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Altitudinal and temporal evapotranspiration dynamics via remote sensing and vegetation index-based modelling over a scarce-monitored, high-altitudinal Andean páramo ecosystem of Southern Ecuador

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In the tropical Andes, the páramo ecosystem is known as water towers and the main water supplier for the cities of the Andean region. Nevertheless, considering that evapotranspiration (ET) is the major water loss and the lack of in situ evapotranspiration measurements in high altitudinal páramo ecosystems, ET dynamics on the hydrological regulation remains largely unexplored. Therefore, to close this gap, we focused on a remote sensing approach. This study addressed the altitudinal and temporal dynamics of actual evapotranspiration using a crop coefficient based on a Vegetation Index (VI) model. Enhanced Vegetation Index (EVI), Normalized Difference Vegetation Index (NDVI) and Soil-Adjusted Vegetation Index (SAVI) retrieved from Landsat imagery were evaluated. Four remote sensing images and ground-level meteorological data for a 10-month period were used to create ET maps from each VI. A cubic spline interpolation was used to obtain daily ET time series between two satellite overpass dates. Aggregated monthly values were used to validate against ET calculated from water balance. Results revealed that EVI-based ET outperformed the other VI-based ET. The results showed 30% of subestimation (Pbias%) in relation to the water balance. For upgraded results, an extended satellite images time series and a fine calibration are needed. Regarding the altitudinal variability, ET exhibited a strong dependence on land cover characteristics. Our work provides a plausible method to estimate ET in páramo ecosystems in the absence of ET measurements and with a scarcity of clear sky images, further evaluation is necessary to improve ET estimations using remote sensing in the future.
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Vol.:(0123456789)
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Environmental Earth Sciences (2019) 78:340
https://doi.org/10.1007/s12665-019-8337-6
ORIGINAL ARTICLE
Altitudinal andtemporal evapotranspiration dynamics
viaremote sensing andvegetation index‑based modelling
overascarce‑monitored, high‑altitudinal Andean páramo ecosystem
ofSouthern Ecuador
MayraRamón‑Reinozo1· DanielaBallari2· JuanJ.Cabrera1· PatricioCrespo1· GaloCarrillo‑Rojas1,3
Received: 19 October 2018 / Accepted: 18 May 2019 / Published online: 31 May 2019
© Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
In the tropical Andes, the páramo ecosystem is known as water towers and the main water supplier for the cities of the Andean
region. Nevertheless, considering that evapotranspiration (ET) is the major water loss and the lack of insitu evapotranspi-
ration measurements in high altitudinal páramo ecosystems, ET dynamics on the hydrological regulation remains largely
unexplored. Therefore, to close this gap, we focused on a remote sensing approach. This study addressed the altitudinal and
temporal dynamics of actual evapotranspiration using a crop coefficient based on a Vegetation Index (VI) model. Enhanced
Vegetation Index (EVI), Normalized Difference Vegetation Index (NDVI) and Soil-Adjusted Vegetation Index (SAVI)
retrieved from Landsat imagery were evaluated. Four remote sensing images and ground-level meteorological data for a
10-month period were used to create ET maps from each VI. A cubic spline interpolation was used to obtain daily ET time
series between two satellite overpass dates. Aggregated monthly values were used to validate against ET calculated from
water balance. Results revealed that EVI-based ET outperformed the other VI-based ET. The results showed 30% of sub-
estimation (Pbias%) in relation to the water balance. For upgraded results, an extended satellite images time series and a fine
calibration are needed. Regarding the altitudinal variability, ET exhibited a strong dependence on land cover characteristics.
Our work provides a plausible method to estimate ET in páramo ecosystems in the absence of ET measurements and with a
scarcity of clear sky images, further evaluation is necessary to improve ET estimations using remote sensing in the future.
Keywords Evapotranspiration· Ecuador· Crop coefficient· Páramo· Remote sensing
Introduction
The tropical Andes is one of the most outstanding biodi-
verse regions of the world. This Hotspot extends through
five countries: Venezuela, Colombia, Ecuador, Bolivia and
Peru. One of the main ecosystems in the Andes mountains
is the páramo (from 3000 to 4500m.a.s.l), which is known
as South America’s water towers, being the major water
supplier for domestic, agricultural, and industrial use and
for hydroelectric power generation (Crespo etal. 2011).
In addition, the high altitudinal páramo sustains great end-
emism, as well as other tropical ecosystems downstream
* Mayra Ramón-Reinozo
mali-er2@hotmail.com
Daniela Ballari
dballari@uazuay.edu.ec
Juan J. Cabrera
juan.cabrerab91@ucuenca.edu.ec
Patricio Crespo
patricio.crespo@ucuenca.edu.ec
Galo Carrillo-Rojas
galo.carrillo@ucuenca.edu.ec
1 Departamento de Recursos Hídricos y Ciencias Ambientales,
Facultad de Ingeniería, Facultad de Ciencias Químicas,
Facultad de Ciencias Agropecuarias, Universidad de Cuenca,
Ecocampus Balzay, Cuenca010203, Ecuador
2 Facultad de Ciencia y Tecnología, Instituto de Estudios de
Régimen Seccional del Ecuador, Universidad del Azuay,
Av. 24 de Mayo s/n, Cuenca010204, Ecuador
3 Laboratory forClimatology andRemote Sensing,
Faculty ofGeography, Philipps-Universität Marburg,
Deutschhausstr. 12, Marburg35032, Germany
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... The rapid development of remote sensing technology has promoted the retrieval of information on regional ET, making it an important research direction (Liu et al. 2017a, Delogu et al. 2018, Ferreira Silva et al. 2019. Remote sensing overcomes the shortcomings of manual measurements to obtain point data and significantly reduces the workload of field investigations (Ramon-Reinozo et al. 2019). Various ET calculation methods based on remote sensing data have been developed (Zhang et al. 2016;Strbac et al. 2017;Ramon-Reinozo et al. 2019). ...
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