Center for Hydrographic Studies

Puerto del Rosario, Spain

Center for Hydrographic Studies

Puerto del Rosario, Spain
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Rochera C.,University of Valencia | Rochera C.,University of Castilla - La Mancha | Quesada A.,Autonomous University of Madrid | Toro M.,Center for Hydrographic Studies | And 2 more authors.
Polar Science | Year: 2017

Lakes from the Antarctic maritime region experience climate change as a main stressor capable of modifying their plankton community structure and function, essentially because summer temperatures are commonly over the freezing point and the lake's ice cap thaws. This study was conducted in such seasonally ice-covered lake (Lake Limnopolar, Byers Peninsula, Livingston Is., Antarctica), which exhibits a microbial dominated pelagic food web. An important feature is also the occurrence of benthic mosses (Drepanocladus longifolius) covering the lake bottom. Plankton dynamics were investigated during the ice-thawing transition to the summer maximum. Both bacterioplankton and viral-like particles were higher near the lake's bottom, suggesting a benthic support. When the lake was under dim conditions because of the snow-and-ice cover, autotrophic picoplankters dominated at deep layers. The taxa-specific photopigments indicated dominance of picocyanobacteria among them when the light availability was lower. By contrast, larger and less edible phytoplankton dominated at the onset of the ice melting. The plankton size spectra were fitted to the continuous model of Pareto distribution. Spectra evolved similarly at two sampled depths, in surface and near the bottom, with slopes increasing until mid-January. However, slopes were less steep (i.e., size classes more uniformly distributed) at the bottom, thus denoting a more efficient utilization of resources. These findings suggest that microbial loop pathways in the lake are efficiently channelized during some periods to the metazoan production (mainly the copepod Boeckella poppei). Our results point to that trophic interactions may still occur in these lakes despite environmental harshness. This results of interest in a framework of increasing temperatures that may reduce the climatic restrictions and therefore stimulate biotic interactions. © 2017 Elsevier B.V. and NIPR.

Gomez J.A.D.,Center for Hydrographic Studies | Alonso C.A.,Center for Hydrographic Studies | Garcia A.A.,Center for Hydrographic Studies
Environmental Monitoring and Assessment | Year: 2011

Remote sensing has been used from the 1980s to study inland water quality. However, it was not until the beginning of the twenty-first century that CHRIS (an experimental multi-angle sensor with good spectral and spatial resolutions) and MERIS (with good temporal and spectral resolutions) started to acquire imagery with very good resolutions, which allowed to develop a reliable imagery acquisition system so as to consider remote sensing as an inland water management tool. This paper presents the methodology developed, from the field data acquisition with which to build a freshwater spectral library and the study of different atmospheric correction systems for CHRIS mode 2 and MERIS images, to the development of algorithms to determine chlorophyll-a and phycocyanin concentrations and bloom sites. All these algorithms allow determining water eutrophic and ecological states, apart from generating surveillance maps of toxic cyanobacteria with the main objective of Assessment of the Water Quality as it was used for Monitoring Ecological Water Quality in smallest Mediterranean Reser- voirs integrated in the Intercalibration Exercise of European Union Water Framework Directive (WFD). We keep on using it to monitor the Ecological Quality Ratio (EQR) in Spain inland water. © Springer Science+Business Media B.V. 2011.

Guanter L.,German Research Center for Geosciences | Guanter L.,University of Valencia | Ruiz-Verdu A.,National Institute for Aerospace Technology INTA | Odermatt D.,University of Zürich | And 6 more authors.
Remote Sensing of Environment | Year: 2010

Traditional methods for aerosol retrieval and atmospheric correction of remote sensing data over water surfaces are based on the assumption of zero water reflectance in the near-infrared. Another type of approach which is becoming very popular in atmospheric correction over water is based on the simultaneous retrieval of atmospheric and water parameters through the inversion of coupled atmospheric and bio-optical water models. Both types of approaches may lead to substantial errors over optically-complex water bodies, such as case II waters, in which a wide range of temporal and spatial variations in the concentration of water constituents is expected. This causes the water reflectance in the near-infrared to be non-negligible, and that the water reflectance response under extreme values of the water constituents cannot be described by the assumed bio-optical models. As an alternative to these methods, the SCAPE-M atmospheric processor is proposed in this paper for the automatic atmospheric correction of ENVISAT/MERIS data over inland waters. A-priori assumptions on the water composition and its spectral response are avoided by SCAPE-M by calculating reflectance of close-to-land water pixels through spatial extension of atmospheric parameters derived over neighboring land pixels. This approach is supported by the results obtained from the validation of SCAPE-M over a number of European inland water validation sites which is presented in this work. MERIS-derived aerosol optical thickness, water reflectance and water pigments are compared to in-situ data acquired concurrently to MERIS images in 20 validation match-ups. SCAPE-M has also been compared to specific processors designed for the retrieval of lake water constituents from MERIS data. The performance of SCAPE-M to reproduce ground-based measurements under a range of water types and the ability of MERIS data to monitor chlorophyll-a and phycocyanin pigments using semiempirical algorithms after SCAPE-M processing are discussed. It has been found that SCAPE-M is able to provide high accurate water reflectance over turbid waters, outperforming models based on site-specific bio-optical models, although problems of SCAPE-M to cope with clear waters in some cases have also been identified. © 2009 Elsevier Inc. All rights reserved.

Rodriguez A.,University of La Coruña | Bermudez M.,University of La Coruña | Rabunal J.R.,University of La Coruña | Puertas J.,University of La Coruña | And 3 more authors.
Journal of Computing in Civil Engineering | Year: 2011

Vertical slot fishways are hydraulic structures that allow the upstream migration of fish through obstructions in rivers. The appropriate design of a vertical slot fishway depends on the interplay between hydraulic and biological variables because the hydrodynamic properties of the fishway must match the requirements of the fish species for which it is intended. One of the primary difficulties associated with studies of real fish behavior in fishway models is that the existing mechanisms to measure the behavior of the fish in these assays, such as direct observation or placement of sensors on the specimens, are impractical or unduly affect the animal behavior. This paper proposes a new procedure for measuring the behavior of the fish. The proposed technique uses artificial neural networks and computer vision techniques to analyze images obtained from the assays by means of a camera system designed for fishway integration. It is expected that this technique will provide detailed information about the fish behavior, and it will help to improve fish passage devices, which is currently a subject of interest in the area of civil engineering. A series of assays has been performed to validate this new approach in a full-scale fishway model with living fish. We have obtained very promising results that allow accurate reconstruction of the movements of the fish within the fishway. © 2011 American Society of Civil Engineers.

Molina-Navarro E.,University of Alcalá | Martinez-Perez S.,University of Alcalá | Sastre-Merlin A.,University of Alcalá | Del Pozo D.M.,Center for Hydrographic Studies
Limnetica | Year: 2012

The creation of dams in the riverine zone of large reservoirs is an innovative action whose primary goal is to create water bodies that ensure a stable level of water there.. We have termed these bodies of water 'limno-reservoirs' because their water level becomes constant and independent of the fluctuations occurring in the main reservoir. In addition, limno-reservoirs represent environmental initiatives with corrective and/or compensatory effects. Pareja Limno-reservoir, located near the left side of Entrepeñas Reservoir (Guadalajara province, central Spain), is one of the first initiatives of this type. We are investigating the hydrology, limnology, microbiology, siltation risk and other aspects of this site. This paper focuses on the limnological study of the Pareja Limno-reservoir. To conduct this research, twelve seasonal sample collections at two sampling points (the dam and inflow zones) have been made in Pareja Limno-reservoir (spring 2008-winter 2011). The primary goal of this study is to describe the limnological characteristics of the limno-reservoir, with especial interest in the study of the zooplankton community. The results of the study show that the Pareja Limno-reservoir follows a warm monomictic water stratification pattern. The highest nutrient concentrations were found in the winter, whereas the highest chlorophyll a and phytoplankton biomass values (dominated by Bacillariophyta) were found in the summer and autumn. The results obtained suggest that the Pareja Limnoreservoir is oligo-mesotrophic. The total zooplankton species richness was high, especially in the inflow zone. The most frequently found species are in agreement with those described in other studies performed on the Iberian Peninsula. Rotifers and copepods showed higher relative abundances than cladocerans. © Asociacion Iberica de Limnologia, Madrid. Spain.

Aragon C.A.,Foundation Center for New Water Technologies | Ortega E.,Center for Hydrographic Studies | Ferrer Y.,Center for Hydrographic Studies | Salas J.J.,Foundation Center for New Water Technologies
Desalination and Water Treatment | Year: 2013

Since the 1st of January of 2006, all the agglomerations in the EU Member States must have a collection and treatment system for urban wastewater. The large and medium size populations were the first in being provided by treatment infrastructures, according to the 91/271/ EEC Directive's schedule, meanwhile the small populations (less than 2,000 population equivalent) have been pushed into the background. One of the objectives of the Spanish Programme on Sanitation and Wastewater Treatment (2007-2015) is to address the sanitation and treatment of small populations. However, the information regarding the status of sanitation in those populations is limited and not clear. In order to moderate this lack of information, the Centre for Studies and Experimentation of Public Works and the Centre for New Water Technologies, commissioned by the former Ministry of Environment, have conducted a study based on the compilation and analysis of both diverse official documents and direct inquiries to the responsible authorities in the matter. According to the information compiled, it can be concluded that the coverage of sanitation and wastewater treatment in small Spanish populations is less than 50% and it is estimated that more than 6,000 small size wastewater treatment plants should be built in the near future where long-term solutions must be promoted. © 2013 Balaban Desalination Publications.

Tornos L.,Center for Hydrographic Studies | Huesca M.,University of California at Davis | Dominguez J.A.,Spanish University for Distance Education (UNED) | Moyano M.C.,Center for Hydrographic Studies | And 3 more authors.
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2015

Rice agricultural practices and hydroperiod dates must be determined to obtain information on water management practices and their environmental effects. Spectral indices derived from an 8-day MODIS composite allows to identify rice phenometrics at varying degrees of success. The aims of this study were (1) to assess the dynamics of the Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI(1) and NDWI(2)) and Shortwave Angle Slope Index (SASI) in relation to rice agricultural practices and hydroperiod, and (2) to assess the capability for these indices to detect phenometrics in rice under different flooding regimes. Two rice farming areas in Spain that are governed under different water management practices, the Ebro Delta and Orellana, were studied over a 12-year period (2001-2012). The index time series autocorrelation function was calculated to determine index dynamics in both areas. Secondly, average indices were calculated to identify significant points close to key agricultural and flooding dates, and index behaviors and capacities to identify phenometrics were assessed on a pixel level. The index autocorrelation function produced a regular pattern in both zones, being remarkably homogeneous in the Ebro Delta. It was concluded that a combination of NDVI, NDWI(1), NDWI(2) and SASI may improve the results obtained through each index. NDVI was more effective at detecting the heading date and flooding trends in the Ebro Delta. NDWI(1), NDWI(2) and SASI identified the harvest and the end of environmental flooding in the Delta, and the flooding in Orellana, more effectively. These results may set strong foundations for the development of new strategies in rice monitoring systems, providing useful information to policy makers and environmental studies. © 2014 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).

Though axisymmetric modelling is not widely used it can be incorporated into MODFLOW by "tricking" the grids with a log-scaling method to simulate the radial flow to a well and to upgrade hydraulic properties. Furthermore, it may reduce computer runtimes considerably by decreasing the number of dimensions.The Almonte-Marismas aquifer is a heterogeneous multi-layer aquifer underlying the Doñana area, one of the most important wetlands in Europe. The characterization of hydraulic conductivity is of great importance, because this factor is included in the regional groundwater model, the main water-management support tool in the area. Classical interpretations of existing pumping tests have never taken into account anisotropy, heterogeneity and large head gradients. Thus, to improve the characterization of hydraulic conductivity in the groundwater model, five former pumping tests, located in different hydrogeological areas, have been modelled numerically to represent radial flow in different parts of the aquifer.These numerical simulations have proved to be suitable for reproducing groundwater flow during a pumping test, to corroborate hypotheses concerning unconfined or semi-confined aquifers and even to estimate different hydraulic conductivity values for each lithological layer drilled, which constitutes the main improvement of this model in comparison with classical methods. A comparison of the results shows that the values of the numerical model are similar to those obtained by classical analytic techniques but are always lower for the most permeable layer. It is also clear that the less complex the lithological distribution the more accurate the estimations of hydraulic conductivity.

PubMed | IRSTEA, Center for Hydrographic Studies, National Administration Apele Romane, National Research Council Italy and 3 more.
Type: | Journal: The Science of the total environment | Year: 2015

The status of European legislation regarding inland water quality after the enactment of the Water Framework Directive (WFD) originated scientific effort to develop reliable methods, primarily based on biological parameters. An important aspect of the process was to ensure that quality assessment was comparable between the different Member States. The Intercalibration process (IC), required in the WFD ensures the unbiased application of the norm. The presented results were developed in the context of the 2nd IC phase. An overview of the reservoir type definition of the Lake Mediterranean Geographical Intercalibration Group, where four types were considered divided by both alkalinity and climate, together with the results for selection of Maximum Ecological Potential sites (MEP) are presented. MEP reservoirs were selected based on pressure and biological variables. Three phytoplankton-based assessment methods were intercalibrated using data from Mediterranean countries. The Mediterranean Assessment System for Reservoirs Phytoplankton (Spain), the New Mediterranean Assessment System for Reservoirs Phytoplankton (Portugal and Cyprus) and the New Italian Method (Italy) were applied. These three methods were compared through option 3 of the Intercalibration Guide. The similarity of the assessments was quantified, and the Good/Moderate (GM) boundaries assessed. All three methods stood as comparable at the GM boundary except for the MASRP in siliceous wet reservoirs, which was slightly stricter. Finally, the main taxonomic groups represented in the phytoplankton community at MEP conditions were identified, as well as their main changes with an increasing trophic status. MEP sites are dominated by chrysophytes in siliceous wet reservoirs and by the diatoms Cyclotella and Achnanthes in calcareous ones. Cyanobacteria take over the community in both calcareous and siliceous wet reservoirs as eutrophication increases. In summary, the relevance and reliability of the quality assessment methods compared were confirmed both from an ecological perspective and a health risk management point of view.

PubMed | University of Nottingham, University of Quebec at Chicoutimi, University of Saskatchewan, University of California at Santa Barbara and 35 more.
Type: Review | Journal: Ecology letters | Year: 2016

Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experience periods of snow and ice cover. Relatively little is known of winter ecology in these systems, due to a historical research focus on summer growing seasons. We executed the first global quantitative synthesis on under-ice lake ecology, including 36 abiotic and biotic variables from 42 research groups and 101 lakes, examining seasonal differences and connections as well as how seasonal differences vary with geophysical factors. Plankton were more abundant under ice than expected; mean winter values were 43.2% of summer values for chlorophyll a, 15.8% of summer phytoplankton biovolume and 25.3% of summer zooplankton density. Dissolved nitrogen concentrations were typically higher during winter, and these differences were exaggerated in smaller lakes. Lake size also influenced winter-summer patterns for dissolved organic carbon (DOC), with higher winter DOC in smaller lakes. At coarse levels of taxonomic aggregation, phytoplankton and zooplankton community composition showed few systematic differences between seasons, although literature suggests that seasonal differences are frequently lake-specific, species-specific, or occur at the level of functional group. Within the subset of lakes that had longer time series, winter influenced the subsequent summer for some nutrient variables and zooplankton biomass.

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