The 3-year PhD program will be funded by IDEWA (Irrigation and Drainage monitoring by remote sensing for Ecosystems and Water resources management, 2020-2023) project as part of the PRIMA (http://prima-med.org) program. Although the PhD work will be mainly based at CESBIO, Toulouse, mobilities (up to 12 months) to Spain and Morocco will be proposed as part of the Research and Innovation Staff Exchange ACCWA project (https://accwa.isardsat.space/). A top-up allowance of 2100 € per month will be paid to the PhD candidate during mobility periods. A joint supervision (co-tutelle) between Université de Toulouse and Universitat de Lleida is envisaged.
IDEWA aims at monitoring the drainage over irrigated areas at integrated spatial scales and assessing its impact on river outflows and downstream water quality by using remote sensing data. It gathers scientists from Universitat de Lleida (UdL), Observatori de l'Ebre (OE), Instituto di Metodologie per l'Analisi Ambientale (IMAA), Université Cadi Ayyad de Marrakech (UCAM) and Center for the Study of the Biosphere from Space (CESBIO).
Improving water productivity of irrigated land in semiarid areas in the Mediterranean Basin is considered a priority task at European level. There are significant knowledge gaps about how much water will be available for a complete growing season and how much should be used for scheduling irrigation efficiently. Within this framework, it is worth acquiring more information on water exploitation to improve agricultural planning and to better manage water resources at different scales.
Agriculture is a key factor influencing water resources and the relationship between water availability and food production is an open task that deserves to be addressed due to population growth. The Mediterranean countries are particularly sensitive to water resource issues as irrigation can represent up to 70% of water uses. Developing and implementing practical measures and tools that support a more productive and sustainable management of water resources plays a crucial role within the European framework.
IDEWA proposes the development of innovative irrigation management tools based on timely available multi-sensor remote sensing data that will allow monitoring: i) water use and drainage at field and basin scale and ii) the effects on ecosystem. Although drainage is poorly investigated or quantified, it is a key water component controlling both soil salinity over irrigated areas and main stream through return flows. IDEWA aims at explicitly including drainage in the water balance estimation at field and basin scale, in order to link water productivity, water quality and ecosystem preservation issues, and to provide a decision support system useful for their joint management.
The PhD thesis aims to develop the remote sensing tools allowing the water budget to be closed at the scales ranging from the crop field to the irrigated perimeter by taking into account drainage to support a sustainable agriculture. Specifically, the PhD candidate will build on the remote sensing products recently developed over the study area including soil moisture (SM), evapotranspiration (ET) and vegetation water stress indices (VEG) to monitor and assess, for the first time, the drainage term at multiple spatial scales.
We will primarily focus on the irrigated perimeter of Algerri-Balaguer (A-B) located in the Noguera Ribagorçana basin, which a tributary of the Segre river in Spain. This area is unique in the sense that drainage is actually measured at an integrated spatial scale. During the land consolidation 20 years ago, a drainage system had been installed in each field and linked to a network of pipelines buried under the root zone. Such a configuration, akin to a huge passive lysimeter of several thousands of hectares, represents a unique opportunity to develop and test the remote sensing estimation of drainage.
The main challenge will be to understand relationships between irrigation and drainage at integrated spatial scales from the crop field to the irrigated perimeter. It will involve coupling a water budget model based on the dual crop coefficient FAO-56 method (FAO-2Kc) with high-resolution satellite data to simulate the input (irrigation) and output (ET, drainage) water fluxes of irrigated crops. In situ measurements available over several experimental fields will be used to calibrate/validate the remote sensing-based approaches. In particular, we have identified four successive steps in which the FAO-2Kc model will be forced by a vegetation index (Satellite Monitoring of Irrigation, SAMIR software):
- Estimating drainage at the crop field scale (in situ calibration): the drainage modeling will be calibrated at the crop field scale using in situ (SM, VEG and ET) observations.
- Estimating drainage at the crop field scale (satellite calibration): the drainage modeling is calibrated at the crop field scale using remote sensing (SM, VEG and ET) data.
- Estimating drainage at the irrigated perimeter scale (global calibration): the drainage modeling is calibrated at the perimeter scale by adjusting global effective parameters from the drainage observed in situ over A-B.
- Estimating drainage at the irrigated perimeter scale (distributed calibration): the drainage modeling is calibrated independently for each crop field using remote sensing (SM, VEG and ET) data.
The PhD candidate will be in contact with irrigation local community in order to contribute to the bi-directional knowledge transfer i.e. ensure that the researches address the users' needs and that the research results reach the targeted community by strengthening their skills, competencies and abilities.