Estimating Evapotranspiration through Sentinel Missions Imagery and Eddy Covariance Technique in an Irrigated Olive Crop in Andalusia, Spain: Influence of Weed Cover.

Abstract:

Olive tree crops have very important socio-economic benefits and environmental impacts, especially in Mediterranean ecosystems where about 98% of world production is concentrated. In Spain there is 2.7 Mha of which more than a half are in Andalusia (Southeastern Iberian Peninsula). In a context of climate change, and water limitations, it is needed adaptative management actions to facilitate the crop adaptation to these condition and climate change perspective. Hence, one of the most relevant actions is to optimize the efficiency in use and management of water, for which ecosystem evapotranspiration modeling/quantification is needed. Additionally, one common practice applied in olive crop plantations has been the maintenance of spontaneous resident vegetation cover in the alleys from autumn to spring to protect the soil against erosion. Most studies are focused on the effect of weed-cover into soil properties, but little is know about their effects into the ecosystem evapotranspiration. This study is carried out on two parcels of an irrigated olive grove in Jaén (Spain, 3.228639 W, 37.913025 N) under two different treatments: 1) natural weed cover is maintained from autumn to spring, and after this period, weed cover is cut and kept on the surface; 2) weed free cover in which a glyphosate-based herbicide is applied to avoid weed growth. To obtain evapotranspiration estimates the Two Source Energy Balance model (Norman et al., 1995) has been applied as was proposed by Guzinski and Nieto et al. (2019), in which use a fusion methodology (Gao et al., 2012) combining Sentinel-3 SLSTR and Sentinel-2 MSI images in order to upscale the thermal infrared coarser spatial resolution at the optical imagery finer spatial resolution. Actual evapotranspiration was obtained at 20 m of spatial resolution from October 2016 to September 2019, depending on availability of Sentinel images and cloud cover. Estimations obtained were validated matching those with eddy covariance measures, showing root mean square errors of 0.77 mm (weed-free plot) and 0.73 mm (weed-cover plot) in daily evapotranspiration.

Gao, F., Kustas, W. P., & Anderson, M. C. (2012). A data mining approach for sharpening thermal satellite imagery over land. Remote Sensing, 4(11), 3287–3319. https://doi.org/10.3390/rs4113287

Guzinski, R., & Nieto, H. (2019). Evaluating the feasibility of using Sentinel-2 and Sentinel-3 satellites for high-resolution evapotranspiration estimations. Remote Sensing of Environment, 221, 157–172. https://doi.org/10.1016/j.rse.2018.11.019

Norman, J. M., Kustas, W. P., & Humes, K. S. (1995). Source approach for estimating soil and vegetation energy fluxes in observations of directional radiometric surface temperature. Agricultural and Forest Meteorology, 77(3–4), 263–293. https://doi.org/10.1016/0168-1923(95)02265-Y