Agrometerological study of semi-arid areas : an experiment for analysing the potential of time series of FORMOSAT-2 images (Tensift-Marrakech plain)

Earth Observing Systems designed to provide both high spatial resolution (10m) and high capacity of time revisit (a few days) offer strong opportunities for the management of agricultural water resources. The FORMOSAT-2 satellite is the first and only satellite with the ability to provide daily high-resolution images over a particular area with constant viewing angles. As part of the SudMed project, one of the first time series of FORMOSAT-2 images has been acquired over the semi-arid Tensift-Marrakech plain. Along with these acquisitions, an experimental data set has been collected to monitor land-cover/land-use, soil characteristics, vegetation dynamics and surface fluxes. This paper presents a first analysis of the potential of these data for agrometerological study of semi-arid areas

A new irrigation priority index based on remote sensing data for assessing the networks irrigation scheduling

Irrigation scheduling has become an important tool that significantly influences growth, development and production of crops, especially in arid and semi-arid regions of the South Mediterranean. In these regions, most of the irrigation scheduling of the gravity irrigation networks are not optimized in terms of timing and water quantity. In this paper, we present a way of characterizing the irrigation distribution by the extensively used irrigation systems through a new irrigation index: the "irrigation priority index" (IPI). This normalized indicator takes into account the water stress coefficient and the time of irrigation with regard to the duration of an irrigation round. The IPI ranges between -1 and 1 and decreases with irrigation priority. The IPI was used to evaluate the actual irrigation scheduling in an irrigated perimeter of 2800 ha of Tensift Al Haouz plain close to Marrakech in Morocco during the 2002-2003 winter wheat season. The obtained results showed that about 32% of the R3 zone plots receive late irrigation, when the stress was maximum (IPI less than -0.3). The sensitivity of grain yield to the IPI values was evaluated on a data set of wheat yields acquired on the 2008-2009 season. The spatial yield was simply calculated using a linear relationship between wheat yields and the spatial accumulated NDVI (Normalized Difference Vegetation Index) of the last 10 days of March (R-2 = 0.84). The result showed a clear relationship between grain yield and [PI. Indeed, with significantly positive IPI10.37, 0.63], production ranged from 3.8 to 4.7 t/ha, whereas, it was less than 2.6 t/ha when the IPI values are ranged from -0.52 to -0.16

Assessment of equity and adequacy of water delivery in irrigation systems using remote sensing-based indicators in semi-arid region, Morocco

The irrigation performance criteria of equity and adequacy are of primary concern for irrigation managers. The input data required at various scales to assess irrigation performance, often not available, need costly intensive field campaigns. Remote sensing techniques, used to directly estimate crop evapotranspiration (ETc), became recently an attractive option to assess irrigation performance from individual fields to irrigation scheme or river basin scale. In this study, ETc maps were obtained by combining the FAO-56 dual approach with relationships between crop biophysical variables and NDVI (Normalized Difference Vegetation Index), using high spatial resolution time series of SPOT and Landsat images. This approach was applied for 2002/2003 growing season in Haouz plain, Morocco. Remote sensing-based indicators, reflecting equity and adequacy of the irrigation water delivery were estimated. Adequacy was determined according to Relative Irrigation supply (RIS), Depleted Fraction (DF) and Relative Evapotranspiration (RET) and equity according to the coefficient of variation of ETc. The analysis of these indicators exhibits a great variability among fields. Variability in irrigation performance at all levels, associated factors and possible improvements are discussed. This study demonstrates how remote sensing-based estimates of water consumption provide better estimates of irrigation performance at different scales than the traditional field survey methods

A life-size and near real-time test of irrigation scheduling with a sentinel-2 like time series (SPOT4-Take5) in Morocco

This paper describes the setting and results of a real-time experiment of irrigation scheduling by a time series of optical satellite images under real conditions, which was carried out on durum wheat in the Haouz plain (Marrakech, Morocco), during the 2012/13 agricultural season. For the purpose of this experiment, the irrigation of a reference plot was driven by the farmer according to, mainly empirical, irrigation scheduling while test plot irrigations were being managed following the FAO-56 method, driven by remote sensing. Images were issued from the SPOT4 (Take5) data set, which aimed at delivering image time series at a decametric resolution with less than five-day satellite overpass similar to the time series ESA Sentinel-2 satellites will produce in the coming years. With a Root Mean Square Error (RMSE) of 0.91mm per day, the comparison between daily actual evapotranspiration measured by eddy-covariance and the simulated one is satisfactory, but even better at a five-day integration (0.59mm per day). Finally, despite a chaotic beginning of the experiment-the experimental plot had not been irrigated to get rid of a slaking crust, which prevented good emergence-our plot caught up and yielded almost the same grain crop with 14% less irrigation water. This experiment opens up interesting opportunities for operational scheduling of flooding irrigation sectors that dominate in the semi-arid Mediterranean area

Irrigation scheduling of a classical gravity network based on the Covariance Matrix Adaptation - Evolutionary Strategy algorithm

Irrigation scheduling is an important task that significantly influences water conservation and crop production. For most gravity irrigation networks located in semi-arid areas, irrigation scheduling is based on available water regardless of crops water needs. The objective of this study is to propose a new approach for optimizing irrigation scheduling taking into account crops water demand, based on the Covariance Matrix Adaptation - Evolution Strategy (CMA-ES) evolutionary strategy algorithm. The objective function, that must be minimized, of this optimization problem is defined as the sum of two terms. The first term is the Irrigation Priority Index (IPI) which characterizes the degree of imbalance between water stress and irrigation timing of the plot. The second one takes into account the various constraints that relate to canals capacity, tasks timing, geographical distances and canal flow rate variations. The approach was applied to an agricultural sector located at 40 km from the city of Marrakech (Morocco). Optimal schedule for the third irrigation, of the 2011-2012 agricultural season, is provided and the comparisons between schedules before and after optimization are made. The obtained results demonstrate that such approach allows reducing the proportion of late irrigated plots (from 22% to 8%) and increasing the proportion of plots irrigated at an appropriate time (from 28% to 40%). We conclude that this approach can be considered as an efficient tool for planning irrigation schedules by considering crops water needs

Estimation spatialisée de l'Evapotranspiration des cultures irriguées par télédétection. Application à la gestion de l'Irrigation dans la plaine du Haouz (Marrakech, Maroc).

Satellite monitoring of irrigation (SAMIR) est un logiciel de spatialisation de l'évapotranspiration (ET) et du bilan hydrique des cultures irriguées sur de grandes surfaces, basé sur l'utilisation d'images satellitaires. Cette source d'information fournit une vision synoptique et périodique de la localisation et du développement des cultures, donnée critique pour une estimation fiable de l'ET. Cette dernière est calculée au moyen de la méthode FAO, bien adaptée au calcul sur de grandes surfaces où l'information disponible sur le sol et les cultures est limitée. Le bilan hydrique de la culture est obtenu en couplant au modèle FAO un module sol en trois compartiments (surface, racinaire, profond). Le calcul du bilan nécessite des données liées au climat (estimation de l'ET de référence et précipitations), à l'occupation du sol et à la phénologie de la végétation (pour estimer les coefficients culturaux de la méthode FAO), ces deux dernières données étant issues de la télédétection. Les données concernant l'irrigation sont soit introduites si elles sont connues, soit le plus souvent estimées à partir du calcul du bilan hydrique, en faisant des hypothèses sur la gestion de l'eau pratiquée et notamment sur le taux de stress hydrique toléré. Cet outil est développé en partenariat avec un utilisateur potentiel au Maroc, l'Office régional de mise en valeur agricole du Haouz (ORMVAH). L'irrigation estimée à l'échelle des secteurs irrigués peut être comparée aux apports connus des barrages et des seguias issues des montagnes pour estimer les pompages pratiqués dans la nappe souterraine. Dans un contexte de forte tension sur les ressources en eau, cette application montre les potentialités de l'imagerie satellitaire, pour le suivi du bilan hydrique des surfaces irriguées et la gestion des ressources à l'échelle du bassinversan

Remote Sensing of Water Resources in Semi-Arid Mediterranean Areas : the joint international laboratory TREMA

Monitoring of water resources and a better understanding of the eco-hydrological processes governing their dynamics are necessary to anticipate and develop measures to adapt to climate and water-use changes. Focusing on this aim, a research project carried out within the framework of French-Moroccan cooperation demonstrated how remote sensing can help improve the monitoring and modelling of water resources in semi-arid Mediterranean regions. The study area is the Tensift Basin located near Marrakech (Morocco) - a typical Southern Mediterranean catchment with water production in the mountains and downstream consumption mainly driven by agriculture. Following a description of the institutional context and the experimental network, the main recent research results are presented: (1) methodological development for the retrieval of key components of the water cycle in a snow-covered area from remote-sensing imagery (disaggregated soil moisture from soil moisture and ocean salinity) at the kilometre scale, based on the Moderate Resolution Imaging Spectroradiometer (MODIS); (2) the use of remote-sensing products together with land-surface modelling for the monitoring of evapotranspiration; and (3) phenomenological modelling based only on time series of remote-sensing data with application to forecasting of cereal yields. Finally, the issue of transfer of research results is also addressed through two remote sensing-based tools developed together with the project partners involved in water management and irrigation planning