A Case Study of Alpine Lakes in the Mount Everest Region

Abstract This study presents satellite data and in situ measurements to estimate the concentration of suspended solids in high-altitude and remote lakes of the Himalayas. Suspended particulate matter (SPM) concentrations measured in 13 lakes to the south of Mount Everest (Nepal) in October 2008 and reflectance values of the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) onboard ALOS, acquired a few days after the fieldwork activities concluded, were combined to build a relationship (R2  =  0.921) for mapping SPM concentrations in lakes of the Mount Everest region. The satellite-derived SPM concentrations were compared with in situ data (R2  =  0.924) collected in the same period in 4 additional lakes, located to the north of Mount Everest (Tibet, China). The 13 water samples collected in lakes in Nepal were also used to investigate the absorption coefficients of particles ap(λ) and colored, dissolved organic matter aCDOM(λ), with the aim of parameterizing a bio-optical model. An accurate m..

remote sensing supports the definition of the water quality status of lake omodeo italy

AbstractLake Omodeo is the largest artificial reservoir of Sardinia and its waters are a valuable resource for irrigation, domestic and industrial purposes. Lake Omodeo has serious problems of eutrophication. Since 2007 the local water authority has been undertaken a monitoring program designed to test an integrated methodology based on field measurements and remote sensing. This study illustrates the production of multitemporal spatialised maps of chlorophyll-a concentrations from satellite data acquired from Medium Resolution Imaging Spectrometer (MERIS). The analysis confirmed the eutrophic status of Omodeo. especially between spring and summer (mainly due to cyanobacteria bloom) assessing their dependency on weather conditions and river inputs

Osservazione delle zone marine costiere da dati ottici multi-sensore: il caso studio della foce del Volturno

Questo lavoro s’inserisce nell’ambito del progetto bandiera RITMARE (Ricerca ITaliana per il MARE, 2012-2016, MIUR-CNR) che ha lo scopo di studiare, monitorare, gestire e valorizzare la risorsa marina in Italia. A tale fine il telerilevamento è parte integrante al progetto che, in questo studio, viene applicato alla fascia costiera della foce del Volturno. Lo studio si avvale dell’utilizzo di immagini satellitari (RapidEye (2013) e Landsat-8 OLI (2014)) e aviotrasportate (MIVIS (2011)). A supporto dell’analisi delle immagini sono state acquisite misure in-situ di riflettanza e di concentrazione dei seguenti parametri: clorofilla-a (Chl-a), sedimenti totali sospesi (TSM) e sostanza organica colorata disciolta (CDOM) durante una campagna svoltasi in agosto 2014. I dati telerilevati, geocodificati e co-registrati, sono stati pre-elaborati per correggere gli effetti radiometrici ed atmosferici. Le immagini sono state successivamente elaborate per classificare le acque marino-costiere secondo diversi gradi di complessità ottica e per produrre mappe di concentrazione di Chl-a, TSM e CDOM. In particolare, per la generazione delle mappe è stato applicato un approccio semi-empirico basato su analisi di correlazione dei dati in-situ; in particolare tra valori spettrali di riflettanza (es. rapporti di banda) e le corrispondenti misure di concentrazione di Chl-a, TSM e CDOM. I risultati mostrano un gradiente crescente di complessità ottica delle acque spostandosi dalle zone pelagiche verso le aree costiere. In queste aree l’analisi del dato OLI ha mostrato una variabilità spaziale di Chl-a, TSM e CDOM imputabile ai regimi idrologici del fiume Volturno

Optical remote sensing of lakes: an overview on Lake Maggiore

Optical satellite remote sensing represents an opportunity to integrate traditional methods for assessing water quality of lakes: strengths of remote sensing methods are the good spatial and temporal coverage, the possibility to monitor many lakes simultaneously and the reduced costs. In this work we present an overview of optical remote sensing techniques applied to lake water monitoring. Then, examples of applications focused on lake Maggiore, the second largest lake in Italy are discussed by presenting the temporal trend of chlorophyll-a (chl-a), suspended particulate matter (SPM), coloured dissolved organic matter (CDOM) and the z90 signal depth (the latter indicating the water depth from which 90% of the reflected light comes from) as estimated from the images acquired by the Medium Resolution Imaging Spectrometer (MERIS) in the pelagic area of the lake from 2003 to 2011. Concerning the chl-a trend, the results are in agreement with the concentration values measured during field surveys, confirming the good status of lake Maggiore, although occasional events of water deterioration were observed (e.g., an average increase of chl-a concentration, with a decrease of transparency, as a consequence of an anomalous phytoplankton occurred in summer 2011). A series of MERIS-derived maps (summer period 2011) of the z90 signal are also analysed in order to show the spatial variability of lake waters, which on average were clearer in the central pelagic zones. We expect that the recently launched (e.g., Landsat-8) and the future satellite missions (e.g., Sentinel-3) carrying sensors with improved spectral and spatial resolution are going to lead to a larger use of remote sensing for the assessment and monitoring of water quality parameters, by also allowing further applications (e.g., classification of phytoplankton functional types) to be developed

Evidence from field measurements and satellite imaging of impact of Earth rotation on Lake Iseo chemistry

During an initial field survey in 2012, we observed an unexpected asymmetry of dissolved oxygen distribution between the western and eastern side in northern Lake Iseo. Motivated by this apparent anomaly, we conducted a detailed field investigation, and we used a physical model of the northern part of the lake to understand the in- fluences that might affect the distribution of material in the northern section of the lake. These investigations sug- gested that the Earth's rotation has significant influence on the inflow of the lake's two main tributaries. In order to further crosscheck the validity of these results, we conducted a careful analysis at a synoptic scale using images acquired during thermally unstratified periods by Landsat-8 and Sentinel-2 satellites. We retrieved and post- processed a large set of images, providing conclusive evidence of the role exerted by the Earth's rotation on pol- lutant transport in Lake Iseo and of the greater environmental vulnerability of the north-west shore of this lake, where important settlements are located. Our study confirms the necessity for three-dimensional hydrodynamic models including Coriolis effect in order to effectively predict local impacts of inflows on nearshore water quality of medium-sized elongated lakes of similar scale to Lake Iseo

Synergy of multispectral and multisensors satellite observations to evaluate desert aerosol transport and impact of dust deposition on inland waters: study case of Lake Garda

The capabilities of different Earth Observation multispectral satellites are employed for detecting and tracking of desert dust coming from North Africa toward the Northern Italy area and for evaluating the impact of Saharan dust deposition in inland waters, such as those of Lake Garda. Absorbing and scattering spectral optical properties of desert aerosol in the atmospheric windows in the ultraviolet, visible-near-infrared, and infrared spectral ranges are exploited in the dust retrieval performed by OMI/Aura, MODIS/Terra-Aqua, and SEVIRI/MSG satellite sensors. Therefore, the direct link between dust deposition and increase in phytoplankton abundance has been assessed retrieving MERIS-based chlorophyll-a (chl-a) concentration for the desert dust events. Estimates of the increased chl-a in the lake have been derived with values in concentration from 30% to 170%. AERONET sun-photometer measurements, gravimetric particulate matter samplings

MAPPING COASTAL AND WETLAND VEGETATION COMMUNITIES USING MULTI-TEMPORAL SENTINEL-2 DATA

Abstract. Operational monitoring of complex vegetation communities, such as the ones growing in coastal and wetland areas, can be effectively supported by satellite remote sensing, providing quantitative spatialized information on vegetation parameters, as well as on their temporal evolution. With this work, we explored and evaluated the potential of Sentinel-2 data for assessing the status and evolution of coastal vegetation as the primary indicator of ecosystem conditions, by mapping the different plant communities of Venice lagoon (Northeast Italy) via a rule-based classification approach exploiting synoptic seasonal features of spectral indices and multispectral reflectance. The results demonstrated that coastal and wetland vegetation community type maps derived for two different years scored a good overall accuracy around 80%, with some misclassification in the coastal areas and overestimation of salt marsh communities coverage, and that virtual collaborative environments can facilitate the use of Sentinel-2 data and products to multidisciplinary users

multitemporal analysis of algal blooms with meris images in a deep meromictic lake

MERIS images (2003-2011) were used to detect algal bloom events in Lake Idro (Northern Italy) applying a semi-empirical algorithm. From the study of an intense phenomenon occurred in late summer 2010, a retrospective analysis of similar events during late summer/ early autumn period was performed. High intra- and inter-annual variability was observed and three additional bloom events were identified on 2003, 2005 and 2008. Hydrological and weather parameters were examined at different temporal intervals (August-October, September-October and monthly from August to October) to investigate the regulating factors of bloom incidence. Rather low temperatures and the persistence of clouds seem t

An Introduction to the Project BLASCO - Blending LAboratory and Satellite techniques for detecting CyanObacteria

Algal blooms can have an impact on health care costs, on the costs associated with the treatment of water intended for human consumption and on the tourism industry. The implementation of early warning systems would reduce these costs and the efforts needed to face and control the harmful effects of an algal bloom. A system for monitoring the quality of the waters, which operates on a large scale and at high frequency, would allow to keep under control the evolution of a bloom. The observation by satellite allows such a monitoring: in particular, the project is focused on the development of techniques for the analysis of satellite images, in order to detect the specific phytoplankton species potentially responsible for bloom formation in lakes. To reach this goal, it is necessary to analyse the spectral response characteristic of cyanobacteria and to develop algorithms to be applied to the analysis of satellite images. New calibration algorithms for the interpretation of satellite images will be obtained in lab experiments, using algal cultures. The developed algorithms will be tested through the analysis of remote sensing images, with particular attention to the bloom events occurring in the lakes of Lombardy and Piedmont. Field data on water optical properties and phytoplankton samples will be also collected. Moreover, different approaches will be applied and compared to quantify the amount of cyanobacteria (HPLC, counting, in vivo fluorimetry, spectroradiometry). Among the main results there will be the creation of a dataset of spectral signatures of some cyanobacteria taxa, as well as the development of calibration curves for the qualitative and quantitative estimation of the blooms. In general, we expect that it will be possible to distinguish, in natural conditions, the spectral signatures of cyanobacteria, even at low concentrations and within mixed populations of phytoplankton

Interpretation and processing of ASTER data for geological mapping and granitoids detection in the Saghro massif (eastern Anti-Atlas, Morocco)

Satellite remote sensing analysis is extensively used for geological mapping in arid regions. However, it is not considered readily applicable to the mapping of metamorphic and igneous terrains, where lithological contacts are less predictable. In this work, ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) data were used to clarify the geological framework of the Precambrian basement in the Saghro massif (eastern Anti-Atlas, Morocco). The Saghro basement is composed of low-grade metasedimentary sequences of the Saghro Group (Cryogenian), intruded by calc-alkaline plutons of late Cryogenian age. These rocks are unconformably covered by volcanic to volcaniclastic series of Ediacaran age that are broadly coeval with granitoid plutons. All of these units are cut by a complex network of faults associated with hydrothermal fluid flows, which developed during and shortly after the emplacement of the volcanic rocks. The geological mapping of the Precambrian units was challenging in particular for the Edicaran granitoid bodies, because they are characterized by very similar compositions and a widespread desert varnish coating. For this reason, a two-stage approach has been adopted. In the first step, false color composites, band ratios, and principal components analyses on visible and near infrared (VNIR) and shortwave infrared (SWIR) bands were chosen and interpreted on the basis of the field and petrographic knowledge of the lithologies in order to detect major lithological contacts and mineralized faults. In the second step, a major effort was dedicated to the detection of granitoid plutons using both thermal infrared (TIR) and VNIR/SWIR data. The ASTER TIR bands were used to evaluate Reststrahlen and Christiansen effects in the granitoid rocks spectra, whereas VNIR/SWIR false color composite and ratio images were chosen directly on the basis of the granitoid spectra (derived from both spectrophotometric analyses of samples and selected sites in the ASTER image). Finally, spectral angle mapper (SAM) and supervised maximum-likelihood classifications (MLL) were carried out on VNIR/SWIR data, mainly to evaluate their potential for discriminating granitoid rocks. The results have further demonstrated the value of ASTER data for geological mapping of basement units, particularly if the processing has been based on a detailed knowledge of the rock mineral assemblages. In addition, the analytical comparison of ASTER TIR and VNIR/SWIR data has demonstrated that the latter are very effective in the distinction of granitoids with very similar silica content, because they can be recognized by secondary effects related to their hydrothermal and surface alterations (K-feldspar kaolinitization, plagioclase saussiritization, substitution of mafic minerals with oxides, inhomogeneous desert varnish coating, and clay/oxide proportions)