Andy Wong
UC Davis | PhD Candidate
| Subject Areas: | Water Management, Evapotranspiration, Data Science, Remote Sensing |
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ABSTRACT:
Spatial estimates of crop evapotranspiration with high accuracy from the field to watershed scale have become increasingly important for water management, particularly over irrigated agriculture in semi-arid regions. Here, we provide a comprehensive assessment on patterns of annual agricultural water use over California’s Central Valley, using 30-m daily evapotranspiration estimates based on Landsat satellite data. A semi-empirical Priestley-Taylor approach was locally optimized and cross-validated with available field measurements for major crops including alfalfa, almond, citrus, corn, pasture, and rice. The evapotranspiration estimates explained more than 70% variance in daily measurements from independent sites with an RMSE of 0.88 mm day-1. When aggregated over the Valley, we estimated an average evapotranspiration of 820 +- 290 mm yr-1 in 2014. Agricultural water use varied significantly across and within crop types, with a coefficient of variation ranging from 8% for Rice (1110 +- 85 mm yr-1) to 59% for Pistachio (592 +- 352 mm yr-1). Total water use in 2016 increased by 9.6%, as compared to 2014, mostly because of land-use conversion from fallow/idle land to cropland. Analysis across 134 Groundwater Sustainability Agencies (GSAs) further showed a large variation of agricultural evapotranspiration among and within GSAs, especially for tree crops, e.g., almond evapotranspiration ranging from 339 +- 80 mm yr-1 in Tracy to 1240 +- 136 mm yr-1 in Tri-County Water Authority. Continuous monitoring and assessment of the dynamics and spatial heterogeneity of agricultural evapotranspiration provide data-driven guidance for more effective land use and water planning across scales.
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Created: Nov. 22, 2019, 2:46 a.m.
Authors: Wong, Andy · Y. Jin · J. Medellín-Azuara · KT. Paw U · E. R. Kent · J. M. Clay · F. Gao · J. B. Fisher · G. Rivera · C. M. Lee · K. S. Hemes · E. Eichelmann · D. D. Baldocchi · S. J. Hook
ABSTRACT:
Spatial estimates of crop evapotranspiration with high accuracy from the field to watershed scale have become increasingly important for water management, particularly over irrigated agriculture in semi-arid regions. Here, we provide a comprehensive assessment on patterns of annual agricultural water use over California’s Central Valley, using 30-m daily evapotranspiration estimates based on Landsat satellite data. A semi-empirical Priestley-Taylor approach was locally optimized and cross-validated with available field measurements for major crops including alfalfa, almond, citrus, corn, pasture, and rice. The evapotranspiration estimates explained more than 70% variance in daily measurements from independent sites with an RMSE of 0.88 mm day-1. When aggregated over the Valley, we estimated an average evapotranspiration of 820 +- 290 mm yr-1 in 2014. Agricultural water use varied significantly across and within crop types, with a coefficient of variation ranging from 8% for Rice (1110 +- 85 mm yr-1) to 59% for Pistachio (592 +- 352 mm yr-1). Total water use in 2016 increased by 9.6%, as compared to 2014, mostly because of land-use conversion from fallow/idle land to cropland. Analysis across 134 Groundwater Sustainability Agencies (GSAs) further showed a large variation of agricultural evapotranspiration among and within GSAs, especially for tree crops, e.g., almond evapotranspiration ranging from 339 +- 80 mm yr-1 in Tracy to 1240 +- 136 mm yr-1 in Tri-County Water Authority. Continuous monitoring and assessment of the dynamics and spatial heterogeneity of agricultural evapotranspiration provide data-driven guidance for more effective land use and water planning across scales.