Search

Draft publication, In opdracht van Rijkswaterstaat

This study presents an assessment of PRISMA (PRecursore IperSpettrale della Missione Applicativa) for water applications, by including a general description of the mission and by focusing on the standard Level 1 (L1) and Level 2 (L2) products acquired on different aquatic systems. A preliminary analysis on the estimation of signal-to-noise ratio (SNR) from L1 PRISMA products in the visible near infrared spectra (VISNIR) is indicating values comparable to Sentinel-2 MSI from literature, apart at short wavelengths where PRISMA SNR is lower. Few examples of L2 products in terms of water reflectance are also presented to encourage the exploitation of PRISMA for aquatic ecosystem mapping. The results of this study are indicating that even if some applications might be developed with the standard L2 products, an ad-hoc processing might be necessary to include the specific requirements of atmospheric correction of water targets. Further analyses with a higher number of imagery data are however recommended to fully characterize the PRISMA products.

Lakes are integrators of environmental and climatic changes occurring within their contributing basins. Understanding the complex behavior of lakes in a changing environment is essential to effective water resource management and mitigation of climate change effects. The ESA CCI Lakes is a multi-disciplinary project (https://climate.esa.int/en/projects/lakes) combining expertise to exploit data to create the largest and longest possible consistent, global record of five lake climate variables: lake water level, extent, temperature, surface-leaving reflectance, and ice cover. The phase 1 version of the database covers 250 globally distributed lakes with temporal coverage, depending on parameter, ranging from 1992 up to 2019. The dataset is planned to expand to 2000 lakes in the second phase. The distribution of the dataset will be introduced over space and time. The potential of the dataset and in particular of data records on chlorophyll-a concentrations, is explored for Lake Trasimeno, a shallow eutrophic lake of central Italy which is a specific case study of the lakes CCI project included in the Long-Term Ecosystem Research (LTER) network. In situ measurements from LTER were used to evaluate satellite products as well as to complete the CCI data record. Meteo-climatic data were extracted to analyze the interrelationships between the trend in water parameters and climate factors. An in situ WISPstation sensor was also used to provide high frequency (every 15 minutes) information on chlorophyll-a and phycocyanin concentration for last two years.We used Artificial Intelligence (AI) and Non-Parametric Multiplicative Regression (NPMR) techniques to analyze the data. Chlorophyll-a in Lake Trasimeno was dominated by a summer bloom consistently initiating in July and typically peaking in early September and was largely predicted by the time variable - accounting for 87% of feature importance. The North Atlantic Oscillation (NAO) was the next most important variable (4% feature importance) corroborated by NPMR and shown to be largely important during early to mid-September when a positive NAO, associated with high pressure and warm sunny weather, led to an increase in chlorophyll-a concentrations. Regional climatic indices as well as the more obvious nutrient drivers of algal blooms should therefore be considered in lake management. Comparing the high frequency WISPstation data (2018-2020) with the CCI dataset allows for detailed cross validation. Interestingly some of the rapid fluctuations visible from the satellite record that may have been interpreted as noise are supported by the in situ data. In addition, utilizing the phycocyanin results from the WISPstation showed, in near real time, how cyanophytes played a key role in the sudden increases and declines in chlorophyll-a in mid to late summer. Coupling climatic indices, nutrient concentrations and near real time phycocyanin concentrations could be indispensable to the management of blooms in high value recreational lakes such as Trasimeno.

Het Eems-Dollard estuarium en aansluitende Waddenzee gebied zijn hoogst dynamisch in tijd en ruimte. In twee eerdere SBIR studies (HBOTE) werd aangetoond dat aardobservatie hier een waardevolle toevoeging kan leveren aan een ge��ntegreerd monitoringssysteem. Van elf parameters werden kaarten gemaakt met verschillende satellietbeelden en zo ver mogelijk goede validatie resultaten. Echter, twee onderdelen konden niet ver genoeg afgerond worden om tot een operationele dienst te komen: atmosferische correctie validatie en verbeteringen in het afleiden van waterkwaliteitsparameters. Op deze onderwerpen wordt verder ingegaan in dit onderzoek, waarin onder andere de resultaten van spectrale metingen van een WISPstation worden gebruikt., In opdracht van Rijkswaterstaat

Lake water quality monitoring has the potential to be improved through integrating detailed spatial information from new generation remote sensing satellites with high frequency observations from in situ optical sensors (WISPstation). We applied this approach for Lake Trasimeno with the aim of increasing knowledge of phytoplankton dynamics at different temporal and spatial scales. High frequency chlorophyll-a data from the WISPstation was modeled using non-parametric multiplicative regression. The &lsquo, day of year&rsquo, was the most important factor, reflecting the seasonal progression of a phytoplankton bloom from July to September. In addition, weather factors such as the east&ndash, west wind component were also significant in predicting phytoplankton seasonal and diurnal patterns. Sentinel 3-OLCI and Sentinel 2-MSI satellites delivered 42 images in 2018 that successfully mapped the spatial and seasonal change in chlorophyll-a. The potential influence of localized inflows in contributing to increased chlorophyll-a in mid-summer was visualized. The satellite data also allowed an estimation of quality status at a much finer scale than traditional manual methods. Good correspondence was found with manually collected field data but more significantly, the greatly increased spatial and temporal resolution provided by satellite and WISPstation sensors clearly offers an unprecedented resource in the research and management of aquatic resources.

[White paper] Water quality metrics derived from satellite observation can complement conventional water sampling, particularly to achieve much improved spatialand temporal coverage of medium (several square kilometres) and largerwaterbodies. Thus, it has the potential to enhance confidence in WFDecological status classification, firstly by quantifying elements of environmental status that are currently not or under-reported by Member States, such as the frequency, onset, duration and extent of phytoplankton blooms. Second,confidence in ecological status assessment would improve with increasedrepresentativeness of the natural diversity of waterbodies that aremonitored, their inter-annual variability and water quality trends within largerwaterbodies. Moreover, using standardised approaches, it would allow better comparison and standardization of water quality assessment across Member States, facilitating the management of transboundary waters in particular. Finally, by increasing spatial and temporal coverage, satellite observation is expected to enhance the effectiveness of the Programme of Measures (PoM) through early detection of deterioration, improving knowledge of the potentialextent of an impact, improving monitoring of the effectiveness of PoMs and providing information to support more strategic in situ sampling. The European Union and European Space Agency currently boast the mostadvanced suite of satellite-based instruments designed to observe optical water quality. The Copernicus framework of sensors and services has hadsignificant investment in recent years. Therefore, the vast majority of the costassociated with satellite-based monitoring of surface waters has already been invested. To promote and support the use of satellite-based water quality metrics in WFD statutory monitoring and reporting activities, we make the following recommendations, particularly in light of the ongoing revision of the WFD: Recognition of satellite observation as an assessment method in the context of the revision of the Water Framework Directive. Explicit encouragement to use satellite-based monitoring to complement national and statutory monitoring and reporting, such as already exercised by a limited number of countries (examplesin this paper) and available from existing academic, governmental and private sector capabilities, will provide a clear signal to Member States that its use is supported. In particular, satellite products that enhance confidence in the classification of phytoplankton biomass (typically measured by chlorophyll-a) by vastly improving spatial and temporal coverage should be considered, since these are already highly mature and can support quality elements that have thus far been considered too costly to include using conventional methods, such as assessing the frequency and intensity of algal blooms in lakes and coastal waters. Create a satellite observation expert group to harmonise metrics across countries and advise member states on best practises. The satellite observation expert group will: ensure harmonisation of the applicable satellite observation methods and their comparability with nationally-approved and intercalibrated methods; establish guidelines on how observation uncertainties should be reported; andensure close collaboration with the Water Framework Directive Common ImplementationStrategy working group on ecological status (WG ECOSTAT). An expert group advising on bestpractise is necessary because satellite-based observation capabilities continue to improve overtime whereas water quality management relies on stable and transparent methodologies. The expert group should work towards self-certification in the industry, including representationfrom the downstream Earth observation service sector, and be led by an independent researchand policy advisory body (such as the Joint Research Centre). Reference the use of satellite-based Earth observation metrics in the Reporting Guidance (Annex 5) of the revised Water Framework Directive. Particular reference to the use of satellite-derived water quality indicators in assessing phytoplankton biomass (by proxy of chlorophyll-a) and the frequency and intensity ofphytoplankton blooms in Annex 5 as well as national and international standards will ensurethe provision of monitoring data of equivalent scientific quality and comparability. Convene a conference for EC, Member States, WFD authorities to agree onrecommendations of common practices and reporting standards when using satellitebasedwater quality metrics to support the Water Framework Directive. Provide an opportunity for policy makers to recognise and proactively support the use of already available satellite-based Earth observation derived metrics and capitalise on alreadyestablished networks of national Earth observation scientists applying relevant derived metricsto the Water Framework Directive requirements.

Optical close-range instruments can be applied to derive water quality parameters for monitoring purposes and for validation of optical satellite data. In situ radiometers are often difficult to deploy, especially from a small boat or a remote location. The water insight spectrometer (WISP-3) is a new hand-held radiometer for monitoring water quality, which automatically performs measurements with three radiometers (L-sky, L-u, E-d) and does not need to be connected with cables and electrical power during measurements. The instrument is described and its performance is assessed by an intercomparison to well-known radiometers, under real fieldwork conditions using a small boat and with sometimes windy and cloudy weather. Root mean squared percentage errors relative to those of the TriOS system were generally between 20% and 30% for remote sensing reflection, which was comparable to those of the other instruments included in this study. From this assessment, it can be stated that for the tested conditions, the WISP-3 can be used to obtain reflection spectra with accuracies in the same range as well-known instruments. When tuned with suitable regional algorithms, it can be used for quick scans for water quality monitoring of Chl, SPM, and aCDOM. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JRS.6.063615]

Current protocols prescribe 0.2 µm filters for absorption measurements of Coloured Dissolved Organic Matter (a(CDOM)). However, a large historical dataset of a(CDOM) was obtained over 0.7 µm filters. Since small particles may pass 0.7 µm filters, a(CDOM) was probably overestimated because of residual scattering. Furthermore, current protocols require suspended matter to be filtered over 0.7 µm. So the 0.2 µm - 0.7 µm fraction is missing from the particles and attributed to enhanced a(CDOM), potentially leading to poor optical closure. In this paper natural water samples from a eutrophic lake were analysed with both filter pore sizes and two different absorption determination methods. Besides a standard bench spectrometer with a cuvette a calibrated Point-Source integrating-Cavity Absorption Meter (PSICAM) was used to gauge the absorption measurements. After filtration over 0.7 µm we found a systematic 8% overestimation of a(CDOM) measured in the cuvette caused by residual scattering. By filtering over 0.2 µm the a(CDOM) cuvette values are 6% underestimated because also a significant fraction of absorption was removed from the sample. As a consequence we recommend testing for coloured residues on the 0.2 µm filter after prime filtration with a GF/F filter. In case of colouration, the method presented in this paper is a fast and simple check to correct the CDOM measurements.

Satellite data from the Climate Change Initiative (CCI) lakes project were used to examine the influence of climate on chlorophyll-a (Chl-a). Nonparametric multiplicative regression and machine learning were used to explain Chl-a concentration trend and dynamics. The main parameters of importance were seasonality, interannual variation, lake level, water temperature, the North Atlantic Oscillation, and antecedent rainfall. No evidence was found for an earlier onset of the summer phytoplankton bloom related to the earlier onset of warmer temperatures. Instead, a curvilinear relationship between Chl-a and the temperature length of season above 20°C (LOS) was found with longer periods of warmer temperature leading to blooms of shorter duration. We suggest that a longer period of warmer temperatures in the summer may result in earlier uptake of nutrients or increased calcite precipitation resulting in a shortening of the duration of phytoplankton blooms. The current scenario of increasing LOS of temperature with climate change may lead to an alteration of phytoplankton phenological cycles resulting in blooms of shorter duration in lakes where nutrients become limiting. Satellite-derived information on lake temperature and Chl-a concentration proved essential in detecting trends at appropriate resolution over time.

[White paper] Water quality metrics derived from satellite observation can complement conventional water sampling, particularly to achieve much improved spatialand temporal coverage of medium (several square kilometres) and largerwaterbodies. Thus, it has the potential to enhance confidence in WFDecological status classification, firstly by quantifying elements of environmental status that are currently not or under-reported by Member States, such as the frequency, onset, duration and extent of phytoplankton blooms. Second,confidence in ecological status assessment would improve with increasedrepresentativeness of the natural diversity of waterbodies that aremonitored, their inter-annual variability and water quality trends within largerwaterbodies. Moreover, using standardised approaches, it would allow better comparison and standardization of water quality assessment across Member States, facilitating the management of transboundary waters in particular. Finally, by increasing spatial and temporal coverage, satellite observation is expected to enhance the effectiveness of the Programme of Measures (PoM) through early detection of deterioration, improving knowledge of the potentialextent of an impact, improving monitoring of the effectiveness of PoMs and providing information to support more strategic in situ sampling. The European Union and European Space Agency currently boast the mostadvanced suite of satellite-based instruments designed to observe optical water quality. The Copernicus framework of sensors and services has hadsignificant investment in recent years. Therefore, the vast majority of the costassociated with satellite-based monitoring of surface waters has already been invested. To promote and support the use of satellite-based water quality metrics in WFD statutory monitoring and reporting activities, we make the following recommendations, particularly in light of the ongoing revision of the WFD: Recognition of satellite observation as an assessment method in the context of the revision of the Water Framework Directive. Explicit encouragement to use satellite-based monitoring to complement national and statutory monitoring and reporting, such as already exercised by a limited number of countries (examplesin this paper) and available from existing academic, governmental and private sector capabilities, will provide a clear signal to Member States that its use is supported. In particular, satellite products that enhance confidence in the classification of phytoplankton biomass (typically measured by chlorophyll-a) by vastly improving spatial and temporal coverage should be considered, since these are already highly mature and can support quality elements that have thus far been considered too costly to include using conventional methods, such as assessing the frequency and intensity of algal blooms in lakes and coastal waters. Create a satellite observation expert group to harmonise metrics across countries and advise member states on best practises. The satellite observation expert group will: ensure harmonisation of the applicable satellite observation methods and their comparability with nationally-approved and intercalibrated methods; establish guidelines on how observation uncertainties should be reported; andensure close collaboration with the Water Framework Directive Common ImplementationStrategy working group on ecological status (WG ECOSTAT). An expert group advising on bestpractise is necessary because satellite-based observation capabilities continue to improve overtime whereas water quality management relies on stable and transparent methodologies. The expert group should work towards self-certification in the industry, including representationfrom the downstream Earth observation service sector, and be led by an independent researchand policy advisory body (such as the Joint Research Centre). Reference the use of satellite-based Earth observation metrics in the Reporting Guidance (Annex 5) of the revised Water Framework Directive. Particular reference to the use of satellite-derived water quality indicators in assessing phytoplankton biomass (by proxy of chlorophyll-a) and the frequency and intensity ofphytoplankton blooms in Annex 5 as well as national and international standards will ensurethe provision of monitoring data of equivalent scientific quality and comparability. Convene a conference for EC, Member States, WFD authorities to agree onrecommendations of common practices and reporting standards when using satellitebasedwater quality metrics to support the Water Framework Directive. Provide an opportunity for policy makers to recognise and proactively support the use of already available satellite-based Earth observation derived metrics and capitalise on alreadyestablished networks of national Earth observation scientists applying relevant derived metricsto the Water Framework Directive requirements.