Irrigation water use ; Modelling ; Modules ; Optimization ; Remote sensing ; Resource allocation ; Root zone ; Root zone soil moisture ; Simplified surfaces ; Soil ; Soil moisture ; Soil moisture estimation ; Spatial distribution ; Surface energy ; Surface energy balance ; Surface properties ; Surveying ; Transport ; Uncertainty ; Water consumption ; Water resources ; Water stress ; Water use ; Water use efficiency
  • É parte de: Water resources research, 2021-12, Vol.57 (12), p.n/a
  • Descrição: Estimation of irrigation water use (IWU) is critical to assessing water use efficiency and optimizing water resource allocation. However, diversity in irrigation scheduling, irrigation system, and crop type has imposed restrictions on deriving the accurate spatial distribution of IWU. Existing approaches of deriving IWU may have large uncertainty, due mostly to methodological limitations, inadequate inputs, and the mismatch in spatiotemporal scale between IWU estimates and in situ counterparts. Remote sensing has the potential to provide valuable information on moisture transport, which could unravel water consumption by crops. First, we developed a robust relationship between root zone soil moisture (RZSM) and the ratio of actual evapotranspiration (ETa) to reference ET from the land components of European ReAnalysis‐5 (ERA5L) without an irrigation module across the Contiguous United States (CONUS). Second, RZSM under irrigation was derived from the developed relationship and remotely sensed ETa from the operational Simplified Surface Energy Balance (SSEBop) model during 2000–2020. Third, IWU over the two decades was derived based on increases in RZSM and ETa due to irrigation using remotely sensed and model‐based variables, along with our derived formulas considering groundwater recharge originating from irrigation. The IWU estimates were fairly reliable compared with reported IWU from the Farm and Ranch Irrigation Survey at the state‐level in four years, with the coefficient of determination ranging from 0.74 to 0.84, root mean square error ranging from 1.90 to 2.33 km3/yr, and bias ranging from −0.11 to 0.15 km3/yr. Integration of remotely sensed ETa with ERA5L output resulted in IWU estimates of much higher accuracy than published studies. The IWU estimates across the CONUS reflected an increasing trend (∼2.71 km3/yr2) during 2000–2007 but a decreasing trend (∼0.90 km3/yr2) during 2008–2020, due to efficient irrigation practices and increased precipitation. Plain Language Summary Irrigation water use (IWU) applied by farmers or districts to alleviate crop water stress, is particularly important to assess water use efficiency and to optimize water resources allocation. There have been many studies that proposed approaches to derive IWU that is, however, subject to large uncertainty due to methodological limitations and/or inadequate data input. Remote sensing could provide valuable information on moisture transport induced by climate variability and human intervention, which has the potential to address restrictions on deriving accurate IWU. A novel IWU estimation approach jointly using remotely sensed actual evapotranspiration (ET), modeled root zone soil moisture and actual ET from land components of European ReAnalysis‐5 without an irrigation module, and irrigated area fraction was developed to generate IWU over the contiguous United States (CONUS) during 2000–2020. IWU estimates from the developed approach were evaluated against reported IWU at the state‐level in four years, with accuracy comparable to or higher than existing studies/approaches. Spatially averaged annual IWU estimates in the CONUS increased by 2.71 km3/yr2 during 2000‐2007 but decreased by 0.90 km3/yr2 during 2008–2020. This study has important implications for agricultural management over the CONUS and could be applicable to similar regions globally whose agriculture depends heavily on irrigation. Key Points Irrigation water use (IWU) across the Contiguous United States (CONUS) over the last two decades was estimated using our derived formulas considering ratio of actual evapotranspiration (ETa), root zone soil moisture (RZSM), and groundwater recharge Performance of IWU estimates was evaluated with reported annual IWU and IWW, and showed the utility of this approach over large areas Spatiotemporal variations in IWU were discussed, indicating that the CONUS is not confronted with the paradox of irrigation efficiency
  • Editor: Washington: John Wiley & Sons, Inc
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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