Benoît Duchemin

• Institute of Research for Development

VALERI : a network of sites and methodology for the validation of medium spatial resolution land products

Regional analysis of water use efficiency (WUE) is a relevant method for diagnosing the performance of irrigation systems in water-limited environments. In this study, we investigated the potential of FORMOSAT-2 images to provide spatial estimates of WUE over irrigated wheat crops cultivated within the semi-arid Yaqui Valley, in the northwest of Me...

The sustainable management of water resources worldwide is one of the most important challenges of the 21st century. In the Tensift-Haouz plain, located in central Morocco and characterized by a semi-arid climate, more than 85% of available water is used for agriculture. Precipitation, which is concentrated over the High-Atlas mountain range, falls...

Compte-tenu de l'importance de la production de blé pour l'économie marocaine, les décideurs doivent disposer d'informations précises sur la production de blé tôt dans la saison afin d'anticiper les besoins en importation. Dans cette étude, nous avons analysé (1) les rendements en blé tendre (1983-2008) de la province de Settat (2) les précipitatio...

The dominant patterns of vegetation cover interannual variability over Morocco are isolated using rotated extended empirical orthogonal functions applied to AVHRR NDVI data (1982–2008). The three leading modes capture the NDVI signal at the vegetation peak for three distinct locations: mode 1 (18.7% of total variance) is located along the Atlantic...

In semi-arid areas, it can be challenging to monitor the crop canopy and the production capacity of plants, especially cereals. In this context, the aim of the present study is to analyze the characteristics of cereals. Firstly, statistical analysis is used to characterize the vegetation's dynamics and grain yield, based on remotely sensed (satelli...

In semi-arid areas, a strongly variable climate represents a major risk for food safety. An operational grain yield forecasting system, which could help decision-makers to make early assessments and plan annual imports, is thus needed. It can be challenging to monitor the crop canopy and production capacity of plants, especially cereals. In this co...

In Morocco, wheat production shows a high inter-annual variability due to uncertain rainfall. In view of the importance of this resource to the country's economy, it is important to gain a better understanding of the natural large-scale climate oscillation governing this variability. In this study, we analyzed de-trended (1) time series of common w...

(Full text: http://w3.avignon.inra.fr/valeri/documents/VALERI-RSESubmitted.pdf) *** Validation is mandatory to quantify the reliability of satellite biophysical products that are now routinely generated by a range of sensors. This paper presents the VALERI project dedicated to the validation of the products derived from medium resolution satellite...

In semi-arid region and especially in irrigated areas, agriculture represents a major contribution to food security. These areas significantly contribute to the increase of global production. A challenging objective is thus to ensure food security. Therefore an operational forecasting system for the grain yields is required and could help decision-...

In semi-arid regions, and northern Africa in particular, the scarcity of rainfall and the occurrence of long periods of drought, represent one of the main environmental factors having a negative effect on agricultural productivity. This is the case in Central Tunisia, where the monitoring of agricultural and water resources is of prime importance....

The objective of this study is to develop an approach for monitoring land use over the semi-arid Tensift–Marrakech plain, a 3000 km2 intensively cropped area in Morocco. In this objective, the linear unmixing method is adapted to process a 6-year archive of Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index...

This paper reports the results of using three empirical methods (Makkink, Priestley-Taylor and Hargreaves) for estimating the reference evapotranspiration (ET 0) in the semi-arid region of Tensift Al Haouz, Marrakech (center of Morocco). The Penman-Monteith equation, standardized by the Food and Agriculture Organization (FAO-PM), is used to evaluat...

The analysis of vegetation dynamics is essential in semi-arid regions, in particular because of the frequent occurrence of long periods of drought. In this paper, multi-temporal series of the Normalized Difference of Vegetation Index (NDVI), derived from SPOT-VEGETATION satellite data between September 1998 and June 2010, were used to analyze the v...

In irrigation schemes under rotational water supply in semi-arid region, the water allocation and irrigation scheduling are often based on a fixed-area proportionate water depth with every irrigation cycle irrespective of crops and their growth stages, for an equitable water supply. An experiment was conducted during the 2004- 2005 season in Haouz...

Understanding the spatial distribution of air temperature in mountainous areas is essential in hydrological modelling. In the Moroccan High-Atlas range, the meteorological stations network is sparse. In order to get additional information, we investigated the thermal infrared data supplied by the Enhanced Thematic Mapper (ETM+) sensor onboard the L...

The present paper proposes a method for the evaluation of soil evaporation, using soil moisture estimations based on radar satellite measurements. We present firstly an approach for the estimation and monitoring of soil moisture in a semi-arid region in North Africa, using ENVISAT ASAR images, over two types of vegetation covers. The first mapping...

The objective of this study is to get a better understanding of radar signal over irrigated wheat fields and to assess the potentialities of radar observations for the monitoring of soil moisture. Emphasis is put on the use of high spatial and temporal resolution satellite data (Envisat/ASAR and Formosat-2). Time series of images were collected ove...

On the basis of a 12 year time series of snow indices derived from SPOT/VEGETATION radiances, we present an analysis of the interannual variability of mountains snow coverage in the Himalayan mountains. This analysis is principally performed with regard to the interannual meteorological fluctuations like the South Asian Monsoon and the mid latitude...

The temporal frequency of the thermal data provided by current spaceborne high-resolution imagery systems is inadequate for agricultural applications. As an alternative to the lack of high-resolution observations, kilometric thermal data can be disaggregated using a green (photosynthetically active) vegetation index e.g. NDVI (Normalized Difference...

In this paper, we propose an approach for the estimation and monitoring of soil moisture in a semi-arid region in North Africa, using ENVISAT ASAR images. Our approach is based on soil moisture mapping over two types of vegetation covers. The first mapping process is dedicated solely to the monitoring of moisture variability related to rainfall eve...

The SudMed project aims since 2002 at modelling the hydrological cycle in the Tensift semi arid watershed located in central Morocco. To reach these modelling objectives, emphasis is put on the use of high and low resolution remote sensing data, in the visible, near infrared, thermal, and microwave domains, to initialize, to force or to control the...

The aim of this study is to propose methods to improve crop and water management in Mediterranean regions. At landscape scale, there is a very large spatial variability of agricultural practices, particularly for grasslands irrigated by flooding. These grasslands are harvested three times per year and produce high quality hay, but their productions...

The aim of this study is to propose methods to improve crop and water management in Mediterranean regions. At landscape scale, there is a spatial variability of agricultural practices, particularly for grasslands irrigated by flooding. These grasslands are harvested three times per year and produce high quality hay, but their productions decreased...

The objective of this study is to get a better understanding of radar signal over irrigated wheat fields and to assess the potentialities of radar observations for the monitoring of soil moisture. Emphasis is put on the use of high spatial and temporal resolution satellite data (ENVISAT/ASAR and FORMOSAT-2). Time series of images were collected ove...

The present paper proposes an empirical approach for the modeling of vegetation development, using moisture measurements only. The study is based simply on the use of two databases: one containing soil moisture products derived from ERS scatterometer data over the period 1991-2006 and the other containing normalized difference vegetation indices (N...

Carbon and water cycles are closely related to agricultural activities. Agriculture has been indeed identified by IPCC 2007 report as one of the options to sequester carbon in soil. Concerning the water resources, their consumptions by irrigated crops are called into question in view of demographic pressure. In the prospect of an assessment of carb...

The potential of FORMOSAT-2 and ENVISAT/ASAR for the monitoring of irrigated wheat crops over Tensift/Marrakech semi-arid plain in Morocco is investigated. The green leaf area index (GLAI) was obtained from time series of vegetation index acquired by the FORMOSAT-2 instrument with a 25% accuracy. This information was then incorporated into a canopy...

The High-Atlas Mountainous region in Morocco is a true Water tower for the neighbouring arid plains, where the water resources at e intensively and increasingly Subjected to exploitation for agriculture and tourism In order to manage this resource sustainably, it is necessary to describe accurately all the processes that contribute to the hydrologi...

The aim of this study was to combine the FAO-56 dual approach and remotely-sensed data for mapping water use (ETc) in irrigated wheat crops of a semi-arid region. The method is based on the relationships established between Normalized Difference Vegetation Index (NDVI) and crop biophysical variables such as basal crop coefficient, cover fraction an...

Résumé : Cette étude consiste à utiliser les données de télédétection pour obtenir des informations spatialisées sur les dates de semis et sur la fertilisation de la culture de blé dans la région des Alpilles dans le Sud-Est de la France. Le travail a été réalisé en trois étapes: 1) L'indice foliaire (LAI, Leaf Area Index) a été estimé à partir des...

The objective of this study is to get a better understanding of radar signal over irrigated wheat fields and to assess the potentialities of radar observations for the monitoring of soil moisture. Emphasis is put on the use of high spatial and temporal resolution satellite data (ENVISAT/ASAR and FORMOSAT-2). Time series of images were collected ove...

On the basis of a 10 year time series of snow indices derived from radiances sensed by the SPOT/VEGETATION satellites, we present an analysis of the interannual variability of mountains snow coverage around the Mediterranean basin. This analysis is principally performed with regard to the Northern Atlantic Oscillation (NAO) which can be considered...

In the centre of Morocco, the High Atlas mountain range represents the most important water storage for the neighbouring arid plains through liquid and solid precipitation. In this context, we evaluated the performance of the Snowmelt Runoff Model (SRM) on the five main tributary watersheds of the High Atlas range. Due to the very low density of cl...

This study focused on the feasibility of using remote sensing data acquired at high spatial and temporal resolution (FORMOSAT-2 images(http://www.spotimage.fr/web/en/977--formosat-2-images.php) for crop monitoring at regional scale. The monitoring of agricultural practices such as grassland mowing and irrigation is essential to simulate accurately...

The recent availability of high spatial resolution sensors offers new perspectives for terrestrial applications (agriculture, risks). The aim of this work is to develop a methodology for deriving biophysical variables (Green Leaf Area Index - GLAI, phytomass) from multi-temporal observations at high spatial resolution in order to run a crop model a...

The objective of this study is to present a new application of optical and radar remote sensing with high spatial (∼10 m) and temporal (a few days) resolutions for the detection of tillage and irrigation operations. The analysis was performed for irrigated wheat crops in the semi-arid Tensift/Marrakech plain (Central Morocco) using three FORMOSAT-2...

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, donn...

In the centre of Morocco, the High-Atlas range represents the most important water storage for the neighbouring arid plains through liquid but also solid precipitation. Snow in this mountain may represent an important source of water for downstream populations especially in spring and early summer. Therefore, monitoring efficiently the evolution of...

Leaf area index (LAI) is the main determinant of light interception, and, thus of canopy assimilation and transpiration. For tree orchards, measurements of LAI using direct methods are extremely difficult, expensive, and often not feasible. In this study, the objective is to evaluate two indirect methods: plant canopy analyser (PCA, LAI-2000) and h...

Irrigated agriculture is the largest consumer of water worldwide, and especially in semi-arid areas such as southern Mediterranean countries. Agricultural water use is difficult to estimate over large areas, since several irrigation networks may co-exist and since farmers operate private pumping stations. In this context, the objective of this work...

SAMIR is software computing spatialized estimates of evapotranspiration (ET) and irrigation water budget on large areas, based on the use of satellite images. Remote sensing offers a synoptic view of the vegetation development, which is a key information for ET reliable computing. ET is obtained using the FAO method, well suited for computation ove...

SAMIR is software computing spatialized estimates of evapotranspiration (ET) and irrigation water budget on large areas, based on the use of satellite images. Remote sensing offers a synoptic view of the vegetation development, which is a key information for ET reliable computing. ET is obtained using the FAO method, well suited for computation ove...

Recent efforts have been concentrated in the development of models to understand and predict the impact of environmental changes on hydrological cycle and water resources in arid and semi-arid regions. In this context, remote sensing data have been widely used to initialize, to force, or to control the simulations of these models. However, for seve...

Recent efforts have been concentrated in the development of models to understand and predict the impact of environmental changes on hydrological cycle and water resources in arid and semi-arid regions. In this context, remote sensing data have been widely used to initialize, to force, or to control the simulations of these models. However, for seve...

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 con...

In this study we investigated the perspective offered by coupling a simple vegetation growth model and ground-based remotely-sensed data for the monitoring of wheat production. A simple model was developed to simulate the time courses of green leaf area index (GLAI), dry above-ground phytomass (DAM) and grain yield (GY). A comprehensive sensitivity...

This paper presents a new method developed for the atmospheric correction of the images that will be acquired by the Venμs satellite after its launch expected in early 2010. Every two days, the Venμs mission will provide 10 m resolution images of 50 sites, in 12 narrow spectral bands ranging from 415 nm to 910 nm. The sun-synchronous Venμs orbit wi...

The aim of this study is to use the FAO-56-based single crop coefficient approach to estimate actual evapotranspiration (AET) of an olive (Olea europaea L.) orchard in the Mediterranean semi arid region of Tensift-basin (central Morocco) during two consecutive growing seasons (2003 and 2004). The results showed that using crop coefficients Kc sugge...

A time series of eight high-resolution Landsat TM images, ranging over the crop season, has been acquired over an irrigated area in central Morocco. From this time series, a Normalized Difference Vegetation Index (NDVI) profile was generated for each pixel. In order to get significant profiles, the images were radiometrically corrected, first, usin...

Recent efforts have been concentrated in the development of models to understand and predict the impact of environmental changes on hydrological cycle and water resources in arid and semi-arid regions. In this context, remote sensing data have been widely used to initialize, to force or to control the simulations of these models. However, for sever...

Remote sensing data in the thermal infra red (TIR) part of the spectrum provides indirect estimates of water stress – defined as a function of the ratio between actual and potential evaporation rates – at the earth surface. During the first stage of evaporation (‘‘energy limited'' evaporation), this ratio is close to one. During the second stage of...

The knowledge of land cover is a prerequisite for efficient agricultural water management and sustainable development of semi-arid areas. Remote sensing is the only feasible mean of providing this information with a consistent space and time basis. In this context, the objective of this communication is to present a first analysis of high resolutio...

In the first part of this work, the shoot growth module and grain yield of the STICS crop model were calibrated and validated by using field data which was collected from irrigated winter wheat fields in the Haouz plain near Marrakech. The calibration was performed on the thermal units between the four phenological stages that control the dynamics...

Experimental studies indicate that evaporative fraction (EF), the ratio between the latent heat flux and the available energy at the land surface, is a normalized diagnostic that is nearly constant during daytime under fair weather conditions (so-called daytime self-preservation). This study examines this observation and investigates contributions...

Land surface emissivity in the thermal infrared usually increases when the vegetation amount increases, reaching values that are larger than 0.98. During an experiment in Morocco over dry barley crops, it was found that emissivity may be significantly lower than 0.98 at full cover and that in some situations, it might decrease with increasing amoun...

This study was performed to test three methods based on the FAO-56 "dual" crop coefficient approach to estimate actual evapotranspiration (AET) for winter wheat under different irrigation treatments in the semi-arid region of Tensift Al Haouz, Marrakech (center of Morocco). The three methods differ in the calculation of the basal crop coefficient (...

In the first part of this work, the shoot growth module and grain yield of the STICS crop model were calibrated and validated by using field data which was collected from irrigated winter wheat fields in the Haouz plain near Marrakech. The calibration was performed on the thermal units between the four phenological stages that control the dynamics...

La chaîne montagneuse du Haut Atlas marocain constitue un véritable château d'eau pour les plaines arides avoisinantes. C'est le cas de la plaine du Haouz dans la région de Marrakech, où les ressources en eaux connaissent une exploitation intensive (activités agricoles et tourisme). La gestion durable de ces ressources est ainsi une priorité pour l...

Usually, reflectance time series in the visible or near-infrared domain, such as those provided by SPOT satellites or by wide field of view instruments (VGT, MERIS, MODIS) are degraded by two geo-physical sources of variability: 1) atmospheric effects, mainly because of aerosol scattering, difficult to correct because Aerosol Optical Properties (AO...

The rationale of this research is to investigate approaches based on modelling and remote sensing data for estimating the spatial distribution of yield and irrigation of wheat in semi-arid areas. The specific objective is to compare the performances of two approaches to test the STICS crop model using remotely sensed estimates of leaf area index (L...

The monitoring of crop production and irrigation at a regional scale can be based on the use of ecosystem process models and remote sensing data. The former simulate the time courses of the main biophysical variables which affect crop photosynthesis and water consumption at a fine time step (hourly or daily); the latter allows to provide the spatia...

Earth Observing Systems designed to provide both high spatial resolution (10 m) and frequent time of revisit (a few days) offer strong opportunities for the management of terrestrial water and agricultural resources. The FORMOSAT-2 taiwanese satellite is the first and only system with the ability to provide daily images over a particular area at a...

Dynamics of snow in semi-arid mountains are poorly investigated despite the fact that snow may represent an important source of water for downstream populations especially in the spring and early summer. Data acquired by space-borne optical sensors (i.e. reflectance and derived snow indices) may be suitable for spatial and temporal monitoring of sn...

We summarize a state-of-the-art aerosol assimilation effort aimed at recreating the 4D aerosol (including dust and anthropogenic aerosols) heating rates and surface solar fluxes in Asia. This project was launched to better understand aerosols, their radiative forcing and regional climatic impacts in Asia. The PNNL regional model was used to provide...

Global temporal composites of surface reflectances are among the most commonly used products of wide field-of-view satellite-borne instruments such as the Advanced Very High Resolution Radiometer (AVHRR), the MODerate resolution Imaging Spectroradiometer (MODIS) and VEGETATION. The multi-temporal and spatial consistencies of these composites are ke...

The objectives of the VALERI project are to provide high spatial resolution maps of biophysical variables typically LAI, fAPAR and fCover, estimated with site-based ground measurements to validate products derived from satellite observations. For this purpose, the VALERI project offers: - a methodological framework designed for the derivation of th...

For a regional assessment of water needs and consumption in semiarid agricultural zones, one needs robust and simple tools that provide space-time estimates of evaporation losses. Most operational evaporation estimates rely on semiempirical relationships that are not generally applicable. Several authors have proposed physically based simple expres...

Une étude expérimentale des paramètres géométriques d’un couvert végétal a été faite, par la méthode des silhouettes, sur un couvert de maïs durant le stade de remplissage des grains. Ce stade est connu d’être influencé par la température des grains qui est à son tour très sensible à la géométrie du couvert. Les résultats obtenus ont montré une var...

During the 1999/2000 agricultural seasons, an experiment was carried out on winter wheat fields in the semiarid Yaqui Valley (Northwest Mexico). This data set was used to calibrate the evolution of the leaf area index (LAI) simulated by STICS, which was found to be in excellent agreement with estimates obtained from field reflectance measurements....

Abstract – During the 1999/2000 agricultural seasons, an experiment was carried out on winter wheat fields in the semiarid Yaqui Valley(Northwest Mexico). This data set was used to calibrate the evolution of the leaf area index (LAI) simulated by STICS, which was found to bein excellent agreement with estimates obtained from field reflectance measu...

The VEGETATION instrument is the starting point of a European Earth monitoring system that was developed jointly by France, the European Commission, Belgium, Italy and Sweden. Since April 1998, VEGETATION has provided a high quality global monitoring of the day-to-day land cover dynamics at 1 km resolution. The whole dataset is now available free o...

The SUD-MED project aims at monitoring water resources over Mediterranean regions. As part of the project, this paper presents a method we developed for estimating cereal water requirement. The method consists in driving the simple model developed by the FAO with remotely-sensed data. It was tested on an little area cultivated with wheat in the sem...

This study is part of the SUDMED project from IRD (Research Institute for Development), CESBIO, University of Marrakech and Moroccan administrations in charge of agriculture, forestry and water management. The objective of this project is the hydro-ecological modeling of hydrological resources on the Marrakech region. In this context, it is importa...

This paper presents a new approach to aggregate spatially distributed land surface heat fluxes and landscape characteristics, adopting a probabilistic point of view and using remote sensing data. This method is tested in the Marrakech plain (Morocco), with different remote sensing sensors, and different probabilistic approaches, in order to reach t...