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Papers by Vincent Simonneaux
International Journal of Remote Sensing, 2008
Recent efforts have been concentrated in the development of models to understand and predict the ... more 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 several reasons, including the difficulty in establishing relationships between observational and model variables, the potential offered by satellite data has not been fully used. As a matter of fact, a few hydrological studies that use remote sensing data emanating from different sources (sensors, platforms) have been performed. In this context, the SUDMED programme has been designed in 2002 to address the issue of improving our understanding about the hydrological functioning of the Tensift basin, which is a semi-arid basin situated in central Morocco. The first goal is model development and/or refinement, for investigating the hydrological responses to future scenario about climate change and human pressure. The second aim is the effective use of remote sensing observations in conjunction with process models, to provide operational prognostics for improving water-resource management. The objective of this paper is to present the SUDMED programme, its objectives, and its thrust areas, and to provide an overview of
We present a robust an reproducible method to map the main land cover classes in an irrigated are... more We present a robust an reproducible method to map the main land cover classes in an irrigated area near Marrakech (bare soil, herbaceous crops, trees on bare soil, trees on herbaceous understory), using a time series of 9 SPOT high resolution images. The images were first radiometricaly corrected in reflectance using a physical model (SMAC) [6], then applying an adjustment based on invariant objects located on the scene [8]. The 9 images were then used to generate a NDVI profile for each pixel, which was analyzed using simple decision rules [3][5] to assign it to a landcover class, considering simple criteria like the minimum, maximum, and dynamic of the NDVI [2][5].
RESUME Située au cœur du Haut Atlas central, la vallée des Ait Bouguemez abrite une trentaine de ... more RESUME Située au cœur du Haut Atlas central, la vallée des Ait Bouguemez abrite une trentaine de villages. Sur chaque village, les ressources forestières sont représentées essentiellement par des junipéraies rouges et thuriféraies. Elles font l’objet d’une territorialisation spatiale et temporelle sous l’institution de l’«Agdal» qui désigne l’ensemble des règles d’usages correspondant à des mises en défens traditionnelles définissant l’alternance de périodes d’ouvertures et de fermetures du territoire. L’objectif de ce travail est d’évaluer l’impact de ce mode de gestion séculaire sur la dynamique forestière dans cette zone de montagne. Mots clés : Genévrier, Agdal, Dynamique forestière, Télédétection. ABSTRACT Impact of collective management of natural populations of Juniper on forestry dynamics in a mountain’s valley: Case of the high valley of Ait Bouguemez (Central High Atlas, Morocco) Located in the middle of the Central High Atlas, between 1800 and 2200 meters, the Ait Bouguem...
Distributed hydrological modelling in cropland areas requires an accurate estimation of evapotran... more Distributed hydrological modelling in cropland areas requires an accurate estimation of evapotranspiration (ET). Remotely sensed data can support ET computation by providing valuable information on the vegetation condition. Here, we assessed the potential of high-resolution satellite imagery to monitor crop evapotranspiration over a small rural catchment area of South-West France (3.35 km2). We used a series of 88 Normalized Difference Vegetation Index (NDVI) maps spanning 2006-2009 derived from Formosat-2 images (8-m spatial resolution) to drive a dual crop coefficient model (SAMIR model). This model is based on the FAO-56 method and includes a conceptual soil module to account for soil water storage and drainage. The model was first applied at the plot scale (i.e. in 1-D mode) over a research site located in the watershed, which is instrumented with an eddy covariance system and soil moisture probes. This comparison enabled to identify the most critical model parameters and to adj...
A time series of 27 Landsat images (MSS and TM) over an ecological study area in Tunisia has been... more A time series of 27 Landsat images (MSS and TM) over an ecological study area in Tunisia has been georeferenced and resampled. Conversion of DNs into ground reflectance has been done in two steps: full atmospheric correction of the most recent images and regression method with pseudo-invariant features detected through statistical analysis. Three different approaches of change detection have been tested : change in classes through time, vegetation and colour indices linear trend analysis and Fourier decomposition. Strong degradation and then recovery has been evidenced during the 30 years time span, demonstrating the necessity of long term monitoring for desertification assessment.
The Rheraya watershed (225 km2) is located in a semi-arid climat, in the High Atlas of Morocco. T... more The Rheraya watershed (225 km2) is located in a semi-arid climat, in the High Atlas of Morocco. The land cover includes mainly degraded rangelands on the slopes, and some irrigated crops in the valleys. The average annual rainfall ranges between 300 and 500 mm depending on the site location. Six erosion plots of about 150 m2, located on various soil and land cover conditions were measured during four years. The observations showed very rare runoff events in the main part of the watershed, and producing a low sediment load (between 0.015 and 2.5 t/ha/year). Conversely, runoff was much more frequent on silty badlands, producing about 95% of the watershed sediment (350 t/ha/year) despite their area was only 1% of the watershed. The resulting average erosion over the watershed was about 3-4 t/ha/year, which is of the same order than the mean sediment exportation at the outlet, indicating a sediment delivery ratio around 1. STREAM is a semi empirical distributed erosion model initially designed for agricultural landscapes, taking into account as the main drivers of erosion, the vegetation cover, the soil surface states and the soil roughness. These surface characteristics are input by the user for each pixel, allowing the computing of the infiltration capacity and the runoff turbidity. STREAM works for single rain events, and uses a simple hortonian hypothesis for runoff generation for each pixel, which is subsequently routed down slope using a DEM. The adaptation of this model to the very different context of the Rheraya catchment, with mostly rangelands instead of crops, led us to identify three new drivers of soil infiltration and turbidity, namely the soil type, the soil protection by vegetation or stones, and the soil conservation practices. Infiltration and turbidity for each landscape unit were quantified based on the in situ erosion plot measurements. The results of STREAM simulations for single events were compared to measurements at the catchment's outlet. Despite an overall agreement for the cumulated values over one year, strong discrepancies appears for individual events, due mainly to the fact that STREAM doesn't manage the river bed processes, deposition and erosion, which delay and buffer the sediment delivery.
SAMIR is software computing spatialized estimates of evapotranspiration (ET) and irrigation water... more 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 over large areas, where little information is usually available about crops and soils. The computation of the water budget requires climatic data (reference ET — namely "ET0" — and rainfall data), land cover data, and crop development data (for estimating crop coefficients of the FAO method), these last two types of data being obtained from remote sensing. Irrigation may be an input when it is known, but it is most of the time estimated from the computation of the water budget, using hypotheses on the water management modes and especially the average water stress level allowed. The irrigation estimates at the scale of irrigation sec...
International Journal of Remote Sensing
International Journal of Remote Sensing, 2008
Recent efforts have been concentrated in the development of models to understand and predict the ... more 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 several reasons, including the difficulty in establishing relationships between observational and model variables, the potential offered by satellite data has not been fully used. As a matter of fact, a few hydrological studies that use remote sensing data emanating from different sources (sensors, platforms) have been performed. In this context, the SUDMED programme has been designed in 2002 to address the issue of improving our understanding about the hydrological functioning of the Tensift basin, which is a semi-arid basin situated in central Morocco. The first goal is model development and/or refinement, for investigating the hydrological responses to future scenario about climate change and human pressure. The second aim is the effective use of remote sensing observations in conjunction with process models, to provide operational prognostics for improving water-resource management. The objective of this paper is to present the SUDMED programme, its objectives, and its thrust areas, and to provide an overview of
We present a robust an reproducible method to map the main land cover classes in an irrigated are... more We present a robust an reproducible method to map the main land cover classes in an irrigated area near Marrakech (bare soil, herbaceous crops, trees on bare soil, trees on herbaceous understory), using a time series of 9 SPOT high resolution images. The images were first radiometricaly corrected in reflectance using a physical model (SMAC) [6], then applying an adjustment based on invariant objects located on the scene [8]. The 9 images were then used to generate a NDVI profile for each pixel, which was analyzed using simple decision rules [3][5] to assign it to a landcover class, considering simple criteria like the minimum, maximum, and dynamic of the NDVI [2][5].
RESUME Située au cœur du Haut Atlas central, la vallée des Ait Bouguemez abrite une trentaine de ... more RESUME Située au cœur du Haut Atlas central, la vallée des Ait Bouguemez abrite une trentaine de villages. Sur chaque village, les ressources forestières sont représentées essentiellement par des junipéraies rouges et thuriféraies. Elles font l’objet d’une territorialisation spatiale et temporelle sous l’institution de l’«Agdal» qui désigne l’ensemble des règles d’usages correspondant à des mises en défens traditionnelles définissant l’alternance de périodes d’ouvertures et de fermetures du territoire. L’objectif de ce travail est d’évaluer l’impact de ce mode de gestion séculaire sur la dynamique forestière dans cette zone de montagne. Mots clés : Genévrier, Agdal, Dynamique forestière, Télédétection. ABSTRACT Impact of collective management of natural populations of Juniper on forestry dynamics in a mountain’s valley: Case of the high valley of Ait Bouguemez (Central High Atlas, Morocco) Located in the middle of the Central High Atlas, between 1800 and 2200 meters, the Ait Bouguem...
Distributed hydrological modelling in cropland areas requires an accurate estimation of evapotran... more Distributed hydrological modelling in cropland areas requires an accurate estimation of evapotranspiration (ET). Remotely sensed data can support ET computation by providing valuable information on the vegetation condition. Here, we assessed the potential of high-resolution satellite imagery to monitor crop evapotranspiration over a small rural catchment area of South-West France (3.35 km2). We used a series of 88 Normalized Difference Vegetation Index (NDVI) maps spanning 2006-2009 derived from Formosat-2 images (8-m spatial resolution) to drive a dual crop coefficient model (SAMIR model). This model is based on the FAO-56 method and includes a conceptual soil module to account for soil water storage and drainage. The model was first applied at the plot scale (i.e. in 1-D mode) over a research site located in the watershed, which is instrumented with an eddy covariance system and soil moisture probes. This comparison enabled to identify the most critical model parameters and to adj...
A time series of 27 Landsat images (MSS and TM) over an ecological study area in Tunisia has been... more A time series of 27 Landsat images (MSS and TM) over an ecological study area in Tunisia has been georeferenced and resampled. Conversion of DNs into ground reflectance has been done in two steps: full atmospheric correction of the most recent images and regression method with pseudo-invariant features detected through statistical analysis. Three different approaches of change detection have been tested : change in classes through time, vegetation and colour indices linear trend analysis and Fourier decomposition. Strong degradation and then recovery has been evidenced during the 30 years time span, demonstrating the necessity of long term monitoring for desertification assessment.
The Rheraya watershed (225 km2) is located in a semi-arid climat, in the High Atlas of Morocco. T... more The Rheraya watershed (225 km2) is located in a semi-arid climat, in the High Atlas of Morocco. The land cover includes mainly degraded rangelands on the slopes, and some irrigated crops in the valleys. The average annual rainfall ranges between 300 and 500 mm depending on the site location. Six erosion plots of about 150 m2, located on various soil and land cover conditions were measured during four years. The observations showed very rare runoff events in the main part of the watershed, and producing a low sediment load (between 0.015 and 2.5 t/ha/year). Conversely, runoff was much more frequent on silty badlands, producing about 95% of the watershed sediment (350 t/ha/year) despite their area was only 1% of the watershed. The resulting average erosion over the watershed was about 3-4 t/ha/year, which is of the same order than the mean sediment exportation at the outlet, indicating a sediment delivery ratio around 1. STREAM is a semi empirical distributed erosion model initially designed for agricultural landscapes, taking into account as the main drivers of erosion, the vegetation cover, the soil surface states and the soil roughness. These surface characteristics are input by the user for each pixel, allowing the computing of the infiltration capacity and the runoff turbidity. STREAM works for single rain events, and uses a simple hortonian hypothesis for runoff generation for each pixel, which is subsequently routed down slope using a DEM. The adaptation of this model to the very different context of the Rheraya catchment, with mostly rangelands instead of crops, led us to identify three new drivers of soil infiltration and turbidity, namely the soil type, the soil protection by vegetation or stones, and the soil conservation practices. Infiltration and turbidity for each landscape unit were quantified based on the in situ erosion plot measurements. The results of STREAM simulations for single events were compared to measurements at the catchment's outlet. Despite an overall agreement for the cumulated values over one year, strong discrepancies appears for individual events, due mainly to the fact that STREAM doesn't manage the river bed processes, deposition and erosion, which delay and buffer the sediment delivery.
SAMIR is software computing spatialized estimates of evapotranspiration (ET) and irrigation water... more 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 over large areas, where little information is usually available about crops and soils. The computation of the water budget requires climatic data (reference ET — namely "ET0" — and rainfall data), land cover data, and crop development data (for estimating crop coefficients of the FAO method), these last two types of data being obtained from remote sensing. Irrigation may be an input when it is known, but it is most of the time estimated from the computation of the water budget, using hypotheses on the water management modes and especially the average water stress level allowed. The irrigation estimates at the scale of irrigation sec...
International Journal of Remote Sensing