Jean Michel Martinez

Institute of Research for Development | IRD · 234 - Geosciences Environnement Toulouse (GET)

Satellite images can now be used to assess river sediment discharge, and systematic studies over rivers and lakes are required to support such applications and document the variability of inland water optical properties at the watershed scale. The optical properties of the Amazon Basin waters were analyzed from in situ measurements of the remote se...

River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle1. A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial ecosystems2. It is generally assumed that inland waters emit c...

This work aimed to assess the potential of unmanned aerial vehicle (UAV) multi- and hyper-spectral platforms to estimate chlorophyll-a (Chl-a) and cyanobacteria in experimental fishponds in Brazil. In addition to spectral resolutions, the tested platforms differ in the price, payload, imaging system, and processing. Hyperspectral airborne surveys w...

Dissolved organic matter (DOM) is a crucial component of continental aquatic ecosystems. It plays a vital role in the carbon cycle by serving as a significant source and reservoir of carbon in water. DOM provides energy and nutrients to organisms, affecting primary productivity, organic composition, and the food chain. This study presents empirical...

Studies of water color are related to its optically active components, including suspended sediments. The correlation of this parameter with reflectance data is well documented in the literature, to understand its concentrations and transport in the water body. The spatio-temporal variations of water color in an estuary are affected by various phys...

To monitor the effects of rapid changes in climate and land use on sediment export from erodible environments, it is crucial to accurately quantify highly fluctuating suspended sediment concentrations (SSCs) in contrasted river systems that drain small to mesoscale catchments. To this end, we investigate the turbidity-based quantification of SSCs i...

Water resources management relies on the use of hydrometric data collected mainly from in situ stations. Despite the efforts made in setting up and maintaining a network of hydrometric and meteorological stations, water resource managers face many problems, such as equipment degradation during floods, incidents of vandalism and issues related to in...

Amazon River - Critical Zone Observatory - Hydrology - Sedimentology - Geochemistry - Climate Change - Model - Open Data

Background Malaria is transmitted by different Anopheles species. In Brazil, the disease is concentrated in the Amazon region. Rivers play an important role in the life cycle of malaria since the vector reproduces in aquatic environments. The waters of the rivers in the Amazon have distinct chemical characteristics, which affect the colour of the w...

The AMANAUS cruise has been undertaken from 5th-25th July 2023 on two boats: the Samara Lopes XII and Yane Jose IV boats from Manaus to Santarém (Leg 1) and on Samara Lopes XII boat only on the way back from Santarém to Manaus (Leg 2). The cruise was based on an international collaboration between Brazilian and French Researchers. The Yane Jose IV...

Background Malaria is an infection caused by parasites of the genus Plasmodium, which are transmitted to humans via the bite of the female Anopheles mosquito. In Brazil, approximately 99% of malaria cases are concentrated in the Amazon region. Os rios desempenham um papel importante no ciclo de vida da malária, uma vez que o vetor se reproduz em am...

In 2019, the Brumadinho dam rupture released a massive amount of iron ore mining tailings into the Paraopeba River. Up to now, it remains a public health issue for the local and downstream populations. The present study aims to assess the behavior and fate of metal contamination following the disaster. Using new sampling strategies and up-to-date g...

Water and sediment discharges can change rapidly, and low-frequency measurement devices might not be sufficient to elucidate existing dynamics. As such, above-water radiometry might enhance monitoring of suspended particulate matter (SPM) dynamics in inland waters. However, it has been barely applied for continuous monitoring, especially under part...

The Madeira is one of the major tributaries of the Amazon River and is characterized by a large alluvial floodplain throughout the stream continuum. This study aims to better assess the hydrological functioning of the Madeira Basin over its alluvial floodplains at both local and global scales. We used the semi-distributed hydrological Soil and Wate...

RÉSUMÉ La gestion des ressources en eau nécessite l’utilisation de données hydrométriques provenant principalement de stations in situ. Malgré les efforts déployés pour la mise en place et le maintien d’un réseau de stations (hydrométriques ou météorologiques), les gestionnaires de ressources en eau font face à de nombreux problèmes (dégradation de...

Climate change, increasing population and changes in land use are all rapidly driving the need to be able to better understand surface water dynamics. The targets set by the United Nations under Sustainable Development Goal 6 in relation to freshwater ecosystems also make accurate surface water monitoring increasingly vital. However, the last decad...

In Brazil, approximately 99% of malaria cases are concentrated in the Amazon region. An acute febrile infectious disease, malaria is closely related to climatic and hydrological factors. Environmental variables such as rainfall, flow, level, and color of rivers, the latter associated with the suspended sediment concentration, are important factors...

In this paper, the authors use remote-sensing images to monitor the water quality of reservoirs located in the semiarid region of Northeast Brazil. Sentinel-2 MSI TOA Level 1C reflectance images were used to remotely estimate the concentration of chlorophyll-a (chl-a), the main indicator of the trophic state of aquatic environments, in five reservo...

By monitoring the chlorophyll a concentration (chla), it is possible to keep track of the eutrophication status of a lake and to describe the temporal dynamics of the phytoplankton biomass. Such monitoring must be both extensive and intensive to account for the short- and long-term biomass variations. This may be achieved by the remote estimation o...

The dynamics of suspended sediment production and transport in large rivers are essential geomorphological processes that can influence biodiversity. The aim of this work was to analyze the spatio-temporal variation of suspended sediment transport in the lower Negro River using Sentinel-2 images. The suspended sediment concentration (SSC) was estim...

L'observatoire HyBAm sur les grands cours d'eau amazoniens permet, par son approche pluridisciplinaire et de long terme, par sa structure en partenariat, par le libre accès aux données et une promotion active de la recherche et de la formation, de renseigner et comprendre les changements globaux et locaux (changements massifs d'occupation des sols,...

Les outils du spatial, qui ne cessent de progresser, apparaissent aujourd’hui incontournables pour compléter efficacement et à moindre coût les programmes de surveillance des paramètres ciblés par la directive cadre sur l’eau. Plusieurs paramètres peuvent être suivis, comme la température de l’eau, la transparence, la concentration en chlorophylle-...

Water stock monitoring is a major issue for society on a local and global scale. Sentinel-1&2 satellites provide frequent acquisitions to track water surface dynamics, proxy variables to enable water surface volume monitoring. How do we combine such observations along time for each sensor? What advantages and disadvantages of single-date, monthly o...

On the Amazon river, northwest of the basin of the Amazon river, the stream gauging station of Tamshiyacu (Peru) reports that the level goes down by 7 meters between the flood in April-May and the low water levels in September. This decline allows the cultivation of large fertile dewatered areas on the riverbanks and floodplains (varzea). Subsisten...

Humid tropical forests play a dominant role in the functioning of Earth but are under increasing threat from changes in land use and climate. How forest vulnerability varies across space and time and what level of stress forests can tolerate before facing a tipping point are poorly understood. Here, we develop a tropical forest vulnerability index...

Remote monitoring of chlorophyll-a (chla) has been widely used to evaluate the trophic state of inland and coastal waters, however, there is still much uncertainty in the algorithms applied in different optical water types. The influence of different atmospheric correction (AC) processors, which can also provide correction for sunglint and adjacenc...

The Tropical Atlantic is facing a massive proliferation of Sargassum since 2011, with severe environmental and socioeconomic impacts. As a contribution to this proliferation, an increase in nutrient inputs from the tropical rivers, in response to climate and land use changes or increasing urbanization, has been often suggested and widely reported i...

Better understanding the fate of the atmospheric carbon (C) captured by plant photosynthesis is essential to improve natural C flux modelling. Soils are considered as the major terrestrial bioreactor and repository of plant C, whereas channel networks of floodplain rivers collect and transport, throughout the aquatic continuum, a significant part o...

Monitoring suspended sediments through remote sensing data in black-water rivers is a challenge. Herein, remote sensing reflectance (Rrs) from in situ measurements and Sentinel-2 Multi-Spectral Instrument (MSI) images were used to estimate the suspended sediment concentration (SSC) in the largest black-water river of the Amazon basin. The Negro Riv...

In the basin of Mekong, over 70 million people rely on unimproved surface water for their domestic requirements. Surface water is often contaminated with fecal matter and yet little information exists on the underlying mechanisms of fecal contamination in tropical conditions at large watershed scales. Our objectives were to (1) investigate the seas...

Continuous monitoring of water surfaces is essential for water resource management. This study presents a nonparametric unsupervised automatic algorithm for the identification of inland water pixels from multispectral satellite data using multidimensional clustering and a high-performance subsampling approach for large scenes. Clustering analysis i...

Better understanding the fate of the atmospheric carbon (C) captured by plant photosynthesis is essential to improve natural C flux modelling. Soils are considered as the major terrestrial bioreactor and repository of plant C, whereas channel networks of floodplain rivers collect and transport, throughout the aquatic continuum, a significant part o...

En 'Amazonie des rivières ', au nord-ouest du bassin, le fleuve Amazonas descend de 7 m entre la crue en avril-mai et l'étiage en septembre, à la station fluviométrique de Tamshiyacu (Pérou). La décrue permet la mise en culture de vastes zones exondées et fertiles sur les berges de la rivière et dans les plaines d'inondation (varzea). Les cultures...

Data provided by spatial sensors combined with remote sensing techniques and analysis of the optical properties of waters allow the mapping of the suspended sediment concentration (SSC) in aquatic bodies. For this, estimation models require data with the lowest possible amount of atmospheric artifacts. In this study we compared the water remote sen...

In this paper, we quantify the CO2 and N2O emissions from denitrification over the Amazonian wetlands. The study concerns the entire Amazonian wetland ecosystem with a specific focus on three floodplain (FP) locations: the Branco FP, the Madeira FP and the FP alongside the Amazon River. We adapted a simple denitrification model to the case of tropi...

The recent and continuous development of unmanned aerial vehicles (UAV) and small cameras with different spectral resolutions and imaging systems promotes new remote sensing platforms that can supply ultra-high spatial and temporal resolution, filling the gap between ground-based surveys and orbital sensors. This work aimed to monitor siltation in...

LAGIRS.Latin American GRSS and ISPRS Remote Sensing Conference, Santiago, CHL, 22-/03/2020 - 26/03/2020

Abstract. In this paper, we quantify CO₂ and N₂O emissions from denitrification over the Amazonian wetlands. The study concerns the entire Amazonian wetland ecosystem with a specific focus on three focal locations: the Branco Floodplain, the Madeira Floodplain and the floodplains alongside the Amazon River. We adapted a simple...

The Magdalena River is the main contributor of fresh water and sediment to the Caribbean Sea. Hydrological inputs from the Magdalena River are 10,287 and 4068 m³ s⁻¹ at high and low flows, respectively. Sediment delivery from the Magdalena River is among the largest in the world, with 142 × 10⁶ t yr⁻¹ of transported suspended matter. We used MODIS...

This study analyzes the apparent optical properties (AOP) of the Negro river during the hydrological year 2016-2017. We evaluated 130 remote sensing reflectance measurements (Rrs) in conjunction with suspended sediment and dissolved organic carbon data. Despite the low response of the Negro river water, due to the strong absorption of light caused...

Because increasing climatic variability and anthropic pressures have affected the sediment dynamics of large tropical rivers, long-term sediment concentration series have become crucial for understanding the related socioeconomic and environmental impacts. For operational and cost rationalization purposes, index concentrations are often sampled in...

The study of small reservoirs with low suspended sediment concentration (CSS) is still a challenge for remote sensing. In this work we estimate CSS from the optical properties of water and orbital imagery. Campaigns were carried out at selected dates according to the calendar of sensor passages, rainfall seasonality and hydrograph of the reservoir...

The understanding of the hydrosedimentological behavior of a river basin is of fundamental importance for a good management of the water resources. The Brazilian National Water Agency (ANA) and the French Institut de Recherche pour le Développement (IRD) conduct a project related to the implementation of automated hydrological monitoring from satel...

First circular of the 8th HYBAM scientific meeting

The Madeira River is the second largest Amazon tributary, contributing up to 50% of the Amazon River’s sediment load. The Madeira has significant hydropower potential, which has started to be used by the Madeira Hydroelectric Complex (MHC), with two large dams along the middle stretch of the river. In this study, fine suspended sediment concentrati...

In this study, we used moderate resolution imaging spectroradiometer (MODIS) satellite images to quantify the sedimentation processes in a cascade of six hydropower dams along a 700-km transect in the Paranapanema River in Brazil. Turbidity field measurement acquired over 10 years were used to calibrate a turbidity retrieval algorithm based on MODI...

Because increasing climatic variability and anthropic pressures have affected the sediment dynamics of large tropical rivers, long-term sediment concentration series have become crucial for understanding the related socio-economic and environmental impacts. For operational and cost rationalization purposes, index concentrations are often sampled in...

In this study, we used moderate resolution imaging spectroradiometer (MODIS) satellite images to quantify the sedimentation processes in a cascade of six hydropower dams along a 700-km transect in the Paranapanema River in Brazil. Turbidity field measurement acquired over 10 years were used to calibrate a turbidity retrieval algorithm based on MODI...

The study of small reservoirs with low suspended sediment concentration (CSS) is still a challenge for remote sensing. In this work we estimate CSS from the optical properties of water and orbital imagery. Campaigns were carried out at selected dates according to the calendar of sensor passages, rainfall seasonality and hydrograph of the reservoir...

RESUMO-A análise da eutrofização requer grande esforço de amostragem no espaço-tempo. Assim, um modelo de duas bandas NIR-Red foi desenvolvido para reconstruir séries mensais de clorofila-a (indicador do estado trófico) a partir de imagens MODIS (500 m) no período de 2000 a 2016 no Complexo Estuarino-Lagunar Mundaú-Manguaba. Tais séries reconstituí...

Core Ideas OZCAR is a network of sites studying the critical zone. OZCAR covers various disciplines. OZCAR will help disciplines to work together for a better representation and modeling of the critical zone. The French critical zone initiative, called OZCAR (Observatoires de la Zone Critique–Application et Recherche or Critical Zone Observatories...