To see the other types of publications on this topic, follow the link: Hydrographic system. eng.
Journal articles on the topic 'Hydrographic system. eng'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Hydrographic system. eng.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Urbahs, Aleksandrs, Rima Mickevičienė, Vasilij Djačkov, Kristīne Carjova, Valdas Jankūnas, Mindaugas Zakarauskas, Natalia Panova, and Dita Lasmane. "Analysis of an Unmanned Aerial Vehicle Monitoring System for Resurveying of Shipping Routes." Transport and Aerospace Engineering 3, no. 1 (December 1, 2016): 102–11. http://dx.doi.org/10.1515/tae-2016-0012.
Full textAbstract:
Abstract The paper gives brief description of the conventional and innovative hydrography survey methods and constraints connected with the realization. Proposed hydrographic survey system based on the use of Unmanned Aerial and Maritime systems provides functionality to conduct hydrographic measurements and environment monitoring. System can be easily adapted to fulfil marine safety and security operations, e.g. intrusion threat monitoring, hazardous pollutions monitoring and prevention operations, icing conditions monitoring.
2
Sartor, J. "Simulating the influence of backwater effects in sewer systems using hydrological model components." Water Science and Technology 39, no. 9 (May 1, 1999): 145–52. http://dx.doi.org/10.2166/wst.1999.0463.
Full textAbstract:
A long term simulation for a sewer network by dynamic flow routing models is very time consuming. The alternative hydrological methods (e.g. until hydrographs) have the disadvantage that they are unable to simulate backwater conditions which may significantly effect the flow hydrograph. As one possible solution this payer presents a simulation concept which includes hydrological components to model the effects of backwater or overtopping street level. However, each model component requires a calibration on dynamic routing results because the investigations showed that each sewer system reacts very individually at backwater conditions. This new concept was developed and verified at eight sewer systems.
3
Sun, Qiang, Christopher M. Little, Alice M. Barthel, and Laurie Padman. "A clustering-based approach to ocean model–data comparison around Antarctica." Ocean Science 17, no. 1 (January 19, 2021): 131–45. http://dx.doi.org/10.5194/os-17-131-2021.
Full textAbstract:
Abstract. The Antarctic Continental Shelf seas (ACSS) are a critical, rapidly changing element of the Earth system. Analyses of global-scale general circulation model (GCM) simulations, including those available through the Coupled Model Intercomparison Project, Phase 6 (CMIP6), can help reveal the origins of observed changes and predict the future evolution of the ACSS. However, an evaluation of ACSS hydrography in GCMs is vital: previous CMIP ensembles exhibit substantial mean-state biases (reflecting, for example, misplaced water masses) with a wide inter-model spread. Because the ACSS are also a sparely sampled region, grid-point-based model assessments are of limited value. Our goal is to demonstrate the utility of clustering tools for identifying hydrographic regimes that are common to different source fields (model or data), while allowing for biases in other metrics (e.g., water mass core properties) and shifts in region boundaries. We apply K-means clustering to hydrographic metrics based on the stratification from one GCM (Community Earth System Model version 2; CESM2) and one observation-based product (World Ocean Atlas 2018; WOA), focusing on the Amundsen, Bellingshausen and Ross seas. When applied to WOA temperature and salinity profiles, clustering identifies “primary” and “mixed” regimes that have physically interpretable bases. For example, meltwater-freshened coastal currents in the Amundsen Sea and a region of high-salinity shelf water formation in the southwestern Ross Sea emerge naturally from the algorithm. Both regions also exhibit clearly differentiated inner- and outer-shelf regimes. The same analysis applied to CESM2 demonstrates that, although mean-state model biases in water mass T–S characteristics can be substantial, using a clustering approach highlights that the relative differences between regimes and the locations where each regime dominates are well represented in the model. CESM2 is generally fresher and warmer than WOA and has a limited fresh-water-enriched coastal regimes. Given the sparsity of observations of the ACSS, this technique is a promising tool for the evaluation of a larger model ensemble (e.g., CMIP6) on a circum-Antarctic basis.
4
Elsobeiey, Mohamed Elsayed. "Accuracy Assessment of Satellite-Based Correction Service and Virtual GNSS Reference Station for Hydrographic Surveying." Journal of Marine Science and Engineering 8, no. 7 (July 20, 2020): 542. http://dx.doi.org/10.3390/jmse8070542.
Full textAbstract:
The aim of this paper is to assess the performance of satellite-based correction service, Trimble PP-RTX, and Virtual Reference Stations (VRS) for bathymetry determination, and check how far these techniques meet the minimum standards of the International Hydrography Organization (IHO) for hydrographic surveys. To this end, a three-hour duration session was conducted at Sharm Obhur using KAU-Hydrography 1 vessel. This session includes Global Navigation Satellite System (GNSS) data at the base station using Trimble SPS855 GNSS receiver, multibeam records using Kongsberg EM 712 multibeam echo sounder, sound velocity profile using Valeport’s sound velocity profiler, Applanix POS MV measurements, and real-time PP-RTX corrections. Moreover, the VRS GNSS data was generated using Kingdom of Saudi Arabia Continuous Operation Reference Station network (KSA-CORS). It is shown that the Total Horizontal Uncertainty (THU) and Total Vertical Uncertainty (TVU) of the PP-RTX technique are 5.50 cm and 5.90 cm, respectively, which meets the IHO minimum standards for all survey orders at 95% confidence level. The THU and TVU of the VRS technique, on the other hand, are 5.75 cm and 7.05 cm at 95% confidence level, respectively. These values meet the IHO standards for all survey orders as well. Statistical analysis of the seabed surface differences showed a −0.07 cm average difference between the PP-RTX seabed surface and the reference seabed surface with a standard deviation of 3.60 cm. However, the average difference between the VRS-based seabed surface and the reference seabed surface is −0.03 cm and a standard deviation of 3.61 cm.
5
Afkril, Baina, M. Pramono Hadi, and Slamet Suprayogi. "A New Algorithm For The Grid Cell-Based Runoff Routing Model Based on Travel Time Concept." Geosfera Indonesia 5, no. 2 (June 1, 2020): 160. http://dx.doi.org/10.19184/geosi.v5i2.17351.
Full textAbstract:
The grid cell-based routing model has recently been used to simulate direct runoff hydrographs at catchment scales. This study develops a flexible event-based runoff routing algorithm to simulate a direct runoff hydrograph (DRH). The experiment was based on the spatiotemporal inputs of a hydrological data set. The flexibility is based on the time step and grid cell size applied in the original STORE-DHM. Rainfall distribution was obtained using radar data adjusted by the measured point ground, while the runoff yield was determined using the NRCS-CN method. The parameter distribution was captured in the GIS environment as raster data formats. Furthermore, it was converted into ASCII data formats for scripting the routing algorithm using Matlab programming codes. The model algorithm was tested for storm events within two small study river systems in Yogyakarta, Indonesia. One event in each catchment was selected and calibrated to the observed hydrograph, treating the Curve Number (CN) and Manning coefficient (n) values as parameter calibrations. In the end, two events were selected for validation. The proposed routing model algorithm simulates DRHs of all selected events in the study areas with excellent performance. The Nash-Sutcliffe coefficient was greater than 0.75 for all DRH during validation, and the volume bias and peak discharge error were less than 25%.
Keywords: Algorithm; Cell-based runoff routing; Travel time; GIS; Direct runoff hydrograph.
Copyright (c) 2020 Geosfera Indonesia Journal and Department of Geography Education, University of Jember
This work is licensed under a Creative Commons Attribution-Share A like 4.0 International License
6
Skopeliti, Andriani, Lysandros Tsoulos, and Shachak Pe’eri. "Depth Contours and Coastline Generalization for Harbour and Approach Nautical Charts." ISPRS International Journal of Geo-Information 10, no. 4 (March 25, 2021): 197. http://dx.doi.org/10.3390/ijgi10040197.
Full textAbstract:
Generalization of nautical charts and electronic nautical charts (ENCs) is a critical process which aims at the safety of navigation and clear cartographic presentation. This paper elaborates on the problem of depth contours and coastline generalization—natural and artificial—for medium-scale charts (harbour and approach) taking into account International Hydrographic Organization (IHO) standards, hydrographic offices’ (HOs) best practices and cartographic literature. Additional factors considered are scale, depth, and seafloor characteristics. The proposed method for depth contour generalization utilizes contours created from high-resolution digital elevation models (DEMs) or those already portrayed on nautical charts. Moreover, it ensures consistency with generalized soundings. Regarding natural coastline generalization, the focus was on managing the resolution, while maintaining the shape, and on the islands. For the provision of a suitable generalization solution for the artificial shoreline, it was preprocessed in order to automatically recognize the shape of each structure as perceived by humans (e.g., a pier that looks like a T). The proposed generalization methodology is implemented with custom-developed routines utilizing standard geo-processing functions available in a geographic information system (GIS) environment and thus can be adopted by hydrographic agencies to support their ENC and nautical chart production. The methodology has been tested in the New York Lower Bay area in the U.S.A. Results have successfully delineated depth contours and coastline at scales 1:10 K, 1:20 K, 1:40 K and 1:80 K.
7
Wu, Ray-Shyan, Fiaz Hussain, Yuan-Chien Lin, Tzu-Yu Yeh, and Kai-Chun Yu. "Characterization of Regional Groundwater System Based on Aquifer Response to Recharge–Discharge Phenomenon and Hierarchical Clustering Analysis." Water 13, no. 18 (September 15, 2021): 2535. http://dx.doi.org/10.3390/w13182535.
Full textAbstract:
The investigations of groundwater hydrograph reasonably reflect the aquifer response to recharge–discharge phenomenon and its characteristics. A better understanding of aquifer characteristics such as regional aquifer classification, recharge and discharge patterns, aquifer geology and flow patterns are the surface indicators that may be more effective and less costly for interpreting basic regional hydrogeological conditions and assessments. This study deals with the application of Hierarchical Clustering Analysis to understand the groundwater spatio-temporal patterns and to visualize/classify the nature of the aquifer in the regional area of Kaohsiung City, Taiwan. Groundwater level fluctuation patterns and slopes of rising and recession limbs are used to identify the pumping effects and classify aquifers. The results of clustering analysis show that the groundwater observation wells in the study area can be divided into five major characteristics along with the upstream to downstream of Kaoping River. The clusters are consistent with basic lithology distribution and age of sedimentary, which represents the characteristics of groundwater level fluctuation. The identified groundwater hydrographs patterns provide newer insights related to aquifer response to recharge–discharge phenomenon, types of aquifers and their behaviors. The knowledge of water level fluctuations in the observation wells provides a piece of prior information about the abstraction of groundwater. The proposed aquifer classification and pumping effect have great potential for applied use in groundwater management e.g., save drilling cost.
8
Xu, Jin, Baozhu Jia, Xinxiang Pan, Ronghui Li, Liang Cao, Can Cui, Haixia Wang, and Bo Li. "Hydrographic data inspection and disaster monitoring using shipborne radar small range images with electronic navigation chart." PeerJ Computer Science 6 (September 14, 2020): e290. http://dx.doi.org/10.7717/peerj-cs.290.
Full textAbstract:
Shipborne radars cannot only enable navigation and collision avoidance but also play an important role in the fields of hydrographic data inspection and disaster monitoring. In this paper, target extraction methods for oil films, ships and coastlines from original shipborne radar images are proposed. First, the shipborne radar video images are acquired by a signal acquisition card. Second, based on remote sensing image processing technology, the radar images are preprocessed, and the contours of the targets are extracted. Then, the targets identified in the radar images are integrated into an electronic navigation chart (ENC) by a geographic information system. The experiments show that the proposed target segmentation methods of shipborne radar images are effective. Using the geometric feature information of the targets identified in the shipborne radar images, information matching between radar images and ENC can be realized for hydrographic data inspection and disaster monitoring.
9
Teixeira, Thiara Messias de Almeida, Vládia Pinto Vidal de Oliveira, and Amom Chrystian de Oliveira Teixeira. "Fragilidade Ambiental da Bacia Hidrográfica do Rio São João de Tiba, Extremo Sul da Bahia." Revista Brasileira de Geografia Física 14, no. 4 (2021): 1941–56. http://dx.doi.org/10.26848/rbgf.v14.4.p1941-1956.
Full textAbstract:
The objective of this research was to produce a synthesis map of the environmental fragility of the São João de Tiba Hydrographic Basin located in the South End of Bahia. The basin was incorporated into the process of economic and private megaprojects of extensive territorial occupation such as cellulose, resulting in marked exploitation of natural resources and intense transformations in the landscape. The mapping was done in ArcGis 10 and used the SEI and CPRM geocartographic database. The integrated analysis of the basin allowed the production of products synthesizing the environmental dynamics that present different degrees of fragility of the natural and anthropized environments, which was constituted in a qualitative evaluation, produced from the environmental information. The basin has areas with environmental restrictions that present land uses incompatible with their natural characteristics, generating conditions of degradation of the landscape in the environmental systems in which they are found, what has contributed to the increase of environmental fragility.
10
Stateczny, Andrzej, Marta Włodarczyk-Sielicka, and Grzegorz Zaniewicz. "Using High-Density Bathymetric Data for the Production of Precise ENC." Annual of Navigation 19, no. 2 (December 1, 2012): 99–108. http://dx.doi.org/10.2478/v10367-012-0020-x.
Full textAbstract:
Abstract Due to an increasing trend of replacing traditional paper navigational charts with electronic ones, requirements for the creation of new ENC have been steadily growing. One example is the precise electronic navigational chart, which is based on accurate mapping of topographic and hydrographic elements. Information about depth of the waters contained on the charts are crucial for the safety of navigation. During the production of precise navigational charts, bathymetric information acquired by a multi-beam sonar system (or swath-bathymetry interferometric system) is used. A multi-beam sonar system emits several signal beams from a single transducer in different directions, which allows to cover a hundred percent of the survey area. The authors of the article carried out an analysis of bathymetric data in terms of differences in their preparation for the production of precise ENC.
11
Wlodarczyk-Sielicka, Marta, and Wioleta Blaszczak-Bak. "Processing of Bathymetric Data: The Fusion of New Reduction Methods for Spatial Big Data." Sensors 20, no. 21 (October 30, 2020): 6207. http://dx.doi.org/10.3390/s20216207.
Full textAbstract:
Floating autonomous vehicles are very often equipped with modern systems that collect information about the situation under the water surface, e.g., the depth or type of bottom and obstructions on the seafloor. One such system is the multibeam echosounder (MBES), which collects very large sets of bathymetric data. The development and analysis of such large sets are laborious and expensive. Reduction of the spatial data obtained from bathymetric and other systems collecting spatial data is currently widely used. In commercial programs used in the development of data from hydrographic systems, methods of interpolation to a specific mesh size are very frequently used. The authors of this article previously proposed original the true bathymetric data reduction method (TBDRed) and Optimum Dataset (OptD) reduction methods, which maintain the actual position and depth for each of the measured points, without their interpolation. The effectiveness of the proposed methods has already been presented in previous articles. This article proposes the fusion of original reduction methods, which is a new and innovative approach to the problem of bathymetric data reduction. The article contains a description of the methods used and the methodology of developing bathymetric data. The proposed fusion of reduction methods allows the generation of numerical models that can be a safe, reliable source of information, and a basis for design. Numerical models can also be used in comparative navigation, during the creation of electronic navigation maps and other hydrographic products.
12
Saul, A. J., and D. R. Ellis. "Sediment Deposition in Storage Tanks." Water Science and Technology 25, no. 8 (April 1, 1992): 189–98. http://dx.doi.org/10.2166/wst.1992.0193.
Full textAbstract:
The use of storage tanks in sewerage systems has increased in recent years. The primary functions of such tanks are to attenuate flow and to retain pollutants within the sewer system. The size of the required storage volume is dependent on the purpose for which the tank is to be used but the end product of any design analysis is the definition of fixed volume of storage which has to be included as part of the sewerage system. The main problem is to provide storage and effective separation of gross and suspended solids without incurring poor self cleansing and associated high maintenance costs. The work outlined in this paper involved the development of a laboratory computer controlled monitoring system for the purpose of flow visualisation and for the comparative assessment of the sediment deposition and removal performance of different geometric configurations of storage tank. These systems used sophisticated control procedures and the latter had the facility to generate a flow hydrograph of any shape and duration and to superimpose on this hydrograph a pollutograph of synthetic sediment, in this case crushed olive stone wood flour. Particular attention was focused on the optimum length to breadth ratio for a given storage volume, the configuration of the chamber floor - number, shape and gradient of dry weather flow channels and benching (gradient; the type of roof support and the effect of multiple storms on the redistribution of deposited sediment. The results of the work illustrated that very complex flow patterns were established within the storage tanks as the flow hydrograph was discharged through the system and that these flow patterns governed the sediment settlement, re-entrainment and transport processes in the tank. The velocity distribution within each chamber was a function of tank geometry, the shape, volume, and duration of the inflow hydrograph and the throughflow setting. The paper is concluded by a series of recommendations to aid the design of storage tanks.
13
Pagonas, M., and N. Kontopoulos. "Morphometric and hydrographie characteristics of torrents of NW Péloponnèse, Greece." Bulletin of the Geological Society of Greece 40, no. 4 (January 1, 2007): 1578. http://dx.doi.org/10.12681/bgsg.17062.
Full textAbstract:
The study area includes the catchments of Selemnos, Xylokeras and Volinaios torrents, with 456 streams of 277.848 km total length. The pattern is generally dendritic. A quantitative analysis of the drainage systems of the study area was interpreted and then correlated to the fault systems that appear in the area. The main direction of the streams and the tectonic features is WSW-ENE. The drainage density and stream frequency is highly variable as a result of many factors, most important of which is lithology with high infiltration capacity. The number and the length of most streams show divergence of the 1st and 2nd law of Horton since they have dissimilar values from those theoretically expected.
14
Fratantoni, Paula S., and Robert S. Pickart. "The Western North Atlantic Shelfbreak Current System in Summer." Journal of Physical Oceanography 37, no. 10 (October 1, 2007): 2509–33. http://dx.doi.org/10.1175/jpo3123.1.
Full textAbstract:
Abstract Twelve years of historical hydrographic data, spanning the period 1990–2001, are analyzed to examine the along-stream evolution of the western North Atlantic Ocean shelfbreak front and current, following its path between the west coast of Greenland and the Middle Atlantic Bight. Over 700 synoptic sections are used to construct a mean three-dimensional description of the summer shelfbreak front and to quantify the along-stream evolution in properties, including frontal strength and grounding position. Results show that there are actually two fronts in the northern part of the domain—a shallow front located near the shelf break and a deeper front centered in the core of Irminger Water over the upper slope. The properties of the deeper Irminger front erode gradually to the south, and the front disappears entirely near the Grand Banks of Newfoundland. The shallow shelfbreak front is identifiable throughout the domain, and its properties exhibit large variations from north to south, with the largest changes occurring near the Tail of the Grand Banks. Despite these structural changes, and large variations in topography, the foot of the shelfbreak front remains within 20 km of the shelf break. The hydrographic sections are also used to examine the evolution of the baroclinic velocity field and its associated volume transport. The baroclinic velocity structure consists of a single velocity core that is stronger and penetrates deeper where the Irminger front is present. The baroclinic volume transport decreases by equal amounts at the southern end of the Labrador Shelf and at the Tail of the Grand Banks. Overall, the results suggest that the Grand Banks is a geographically critical location in the North Atlantic shelfbreak system.
15
Ding, J. Y. "A measure of watershed nonlinearity: interpreting a variable instantaneous unit hydrograph model on two vastly different sized watersheds." Hydrology and Earth System Sciences 15, no. 1 (January 31, 2011): 405–23. http://dx.doi.org/10.5194/hess-15-405-2011.
Full textAbstract:
Abstract. The linear unit hydrograph used in hydrologic design analysis and flood forecasting is known as the transfer function and the kernel function in time series analysis and systems theory, respectively. This paper reviews the use of an input-dependent or variable kernel in a linear convolution integral as a quasi-nonlinear approach to unify nonlinear overland flow, channel routing and catchment runoff processes. The conceptual model of a variable instantaneous unit hydrograph (IUH) is characterized by a nonlinear storage-discharge relation, q = cNsN, where the storage exponent N is an index or degree of watershed nonlinearity, and the scale parameter c is a discharge coefficient. When the causative rainfall excess intensity of a unit hydrograph is known, parameters N and c can be determined directly from its shape factor, which is the product of the unit peak ordinate and the time to peak, an application of the statistical method of moments in its simplest form. The 2-parameter variable IUH model is calibrated by the shape factor method and verified by convolution integral using both the direct and inverse Bakhmeteff varied-flow functions on two watersheds of vastly different sizes, each having a family of four or five unit hydrographs as reported by the well-known Minshall (1960) paper and the seldom-quoted Childs (1958) one, both located in the US. For an 11-hectare catchment near Edwardsville in southern Illinois, calibration for four moderate storms shows an average N value of 1.79, which is 7% higher than the theoretical value of 1.67 by Manning friction law, while the heaviest storm, which is three to six times larger than the next two events in terms of the peak discharge and runoff volume, follows the Chezy law of 1.5. At the other end of scale, for the Naugatuck River at Thomaston in Connecticut having a drainage area of 186.2 km2, the average calibrated N value of 2.28 varies from 1.92 for a minor flood to 2.68 for a hurricane-induced flood, all of which lie between the theoretical value of 1.67 for turbulent overland flow and that of 3.0 for laminar overland flow. Based on analytical results from the small Edwardsville catchment, the 2-parameter variable IUH model is found to be defined by a quadruplet of parameters N, c, the storm duration or computational time step Δt, and the rainfall excess intensity i(0), and that it may be reduced to an 1-parameter one by defaulting the degree of nonlinearity N to 1.67 by Manning friction. For short, intense storms, the essence of the Childs – Minshall nonlinear unit hydrograph phenomenon is encapsulated in a peak flow equation having a single (scale) parameter c, and in which the impact of the rainfall excess intensity increases from the linear assumption by a power of 0.4. To illustrate key steps in generating the direct runoff hydrograph by convolution integral, short examples are given.
16
Pe’eri, Shachak, and Noel Dyer. "Adding value to ENCs: Land features." Abstracts of the ICA 1 (July 15, 2019): 1. http://dx.doi.org/10.5194/ica-abs-1-293-2019.
Full textAbstract:
<p><strong>Abstract.</strong> In the 1990’s, the International Maritime Organization (IMO) adopted the International Hydrographic Office’s (IHO) S-57 performance standards for Electronic Navigation Charts (ENC), which enforce standardized content, structure, and format. The IMO also revised its Safety of Life at Sea (SOLAS) chapter V regulations to require Electronic Chart Display and Information Systems (ECDIS) onboard certain SOLAS class vessels, starting from 2018. These systems allow for navigating with ENC data, which has several advantages over paper charts; however, many mariners still prefer traditional paper or raster charts. Through the feedback of key stakeholders such as local pilot associations, it has become apparent that the preference for raster or paper charts is due to the inclusion of non-critical S-57 land features. These S-57 land features, which are typically not added to ENC products, such as roads and elevation contours, can supplement navigational positioning systems by providing visual references, particularly when other landmarks (e.g., spot elevations on major topographic features) are not present on the ENC. Moreover, charting roads on ENC products can be useful for locating water access points. This paper discusses the addition of roads and land elevation contours to NOAA’s re-schemed ENC suite in an effort to supplement currently charted marine features and land features crossing over water. General cartographic guidelines have also been developed for the representation of these features through ENC scales (i.e., usage bands 3 to 5). Additionally, this paper includes a discussion on the benefits and challenges of incorporating publicly available land transportation data versus traditional sources on ENC products.</p>
17
Takeshita, Y., C. A. Frieder, T. R. Martz, J. R. Ballard, R. A. Feely, S. Kram, S. Nam, M. O. Navarro, N. N. Price, and J. E. Smith. "Including high-frequency variability in coastal ocean acidification projections." Biogeosciences 12, no. 19 (October 14, 2015): 5853–70. http://dx.doi.org/10.5194/bg-12-5853-2015.
Full textAbstract:
Abstract. Assessing the impacts of anthropogenic ocean acidification requires knowledge of present-day and future environmental conditions. Here, we present a simple model for upwelling margins that projects anthropogenic acidification trajectories by combining high-temporal-resolution sensor data, hydrographic surveys for source water characterization, empirical relationships of the CO2 system, and the atmospheric CO2 record. This model characterizes CO2 variability on timescales ranging from hours (e.g., tidal) to months (e.g., seasonal), bridging a critical knowledge gap in ocean acidification research. The amount of anthropogenic carbon in a given water mass is dependent on the age; therefore a density–age relationship was derived for the study region and then combined with the 2013 Intergovernmental Panel on Climate Change CO2 emission scenarios to add density-dependent anthropogenic carbon to the sensor time series. The model was applied to time series from autonomous pH sensors deployed in the surf zone, kelp forest, submarine canyon edge, and shelf break in the upper 100 m of the Southern California Bight. All habitats were within 5 km of one another, and exhibited unique, habitat-specific CO2 variability signatures and acidification trajectories, demonstrating the importance of making projections in the context of habitat-specific CO2 signatures. In general, both the mean and range of pCO2 increase in the future, with the greatest increase in both magnitude and range occurring in the deeper habitats due to reduced buffering capacity. On the other hand, the saturation state of aragonite (ΩAr) decreased in both magnitude and range. This approach can be applied to the entire California Current System, and upwelling margins in general, where sensor and complementary hydrographic data are available.
18
Takeshita, Y., C. A. Frieder, T. R. Martz, J. R. Ballard, R. A. Feely, S. Kram, S. Nam, M. O. Navarro, N. N. Price, and J. E. Smith. "Including high frequency variability in coastal ocean acidification projections." Biogeosciences Discussions 12, no. 9 (May 13, 2015): 7125–76. http://dx.doi.org/10.5194/bgd-12-7125-2015.
Full textAbstract:
Abstract. Assessing the impacts of anthropogenic ocean acidification requires knowledge of present-day and future environmental conditions. Here, we present a simple model for upwelling margins that projects anthropogenic acidification trajectories by combining high-temporal resolution sensor data, hydrographic surveys for source water characterization, empirical relationships of the CO2 system, and the atmospheric CO2 record. This model characterizes CO2 variability on timescales ranging from hours (e.g. tidal) to months (e.g. seasonal), bridging a critical knowledge gap in ocean acidification research. The amount of anthropogenic carbon in a given water mass is dependent on the age, therefore a density–age relationship was derived for the study region, and was combined with the 2013 Intergovernmental Panel on Climate Change CO2 emission scenarios to add density-dependent anthropogenic carbon to the sensor time series. The model was applied to time series from four autonomous pH sensors, each deployed in the surf zone, kelp forest, submarine canyon edge, and shelf break in the upper 100 m of the Southern California Bight. All habitats were within 5 km of one another, and exhibited unique, habitat-specific CO2 variability signatures and acidification trajectories, demonstrating the importance of making projections in the context of habitat-specific CO2 signatures. In general, both the mean and range of pCO2 increase in the future, with the greatest increases in both magnitude and range occurring in the deeper habitats due to reduced buffering capacity. On the other hand, the saturation state of aragonite (ΩAr) decreased in both magnitude and range. This approach can be applied to the entire California Current System, and upwelling margins in general, where sensor and complementary hydrographic data are available.
19
Cortina G., Cecilia Z., Rochelle Wigley, and Shachak Pe'eri. "The GEBCO and NOAA Chart Adequacy Workshop." Abstracts of the ICA 1 (July 15, 2019): 1. http://dx.doi.org/10.5194/ica-abs-1-51-2019.
Full textAbstract:
<p><strong>Abstract.</strong> On July 23, NOAA Coast Survey hosted a three-day Chart Adequacy Workshop that included participants from 13 countries. This is the fourth Chart Adequacy Workshop held at National Oceanic and Atmospheric Administration’s (NOAA) Silver Spring, Maryland campus. This was the fourth workshop hosted by NOAA and Nippon Foundation / General Bathymetric Chart of the Oceans (GEBCO) Training Program at the Center for Coastal and Ocean Mapping, UNH. Unlike previous years (2017, 2016, 2015), the focus of this week was on networking and support for the upcoming International Cartographic Association (ICA) Working Group on Marine Cartography meeting held on July 26 and in preparation for next year’s International Cartographic Conference (ICC).</p><p> The main goal of the workshop is to provide training for professional cartographers and hydrographers on techniques for assessing nautical chart adequacy using publicly-available information, such as satellite images and maritime automatic identification system (AIS) data. . The participants received an overview on Coast Survey datasets, processes, and requirements for nautical charts. They also learned about pre-processing hydrographic data, such as loading charts, uploading imagery, and applying electronic navigation charts (ENCs) and AIS point data. Through a series of lab units, the attendees practiced performing the concepts they learned.</p><p>The 2018 participants were from Australia, Greece, Ireland, Japan, Latvia, Madagascar, Mexico, Nigeria, Peru, Poland, St. Vincent and the Grenadines, Taiwan, and Trinidad and Tobago. The international nature of the event allows the participants to meet and learn from cartographers from a variety of backgrounds and expertises. Thee individuals include Nippon Foundation / GEBCO training program students and those nominated by their home hydrographic offices and their travel was sponsored through funds secured by the workshop organizers.</p><p> The workshop was developed in part too address the need to improve the collection, quality, and availability of hydrographic data world-wide, and increase the standardization of chart adequacy evaluations across the globe. Coast Survey is currently working with the International Hydrographic Organization (IHO) to recommend participants for next year’s workshop towards the end of July, 2019.</p>
20
Armansyah, Dodik, Widodo Pranowo, Yanu Madawanto, and Octav Dirgantara. "Solusi Akses ENC S-63 Pushidrosal Untuk Kapal Angkatan Laut, Pangkalan Dan Marinir." Jurnal Chart Datum 7, no. 1 (July 29, 2021): 37–46. http://dx.doi.org/10.37875/chartdatum.v7i1.188.
Full textAbstract:
PLI (Peta Laut Indonesia) dan ENC (Electronic Nautical Chart) adalah produk utama Pushidrosal sebagai lembaga hidrogafi yang dipergunakan untuk keselamatan navigasi. Konvensi SOLAS (Safety of Life at Sea) mengatur bahwa peta navigasi laut yang legal adalah produk dari lembaga hidrografi yang menjadi perwakilan negara di IHO (International Hydrographic Organization). IMO (International Maritime Organization) telah mewajibkan program ECDIS (Electronic Chart Display Information System) mandatory terutama bagi kapal – kapal yang digunakan untuk pelayaran internasional. Hal tersebut mendorong semakin berkembangnya ENC (Electronic Nautical Chart) sebagai produk utama lembaga hidrografi. Pushidrosal mendistribusikan ENC dengan standar S-63. Standar ENC S-63 menjamin keamanan data melalui metode enkripsi. KAL (Kapal Angkatan Laut), Pangkalan Angkatan Laut dan Marinir memerlukan peta laut yang di-update secara periodik sebagai data referensi wilayahnya. Idealnya unit – unit tersebut mempunyai ECDIS agar dapat mengakses ENC S-63 sebagai produk yang update setiap bulan, namun terkendala oleh biaya yang mahal. Hambatan tersebut kini dapat diatasi dengan adanya software ECS (Electronic Charting System) OpenCPN yang dilengkapi dengan S-63 plugin. Dengan kemampuan tersebut, OpenCPN memberikan solusi bagi KAL, Pangkalan dan Marinir untuk dapat mengakses dan memanfaatkan produk ENC S-63, sehingga peta laut yang menjadi referensi adalah peta digital yang selalu dapat di-update secara periodik dengan mudah.
21
KOUTRAKIS, E., G. EMFIETZIS, G. SYLAIOS, M. ZOIDOU, M. KATSIAPI, and M. MOUSTAKA-GOUNI. "MASSIVE FISH MORTALITY IN ISMARIDA LAKE, GREECE: IDENTIFICATION OF DRIVERS CONTRIBUTING TO THE FISH KILL EVENT." Mediterranean Marine Science 17, no. 1 (March 30, 2016): 280. http://dx.doi.org/10.12681/mms.1481.
Full textAbstract:
During the end of August 2013, a massive fish mortality occurred in Ismarida Lake, a small and shallow system of Northern Greece, where approximately 10-18 tons of euryhaline fish died. This study attempts to describe the event of this fish kill or Massive Fish Mortality (MFM) that occurred in Ismarida Lake during the night of August 28, 2013, and to identify the possible drivers that may have triggered this event. A combined hydrographic, ichthyological and phytoplankton survey were carried out along with a toxicological analysis. Finally, the study proposes both short-term and long-term measures for the management of both quality and quantity of the water (ground and surface) resources in the broader basin of Ismarida Lake.
22
Oddo, P., and A. Guarnieri. "A Study of the hydrographic conditions in the Adriatic Sea from numerical modelling and direct observations (2000–2008)." Ocean Science Discussions 8, no. 2 (March 22, 2011): 565–611. http://dx.doi.org/10.5194/osd-8-565-2011.
Full textAbstract:
Abstract. The inter-annual variability of Adriatic Sea hydrographic characteristics is investigated by means of numerical simulation and direct observation. The period investigated runs from the beginning of 2000 to the end of 2008. The model used to carry out the simulation is derived from the primitive equation component of the Adriatic Forecasting System (AFS). The model is based on the Princeton Ocean Model (POM) adapted in order to reproduce the features of the Adriatic. Both numerical findings and observations agree in depicting a strong inter-annual variability in the entire Adriatic Sea and its sub-basins. The dense water formation process has been found to be intermittent. In addition to inter-annual variability, a long-scale signal has been observed in the salinity content of the basin as a consequence of a prolonged period of reduced Po river runoff and high evaporation rates. As a result, the temperature and salinity of the northern Adriatic dense water vary considerably between the beginning and the end of the period investigated.
23
de Andrade Moraes, Mirene Augusta, Jorge A. García Zumalacarregui, Camila Maria Trein, Vinícius Verna M. Ferreira, and Marcos von Sperling. "Outflow dynamics in a French system of vertical wetlands operating with an extended feeding cycle." Water Science and Technology 79, no. 4 (February 15, 2019): 699–708. http://dx.doi.org/10.2166/wst.2019.088.
Full textAbstract:
Abstract The possibility of using the first stage of the French System (FS) of vertical wetlands composed of only two units in parallel requires hydraulic investigations to allow a better understanding of its operation under tropical climatic environments. This study evaluated the pattern of the outflow hydrograph along an extended cycle of operation (seven days of feeding) and the influence of the sludge deposit, rainfall occurrence and duration of pulse application on the outflow hydrograph in a modified full-scale FS in Brazil. The results indicated that, as the feeding cycle days increased, there was an increase in the time of filtration and the internal storage of the liquid volume, probably due to a reduction in the filter permeability. Greater hydraulic gradient favoured the infiltration velocity, decreased the amount of liquid stored within the system, and delayed the loss of permeability. The sludge layer contributed to a momentary liquid retention, and also allowed greater evapotranspiration, reducing the liquid volume to be treated. The sludge deposit seemed to hinder the liquid percolation, especially at the end of the cycle, modifying the hydraulic conductivity of the filter as a whole. Intense rainfall events demonstrated that precipitation could modify the flow dynamics within the system.
24
Charrieau, Laurie M., Karl Ljung, Frederik Schenk, Ute Daewel, Emma Kritzberg, and Helena L. Filipsson. "Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance." Biogeosciences 16, no. 19 (October 7, 2019): 3835–52. http://dx.doi.org/10.5194/bg-16-3835-2019.
Full textAbstract:
Abstract. The Öresund (the Sound), which is a part of the Danish straits, is linking the marine North Sea and the brackish Baltic Sea. It is a transition zone where ecosystems are subjected to large gradients in terms of salinity, temperature, carbonate chemistry, and dissolved oxygen concentration. In addition to the highly variable environmental conditions, the area is responding to anthropogenic disturbances in, e.g., nutrient loading, temperature, and pH. We have reconstructed environmental changes in the Öresund during the last ca. 200 years, and especially dissolved oxygen concentration, salinity, organic matter content, and pollution levels, using benthic foraminifera and sediment geochemistry. Five zones with characteristic foraminiferal assemblages were identified, each reflecting the environmental conditions for the respective period. The largest changes occurred around 1950, when the foraminiferal assemblage shifted from a low diversity fauna dominated by the species Stainforthia fusiformis to higher diversity and abundance and dominance of the Elphidium species. Concurrently, the grain-size distribution shifted from clayey to sandier sediment. To explore the causes of the environmental changes, we used time series of reconstructed wind conditions coupled with large-scale climate variations as recorded by the North Atlantic Oscillation (NAO) index as well as the ECOSMO II model of currents in the Öresund area. The results indicate increased changes in the water circulation towards stronger currents in the area after the 1950s. The foraminiferal fauna responded quickly (<10 years) to the environmental changes. Notably, when the wind conditions, and thereby the current system, returned in the 1980s to the previous pattern, the foraminiferal assemblage did not rebound. Instead, the foraminiferal faunas displayed a new equilibrium state.
25
Oddo, P., and A. Guarnieri. "A study of the hydrographic conditions in the Adriatic Sea from numerical modelling and direct observations (2000–2008)." Ocean Science 7, no. 5 (September 6, 2011): 549–67. http://dx.doi.org/10.5194/os-7-549-2011.
Full textAbstract:
Abstract. The inter-annual variability of Adriatic Sea hydrographic characteristics is investigated by means of numerical simulation and direct observation. The period under investigation runs from the beginning of 2000 to the end of 2008. The model used to carry out the simulation is derived from the primitive equation component of the Adriatic Forecasting System (AFS). The model is based on the Princeton Ocean Model (POM) adapted in order to reproduce the features of the Adriatic. Both numerical findings and observations agree in depicting a strong inter-annual variability in the entire Adriatic Sea and its sub-basins. Nevertheless, two model deficiencies are identified: an excessive vertical/horizontal mixing and an inaccurate representation of the thermohaline properties of the entering Mediterranean Waters. The dense water formation process has been found to be intermittent. In addition to inter-annual variability, a long-scale signal has been observed in the salinity content of the basin as a consequence of a prolonged period of reduced Po river runoff and high evaporation rates. As a result, the temperature and salinity of the northern Adriatic dense water vary considerably between the beginning and the end of the period investigated.
26
Karpf, Christian, Stefan Hoeft, Claudia Scheffer, Lothar Fuchs, and Peter Krebs. "Groundwater infiltration, surface water inflow and sewerage exfiltration considering hydrodynamic conditions in sewer systems." Water Science and Technology 63, no. 9 (May 1, 2011): 1841–48. http://dx.doi.org/10.2166/wst.2011.388.
Full textAbstract:
Sewer systems are closely interlinked with groundwater and surface water. Due to leaks and regular openings in the sewer system (e.g. combined sewer overflow structures with sometimes reverse pressure conditions), groundwater infiltration and surface water inflow as well as exfiltration of sewage take place and cannot be avoided. In the paper a new hydrodynamic sewer network modelling approach will be presented, which includes – besides precipitation – hydrographs of groundwater and surface water as essential boundary conditions. The concept of the modelling approach and the models to describe the infiltration, inflow and exfiltration fluxes are described. The model application to the sewerage system of the City of Dresden during a flood event with complex conditions shows that the processes of infiltration, exfiltration and surface water inflows can be described with a higher reliability and accuracy, showing that surface water inflow causes a pronounced system reaction. Further, according to the simulation results, a high sensitivity of exfiltration rates on the in-sewer water levels and a relatively low influence of the dynamic conditions on the infiltration rates were found.
27
Gnecco, Ilaria, Anna Palla, and Paolo La Barbera. "A dimensionless approach for the runoff peak assessment: effects of the rainfall event structure." Hydrology and Earth System Sciences 22, no. 2 (February 2, 2018): 943–56. http://dx.doi.org/10.5194/hess-22-943-2018.
Full textAbstract:
Abstract. The present paper proposes a dimensionless analytical framework to investigate the impact of the rainfall event structure on the hydrograph peak. To this end a methodology to describe the rainfall event structure is proposed based on the similarity with the depth–duration–frequency (DDF) curves. The rainfall input consists of a constant hyetograph where all the possible outcomes in the sample space of the rainfall structures can be condensed. Soil abstractions are modelled using the Soil Conservation Service method and the instantaneous unit hydrograph theory is undertaken to determine the dimensionless form of the hydrograph; the two-parameter gamma distribution is selected to test the proposed methodology. The dimensionless approach is introduced in order to implement the analytical framework to any study case (i.e. natural catchment) for which the model assumptions are valid (i.e. linear causative and time-invariant system). A set of analytical expressions are derived in the case of a constant-intensity hyetograph to assess the maximum runoff peak with respect to a given rainfall event structure irrespective of the specific catchment (such as the return period associated with the reference rainfall event). Looking at the results, the curve of the maximum values of the runoff peak reveals a local minimum point corresponding to the design hyetograph derived according to the statistical DDF curve. A specific catchment application is discussed in order to point out the dimensionless procedure implications and to provide some numerical examples of the rainfall structures with respect to observed rainfall events; finally their effects on the hydrograph peak are examined.
28
Kravchuk, O. "SYRIAN-TURKISH RELATIONSHIPS IN THE CONTEXT OF REGIONAL MIDDLE EASTERN INTERNATIONAL RELATIONS SYSTEM." ACTUAL PROBLEMS OF INTERNATIONAL RELATIONS, no. 128 (2016): 28–39. http://dx.doi.org/10.17721/apmv.2016.128.0.28-39.
Full textAbstract:
The article spotlights decisive factors of the Syrian-Turkish interstate relations evolution after the end of the Cold War, special attention was given to clarify place of the water and the Kurdish problems in the relations between the two countries. After World War I in Syria and many other Arab states the Republic of Turkey was seen primarily as a legal successor of the Ottoman Empire that for several centuries colonized these countries and prevented their civilizational development. With the collapse of the bipolar system of international relations between Syria and Turkey broke a serious struggle for influence in the region. An important security problem in the Syrian-Turkish relations was left water, ie the distribution of resources river Euphrates because hydrographic feature of the Middle East is extremely uneven distribution of freshwater. Normalization of bilateral interstate relations delineated only with coming to power in Republic of Turkey the moderate Islamist Justice and Development Party led by Recep Tayyip Erdogan, whose foreign policy aimed at establishing closer ties with the Middle East countries and a visible mediating role in resolving the Arab-Israeli conflict. Immediately after the consolidation of the power vertical Justice and Development Party began to distance itself from Israel in order to establish a more open dialogue with Mashriq states.
29
Håvik, Lisbeth, Mattia Almansi, Kjetil Våge, and Thomas W. N. Haine. "Atlantic-Origin Overflow Water in the East Greenland Current." Journal of Physical Oceanography 49, no. 9 (September 2019): 2255–69. http://dx.doi.org/10.1175/jpo-d-18-0216.1.
Full textAbstract:
AbstractDense water masses transported southward along the east coast of Greenland in the East Greenland Current (EGC) form the largest contribution to the Denmark Strait Overflow. When exiting Denmark Strait these dense water masses sink to depth and feed the deep circulation in the North Atlantic. Based on one year of mooring observations upstream of Denmark Strait and historical hydrographic profiles between Fram Strait and Denmark Strait, we find that a large part (75%) of the overflow water ( ≥ 27.8 kg m−3) transported by the EGC is of Atlantic origin (potential temperature θ > 0°C). The along-stream changes in temperature of the Atlantic-origin Water are moderate north of 69°N at the northern end of Blosseville basin, but southward from this point the temperature decreases more rapidly. We hypothesize that this enhanced modification is related to the bifurcation of the EGC taking place close to 69°N into the shelfbreak EGC and the separated EGC. This is associated with enhanced eddy activity and strong water mass modification reducing the intermediate temperature and salinity maxima of the Atlantic-origin Water. During periods with a large (small) degree of modification the separated current is strong (weak). Output from a high-resolution numerical model supports our hypothesis and reveals that large eddy activity is associated with an offshore shift of the surface freshwater layer that characterizes the Greenland shelf. The intensity of the eddy activity regulates the density and the hydrographic properties of the Denmark Strait Overflow Water transported by the EGC system.
30
Piquet, A. M. T., W. H. van de Poll, R. J. W. Visser, C. Wiencke, H. Bolhuis, and A. G. J. Buma. "Springtime phytoplankton dynamics in the Arctic Krossfjorden and Kongsfjorden (Spitsbergen) as a function of glacier proximity." Biogeosciences Discussions 10, no. 10 (October 1, 2013): 15519–57. http://dx.doi.org/10.5194/bgd-10-15519-2013.
Full textAbstract:
Abstract. The hydrographic properties of the Kongsfjorden – Krossfjorden system (79° N, Spitsbergen) are affected by Atlantic water incursions as well as glacier meltwater runoff. This results in strong physical gradients (temperature, salinity and irradiance) within the fjords. Here, we tested the hypothesis that glaciers affect phytoplankton dynamics as early as the productive spring bloom period. During two campaigns in 2007 (late spring) and 2008 (early spring) we studied hydrographic characteristics and phytoplankton variability along 2 transects in both fjords, using HPLC-CHEMTAX pigment fingerprinting, molecular fingerprinting (DGGE) and sequencing of 18S rRNA genes. The sheltered inner fjord locations remained colder during spring as opposed to the outer locations. Vertical light attenuation coefficients increased from early spring onwards, at all locations, but in particular at the inner locations. During the end of spring, meltwater input had stratified surface waters throughout the fjords. The inner fjord locations were characterized by overall lower phytoplankton biomass. Furthermore HPLC-CHEMTAX data revealed that diatoms and Phaeocystis sp. were replaced by small nano- and picophytoplankton during late spring, coinciding with low nutrient availability. The innermost stations showed higher relative abundances of nano- and picophytoplankton throughout, notably of cyanophytes and cryptophytes. Molecular fingerprinting revealed a high similarity between inner fjord samples from early spring and late spring samples from all locations, while outer samples from early spring clustered separately. We conclude that glacier influence, mediated by early meltwater input, modifies phytoplankton biomass and composition already during the spring bloom period, in favor of low biomass and small cell size communities. This may affect higher trophic levels especially when regional warming further increases the period and volume of meltwater.
31
Perumal, Muthiah, Tommaso Moramarco, Silvia Barbetta, Florisa Melone, and Bhabagrahi Sahoo. "Real-time flood stage forecasting by Variable Parameter Muskingum Stage hydrograph routing method." Hydrology Research 42, no. 2-3 (April 1, 2011): 150–61. http://dx.doi.org/10.2166/nh.2011.063.
Full textAbstract:
The application of a Variable Parameter Muskingum Stage (VPMS) hydrograph routing method for real-time flood forecasting at a river gauging site is demonstrated in this study. The forecast error is estimated using a two-parameter linear autoregressive model with its parameters updated at every routing time interval of 30 minutes at which the stage observations are made. This hydrometric data-based forecast model is applied for forecasting floods at the downstream end of a 15 km reach of the Tiber River in Central Italy. The study reveals that the proposed approach is able to provide reliable forecast of flood estimate for different lead times subject to a maximum lead time nearly equal to the travel time of the flood wave within the selected routing reach. Moreover, a comparative study of the VPMS method for real-time forecasting and the simple stage forecasting model (STAFOM), currently in operation as the Flood Forecasting and Warning System in the Upper-Middle Tiber River basin of Italy, demonstrates the capability of the VPMS model for its field use.
32
Skidmore, Mark L., and Martin J. Sharp. "Drainage system behaviour of a High-Arctic polythermal glacier." Annals of Glaciology 28 (1999): 209–15. http://dx.doi.org/10.3189/172756499781821922.
Full textAbstract:
AbstractMeasurements made at John Evans Glacier, eastern Ellesmere Island, Nunavut, Canada in 1994 and 1996 provide new insight into the internal hydrology of polythermal glaciers. During the early part of each melt season, supraglacial waters enter the glacier via a crevasse field about 4 km from the terminus and are stored in a subglacial reservoir. Release of the water from the reservoir occurs initially via an artesian fountain on the glacier surface and by upwelling of waters through subglacial sediments at the terminus (event1). Channelization of the subglacial waters then occurs and water is discharged as an outburst flood (event 2), which releases a considerably larger volume of water than event 1. Thus, drainage of the subglacial reservoir follows a cyclical pattern in which discharge oscillations increase in amplitude over time. The cycle may end with complete reservoir drainage. The total volume of water released was much greater in 1994 than in 1996, primarily because the 1994 melt season was longer and warmer than the 1996 season. Interannual differences in the form of the outflow hydrographs, and in the extent and timing of connections between the subglacial reservoir and marginal melt streams, are linked to variations in the size and rate of growth of the subglacial reservoir. This hydrological behaviour may have important implications for the dynamics of polythermal glaciers.
33
Fernandes, Manoel Do Couto, João Vicente Marques Lagüéns, and Ana Luiza Coelho Netto. "O processo de ocupação por favelas e sua relação com os eventos de deslizamentos no Maciço da Tijuca/RJ." Anuário do Instituto de Geociências 22 (January 1, 1999): 45–59. http://dx.doi.org/10.11137/1999_0_45-59.
Full textAbstract:
Tijuca massif is marked by mountainous relief which can be devided into five great hydrographic sub-systems (sectors), with They have a different abiotic, biotic and occupation arrangement. This structure is consequence of massif's condition in Rio de Janeiro occupation process. This way, the study to searched understand the importance of slums ocupation in the city expansion in massif direction, and your relation with hydrological and erosive dynamic in study area and lowlands. The results show that slums ocupation in massif's slopes started in the end of last century. Nowadays, slums ocupation is large in sectors which are most degraded with regard to forest coverage substitution (1 and 2), showing the potentiality of this direct vector. Another problem in this kind of occupation is that generally slums location are in the base of hollows, where occour water subsuperficial recharge and increasing landslides probability. About landslides were noted an proportional increasing with regard to enlargementing or appearing of slums.
34
Aryal, R. K., H. K. P. K. Jinadasa, H. Furumai, and F. Nakajima. "A long-term suspended solids runoff simulation in a highway drainage system." Water Science and Technology 52, no. 5 (September 1, 2005): 159–67. http://dx.doi.org/10.2166/wst.2005.0130.
Full textAbstract:
A long-term monitoring investigation was carried out in a highway drainage system in Winterthur, Switzerland. Several runoff quality and quantity simulations were carried out using the distributed model “InfoWorks-CS”. Serial rainfall monitoring data was used for investigation of SS runoff behavior from the highway. Under continuous rainfall conditions, the quantity simulation showed a good agreement with the measured hydrograph. However, in some cases where rainfall was not continuous, overestimation of the peak height was found at the later stage after the end of the rainfall. It was believed that the initial/depression loss on the road surface was recovered during the halting period of rainfall. The consideration of regenerated depression loss significantly improved runoff simulation results in the on-and-off type rainfall events. A single event quality simulation underestimated the SS load in light rainfall events. One of the reasons was possibly inadequate consideration of pipe sediment conditions. A long term simulation was carried out to establish the initial condition of surface and pipe sediment for the target event. The newly simulated pollutograph gave a good agreement with the measured one. It revealed that it was essential to consider appropriateness of the initial condition of pipe sediment as well as surface sediment.
35
Long, A. J. "RRAWFLOW: Rainfall-Response Aquifer and Watershed Flow Model (v1.15)." Geoscientific Model Development 8, no. 3 (March 30, 2015): 865–80. http://dx.doi.org/10.5194/gmd-8-865-2015.
Full textAbstract:
Abstract. The Rainfall-Response Aquifer and Watershed Flow Model (RRAWFLOW) is a lumped-parameter model that simulates streamflow, spring flow, groundwater level, or solute transport for a measurement point in response to a system input of precipitation, recharge, or solute injection. I introduce the first version of RRAWFLOW available for download and public use and describe additional options. The open-source code is written in the R language and is available at http://sd.water.usgs.gov/projects/RRAWFLOW/RRAWFLOW.html along with an example model of streamflow. RRAWFLOW includes a time-series process to estimate recharge from precipitation and simulates the response to recharge by convolution, i.e., the unit-hydrograph approach. Gamma functions are used for estimation of parametric impulse-response functions (IRFs); a combination of two gamma functions results in a double-peaked IRF. A spline fit to a set of control points is introduced as a new method for estimation of nonparametric IRFs. Several options are included to simulate time-variant systems. For many applications, lumped models simulate the system response with equal accuracy to that of distributed models, but moreover, the ease of model construction and calibration of lumped models makes them a good choice for many applications (e.g., estimating missing periods in a hydrologic record). RRAWFLOW provides professional hydrologists and students with an accessible and versatile tool for lumped-parameter modeling.
36
Turkoglu, Muhammet. "Synchronous blooms of the coccolithophore Emiliania huxleyi and three dinoflagellates in the Dardanelles (Turkish Straits System)." Journal of the Marine Biological Association of the United Kingdom 88, no. 3 (May 2008): 433–41. http://dx.doi.org/10.1017/s0025315408000866.
Full textAbstract:
This study focuses on the synchronous blooms of the coccolithophore Emiliania huxleyi and three dinoflagellates Prorocentrum micans, Ceratium furca var. furca and Ceratium fusus var. seta observed between 7 June and 11 July 2003 in the Dardanelles. An analysis of the vertical distribution of the E. huxleyi population size with respect to various environmental parameters was discussed. Additionally, inorganic nutrients and phytoplankton interactions were investigated in relation to the bloom conditions and hydrography of the Dardanelles. The algal bloom started in nearby Izmit Bay (eastern end of the Sea of Marmara) in early June, then quickly spread through the Sea of Marmara and continued until mid-July. Thermal stratification was observed between different water masses at the time of sampling. During the bloom period, cell density of E. huxleyi ranged from 3.58 × 107 to 2.55 × 108 cells l−1 in the superficial layer. Prorocentrum micans was the second most-abundant species and the cell numbers ranged from 1.0 × 106 cells l−1 to 3.3 × 106 cells l−1. Other abundant species in this area included C. furca var. furca and C. fusus var. seta.
37
Lüdke, Jan, Marcus Dengler, Stefan Sommer, David Clemens, Sören Thomsen, Gerd Krahmann, Andrew W. Dale, Eric P. Achterberg, and Martin Visbeck. "Influence of intraseasonal eastern boundary circulation variability on hydrography and biogeochemistry off Peru." Ocean Science 16, no. 6 (November 9, 2020): 1347–66. http://dx.doi.org/10.5194/os-16-1347-2020.
Full textAbstract:
Abstract. The intraseasonal evolution of physical and biogeochemical properties during a coastal trapped wave event off central Peru is analysed using data from an extensive shipboard observational programme conducted between April and June 2017, and remote sensing data. The poleward velocities in the Peru–Chile Undercurrent were highly variable and strongly intensified to above 0.5 m s−1 between the middle and end of May. This intensification was likely caused by a first-baroclinic-mode downwelling coastal trapped wave, excited by a westerly wind anomaly at the Equator and originating at about 95∘ W. Local winds along the South American coast did not impact the wave. Although there is general agreement between the observed cross-shore-depth velocity structure of the coastal trapped wave and the velocity structure of first vertical mode solution of a linear wave model, there are differences in the details of the two flow distributions. The enhanced poleward flow increased water mass advection from the equatorial current system to the study site. The resulting shorter alongshore transit times between the Equator and the coast off central Peru led to a strong increase in nitrate concentrations, less anoxic water, likely less fixed nitrogen loss to N2 and a decrease of the nitrogen deficit compared to the situation before the poleward flow intensification. This study highlights the role of changes in the alongshore advection due to coastal trapped waves for the nutrient budget and the cumulative strength of N cycling in the Peruvian oxygen minimum zone. Enhanced availability of nitrate may impact a range of pelagic and benthic elemental cycles, as it represents a major electron acceptor for organic carbon degradation during denitrification and is involved in sulfide oxidation in sediments.
38
Pringle, William, and Joannes Westerink. "INCORPORATING THREE-DIMENSIONAL BAROCLINIC PROCESSES FOR ACCURATE DEPTH-INTEGRATED COASTAL CIRCULATION MODELLING." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 71. http://dx.doi.org/10.9753/icce.v36.currents.71.
Full textAbstract:
Depth-integrated coastal circulation models have proven to provide high-fidelity solutions to storm surge, tides, tsunamis, and those with wave-coupling (Westerink et al. 2008; Titov & Synolakis 1998). They are able to provide high horizontal resolution, and stable, high-order and low-diffusion numerical schemes making them often more useful than their three-dimensional counterparts despite more assumptions on the physics. However, the assumptions of no baroclinicity means that some processes such as steric effects, barotropic energy to baroclinic tidal energy conversion, and major baroclinic current systems cannot be directly modelled, creating limitations. This is directly problematic for example in storm surge forecasting systems where an offset between measured and predicted hydrographs may be present due to seasonal heating and cooling, changes to nearshore stratification and to the transport rates of major current systems and fresh water outflows.
This study presents a process coupling paradigm to incorporate three-dimensional baroclinic effects into a depth-integrated model from a widely used and available baroclinic model, HYCOM (http://hycom.org). The depth-integrated finite-element model, ADCIRC (Westerink et al. 1992) is able to provide high-resolution to the coastal area, and has proven to be extremely accurate for storm surge modelling in e.g. the Gulf of Mexico (Westerink et al. 2008). However, along the Gulf of Mexico and east-coast of USA there are noticeable seasonal and inter-annual trends in the coastal sea level making forecasting more challenging than hindcasting. We present the effects of applying the information provided by HYCOM to ADCIRC in order to improve predicted hydrographs throughout the year of 2012 and in particular during Hurricane Sandy.
39
Martínez, Carlos, Zoran Vojinovic, Roland Price, and Arlex Sanchez. "Modelling Infiltration Process, Overland Flow and Sewer System Interactions for Urban Flood Mitigation." Water 13, no. 15 (July 24, 2021): 2028. http://dx.doi.org/10.3390/w13152028.
Full textAbstract:
Rainfall-runoff transformation on urban catchments involves physical processes governing runoff production in urban areas (e.g., interception, evaporation, depression, infiltration). Some previous 1D/2D coupled models do not include these processes. Adequate representation of rainfall–runoff–infiltration within a dual drainage model is still needed for practical applications. In this paper we propose a new modelling setup which includes the rainfall–runoff–infiltration process on overland flow and its interaction with a sewer network. We first investigated the performance of an outflow hydrograph generator in a 2D model domain. The effect of infiltration losses on the overland flow was evaluated through an infiltration algorithm added in a so-called Surf-2D model. Then, the surface flow from a surcharge sewer was also investigated by coupling the Surf-2D model with the SWMM 5.1 (Storm Water Management Model). An evaluation of two approaches for representing urban floods was carried out based on two 1D/2D model interactions. Two test cases were implemented to validate the model. In general, similar results in terms of peak discharge, water depths and infiltration losses against other 1D/2D models were observed. The results from two 1D/2D model interactions show significant differences in terms of flood extent, maximum flood depths and inundation volume.
40
Parras-Berrocal, Ivan M., Ruben Vazquez, William Cabos, Dmitry Sein, Rafael Mañanes, Juan Perez-Sanz, and Alfredo Izquierdo. "The climate change signal in the Mediterranean Sea in a regionally coupled atmosphere–ocean model." Ocean Science 16, no. 3 (June 25, 2020): 743–65. http://dx.doi.org/10.5194/os-16-743-2020.
Full textAbstract:
Abstract. We analyze the climate change signal in the Mediterranean Sea using the regionally coupled model REMO–OASIS–MPIOM (ROM; abbreviated from the regional atmosphere model, the OASIS3 coupler and the Max Planck Institute Ocean Model). The ROM oceanic component is global with regionally high horizontal resolution in the Mediterranean Sea so that the water exchanges with the adjacent North Atlantic and Black Sea are explicitly simulated. Simulations forced by ERA-Interim show an accurate representation of the present Mediterranean climate. Our analysis of the RCP8.5 (representative concentration pathway) scenario using the Max Planck Institute Earth System Model shows that the Mediterranean waters will be warmer and saltier throughout most of the basin by the end of this century. In the upper ocean layer, temperature is projected to have a mean increase of 2.7 ∘C, while the mean salinity will increase by 0.2 psu, presenting a decreasing trend in the western Mediterranean in contrast to the rest of the basin. The warming initially takes place at the surface and propagates gradually to deeper layers. Hydrographic changes have an impact on intermediate water characteristics, potentially affecting the Mediterranean thermohaline circulation in the future.
41
Rickard, Graham J., Malcolm J. Roberts, Michael J. M. Williams, Alistair Dunn, and Murray H. Smith. "Mean circulation and hydrography in the Ross Sea sector, Southern Ocean: representation in numerical models." Antarctic Science 22, no. 5 (May 19, 2010): 533–58. http://dx.doi.org/10.1017/s0954102010000246.
Full textAbstract:
AbstractThree models were used to look at the Southern Ocean Ross Sea sector circulation and hydrography. Two were climate models of low (1°) to intermediate resolution (1/3°), and one was an operational high resolution (1/10°) ocean model. Despite model differences (including physics and forcing), mean and monthly variability aspects of off-shelf circulation are consistently represented, and could imply bathymetric constraints. Western and eastern cyclonic gyral systems separated by shallow bathymetry around 180°E redistributing water between the wider Southern Ocean and the Ross Sea are found. Some model seasonal gyral transports increase as the Antarctic Circumpolar Current transport decreases. Model flows at 900 m at the gyral eastern end compare favourably with float data. On-shelf model depth-averaged west–east flow is relatively consistent with that reconstructed from longline fishing records. These flows have components associated with isopycnal gradients in both light and dense waters. The climate models reproduce characteristic isopycnal layer inflections (‘V’s) associated with the observed Antarctic Slope Front and on-shelf deep water formation, and these models transport some 4 Sv of this bottom water northwards across the outer 1000 m shelf isobath. Overall flow complexity suggests care is needed to force regional Ross Sea models.
42
Panda, R., S. K. Padhee, and S. Dutta. "Glof Study in Tawang River Basin, Arunachal Pradesh, India." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-8 (November 27, 2014): 101–9. http://dx.doi.org/10.5194/isprsarchives-xl-8-101-2014.
Full textAbstract:
Glacial lake outburst flood (GLOF) is one of the major unexpected hazards in the high mountain regions susceptible to climate change. The Tawang river basin in Arunachal Pradesh is an unexplored region in the Eastern Himalayas, which is impending to produce several upcoming hydro-electric projects (HEP). The main source of the river system is the snow melt in the Eastern Himalayas, which is composed of several lakes located at the snout of the glacier dammed by the lateral or end moraine. These lakes might prove as potential threat to the future scenario as they have a tendency to produce flash flood with large quantity of sediment load during outbursts. This study provides a methodology to detect the potential lakes as a danger to the HEP sites in the basin, followed by quantification of volume of discharge from the potential lake and prediction of hydrograph at the lake site. The remote location of present lakes induced the use of remote sensing data, which was fulfilled by Landsat-8 satellite imagery with least cloud coverage. Suitable reflectance bands on the basis of spectral responses were used to produce informational layers (NDWI, Potential snow cover map, supervised classification map) in GIS environment for discriminating different land features. The product obtained from vector overlay operation of these layers; representing possible water area, was further utilized in combination with Google earth to identify the lakes within the watershed. Finally those identified lakes were detected as potentially dangerous lakes based on the criteria of elevation, area, proximity from streamline, slope and volume of water held. HEC-RAS simulation model was used with cross sections from Google Earth and field survey as input to simulate dam break like situation; hydrodynamic channel routing of the outburst hydrograph along river reach was carried out to get the GLOF hydrograph at the project sites. It was concluded from the results that, the assessed GLOF would be a lead for the qualitative approximation of the amount of bed load transported along the river reach and thus hydropower project sites.
43
Outram, F. N., C. Lloyd, J. Jonczyk, C. McW H. Benskin, F. Grant, S. R. Dorling, C. J. Steele, et al. "High-resolution monitoring of catchment nutrient response to the end of the 2011–2012 drought in England, captured by the demonstration test catchments." Hydrology and Earth System Sciences Discussions 10, no. 12 (December 11, 2013): 15119–65. http://dx.doi.org/10.5194/hessd-10-15119-2013.
Full textAbstract:
Abstract. The Demonstration Test Catchments (DTC) project is a UK Government funded initiative to test the effectiveness of on-farm mitigation measures designed to reduce agricultural pollution without compromising farm productivity. Three distinct catchments in England have been chosen to test the efficacy of mitigation measures on working farms in small tributary sub-catchments equipped with continuous water quality monitoring stations. The Hampshire Avon in the south is a mixed livestock and arable farming catchment, the River Wensum in the east is a lowland catchment with predominantly arable farming and land use in the River Eden catchment in the north-west is predominantly livestock farming. One of the many strengths of the DTC as a national research platform is that it provides the ability to investigate catchment hydrology and biogeochemical response across different landscapes and geoclimatic characteristics, with a range of differing flow behaviours, geochemistries and nutrient chemistries. Although numerous authors present studies of individual catchment responses to storms, no studies exist of multiple catchment responses to the same rainfall event captured with in situ high-resolution nutrient monitoring at a national scale. This paper brings together findings from all three DTC research groups to compare the response of the catchments to a major storm event in April 2012. This was one of the first weather fronts to track across the country following a prolonged drought period affecting much of the UK through 2011–2012, marking an unusual meteorological transition when a rapid shift from drought to flood risk occurred. The effects of the weather front on discharge and water chemistry parameters, including nitrogen species (NO3-N and NH4-N) and phosphorus fractions (total P (TP) and total reactive P (TRP)), measured at a half-hourly time step are examined. When considered in the context of one hydrological year, flow and concentration duration curves reveal that the weather fronts resulted in extreme flow, nitrate and TP concentrations in all three catchments but with distinct differences in both hydrographs and chemographs. Hysteresis loops constructed from high resolution data are used to highlight an array of potential pollutant sources and delivery pathways. In the Hampshire Avon DTC, transport was dominated by sub-surface processes, where phosphorus, largely in the soluble form, was found to be transport-limited. In the Wensum DTC, transport was largely dominated by rapid sub-surface movement due to the presence of under-drainage, which mobilised large quantities of nitrate during the storm. In the Eden DTC, transport was found to be initially dominated by surface runoff, which switched to subsurface delivery on the falling limb of the hydrograph, with the surface delivery transporting large amounts of particulate phosphorus to the river, with a transport-limited response. The lack of exhaustion of nutrient delivery in response to such extreme flow generation indicates the size of the nutrient pools stored in these catchments, and highlights the scale of the challenges faced by environmental managers when designing mitigation measures to reduce the flux of nutrients to UK river systems from diffuse agricultural sources.
44
Schulz, J. "AIRBORNE TECHNOLOGIES FOR DISASTER MANAGEMENT." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3/W8 (August 22, 2019): 387–93. http://dx.doi.org/10.5194/isprs-archives-xlii-3-w8-387-2019.
Full textAbstract:
<p><strong>Abstract.</strong> Currently, satellite-based systems and UAVs are very popular in the investigation of natural disasters. Both systems have their justification and advantages &ndash; but one should not forget the airborne remote sensing technology. The presentation shows with three examples very clearly how airborne remote sensing is still making great progress and in many cases represents the optimal method of data acquisition.</p> <p>The airborne detection of forest damages (especially currently the bark beetle in spruce stands) can determine the pest attack using CIR aerial images in combination with ALS and hyperspectral systems &ndash; down to the individual tree. Large forest areas of 100 sqkm and more can be recorded from planes on one day (100 sqkm with 10cm GSD on one day).</p> <p>Flood events &ndash; such as on the Elbe in 2013 &ndash; were recorded by many satellites. However, many evaluations require highresolution data (GSD 10cm), e.g. to clarify insurance claims. Here the aircraft system, which was able to fly below the cloud cover and was constantly flying at the height level of the flood peak, proved to be unbeatable.</p> <p>The phenomenon of urban flash floods is one of the consequences of climate change. Cities are not in a position to cope with the water masses of extreme rain events and so are confronted with major damages. In Germany, a number of cities are already preparing to manage short-term but extreme water masses. The complicated hydrographic and hydraulic calculations and simulations require above all one thing &ndash; a precise data basis. This involves, for example, the height of kerbstones and the recording of every gully and every obstacle. Such city-wide data can only be collected effectively by photogrammetric analysis of aerial photography (GSD 5 to 10cm).</p>
45
Davis, Russ E., Lynne D. Talley, Dean Roemmich, W. Brechner Owens, Daniel L. Rudnick, John Toole, Robert Weller, Michael J. McPhaden, and John A. Barth. "100 Years of Progress in Ocean Observing Systems." Meteorological Monographs 59 (January 1, 2019): 3.1–3.46. http://dx.doi.org/10.1175/amsmonographs-d-18-0014.1.
Full textAbstract:
Abstract The history of over 100 years of observing the ocean is reviewed. The evolution of particular classes of ocean measurements (e.g., shipboard hydrography, moorings, and drifting floats) are summarized along with some of the discoveries and dynamical understanding they made possible. By the 1970s, isolated and “expedition” observational approaches were evolving into experimental campaigns that covered large ocean areas and addressed multiscale phenomena using diverse instrumental suites and associated modeling and analysis teams. The Mid-Ocean Dynamics Experiment (MODE) addressed mesoscale “eddies” and their interaction with larger-scale currents using new ocean modeling and experiment design techniques and a suite of developing observational methods. Following MODE, new instrument networks were established to study processes that dominated ocean behavior in different regions. The Tropical Ocean Global Atmosphere program gathered multiyear time series in the tropical Pacific to understand, and eventually predict, evolution of coupled ocean–atmosphere phenomena like El Niño–Southern Oscillation (ENSO). The World Ocean Circulation Experiment (WOCE) sought to quantify ocean transport throughout the global ocean using temperature, salinity, and other tracer measurements along with fewer direct velocity measurements with floats and moorings. Western and eastern boundary currents attracted comprehensive measurements, and various coastal regions, each with its unique scientific and societally important phenomena, became home to regional observing systems. Today, the trend toward networked observing arrays of many instrument types continues to be a productive way to understand and predict large-scale ocean phenomena.
46
Golovlyov, Pavel, Ekaterina Kornilova, Inna Krylenko, Vitaly Belikov, Aleksandr Zavadskii, Eugeniya Fingert, Natalya Borisova, and Elizaveta Morozova. "Numerical modeling and forecast of channel changes on the river Lena near city Yakutsk." Proceedings of the International Association of Hydrological Sciences 381 (August 1, 2019): 65–71. http://dx.doi.org/10.5194/piahs-381-65-2019.
Full textAbstract:
Abstract. STREAM_2D software package was applied to retrospective and predictive simulations of the Lena River near city Yakutsk hydraulic and channel changes during ice-free period. The modelling results indicate significant correspondence of simulated water discharges distribution and water levels with observed ones for the period 2001–2016. Model has captured main erosion and depositional zones observed in the 2009–2016 years. Combination of typical monthly average hydrographs of 1 %, 10 % and 50 % return intervals was used as an initial parameter for 10-year channel changes forecast. According to the simulation results, degradation of the Adamovskaya branch will be continued, which is the most negative impact for the Yakutsk city infrastructure maintenance. At the end of the forecast period the equal distribution between Adamovskaya and Buorylarskaya channels is possible, which is a positive trend from the point of view of the city water supply system.
47
Chen, Kun, Kung-Sik Chan, Kevin M. Bailey, Kerim Aydin, and Lorenzo Ciannelli. "A probabilistic cellular automata approach for predator–prey interactions of arrowtooth flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) in the eastern Bering Sea." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 2 (February 2012): 259–72. http://dx.doi.org/10.1139/f2011-160.
Full textAbstract:
We developed a hybrid cellular automata (CA) modelling approach to explore the dynamics of a key predator–prey interaction in a marine system; our study is motivated by the quest for better understanding of the scale and heterogeneity-related effects on the arrowtooth flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) dynamics during the summer feeding season in the eastern Bering Sea (EBS), but can be readily extended to other systems. The spatially explicit and probabilistic CA model incorporates individual behaviours and strategies and local interactions among species, as well as spatial and temporal heterogeneity due to geographical and (or) environmental changes in the physical environment. The model is hybridized, with an individual-based model (IBM) approach for increasing its capacity and continuum and for balancing between computational efficiency and model validity, which makes it suitable for simulating predator–prey dynamics in a large, complex ecological environment. We focus on the functional and aggregative responses of predators to prey density at different spatial scales, the effects of individual behaviours, and the impacts of systematic heterogeneity. Simulations from the model with suitable parameter values share qualitatively similar features found in field observations, e.g., local aggregations around hydrographical features. Spatial heterogeneity is an important aspect of whether local-scale functional and aggregative responses reflect those operating over large, or global, scales.
48
Cattaneo, Nelly. "Tessenei (1905-1941): intensive farming shaping landscape and social relations in colonial Eritrea." SHS Web of Conferences 63 (2019): 05002. http://dx.doi.org/10.1051/shsconf/20196305002.
Full textAbstract:
In the early 20th century the agrarian policies of the Colonial Government in Eritrea moved from the promotion of Italian family homesteads on the highlands to the exploitation of wide semi-arid areas in the lowlands. In particular the surroundings of Tessenei, close to the Sudanese border, for its geomorphological and hydrographic features, were appropriate for a wide intensive plantation of cotton. Here in 1905 the most meaningful intervention of colonial agrarian valorisation in Eritrea was being planned, but it was realized at the end of the Twenties. Barriers, embankments, canals and drains caused then a radical change in the landscape, imposing a severe geometry over 10.000 hectares of smoothly corrugated lands around the Gash River. Production activities were mainly based on local workers: this had a dramatic impact on traditional culture and social relations, stressed by the fact that in a short while migration from Sudan and Ethiopia was encouraged. By analysing the main features of the spatial organization designed in Tessenei, an attempt to outline the relation between the colonial government and local cultural system will be made; the comprehension of this relation would be important to understand the legacies of the project and its potentialities at present.
49
Christensen, Asbjørn, Henrik Jensen, Henrik Mosegaard, Mike St. John, and Corinna Schrum. "Sandeel (Ammodytes marinus) larval transport patterns in the North Sea from an individual-based hydrodynamic egg and larval model." Canadian Journal of Fisheries and Aquatic Sciences 65, no. 7 (July 2008): 1498–511. http://dx.doi.org/10.1139/f08-073.
Full textAbstract:
We have calculated a time series of larval transport indices for the central and southern North Sea covering 1970–2004, using a combined three-dimensional hydrodynamic and individual-based modelling framework for studying sandeel ( Ammodytes marinus ) eggs, larval transport, and growth. The egg phase is modelled by a stochastic, nonlinear degree-day model describing the extended hatch period. The larval growth model is parameterized by individually back-tracking the local physical environment of larval survivors from their catch location and catch time. Using a detailed map of sandeel habitats in the North Sea, the importance of hydrography for early life stages of sandeel to their recruitment success is explored. We find that the sandeel larval transport patterns in the North Sea are relatively robust toward uncertainties in biological parameters, when mortality aspects are included. We find only weak spatiotemporal correlations between elements of the transport indices in the time series, mainly positive correlation between retention terms for the same year. The transport connectivity of sandeel habitats in the North Sea and the dynamical properties of the North Sea transport system are also analyzed, and we introduce novel a scheme to quantify direct and indirect connectivity on equal footings in terms of an interbank transit time scale.
50
Munyaneza, O., J. Wenninger, and S. Uhlenbrook. "Identification of runoff generation processes using hydrometric and tracer methods in a meso-scale catchment in Rwanda." Hydrology and Earth System Sciences Discussions 9, no. 1 (January 12, 2012): 671–705. http://dx.doi.org/10.5194/hessd-9-671-2012.
Full textAbstract:
Abstract. Understanding of dominant runoff generation processes in the meso-scale Migina catchment (257.4 km2) in Southern Rwanda was improved using analysis of hydrometric data and tracer methods. The paper examines the use of hydrochemical and isotope parameters for separating streamflow into different runoff components by investigating two flood events occurred during the rainy season "Itumba" (March–May) over the period of 2 yr at two gauging stations. Dissolved silica (SiO2), electrical conductivity (EC), deuterium (2H), oxygen-18 (18O), major anions (Cl− and SO42−) and major cations (Na+, K+, Mg2+ and Ca2+) were analyzed during the events. 2H, 18O, Cl− and SiO2 were finally selected to assess the different contributing sources using mass balance equations and end member mixing analysis for two- and three-component hydrograph separation models. The results obtained applying two-component hydrograph separations using dissolved silica and chloride as tracers are generally in line with the results of three-component separations using dissolved silica and deuterium. Subsurface runoff is dominating the total discharge during flood events, More than 80% of the discharge was generated by subsurface runoff for both events. This is supported by observations of shallow groundwater responses in the catchment (depth 0.2–2 m), which show fast infiltration of rainfall water during events. Consequently, shallow groundwater and contributes to subsurface stormflow and baseflow generation. This dominance of subsurface contributions is also in line with the observed low runoff coefficient values (16.7–44.5%) for both events. Groundwater recharge during the wet seasons leads to a perennial river system, and wet season recharge is isotopically characterising all discharge components.