Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Extreme drought boosts CO2 and CH4 emissions from reservoir drawdown areas
Kosten, Sarian ; Berg, Sanne van den; Mendonça, Raquel ; Paranaíba, José R. ; Roland, Fabio ; Sobek, Sebastian ; Hoek, Jamon Van Den; Barros, Nathan - \ 2018
Inland Waters : Journal of the International Society of Limnology 8 (2018)3. - ISSN 2044-2041 - p. 329 - 340.
drought - emission peaks - greenhouse gases - reservoirs - rewetting - sediment

Although previous studies suggest that greenhouse gas (GHG) emissions from reservoir sediment exposed to the atmosphere during drought may be substantial, this process has not been rigorously quantified. Here we determined carbon dioxide (CO2) and methane (CH4) emissions from sediment cores exposed to a drying and rewetting cycle. We found a strong temporal variation in GHG emissions with peaks when the sediment was drained (C emissions from permanently wet sediment and drained sediments were, respectively, 251 and 1646 mg m−2 d−1 for CO2 and 0.8 and 547.4 mg m−2 d−1 for CH4) and then again during rewetting (C emissions from permanently wet sediment and rewetted sediments were, respectively, 456 and 1725mg m−2 d−1 for CO2 and 1.3 and 3.1 mg m−2 d−1 for CH4). To gain insight into the importance of these emissions at a regional scale, we used Landsat satellite imagery to upscale our results to all Brazilian reservoirs. We found that during the extreme drought of 2014–2015, an additional 1299 km2 of sediment was exposed, resulting in an estimated emission of 8.5 × 1011 g of CO2-eq during the first 15 d after the overlying water disappeared and in the first 33 d after rewetting, the same order of magnitude as the year-round GHG emissions of large (∼mean surface water area 454 km2) Brazilian reservoirs, excluding the emissions from the draw-down zone. Our estimate, however, has high uncertainty, with actual emissions likely higher. We therefore argue that the effects of drought on reservoir GHG emissions merits further study, especially because climate models indicate an increase in the frequency of severe droughts in the future. We recommend incorporation of emissions during drying and rewetting into GHG budgets of reservoirs to improve regional GHG emission estimates and to enable comparison between GHG emissions from hydroelectric and other electricity sources. We also emphasize that peak emissions at the onset of drought and the later rewetting should be quantified to obtain reliable emission estimates.

Long-term impact of rainfed agricultural land abandonment on soil erosion in the Western Mediterranean basin
Cerdà, Artemi ; Rodrigo-Comino, Jesús ; Novara, Agata ; Brevik, Eric Charles ; Vaezi, Ali Reza ; Pulido, Manuel ; Giménez-Morera, Antonio ; Keesstra, Saskia Deborah - \ 2018
Progress in Physical Geography 42 (2018)2. - ISSN 0309-1333 - p. 202 - 219.
Land use change - plots - rainfall - runoff - scale - sediment - Spain
Land abandonment is widespread in the Mediterranean mountains. The impact of agricultural abandonment results in a shift in ecosystem evolution due to changes in soil erosion, but little is known about long-term soil and water losses. This paper uses 11 years of measurements in two paired plots (abandoned vs control) with four subplots to determine how soil and water losses evolved after abandonment within an agricultural parcel. For two years (2004–2005) both plots were under tillage, and after 2006 one plot was abandoned. The monitored plots measured runoff and sediment concentration after each rainfall event. The results show that during the two years after abandonment there was an increase in sediment yield followed by a decrease. Once the field was abandoned, a sudden increase in runoff (× 2.1 times) and sediment concentration (× 1.2 times) was found due to the lack of vegetation and tillage. After one year, the sediment concentration and, after two years, the runoff rates were lower in the abandoned than in the tilled plots. This short transition period ended in contrasting responses between the control and abandoned plot as the impact of abandonment resulted in 21 times less sediment yield after nine years of abandonment. This occurred despite the fact that the year after the abandonment the abandoned plot had 2.9 times more erosion due to low vegetation recovery and the development of a soil crust. Agriculture land abandonment resulted in lower erosion rates over the long term, but showed an increase in soil and water losses over the short term (two years). Therefore, in the first two years after abandonment there is a particular need to apply nature-based soil and water conservation strategies to prevent soil erosion.
Data from sediment sampling campaign, Sand Motor
Huisman, B.J.A. ; Bart, L. ; Schipper, M.A. de; Meirelles, S. ; Sirks, E.E. ; Tonnon, P.K. ; Zwaag, J. van der; Wijsman, J.W.M. - \ 2017
composition - NeMo project - sampling - Sand Motor - sediment
Sediment sampling data from measurement campaign at the Sand Motor
Getting a grip on hydrological and sediment connectivity
Masselink, Rens J.H. - \ 2017
University. Promotor(en): Coen Ritsema; Sjoerd van der Zee, co-promotor(en): Saskia Keesstra; Arnaud Temme. - Wageningen : Wageningen University - ISBN 9789463436342 - 158
hydrology - sediment - land degradation - slopes - geological sedimentation - land management - soil physics - hydrologie - landdegradatie - hellingen - geologische sedimentatie - grondbeheer - bodemfysica

Land degradation is a large problem worldwide, especially in agricultural areas. Between 1-6 billion ha of land worldwide is affected by land degradation. With an increasing world population, more food production is needed and, therefore, more land is converted into agricultural areas. This conversion of land to agricultural areas, in turn, leads to more land degradation. Some common forms of land degradation are desertification, salinization and soil erosion by water. The negative effects of soil erosion have been recognized for a long time. Since the early 20th century, researchers have tried to quantify soil displaced due to water, and to measure and model the efficiency of management strategies.

The implications of problems with upscaling, wrong process representation and equifinality include the difficulty to properly predict sediment sources, pathways and sinks within catchments. These problems then can translate into the implementation of sub-optimal management strategies. To deal with these non-linear processes and the lack of proper representation of water and sediment sources, pathways and sinks, the concept of connectivity was developed. Currently, many definitions of connectivity have been proposed, although the definition most used is that of hydrological connectivity by Pringle (2003): ‘Hydrologic connectivity is the water-mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle’.

A unified theory on what constitutes connectivity and how connectivity should be measured or inferred remains one of the biggest challenges within catchment science. In addition, it is unclear whether connectivity should be an output or an input of a model and if an input, whether this should be added explicitly or implicitly. The main objective of this thesis was, therefore, to assess and quantify hydrological and sediment connectivity in a meaningful way, which can further our understanding of hydrological and sediment transport processes and catchment system dynamics.

The study was carried out in three catchments in Navarre, northern Spain. Two catchments, ‘Latxaga’ and ‘La Tejeria’, are agricultural catchments with sizes of 2.07 km2 and 1.69 km2, respectively. The ‘Oskotz Forestal’ catchment is a (semi-)natural catchment, with a size of 5.05 km2. Land cover in the agricultural catchments is mainly winter wheat and barley, while in the Oskotz catchment it is grassland and forest. Latxaga and La Tejeria are mainly underlain by marls and within La Tejeria some sandstone is also present. The geology in Oskotz is characterised by an alternation of marls and sandy limestone.

In chapter 2, I used networks (graph theory) to characterise and quantify overland flow connectivity dynamics on hillslopes in a humid sub-Mediterranean environment by using a combination of high-resolution digital-terrain models, overland flow sensors and a network approach. Results showed that there are significant differences between overland flow connectivity on agricultural areas and semi-natural shrubs areas. Significant positive correlations between connectivity and precipitation characteristics were found. Significant negative correlations between connectivity and soil moisture were found, most likely due to soil water repellency and/or soil surface crusting. The combination of structural networks and dynamic networks for determining potential connectivity and actual connectivity proved a powerful tool for analysing overland flow connectivity.

In chapter 3, I determined the functioning of hillslope-channel connectivity and the continuation of transport of these sediments in the channel. To determine this functioning, I obtained data on sediment transport from the hillslopes to the channels while simultaneously looking at factors that influence sediment export out of the catchment. For measuring hillslope-channel sediment connectivity, Rare-Earth Oxide (REO) tracers were applied to a hillslope in the Latxaga catchment preceding the winter of 2014-2015. The results showed that during the winter there have been no sediments transported from the hillslope into the channel. Analysis of precipitation data showed that although total precipitation quantities did not differ much from the mean, the precipitation intensities were low. Using a Random Forest (RF) machine learning method, I showed that hillslope-channel connectivity in Latxaga is dominated by sediment mobilisation during large (high intensity) precipitation events. Sediments are for a large part exported during those events. Large events also leave behind large amounts of sediments in and near the channel, which is gradually removed by small events.

In chapter 4 I demonstrated that existing data can be used to assess governing factors of connectivity, and how these factors change over time. Data from three catchments in Navarre, Northern Spain, were used to assess factors that influence hydrologic and sediment connectivity. These factors were used as components in a spatially-lumped linear model for discharge and suspended-sediment yield. Three components of connectivity were distinguished: topographical, biological and soil. Changes in the topographical component for the studied periods were considered relatively small, and, therefore, kept constant. Changes in the biological component were determined using the Normalised Difference Vegetation Index. Changes in the soil component were assessed using an Antecedent Precipitation Index. Nash-Sutcliffe model efficiency coefficients were between 0.49 through 0.62 for the discharge models and between 0.23 through 0.3 for the sediment-yield models. I recommended applying the model at smaller spatial scales than catchment scale to minimize the lumping of spatial variability in the components.

In chapter 5, the objective was to better understand the implications of model calibration at different spatial scales on the simulation of hydrology and sediment dynamics of an agricultural catchment. I applied the LAPSUS-D model to the Latxaga catchment. The model was calibrated and validated (4 years: 2011-2015) using three datasets at varying spatial scales: hillslope, catchment and the combined dataset (combined-calibrated model). The hillslope-calibrated model showed mainly infiltration-excess overland flow, the catchment-calibrated mainly saturation-excess overland flow at the footslopes and the combined-calibrated model showed saturation-excess overland flow from the midslopes to the footslopes. For hydrology, the combined-calibrated model simulated the large discharge peaks best, while at the hillslope scale, the hillslope-calibrated model performed best. The hillslope-calibrated model produced the highest model efficiencies for sediments, for calibration (0.618) and validation (0.269). The hillslope-calibrated model was the only model that showed observed gully erosion on a high-resolution DEM and displayed channel sediment dynamics. However, absolute quantities of erosion and deposition within the catchment were too high. The results show that modellers need to be aware of problems associated with automatic calibration, over-calibration and not incorporating measured data at multiple spatial scales. We advocate incorporating runoff and sediment tracing data at multiple scales whenever this is possible and to, furthermore, carry out specific measuring campaigns towards this end, ultimately to get a more comprehensive view on hydrological and sediment connectivity within a catchment.

The combination of chapters in this thesis showed that the connectivity concept is useful for a wide range of studies, from hillslope scale to catchment scale. Using the concept, I was able to determine sediment dynamics for a humid-Mediterranean catchment and show that this behaviour is different than previously thought.

Depending of the aim of the study, various concepts of connectivity are useful. Different geologic and climatic settings cause large differences in catchment (sediment) dynamics. It might, therefore, not be necessary, or even possible, to strive for a single, unifying conceptual framework for connectivity. Instead, a collection of frameworks for different settings should be developed. These frameworks should, however, always aim at helping to understand which measurements need to be taken and which type of models and indices should be used for that particular setting.

It is my honest opinion that connectivity is definitely a useful concept to advance our knowledge on water and sediment transport processes further. However, careful consideration is also required as this particular concept will not necessary provide the ultimate explanation and insights in dynamic behaviour within watersheds around the world. The gap between the different spatial and temporal scales is too complex to be bridged with a single concept like connectivity. However, the many studies about connectivity that will be published in the near future will be able to advance knowledge on water and sediment transport processes.

Temperature in water and sediment in the pesticide model TOXSWA : implementation report
Beltman, W.H.J. ; Adriaanse, P.I. ; Jacobs, C.M.J. ; Mulder, H.M. - \ 2017
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research report 2794) - 67
pesticides - water - temperature - models - sediment - surface water - pesticiden - temperatuur - modellen - oppervlaktewater
TOXSWA simuleert het gedrag van stoffen in oppervlaktewater om blootstellingsconcentratie te berekenen voor organismen die in water of sediment leven, als onderdeel van de aquatische risicobeoordeling van gewasbeschermingsmiddelen (GBM). Het vernieuwde concept voor de beschrijving van de temperatuur in het TOXSWA model werd getest aan de hand van een bestaande implementatie van het 1D bulk model.
Lift up of Lowlands : beneficial use of dredged sediments to reverse land subsidence
Figueiredo Oliveira, Bruna Raquel - \ 2017
University. Promotor(en): Huub Rijnaarts, co-promotor(en): Tim Grotenhuis. - Wageningen : Wageningen University - ISBN 9789462578838 - 229
dredgings - dredging - sedimentation - soil - sediment - subsidence - recycling - environmental engineering - bagger - baggeren - sedimentatie - bodem - bodemdaling - milieutechniek

In this thesis, the beneficial use of dredged sediments to reverse land subsidence in lowlands and delta areas is explored. The major constraints for beneficial use of sediments are the contaminant concentrations, and the proper managing of supply and demand of sediments (Chapter 1).

When sediments are transferred from waterways to upland conditions, a series of processes take place that transform the waterlogged sediments into aerated soils, a process known as ripening. To understand the relation between the sediments and the soils formed, physical/chemical and biological processes were studied at three scales: laboratory scale, mesoscale, and field scale. The knowledge obtained with these experiments can provide guidelines to effectively use dredged sediments to reverse land subsidence.

In the laboratory experiments, the environmental conditions were controlled, leading to constant water content and optimal oxygen concentration for biological processes. In the mesoscale experiment, the environmental parameters such as wind, precipitation and temperature, were not controlled as the 1 m3 containers used for these experiments were placed outside, in open air conditions. Still, the water level could be monitored and controlled, and the subsidence of the dredged sediment could be monitored. In the field experiment, the environmental and filling conditions could not be controlled but the changes occurring in the deposit were monitored.

In the first laboratory experiment (Chapter 2) the behaviour of dredged sediments with varying particle size distribution and organic matter content was studied. The dredged sediments were dewatered using suction chambers and then submitted to biochemical ripening during 141 days. The five types of dredged sediments had similar overall behaviour. The most significant observation was that most volume lost during dewatering and biochemical ripening was due to shrinkage and not to organic matter mineralization. Furthermore, the type of organic matter changed in the direction of humification, i.e., more stable compounds were formed. The soils formed from biochemical ripening of dredged sediments had very stable aggregates and the load-bearing capacity was enough to sustain cattle and tractors.

The second laboratory experiment (Chapter 3) was designed to investigate the influence of mixing compost and the solid fraction of swine manure (low in nutrients) with dredged sediments on dewatering and biochemical ripening. When the supply of dredged sediments is too low to compensate for land subsidence, bio-wastes, such as compost and manure, can be mixed with the sediments to reverse land subsidence. The results of this experiment confirm that most volume lost during ripening was due to shrinkage and not due to organic matter mineralization. Adding compost or the solid fraction of manure to the dredged sediments enhances the changes in the type of organic matter and CO2 production, i.e., the addition results in increased rates of organic matter mineralization which is described in the literature as the priming effect. In addition, the undrained shear strength of the mixtures of sediments with compost or manure was three times higher than the measured values for the sediments alone, meaning that organic amendments will improve the characteristics of the soil formed from ripening of sediments.

The mesoscale experiment (Chapter 4) was performed during 400 days in 1m3 containers which allowed to control the water level. Two scenarios were tested: upland deposits in which the sediments are allowed to dry; and underwater deposits in which the water level is always 2 cm above the sediments. It was expected that the upland deposit conditions would lead to a higher subsidence than the underwater conditions. However, subsidence of the sediments was very similar for the two scenarios. Also in these experiments it was observed that most subsidence could be attributed to shrinkage and not organic matter mineralization, and the type of organic matter changed in the direction of humification. Furthermore, the water balance indicated that evapotranspiration results in higher loss of water than drainage. Still, in this case the undrained shear strength after 400 days of experiment was not enough to sustain cattle or tractors even though it increased with time.

The monitored field scale upland deposit of dredged sediments (Chapter 5) is located in the Wormer- en Jisperveld area – North Holland, the Netherlands. The deposit was filled in two stages reaching a maximum height of sediments of 195 cm. After 17 months of monitoring, the subsidence of the sediments was 119 cm to which an extra subsidence of 19.5 cm of the underlying soil due to the overburden pressure was added. The results observed in the upland deposit are in line with the laboratory and mesoscale results since subsidence could also be attributed to shrinkage and no significant changes in the organic matter content were observed. However, in the case of the upland deposit, the type of organic matter changed in the direction of humification during the first 8 months (March to November), then stabilized during 7 months (November to June), and changed in the direction of mineralization afterwards.

The outcomes of this research indicate that dredged sediments have the potential to reverse land subsidence. This statement is supported by the consistent results showing that the decrease in volume of dredged sediments is caused by shrinkage and not to organic matter mineralization as traditionally reported (Chapters 2, 3, 4, and 5).

In addition, in places where composted and stable bio-wastes are available, these can be added to dredged sediments to further reverse land subsidence. Still, in this case special attention should be given to the potential priming effect (Chapter 3).

Finally it is recommended to adapt the current practices of disposal of dredged sediments in upland deposits, since 19.5 cm of subsidence observed for the underlying soil in the upland deposit (Chapter 5), was caused by the overburden pressure of the dredged sediment. From the point of view of avoiding/reversing land subsidence it is recommended to spread thin layers (in the order of cm) of sediments over the land, although this might lead to an increase in the time and costs for the stakeholders involved in dredging and in managing the water boards.

Sustaining reservoir use through sediment trapping in NW Ethiopia
Getahun, Mulatie Mekonnen - \ 2016
University. Promotor(en): Leo Stroosnijder, co-promotor(en): Saskia Keesstra; Jantiene Baartman. - Wageningen : Wageningen University - ISBN 9789462579101 - 132
sediment - soil conservation - reservoirs - dams - models - ethiopia - bodembescherming - dammen - modellen - ethiopië

To increase crop production and improve food self-sufficiency, rain-fed agriculture need to be supplemented with irrigated agriculture. To this end, a large number of reservoirs had been constructed in Ethiopia. However, reservoirs are suffering from sedimentation. This study was conducted in Minizr catchment, NW Ethiopia to (1) quantify the sediment entering Koga reservoir, (2) to assess the functioning and effectiveness of the existing man-made sediment trapping (ST) measures and natural sediment sinks, and (3) to design a possible solution to tackle the problem. Results of three years (2013-2015) field data show that 38% of the transported sediment was trapped within the Minizr catchment. Although considerable efforts were made to trap the sediment within the catchment through implementing various ST measures, lack of an integrated ST approach causes the remaining 62% of the sediment load still entering Koga reservoir.

Antibiotic resistance reservoirs : the cases of sponge and human gut microbiota
Versluis, Dennis - \ 2016
University. Promotor(en): Hauke Smidt, co-promotor(en): Mark van Passel; Detmer Sipkema. - Wageningen : Wageningen University - ISBN 9789462579057 - 197
antibiotic resistance - reservoirs - intestinal microorganisms - luffa - forest soils - sediment - escherichia coli - penicillium - faecal examination - antibioticaresistentie - darmmicro-organismen - bosgronden - fecesonderzoek

One of the major threats to human health in the 21st century is the emergence of pathogenic bacteria that are resistant to multiple antibiotics, thereby limiting treatment options. An important route through which pathogens become resistant is via acquisition of resistance genes from environmental and human-associated bacteria. Yet, it is poorly understood to what extent and by what mechanisms these so-called reservoirs contribute to emerging resistance. Therefore, the work described in this thesis focussed on generating novel insights into different niches as sources of resistance, with a particular focus on the human gut microbiota as well as on microbial communities associated with marine sponges, especially because the latter have been described as one of the richest sources of bioactive secondary metabolites, including a broad range of antimicrobials. Cultivation-based methods were complemented with culture-independent approaches in order to study bacterial taxa that are not readily cultivated.

Using metatranscriptomics it was found that clinically relevant antibiotic resistance genes are expressed in a broad range of environmental niches including human, mouse and pig gut microbiota, sea bacterioplankton, a marine sponge, forest soil and sub-seafloor sediment. The diversity of resistance gene transcripts differed greatly per niche indicating that the environment contains a rich reservoir of functional resistance that could be accessible by pathogens. Even though resistance gene expression might be linked to the presence of natural antibiotics, we did not detect expression of the corresponding secondary metabolite biosynthesis clusters.

Thirty-one antibiotic-resistant bacteria, amongst which three belonging to potentially novel Flavobacteriaceae spp., were isolated from the Mediterranean sponges Aplysina aerophoba, Corticium candelabrum and Petrosia ficiformis. Isolates were identified in a high throughput manner by double-barcoded 16S rRNA gene amplicon sequencing. Furthermore, analysis of sponge tissue-derived bacterial biomass growing on agar media showed that many novel bacterial taxa can still be isolated by conventional cultivation methods. Genomic DNA from the 31 antibiotic resistant bacteria was interrogated with respect to the presence of active resistance genes by functional metagenomics. In addition, we also screened metagenomic libraries prepared from DNA directly isolated from sponge tissue in order to circumvent the need for cultivation. In total, 37 unique resistance genes were identified, and the predicted gene products of 15 of these shared <90% amino acid identity with known gene products. One resistance gene (blaPSV-1), which was classified into a new β-lactamase family, was found to be exclusive to the marine specific genus Pseudovibrio. These findings raised questions as to the functional roles of these genes in sponges, but more importantly, the functionality of these genes in E. coli shows that they can potentially be harnessed by phylogenetically distinct bacteria in other environments, including human pathogens. As such, it is a wake-up call as to the significance of marine resistance reservoirs.

Pseudovibrio, a genus of α-Proteobacteria, was studied in more detail by comparative genomics as it comprises bacteria that potentially play a role as sponge symbionts and marine hubs of antibiotics resistance. Based on gene content, members of the genus Pseudovibrio were found to cluster by sponge sampling location indicating geographic speciation. Furthermore, Pseudovibrio spp. isolated from sponges near the Spanish coast clustered by sponge, suggesting host-specific colonization or adaptation. Strong support for Pseudovibrio spp. forming symbiotic relations with sponges came from the presence of a plethora of (predicted) conserved symbiosis-related functions in their genomes.

A final study aimed to isolate novel antibiotic resistant reservoir species from the human gut microbiota using a targeted approach. Faecal samples from hospitalized patients that received Selective Digestive Decontamination (SDD), a prophylactic treatment with a cocktail of different antibiotics (tobramycin, polymyxin E, amphotericin B and cefotaxime), were inoculated anaerobically on agar media, after which bacterial biomass was analysed by 16S rRNA gene amplicon sequencing. Six novel taxa were identified that, based on their growth on media supplemented with the SDD antibiotics, could serve as clinically relevant reservoirs of antibiotic resistance. For one of these six taxa a member was obtained in pure culture by targeted isolation. The abundance of antibiotic resistant uncultivated taxa in the human gut microbiota warrants further research as to their potential roles in resistance dissemination.

In conclusion, this thesis provides deeper insights into different environmental niches as reservoirs of antibiotic resistance. The results can serve to prime and inspire future research.

Monitoring en Evaluatie Pilot Zandmotor Fase 2 : Datarapport benthos bemonstering vooroever en strand najaar 2015
Wijsman, J.W.M. - \ 2016
IMARES (Rapport / IMARES C006/16) - 71 p.
sediment - benthos - bemonsteren - kustgebieden - terrestrische ecologie - nederland - sampling - coastal areas - terrestrial ecology - netherlands
Van 24 augustus tot en met 16 oktober 2015 is er een bemonstering uitgevoerd van het benthos en de sedimentkarakteristieken bij de Zandmotor. De vooroever is bemonsterd met de Van Veen happer (120 stations) en de bodemschaaf (109 stations). Het strand is bemonsterd tijdens de ebfase met een meetframe (70 stations). In deze rapportage worden de resultaten van het sediment en de schaafbemonstering gepresenteerd en vergeleken met voorgaande jaren.
Beach sand dynamics : measurements, models and scales
Poortinga, A. - \ 2015
University. Promotor(en): Coen Ritsema, co-promotor(en): Saskia Visser; Michel Riksen. - Wageningen : Wageningen University - ISBN 9789462575851 - 235
stranden - zand - modellen - meettechnieken - eolisch zand - sediment - geologische sedimentatie - beaches - sand - models - measurement techniques - aeolian sands - geological sedimentation
Sediment toxicity testing and prospective risk assessment of organic chemicals
Diepens, N.J. - \ 2015
University. Promotor(en): Bart Koelmans, co-promotor(en): Paul van den Brink. - Wageningen : Wageningen University - ISBN 9789462574991 - 346
sediment - toxiciteit - testen - sedimenttest - verontreinigde sedimenten - chemicaliën - risicoschatting - ecotoxicologie - toxicity - testing - sediment test - contaminated sediments - chemicals - risk assessment - ecotoxicology

While providing an option for development in coastal areas, shrimp farming is usually associated with high environmental cost due to the loss of mangrove forest and high social cost as farmers suffer heavy financial losses due to disease outbreaks. Planning shrimp farming requires to integrate risk as well as social and environmental cost. This thesis, using the Mekong Delta as a case, presents an approach to investigate, with local stakeholders, options to plan a resilient and sustainable shrimp farming sector. First, Olivier Joffre analyzed the different shrimp production systems from economic point of view before analyzing farmer’s strategies and providing insights on drivers that will push or, at the opposite, constraint farmers to choose integrated mangrove shrimp systems. This knowledge was integrated in an Agent Based Model (ABM) that was calibrated using Role Playing Games (RPG).

The effect of future scenarios and different policies on the farmers’ decisions was tested using a combination of RPG and ABM. For one coastal district of the Mekong Delta, the results showed that promotion of intensification of shrimp production has a high social cost and decreases the total production in the study area after 10 years. Policies for supporting the spread of integrated mangrove-shrimp systems, such as Payment for Ecosystem Services, or access to an organic value chain, are not strong enough to influence farmers’ decision toward adopting these systems. Without any adaptation to climate change a sharp decrease of the production is expected. The approach brought local farmers’ knowledge to the attention of decision makers.

Impact of improved operation and maintenance on cohesive sediment transport in Gezira Scheme, Sudan
Osman, I.S.E. - \ 2015
University. Promotor(en): E. Schultz, co-promotor(en): A.K. Osman; F.X. Suryadi. - Leiden : CRC Press/Balkema - ISBN 9781138028807 - 183
sediment - geologische sedimentatie - waterbeheer - irrigatiekanalen - irrigatie - irrigatiewater-toedieningsschema - sudan - geological sedimentation - water management - irrigation channels - irrigation - irrigation scheduling

Efficient operation and maintenance of irrigation schemes are needed for improving the hydraulic performance of the canals, enhancing the crop yields and insuring sustainable production. There is a great need to enhance the researches and for a variety of tools such as water control and regulation equipment, decision support systems, as well as field surveys and valuation techniques. Water management becomes difficult when dealing with sediment transport in irrigation canals. Most of the studies simulate the sediment transport of relatively coarse grain sizes. The sediment problem in irrigation canals becomes more complicated when dealing with cohesive sediment transport. Therefore, more research is needed to enhance the understanding of the behaviour of cohesive sediment transport under a variety of operation conditions.

This study has been carried out in the Gezira Scheme in Sudan. The scheme, which is one of the largest irrigation schemes in the world under a single management, is located in the arid and semi-arid region. The scheme is chosen as a case study since it can act as a model for similar irrigation schemes. The scheme has a total area of 880,000 ha and uses 35% of Sudan’s current allocation of Nile waters. This represents 6 – 7 billion m3 per year. The scheme is irrigated from the Blue Nile River, which is characterized by its high load of fine sediment. The scheme is facing severe sediment accumulation in its irrigation canals, which represents a challenge to those responsible for the operation and maintenance of the canals. Each year large investments are required to maintain and to upgrade the canal system to keep it in an acceptable condition.

A large quantity of cohesive sediment enters the scheme every year. According to previous studies, about 60% of the sediment deposits in the irrigation canals. The sediment accumulation in the canals reduces the canal conveyance capacity, causes irrigation difficulties, creates inequity and inadequate water supply and increases the rate of aquatic weed growth. The sedimentation problems are not only seriously affecting the performance of the irrigation canals, but are also jeopardizing their sustainability, as well as affecting crop production. Two canals in the scheme have been selected to be studied in detail: Zananda Major Canal, which takes water from Gezira Main Canal at 57 km from the offtake at Sennar Dam, and Toman Minor Canal at 12.5 km from the offtake of Zananda Major Canal.

The hypothesis of the study postulates that the operation and maintenance of an irrigation scheme has a major influence on the hydrodynamic behaviour of canals and hence on sediment movement and deposition. The aim of this study was to improve the operation and maintenance procedures for better sediment and water management. This can be achieved through better understanding of the sediment processes in the irrigation canals of the Gezira Scheme and to understand clearly the link between irrigation system operation and resulting system performance in terms of transport of cohesive sediment.

Data collection and field measurements have been conducted during the flood season between June and October in 2011 and 2012. Sediment sampling and water level measurements have been conducted on a daily basis at selected locations. The manually recorded water levels include about 1080 readings per year. In addition about 1290 sediment samples were analysed for different locations during the study period. Cross-sectional surveys have been performed at the beginning and end of the flood season to address the spatial and temporal variation of the sediment deposition in the canals under study and to detect changes in the bed profile. The head regulator and outlet control structures were calibrated by using the measured stage-discharge relationships. More elaboration is given to the properties of cohesive sediment and identification of the dominant factors that cause deposition in irrigation canals. Sediment properties were tested such as grain size distribution, mechanical and physico-chemical properties of the sediment. The irrigation schedules, cropped area and sowing dates for different crops were reported. Other data such as canal design data, historical data of the sediment and flow for certain canals were reviewed.

The analysis of the data indicates a variation of the water level along the canals under study. It should be noted that the operation control in Gezira Scheme is by using upstream control structures. The field data show that the flow release in the system is not regularly adjusted in a systematic way to meet the demand and maintain the required water level. Continuous change in gate setting results in instability of the water level. This situation became worse with more sediment deposition. The water level has been raised far above the design level and there is lapse in working levels especially at the major and minor canals. The rise is found to be about 1.6 and 1.2 m above the design level at the head of the major and minor canals under study. Furthermore, reduction in the water depth has been detected along the canals as result of bed rise and enlarging of canal sections due to improper desilting. The results demonstrate that the supply of water was extremely large during the flood season of 2011 compared to the actual crop water requirement, especially during the period of high sediment concentration. The delivery performance ratio indicated an oversupply at the major canal in 2011 during most of the time. The study also provides some valuable insight into the nature of sediment in Gezira Scheme.

There is a limitation in the existing models that deal with fine sediment transport in irrigation canals. Most of the sediment transport models are developed for estuaries and rivers. Therefore there was a great need to develop a simple but effective numerical model that incorporates control structures to simulate the fine sediment transport in irrigation canals. Although there are similarities between rivers and irrigation canals, irrigation canals are different. The presence of a large number of flow control structures and the high influence of the side banks on the velocity distribution create some differences in both types of channels. Hence, it was important to develop a model dealing with fine sediment in irrigation canals, including different types of hydraulic structures.

In line with this the one dimensional numerical model Fine SEDiment Transport (FSEDT) dealing with fine sediment transport in irrigation canals has been developed. The model has been used as a tool to study the mechanism of water and sediment flow under different operation and maintenance scenarios. The water surface profile has been predicted by using the predictor corrector method to solve the gradually varied flow equation. The prediction of sediment concentration is based on the solution of the one dimensional advection-diffusion equation. The bed material exchange was determined based on the Partheniades (1962) and Krone (1965) equations. The change in bed level was computed based on the sediment mass balance equation that was solved numerically by using the finite difference method. The model has been applied in the Gezira Scheme. On the basis of the field data the model has been calibrated and validated. The predicted bed profiles depict good agreement with the measured ones. The model is capable to predict the bed profile for any period of simulation. The model can predict the sediment concentration hydrograph at different points within a canal reach, in addition to the total volume of the sediment deposition in the reach. The output of the model can be presented in tabular or graphical form.

The sediment transport in the irrigation canals has been simulated by adopting different scenarios. The interrelationship between water flow and sediment transport in the irrigation canals under changing flow conditions has been investigated. Two scenarios of operation were tested at the major canal under study. The model evaluated the indent system that has been applied in Gezira Scheme for many years in regard to sediment deposition. Another proposed scenario based on crop water requirement was also tested. In addition, operation under future changed conditions in case of reduction in the sediment concentration was tested. The different operation scenarios have been compared with the existing condition based on data collected during the flood season in 2011 in terms of sedimentation. Based on this, the following remarks are made:

the effect of varying crest settings of the movable weirs has been investigated and less sediment deposition was found to occur when the crest level was set at its lowest position. The sediment transport in the canals is influenced by the operation of the hydraulic structures, especially upstream of movable weirs. The effect is extended to about 3 km upstream of the weir;

for many years the indent system of water allocation was applied in the Gezira Scheme based on duty and cropped area. However, this system of operation has been absent during the last years. The slope of Zananda Major Canal became 13 cm/km and 18 cm/km for the first and second reaches respectivelycampaigns

the reduction of the water delivery during the period of high concentration between 10 July and 10 August, based on the crop water requirement results in reduction in the sediment deposition by 51 and 55% for the first and second reaches respectively when compared to the situation in 2011;

the reduction of the Blue Nile River sediment concentration by 50% as result of the construction of the Ethiopia Renaissance Dam and/or improvement in the land use has been simulated. The results of the simulation of the suspended sediment transport at the major canal indicate that the deposition will be 74 and 81% lower for the first and second reaches respectively when compared with the situation in 2011.

At the minor canals, the night storage weirs were designed as cross structures. The idea behind the night storage system was to store water during the night by closing all field outlet pipes and the gates of the cross structures along the minor canal at 6:00 pm and releasing them at 6:00 am. Although this system has been vanished to keep pace with crop intensification and to cope with the deterioration of the water supply due to the poor maintenance of the canals, this scenario has also been simulated. The hydrodynamic flow in the canals during the filling time has been simulated by using the DUFLOW model since the model can be applied for unsteady flow. A spreadsheet has been designed to predict the deposition every hour based on the output of the DUFLOW model. The night storage system has been compared with the continuous system regarding the sediment transport in addition to other scenarios. It was found that:

the continuous system reduces the amount of deposited sediment by 55% compared to the night storage system;

about 29% of the sediment was reduced in 2011 when the system was operated based on crop water requirement;

the deposition lightly increased with reduced capacity of the field outlet pipes. The

The main findings and the contributions that are made by this study:

the study comes up with a model dealing with cohesive sediment in irrigation canals for effective sediment and water management, which can be applied widely for similar irrigation schemes dealing with fine sediment;

it is possible to improve the sediment and water management by improving the operation and maintenance. The high irrigation efficiency is tending to mitigate the inflow sediment load and as a consequence less deposition is expected;

the study comes up with strategies of water management that can reduce the deposition in irrigation canals by operating the system continuously based on crop water requirement at the period of high sediment concentration with the field outlet pipes operating at their full capacity.

The absence of proper maintenance activities and water management has a prominent role in increasing the deposition along the irrigation canals in Gezira Scheme. Improving the operation and maintenance is not the only way to mitigate the sedimentation in the irrigation canals. A great consideration needs to be given to improve the design since conditions based on the original design have been changed with time such as the operation system (night storage system, indent system), cropping intensity and geometry of the canals. In other words, rehabilitation of the system will not be one of the solutions to mitigate the accumulation of the deposition along the canals but the system itself needs remodelling. The developed model can be used to assess the new design and to evaluate the proposed management plans in terms of transport of cohesive sediment.

Passende Beoordeling Natuurbeschermingswet 1998 voor project Kwelderontwikkeling Koehoal door een slibmotor
Baptist, M.J. - \ 2015
Den Burg : IMARES (Rapport / IMARES Wageningen UR C081/15) - 44
havens - sediment - wetlands - bagger - geologische sedimentatie - natura 2000 - natuurbescherming - waddenzee - friesland - harbours - dredgings - geological sedimentation - nature conservation - wadden sea
Pilotproject om het gebaggerd slib uit de haven van Harlingen te verspreiden over de wadden. In het natura 2000 gebied. Door middel van een experimentele ‘slibmotor’ wordt het sedimentaanbod langs de kust ten noordoosten van Harlingen vergroot met als uiteindelijk doel het areaal kwelders te vergroten.
Post drill survey A6 - A6 2014
Glorius, S.T. ; Weide, B.E. van der; Kaag, N.H.B.M. - \ 2015
Den Helder : IMARES (Report / IMARES Wageningen UR C046/15) - 41
waterbodems - noordzee - sediment - mijnbouw - nadelige gevolgen - natura 2000 - water bottoms - north sea - mining - adverse effects
A consortium has drilled a production well linked to the existing production platform A6-A. This platform is located in an ‘FFH-area’ with a Natura 2000 designation area. Wintershall (one of the consortium partners) has requested IMARES to conduct a post-drilling survey at the A6-A platform site to assess the impact of the drilling activities. The 2014 survey consisted of the same elements (including sampling of sediment, side scan sonar and video recordings from the sea floor), as well as the same sampling grid as in the baseline study in 2011. Results of the post-drilling survey (2014) are analysed and compared with the 2011 survey to assess any impact of the drilling activities.
Intertidal biofilm distribution underpins differential tide-following behavior of two sandpiper species (Calidris mauri and Calidris alpina) during northward migration
Jimenez, A. ; Elner, R.W. ; Favaro, C. ; Rickards, K. ; Ydenberg, R.C. - \ 2015
Estuarine Coastal and Shelf Science 155 (2015). - ISSN 0272-7714 - p. 8 - 16.
fraser-river estuary - western sandpipers - shorebird distribution - sediment - waders - microphytobenthos - invertebrates - predation - abundance - cycle
The discovery that some shorebird species graze heavily on biofilm adds importance to elucidating coastal processes controlling biofilm, as well as impetus to better understand patterns of shorebird use of intertidal flats. Western sandpipers (Calidris mauri) and dunlin (Calidris alpina) stopover in the hundreds of thousands on the Fraser River estuary, British Columbia, Canada, during northward migration to breeding areas. Western sandpipers show greater modification of tongue and bill morphology for biofilm feeding than dunlin, and their diet includes more biofilm. Therefore, we hypothesized that these congeners differentially use the intertidal area. A tide following index (TFI) was used to describe their distributions in the upper intertidal during ebbing tides. Also, we assessed sediment grain size, biofilm (= microphytobenthic or MPB) biomass and invertebrate abundance. Foraging dunlin closely followed the ebbing tide line, exploiting the upper intertidal only as the tide retreated through this area. In contrast, western sandpipers were less prone to follow the tide, and spent more time in the upper intertidal. Microphytobenthic biomass and sediment water content were highest in the upper intertidal, indicating greater biofilm availability for shorebirds in the first 350 m from shore. Invertebrate density did not differ between sections of the upper intertidal. Overall, western sandpiper behaviour and distribution more closely matched MPB biofilm availability than invertebrate availability. Conservation of sandpipers should consider physical processes, such as tides and currents, which maintain the availability of biofilm, a critical food source during global migration.
Lake retention of manufactured nanoparticles
Koelmans, A.A. ; Quik, J.T.K. ; Velzeboer, I. - \ 2015
Environmental Pollution 196 (2015). - ISSN 0269-7491 - p. 171 - 175.
engineered nanomaterials - tio2 nanoparticles - fate models - aggregation - environment - sediment - exposure - heteroaggregation - impacts - release
For twenty-five world lakes and three engineered nanoparticles (ENP), lake retention was calculated using a uniformly mixed lake mass balance model. This follows similar approaches traditionally used in water quality management. Lakes were selected such that lake residence times, depths and areal hydraulic loadings covered the widest possible range among existing lakes. Sedimentation accounted for natural colloid as well as suspended solid settling regimes. An ENP-specific mixed sedimentation regime is proposed. This regime combines ENP sedimentation through slow settling with natural colloids from the water column, with faster settling with suspended solids from a selected part of the water column. Although sedimentation data and hydrodynamic concepts as such were not new, their first time combination for application to ENPs shows in which cases lake retention is important for these particles. In combination with ENP emission data, lake retention translates directly into potential risks of ENPs for lake benthic communities.
Cultivation-Independent Screening Revealed Hot Spots of IncP-1, IncP-7 and IncP-9 Plasmid Occurrence in Different Environmental Habitats
Dealtry, S. ; Ding, G.C. ; Weichelt, V. ; Dunon, V. ; Schluter, A. ; Martini, M.C. ; Papa, M.F. Del; Lagares, A. ; Amos, G.C.A. ; Wellington, E.M.H. ; Gaze, W.H. ; Sipkema, D. ; Sjoling, S. ; Springael, D. ; Heuer, H. ; Elsas, J.D. ; Thomas, C. ; Smalla, K. - \ 2014
PLoS ONE 9 (2014)2. - ISSN 1932-6203
resistance genes - naphthalene - pseudomonas - adaptation - prevalence - transposon - diversity - sediment - biobeds
IncP-1, IncP-7 and IncP-9 plasmids often carry genes encoding enzymes involved in the degradation of man-made and natural contaminants, thus contributing to bacterial survival in polluted environments. However, the lack of suitable molecular tools often limits the detection of these plasmids in the environment. In this study, PCR followed by Southern blot hybridization detected the presence of plasmid-specific sequences in total community (TC-) DNA or fosmid DNA from samples originating from different environments and geographic regions. A novel primer system targeting IncP-9 plasmids was developed and applied along with established primers for IncP-1 and IncP-7. Screening TC- DNA from biopurification systems (BPS) which are used on farms for the purification of pesticide-contaminated water revealed high abundances of IncP-1 plasmids belonging to different subgroups as well as IncP-7 and IncP-9. The novel IncP-9 primer-system targeting the rep gene of nine IncP-9 subgroups allowed the detection of a high diversity of IncP-9 plasmid specific sequences in environments with different sources of pollution. Thus polluted sites are "hot spots'' of plasmids potentially carrying catabolic genes.
Geo-Engineering in Lakes: A Crisis of Confidence?
Spears, B.M. ; Maberly, S.C. ; Pan, G. ; Mackay, E. ; Lurling, M.F.L.L.W. - \ 2014
Environmental Science and Technology 48 (2014)17. - ISSN 0013-936X - p. 9977 - 9979.
phosphorus - sediment - clay
The effective management of lakes suffering from eutrophication is confounded by a mosaic of interactions and feedbacks that are difficult to manipulate. For example, in lake processes can delay the relinquishment of legacy phosphorus (P) manifested within bed sediments for decades, even after effective catchment management. This recovery time is often deemed unacceptable and researchers have explored many in-lake management measures designed to “speed-up” recovery. The manipulation of biogeochemical processes (commonly targeting P) using materials to achieve a desired chemical and/or ecological response has been termed geo-engineering in lakes, and is becoming a commonly considered eutrophication management tool (Figure 1). Although this approach has been employed for many years it remains contentious largely due to variable results reported in the literature. This uncertainty risks ineffective management based on poorly designed or inappropriate applications. To address this, it is important that current levels of confidence in the approach be effectively communicated and that methods of increasing confidence are clearly demonstrated. We draw here on experiences of researchers and water managers at a global scale to demonstrate recent advances and consensus on recommendations (numbered below) for best practice. This information, although vital to underpinning successful management, has not been available in the peer reviewed literature.
Geoengineering in lakes: welcome attraction or fatal distraction?
Mackay, E. ; Maberly, S.C. ; Pan, G. ; Reitzel, K. ; Lurling, M.F.L.L.W. - \ 2014
Inland Waters : Journal of the International Society of Limnology 4 (2014). - ISSN 2044-2041 - p. 349 - 356.
modified bentonite clay - phosphate adsorption - phosphorus release - shallow lakes - water-quality - sediment - nutrient - aluminum - removal - phoslock(r)
The use of geoengineering techniques for phosphorus management offers the promise of greater and quicker chemical and ecological recovery. It can be attractive when used with other restoration measures but should not be considered a panacea. The range of materials being proposed for use as well as the in-lake processes targeted for manipulation continues to grow. With increasing political imperatives to meet regulatory goals for water quality, we recommend a coordinated approach to the scientific understanding, costs, and integration of geoengineering with other approaches to lake management.
Monitoring en Evaluatie Pilot Zandmotor Fase 2 - Datarapport benthos bemonstering vooroever en natte strand najaar 2013
Wijsman, J.W.M. - \ 2014
Yerseke [etc.] : IMARES en Deltares (Rapport / IMARES C150/14 - 1205045-000-ZKS-0101) - 57
sediment - benthos - bemonsteren - kustgebieden - terrestrische ecologie - nederland - sampling - coastal areas - terrestrial ecology - netherlands
Om de effecten van de Zandmotor op de bodemdiergemeenschap te onderzoeken worden er in het najaar bemonsteringen uitgevoerd van sediment en bodemdieren op het strand met een steekframe in de ondiepe kustzone met een Van Veen happer en een bodemschaaf. De Van Veen happer is vooral geschikt voor het bemonsteren de relatief kleinere (maaswijdte zeef is 1 mm), minder zeldzame, in de bodem levende dieren. Het doel van dit datarapport is een overzicht te geven van de resultaten van de bemonstering van het sediment en benthos op het strand en de ondiepe kustzone van de Zandmotor in het najaar van 2013.
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