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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    Bruinvis volgt spiering naar westerschelde
    Ramaker, R. ; Leopold, M.F. - \ 2015
    Resource: weekblad voor Wageningen UR 10 (2015)8. - ISSN 1874-3625 - p. 9 - 9.
    phocoenidae - milieubeleid - westerschelde - habitats - habitatgeschiktheid - osmerus - rivieren - wilde dieren - populatie-ecologie - phocoenidae - environmental policy - western scheldt - habitats - habitat suitability - osmerus - rivers - wild animals - population ecology
    In de Westerschelde zwemmen voor het eerst in decennia weer bruinvissen. De dieren jagen op de eveneens teruggekeerde trekvis spiering. Het is een succesverhaal van het Nederlands milieubeleid, zegt Mardik Leopold, onderzoeker van Imares Wageningen UR, die vandaag promoveert op onderzoek naar het eetgedrag van bruinvissen.
    Reguleringsmechanismen in het kustecosysteem van de Voordelta
    Kooten, T. van; Jansen, H.M. - \ 2015
    IJmuiden : IMARES (Rapport / IMARES C095/15) - 66
    aquatische ecosystemen - benthos - voordelta - kustwateren - zuidwest-nederland - aquatische gemeenschappen - visserij - bodemfauna - rivieren - aquatic ecosystems - benthos - voordelta - coastal water - south-west netherlands - aquatic communities - fisheries - soil fauna - rivers
    Wordt het benthos in het Voordelta kustecosysteem gereguleerd door bottom-up of top-down gerelateerde processen, en hoe zal dit systeem reageren op de maatregelen om de bodemberoerende visserij uit te sluiten in het Bodembeschermingsgebied.
    Perspectieven voor ecosysteemdiensten en natuur van een hoogwatergeul bij Varik Heesselt : een studie voor de NKN-casus Waterveiligheid Deltaprogramma
    Bos, M. ; Hartgers, E.M. ; Goossen, C.M. ; Groot, W.J.M. de; Kwakernaak, C. ; Maas, G.J. ; Levelt, O. ; Schasfoort, F. ; Nienhuis, A. - \ 2015
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2652) - 121
    ecosysteemdiensten - rivieren - hoogwaterbeheersing - waal - regionale planning - betuwe - ecosystem services - rivers - flood control - river waal - regional planning - betuwe
    Doel van dit project is om aan de hand van twee pilots te bepalen wat de mogelijke economische en ecologische meerwaarde is van natuur-inclusieve oplossingen voor waterveiligheidsopgaven uit het Deltaprogramma en wat de meerwaarde van de TEEB-aanpak is in het planvormings- en besluitvormingsproces over deze maatregelen. Dit rapport handelt over de pilot “hoogwatergeul Varik-Heesselt”. De pilot was gericht op toepassing en evaluatie van de TEEB-methode. Het project is in nauw contact met de projectleider van de provincie Gelderland van het lopende planproces uitgevoerd.
    Macroinvertebrate survival during cessation of flow and streambed drying in a lowland stream
    Verdonschot, R.C.M. ; Oosten-Siedlecka, A.M. van; Braak, C.J.F. ter; Verdonschot, P.F.M. - \ 2015
    Freshwater Biology 60 (2015)2. - ISSN 0046-5070 - p. 282 - 296.
    invertebrate communities - prairie stream - desert stream - drought - intermittent - assemblages - responses - rivers - recolonization - resilience
    1.The number of perennial low-order lowland streams likely to experience intermittent flow is predicted to increase in north-western Europe. To understand the effects of such a change on macroinvertebrates, a field experiment was carried out in a currently perennial sandy lowland stream. 2.Using a before–after control–impact design, the flow regime was manipulated to yield two distinct treatments: stagnation (although with little water loss) and drying of the stream (although artificial remnant pools remained in the bed). There was also an unmanipulated control reach. The two treatments were applied simultaneously in separate, consecutive reaches, resulting in 29 days of stagnation and 25 days of streambed drying with surface water only present in the remnant pools. Changes in macroinvertebrate richness, abundance and community composition were recorded, and we assessed whether these changes could be explained by ecological preferences for flow of the various taxa. 3.Stagnation resulted in only minor changes in community composition. A small number of rheophilic taxa disappeared, while taxa preferring standing waters complemented those already present, increasing total biodiversity. In remnant pools in the otherwise dry reach, richness and abundance peaked after they became isolated, indicating a concentration of invertebrates. A subsequent steep decline in richness coincided with hypoxia and increasing conductivity. Culex pipiens/torrentium colonised the pools and was then dominant. Only a small subset of the assemblage successfully used the dry streambed as a refuge. 4.The effect of a shift from perennial to intermittent flow evidently depends on the degree of habitat change. Environmental conditions after cessation of flow are crucial in determining lowland stream macroinvertebrate persistence during water drawdown.
    Dynamics in organic matter processing, ecosystem metabolism and trophic sources for consumers in the Mara River, Kenya
    Masese, F.O. - \ 2015
    Wageningen University. Promotor(en): K.A. Irvine, co-promotor(en): M.E. McClain; G.M. Gettel. - Leiden : CRC Press/Balkema - ISBN 9781138028159 - 195
    organische stof - ecosystemen - landgebruik - ecosysteemdiensten - rivieren - meren - koolstof - stikstof - visserij - aquatische ecologie - organic matter - ecosystems - land use - ecosystem services - rivers - lakes - carbon - nitrogen - fisheries - aquatic ecology

    To properly conserve, restore and manage riverine ecosystems and the services they provide, it is pertinent to understand their functional dynamics. However, there is still a major knowledge gap concerning the functioning of tropical rivers in terms of energy sources supporting riverine fisheries. I reviewed the anthropogenic influences on organic matter processes, energy sources and attributes of riverine food webs in the Lake Victoria basin, but also expanded the review to incorporate recent research findings from the tropics. Contrasting findings have been presented on the diversity of shredders and their role in organic matter processing in tropical streams. Recent tropical research has also highlighted the importance of autochthonous carbon, even in small forested streams. However similar studies are very limited in Afrotropical streams making it difficult to determine their place in emerging patterns of carbon flow in the tropics.

    This study was conducted in the Mara River, which is an important transboundary river with its headwaters in the Mau Forest Complex in Kenya and draining to Lake Victoria through Tanzania. In its headwaters, the basin is drained by two main tributaries, the Amala and Nyangores Rivers which merge in the middle reaches to form the Mara River mainstem. The overall objective of this dissertation was to better understand the functioning of the Mara River by assessing the spatio-temporal dynamics of organic matter sources and supply under different land-use and flow conditions and the influence of these dynamics on energy flow for consumers in the river. I collected benthic macroinvertebrates from open- and closed-canopy streams and classified them into functional feeding groups (FFGs) using gut content analysis. In total, I identified 43 predators, 26 collectors, 19 scrapers and 19 shredders. Species richness was higher in closed-canopy forested streams where shredders were also the dominant group in terms of biomass. Seven shredder taxa occurred only in closed-canopy forested streams highlighting the importance of maintaining water and habitat quality, including the input of leaf litter of the right quality, in the studied streams. The findings suggest that Kenyan highland streams harbor a diverse shredder assemblage contrary to earlier findings that had identified a limited number of shredder taxa.

    I subsequently used the composition of invertebrate functional feeding groups (FFGs) and the ecosystem process of leaf breakdown as structural and functional indicators, respectively, of ecosystem health in upland Kenyan streams. Coarse- and fine-mesh litterbags were used to

    compare microbial (fine-mesh) with shredder + microbial (coarse-mesh) breakdown rates, and by extension, determine the role of shredders in litter processing of leaves of different tree species (native Croton macrostachyus and Syzygium cordatum and the exotic Eucalyptus globulus). Breakdown rates were generally higher in coarse- compared with fine-mesh litterbags for the native leaf species and the relative differences in breakdown rates among leaf species remained unaltered in both agriculture and forest streams. Shredders were relatively more important in forest compared with agriculture streams where microbial breakdown was more important. Moreover, shredder mediated leaf litter breakdown was dependent on leaf species, and was highest for C. macrostachyus and lowest for E. globulus, suggesting that replacement of indigenous riparian vegetation with poorer quality Eucalyptus species along streams has the potential to reduce nutrient cycling in streams.

    To study organic matter dynamics is these streams, I assessed the influence of land use change on the composition and concentration of dissolved organic matter (DOM) and investigated its links with whole-stream ecosystem metabolism. Optical properties of DOM indicated notable shifts in composition along a land use gradient. Forest streams were associated with higher molecular weight and terrestrially derived DOM whereas agriculture streams were associated with autochthonously produced and low molecular weight DOM and photodegradation due to the open canopy. However, aromaticity was high at all sites irrespective of catchment land use. In agricultural areas high aromaticity likely originated from farmlands where soils are mobilized during tillage and carried into streams and rivers by runoff. Gross primary production (GPP) and ecosystem respiration (ER) were generally higher in agriculture streams, because of slightly open canopy and higher nutrient concentrations. The findings of this study are important because, in addition to reinforcing the role of tropical streams and rivers in the global carbon cycle, they highlight the consequences of land use change on ecosystem functioning in a region where land use activities are poised to intensify in response to human population growth.

    Lastly, I used natural abundances of stable carbon (δ13C) and nitrogen (δ15N) isotopes to quantify spatial and temporal patterns of carbon flow in food webs in the longitudinal gradient of the Mara River. River reaches were selected that were under different levels of human and mammalian herbivore (livestock and wildlife) influences. Potential primary producers (terrestrial C3 and C4 producers and periphyton) and consumers (invertebrates and fish) were collected

    during the dry and wet seasons to represent a range of contrasting flow conditions. I used Stable Isotope Analysis in R (SIAR) Bayesian mixing model to partition terrestrial and autochthonous sources of organic carbon supporting consumer trophic groups. Overall periphyton dominated contributions to consumers during the dry season. During the wet season, however, the importance of terrestrially-derived carbon for consumers was higher with the importance of C3 producers declining with distance from the forested upper reaches as the importance of C4 producers increased in river reaches receiving livestock and hippo inputs. This study highlights the importance of large mammalian herbivores on the functioning of riverine ecosystems and the implications of their loss from savanna landscapes that currently harbour remnant populations.

    The results of this dissertation contribute data to discussions on the effects of land use change on the functioning of upland streams and food webs in savanna rivers with regard to carbon flow and the vectoring role played by large mammalian herbivores as they transfer terrestrial organic matter and nutrients into streams and rivers. This study also provides information and recommendations that will guide future research and management actions for the sustainability of the Mara River and linked ecosystems in the Lake Victoria basin.

    Future trends in urbanization and coastal water pollution in the Bay of Bengal: the lived experience
    Zinia, N.J. ; Kroeze, C. - \ 2015
    Environment, Development and Sustainability 17 (2015)3. - ISSN 1387-585X - p. 531 - 546.
    nutrient export - rivers - perspectives - management - phosphorus - nitrogen
    The Bay of Bengal includes coastal seas of several countries, including Bangladesh, India, and Myanmar. We present scenarios for future river export of eutrophying nutrients into the Bay of Bengal, and the role of urbanization therein. We used NEWS (Nutrient Export from WaterSheds) model to analyze trends over the period 1970–2050. The scenarios are based on the Millennium Ecosystem Assessment and indicate the number of people living in urban areas may increase from 22 % in 1970 to about 50 % in 2050. We show that this may considerably increase nutrient levels in rivers from sewage and other sources. For 2050, we calculate that harmful algal blooms may be a potential problem in coastal waters of about 95 % of the total drainage basin of the Bay of Bengal. In addition, we analyze Bangladeshi citizens’ expectations of future trends and how citizens with different worldviews would experience environmental changes (i.e., their lived experience). The citizens indicate that trends as envisaged in our scenarios may be a negative experience. However, some people may experience the trends as positive, because they expected worse.
    Coastal eutrophication in Europe caused by production of energy crops
    Wijnen, J. van; Ivens, W.P.M.F. ; Kroeze, C. ; Löhr, A.J. - \ 2015
    Science of the Total Environment 511 (2015). - ISSN 0048-9697 - p. 101 - 111.
    biomass production - marine ecosystems - future-trends - biofuels - land - rivers - export - agriculture - nitrogen - waters
    In Europe, the use of biodiesel may increase rapidly in the coming decades as a result of policies aiming to increase the use of renewable fuels. Therefore, the production of biofuels from energy crops is expected to increase as well as the use of fertilisers to grow these crops. Since fertilisers are an important cause of eutrophication, the use of biodiesel may have an effect on the water quality in rivers and coastal seas. In this study we explored the possible effects of increased biodiesel use on coastal eutrophication in European seas in the year 2050. To this end, we defined a number of illustrative scenarios in which the biodiesel production increases to about 10–30% of the current diesel use. The scenarios differ with respect to the assumptions on where the energy crops are cultivated: either on land that is currently used for agriculture, or on land used for other purposes. We analysed these scenarios with the Global NEWS (Nutrient Export from WaterSheds) model. We used an existing Millennium Ecosystem Assessment Scenario for 2050, Global Orchestration (GO2050), as a baseline. In this baseline scenario the amount of nitrogen (N) and phosphorus (P) exported by European rivers to coastal seas decreases between 2000 and 2050 as a result of environmental and agricultural policies. In our scenarios with increased biodiesel production the river export of N and P increases between 2000 and 2050, indicating that energy crop production may more than counterbalance this decrease. Largest increases in nutrient export were calculated for the Mediterranean Sea and the Black Sea. Differences in nutrient export among river basins are large.
    Toestand vis en visserij in de zoete Rijkswateren: 2013. Data
    Boois, I.J. de; Graaf, M. de; Griffioen, A.B. ; Keeken, O.A. van; Kuijs, E. ; Os-Koomen, B. van; Westerink, H.J. ; Wiegerinck, Hanz ; Overzee, H.M.J. van - \ 2014
    IJmuiden : IMARES Wageningen UR (Rapport / IMARES Wageningen UR C164a/14) - 468
    zoet water - aquatische ecologie - vissen - monitoring - ijsselmeer - randmeren - rivieren - inventarisaties - fresh water - aquatic ecology - fishes - monitoring - lake ijssel - randmeren - rivers - inventories
    De monitoringen in de zoete Rijkswateren zijn opgezet ten behoeve van het monitoren van de visstand en worden tegenwoordig ook uitgevoerd om de ecologische toestand van de zoete Rijkswateren in kaart te kunnen brengen.
    Multifunctionality of floodplain landscapes: relating management options to ecosystem services
    Schindler, S. ; Sebesvari, Z. ; Damm, C. ; Sluis, T. van der - \ 2014
    Landscape Ecology 29 (2014)2. - ISSN 0921-2973 - p. 229 - 244.
    biodiversity conservation - restoration - indicators - ecology - scales - assessments - knowledge - policy - rivers - reach
    The concept of green infrastructure has been recently taken up by the European Commission for ensuring the provision of ecosystem services (ESS). It aims at the supply of multiple ESS in a given landscape, however, the effects of a full suite of management options on multiple ESS and landscape multifunctionality have rarely been assessed. In this paper we use European floodplain landscapes as example to develop an expert based qualitative conceptual model for the assessment of impacts of landscape scale interventions on multifunctionality. European floodplain landscapes are particularly useful for such approach as they originally provided a high variety and quantity of ESS that has declined due to the strong human impact these landscapes have experienced. We provide an overview of the effects of floodplain management options on landscape multifunctionality by assessing the effects of 38 floodplain management interventions on 21 relevant ESS, as well as on overall ESS supply. We found that restoration and rehabilitation consistently increased the multifunctionality of the landscape by enhancing supply of provisioning, regulation/maintenance, and cultural services. In contrast, conventional technical regulation measures and interventions related to extraction, infrastructure and intensive land use cause decrease in multifunctionality and negative effects for the supply of all three aspects of ESS. The overview of the effects of interventions shall provide guidance for decision makers at multiple governance levels. The presented conceptual model could be effectively applied for other landscapes that have potential for a supply of a high diversity of ESS.
    Toestand vis en visserij in de zoete Rijkswateren. Deel II: Methoden
    Sluis, M.T. van der; Overzee, H.M.J. van; Tien, N.S.H. ; Graaf, M. de; Griffioen, A.B. ; Keeken, O.A. van; Os-Koomen, E. van; Rippen, A.D. ; Wiegerinck, J.A.M. ; Wolfshaar, K.E. van de - \ 2014
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C175/14) - 83
    zoet water - aquatische ecologie - vissen - monitoring - ijsselmeer - randmeren - rivieren - inventarisaties - fresh water - aquatic ecology - fishes - monitoring - lake ijssel - randmeren - rivers - inventories
    Sinds 2013 worden al deze monitoringprogramma’s jaarlijks in één rapportage gebundeld. Dit rapport bevat de gebruikte methodieken van de verschillende vis-monitoringsprogramma’s in de zoete Rijkswateren
    Rivers running deep : complex flow and morphology in the Mahakam River, Indonesia
    Vermeulen, B. - \ 2014
    Wageningen University. Promotor(en): Remko Uijlenhoet, co-promotor(en): Ton Hoitink. - Wageningen : Wageningen University - ISBN 9789462572065 - 150
    rivieren - morfologie - waterstroming - hydrologie - indonesië - rivers - morphology - water flow - hydrology - indonesia

    Rivers in tropical regions often challenge our geomorphological understanding of fluvial systems. Hairpin bends, natural scours, bifurcate meander bends, tie channels and embayments in the river bank are a few examples of features ubiquitous in tropical rivers. Existing observation techniques fall short to grasp the complex governing processes of flow and morphology. In this thesis new observational techniques are introduced and applied to study the Mahakam River, East Kalimantan, Indonesia. The observations reveal a new type of morphological regime, characterized by non-harmonic meanders, scour and strong variation of the cross-sectional area. The anomalous geometry induces a complex three-dimensional flow pattern causing longitudinal flow to be concentrated near the bed of the river.

    In Chapter 2 a wavelet based technique is introduced to characterize meander shape in a quantitative, objective manner. A scale space forest composed of a set of rooted trees represents the meandering planform. Based on the rooted trees, the locally dominant meander wavelengths are defined along the river. Sub-meander scale spectral density in the wavelet transform is used to determine a set of metrics quantifying bend skewness and fattening. Negative fattening parameterizes the so-called non-harmonic or hairpin bend character of meanders. The super-meander scale tree represents the embedding of meanders into larger-scale fluctuations, spanning from double-headed meander scales until the scale of the valley thalweg. The new approach is used to quantify the anomalous planform geometry of the Mahakam River in a comparison with the Red River and the Purus River.

    The geometry of the Mahakam River is analyzed into more detail in Chapter 3, where the highly curved non-harmonic meanders are related to deep scours in the river bed. A total of 35 scours is identified which exceed three times the average river depth, and four scours exceed the river depth over four times. The maximum scour depth strongly correlates with channel curvature and systematically occurs half a river width upstream of the bend apex. Most scours occur in a freely meandering zone of the river. A systematic reconnaissance of the river banks reveals a switch of erosion-deposition patterns at high curvature. Advancing banks normally observed at the inner side of a bend are mostly found at the outer side of high-curvature reaches, while eroding banks switch from the outer side for mildly curved bends to the inner side for bends with high curvature. The overall lateral migration rate of the river is low. These results indicate a switch of morphological regime at high curvatures, which requires detailed flow measurements to unravel the underlying physical processes.

    Taking flow measurements in the deep scours of the Mahakam River presents a challenge to contemporary methods in hydrography. Acoustic Doppler Current Profilers (ADCPs) are capable of profiling flow velocity over large distances from a research vessel, but the existent data processing techniques assume homogeneity of the flow between the divergent acoustic beams. This assumption fails for complex three dimensional flows as found in the scours. In Chapter 4 a new ADCP data processing technique is developed that strongly reduces the extent over which the flow needs to be assumed homogeneous. The new method is applied to flow measurements collected in a river bend with a scour exceeding 40 m depth. Results based on the new approach reveal secondary flow patterns which remain invisible adopting the conventional method.

    Chapter 5 aims to better understand flow in sharp bends, by combining analyses of the flow measurements from a deep scour with Large Eddy Simulations of the flow. The three-dimensional flow field is strongly dominated by horizontal circulations at both sides of the scour. The dramatic increase in cross-sectional area (from 2200 m2 to 7000 m2 ) plays a crucial role in the generation of the two horizontal recirculation cells. An existing formulation to predict water surface gradients in bends is extended to include the effect of cross-sectional area variations, next to the effect of curvature changes. Variation in the cross-sectional area develops adverse water surface gradients explaining the flow recirculation. The depth increase toward the scour causes a strong downward flow (up to 12 cm s − 1 ) creating a non-hydrostatic pressure distribution, steering the core of the flow toward the bed. The latter aspect is poorly reproduced by the Large Eddy Simulations, which may relate to the representation of turbulent shear stresses.

    In Chapter 6 a novel technique is introduced to better monitor turbulence properties in complex river flows from ADCP measurements, exploiting what is discarded in observations of the mean flow. It extends the so-called variance method, using two ADCPs instead of one. The availability of eight acoustic beams, four from each ADCP, changes an otherwise unsolvable set of equations with six unknowns into an overdetermined system of eight equations with six unknowns. This allows to solve for the complete Reynolds stress tensor, yielding profiles of Reynolds stresses over almost the entire water column. Widely applied assumptions on turbulence anisotropy ratios are shown to be incorrect, which reveals a knowledge gap in open channel turbulence.

    Chapter 7 uses the technique developed in Chapter 6 to investigate the degree in which bed shear stress can be monitored continuously from an ADCP mounted horizontally at the river bank (HADCP). A calibrated boundary layer model is applied to estimate time-series of cross-river bed-shear stress profiles from HADCP velocity measurements. It is concluded the HADCP measurement can represent the regional bed shear stresses, as inferred from a logarithmic velocity profile, reasonably well. These regional bed-shear stresses, in turn, poorly represent the local estimates obtained from coupled ADCP measurements, which are more directly related to processes of sediment transport and complex river morphology. Detailed observations of turbulence properties may be the key to improve our understanding of complex river flow and morphology.

    Robust, multifunctional flood defenses in the Dutch rural riverine area
    Loon-Steensma, J.M. van; Vellinga, P. - \ 2014
    Natural Hazards and Earth System Sciences 14 (2014). - ISSN 1561-8633 - p. 1085 - 1098.
    dijken - versterking - rivieren - platteland - hoogwaterbeheersing - gebiedsgericht beleid - nederland - dykes - reinforcement - rivers - rural areas - flood control - integrated spatial planning policy - netherlands - risk-management
    This paper reviews the possible functions as well as strengths, weaknesses, opportunities, and threats for robust flood defenses in the rural riverine areas of the Netherlands on the basis of the recent literature and case studies at five locations in the Netherlands where dike reinforcement is planned. For each of the case studies semi-structured interviews with experts and stakeholders were conducted. At each of the five locations, suitable robust flood defenses could be identified that would contribute to the envisaged functions and ambitions for the respective areas. Primary strengths of a robust, multifunctional dike in comparison to a traditional dike appeared to be the more efficient space use due to the combination of different functions, a longer-term focus and greater safety.
    Human impacts on tides overwhelm the effect of sea level rise on extreme water levels in the Rhine–Meuse delta
    Vellinga, N.E. ; Hoitink, A.J.F. ; Vegt, M. van der; Zhang, W. ; Hoekstra, P. - \ 2014
    Coastal Engineering 90 (2014). - ISSN 0378-3839 - p. 40 - 50.
    rivieren - waterstand - getijden - zeespiegelschommelingen - delta's - menselijke activiteit - inventarisaties - rivers - water level - tides - sea level fluctuations - deltas - human activity - inventories - river flow - netherlands - variability - subsidence - division - china
    With the aim to link tidal and subtidal water level changes to human interventions, 70 years of water level data for the Rhine–Meuse tidal river network is analysed using a variety of statistical methods. Using a novel parameterization of probability density functions, mean high and low water levels are examined, and extreme water levels are investigated by applying the combined Mann–Kendall and Pettitt tests to find trends and trend changes. Tidal water levels are studied based on harmonic analysis. Results show that the mean water levels throughout the system rise with the same pace as the mean sea level. However, high- and low water levels do not show the same increase, and the spatial variability in decadal trends in high- and low water levels is high. High water and low water extremes generally decrease. Both the extreme water level analysis and the harmonic analysis display significant trend breaks in 1970, 1981 and 1997. These breaks can be attributed to the closure of the Haringvliet estuary, the removal of sluices and the removal of a dam, respectively, which radically alter the tidal motion. These results demonstrate that the direct human influence on the tidal motion can overwhelm the effect of mean sea level rise on water level extremes.
    Ex situ treatment of sediments with granular activated carbon : a novel remediation technology
    Rakowska, M.I. - \ 2014
    Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Bart Koelmans; Tim Grotenhuis. - Wageningen : Wageningen University - ISBN 9789461738981 - 240
    polycyclische aromatische koolwaterstoffen - polychloorbifenylen - gechloreerde koolwaterstofpesticiden - verontreinigde sedimenten - remediatie - actieve kool - mariene sedimenten - rivieren - polycyclic aromatic hydrocarbons - polychlorinated biphenyls - organochlorine pesticides - contaminated sediments - remediation - activated carbon - marine sediments - rivers

    Over the last decades, industrial and urban development and emisions of many hazardous organic compounds have threatened the ecological quality of marine and freshwater sediments. Sediments accumulate hydrophobic organic compounds (HOCs) such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and thus may pose serious risks to ecosystems and human health. Over the past years sediment treatment by sorbent addition such as activated carbon (AC) to achieve sequestration of HOCs in situ has been proposed as an alternative approach to traditional remediation technologies such as dredging and disposal. The present research was meant to explore ex situ extraction of sediment by granular AC (GAC) (‘active stripping’) as a novel approach in comparison to traditional in situ AC sediment remediation technologies using amendments of powdered AC (PAC) or GAC.

    Chapter2 discusses the current state of the art in AC amendment technology as a method for sediment remediation. In this chapter, major knowledge gaps are revealed on sediment-AC-HOC interactions controlling the effectiveness of HOC binding such as AC type, particle size, dosage, sediment and sorbate characteristics,and efficiency of AC to reduce bioaccumulation in benthic invertebrates.In addition, the review discusses potential negative effects of AC on aquatic life. Finally, we discuss whether the effects of AC addition can be predicted using fate and transport models.

    Chapter 3explores the potential of GAC in the context of ex situ sediment remediation technology. Since the added GAC would compete for the sorption of HOCs with natural sediment phases, its effectiveness would strongly depend on its dosage. Consequently, in this chapter we investigate the distribution coefficients for short-term sorption processes, and the optimal dosage level of GAC to be used in intensive sediment remediation. A suite of candidate GAC materials is screened for maximum efficiency in extracting PAHs from sediment with very high PAH and oil pollution levels within 24 h. The effectiveness of GAC is compared to a single-step solid phase extraction (SPE) with Tenax beads, Sorption data are interpreted in terms of aqueous phase concentration reduction ratios and distribution coefficients. Despite the considerable fouling of GAC by organic matter and oil, 50-90% of the most available PAH was extracted by the GAC during 28-d contact time, at a dose as low as 4%.

    A prerequisite for the application of active stripping with GAC in contaminatedsediment remediation is effective transport of pollutantsfrom the sediment to the GAC during the relatively short mixing stage. Therefore, in Chapter 4kinetics of PAH transfer from sediment using GAC at a relatively low dose as a solid extraction phase kinetic parameters are obtained by modeling experimental sediment-GAC exchange kinetic data following a two-stage model calibration approach. Rate constants (kGAC) for PAH uptake by GAC range from 0.44 to 0.0005 d-1, whereas GAC sorption coefficients (KGAC) range from 105.57to 108.57L kg-1. These results show that ex situ extraction with GAC is sufficiently fast and effective to reduce the risks of the most available PAHs among those studied, such as fluorene, phenanthrene and anthracene.

    It is unclear how the GAC/sediment mixing step affects desorption kinetics of HOCs for instance by changing the sediment particle size distributions, and whether these factors may influence the effectiveness of ex situ GAC extraction technology. Chapter 5 presents the results of investigations on the effect of mixing intensity on the extraction rate of PAHs from contaminated sediment. Desorption data are interpreted using a radial diffusion model. Mixing caused the 161 µm particles originally present at a stirring rate of 200 rpm to decrease in size to 9 µm at a rate of 600 rpm. Desorption rate constants decreased with increasing PAH hydrophobicity but increased with the intensity of mixing. The results demonstrate that desorption of PAHs is significantly accelerated by a reduction of particle aggregate size caused by shear forces induced by mixing.

    So far, the remediation effectiveness and ecological side effects of AC application have been studied in the short term, and mainly in laboratory studies. However, it is still not clear to what extent these reduced pore water concentrations change over longer times and how they differ for chemicals and for different AC remediation scenarios under field conditions. Chapter 6 presents (pseudo-)equilibrium as well as kinetic parameters for in situ sorption of a series of PAHs and PCBs to powdered and granular activated carbons (AC) after three different sediment treatments: sediment mixed with powdered AC (PAC), sediment mixed with granular AC (GAC), and addition of GAC followed by 2 d mixing and subsequent removal (‘sediment stripping’) in the field. Remediation efficiency is assessed by quantifying fluxes towards SPME passive samplers inserted in the sediment top layer, which shows that efficiency decrease in the order of PAC > GAC stripping > GAC addition. Sorption was very strong to PAC, with log KAC (L/kg) values up to 10.5. Log KAC values for GAC ranged from 6.3 - 7.1 and 4.8 - 6.2 for PAHs and PCBs, respectively. Log KAC values for GAC in the stripped sediment were 7.4 - 8.6 and 5.8 - 7.7 for PAH and PCB. Apparent first order adsorption rate constants for GAC (kGAC) in the stripping scenario were calculated with a first-order kinetic model and ranged from 1.6×10-2 (PHE) to 1.7×10-5 d-1 (InP). This study showed that sediment treatment with PAC is most effective and less prone to organic matter fouling and ongoing natural processes in the field. The effectiveness of GAC is higher in the 48 h sediment stripping scenario than in the GAC amendment approach.

    In Chapter 7 the effects of three different AC treatments (see above) on HOC concentrations in pore water, benthic invertebrates, zooplankton and fish (Leuciscus idus melanotus) are tested. The AC treatments result in a significant decrease in HOC concentrations in pore water, benthic invertebrates, zooplankton, macrophytes and fish. In 6 months, PAC treatment caused a reduction of accumulation of PCBs in fish by a factor of 20 bringing pollutant levels below toxic thresholds. All AC treatments supported growth of fish, but growth was inhibited in the PAC treatment, which is likely to be explained from reduced nutrient concentrations, resulting in lower zooplankton (i.e., food) densities for the fish. During the course of the field study, sediment stripping as well as sediment treatment with GAC turned out to be slower in reducing PCB bioaccumulation in biota, but the treatments were not harmful to any of the biota either.

    In the final chapter (Chapter 8), overarching answers to the main research questions (see above) are formulated and an outlook regarding the actual use of ex situ GAC is provided.

    Toestand vis en visserij in de zoete Rijkswateren. Deel III: Data
    Boois, I.J. de; Overzee, H.M.J. van; Graaf, M. de; Keeken, O.A. van; Kuijs, E.K.M. ; Os-Koomen, E. van; Westerink, H.J. ; Wiegerinck, J.A.M. - \ 2014
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C060/13) - 399
    zoet water - aquatische ecologie - vissen - monitoring - ijsselmeer - randmeren - rivieren - inventarisaties - fresh water - aquatic ecology - fishes - monitoring - lake ijssel - randmeren - rivers - inventories
    Het rapport “Toestand Vis en Visserij in de Zoete Rijkswateren” bestaat uit drie delen. Dit rapport bevat de resultaten van de vismonitoringen in de zoete Rijkswateren. Het omvat de volgende bemonsteringen: - Open water monitoring IJssel- en Markermeer - Oeverbemonstering IJssel- en Markermeer - Bemonstering zeldzame vis IJssel- en Markermeer - Bemonstering diadrome vis Kornwerderzand - Actieve monitoring grote rivieren en delta - Passieve monitoring grote rivieren en delta - Zalmsteekmonitoring grote rivieren De monitoringen in en rond het IJssel- en Markermeer worden gefinancierd door het ministerie van EZ, de monitoringen op de rivieren door Rijkswaterstaat.
    Toestand vis en visserij in de Zoete Rijkswateren: 2012 Deel I: Trends van de visbestanden, vangsten en ecologische kwaliteit ratio's
    Graaf, M. de; Overzee, H.M.J. van; Boois, I.J. de; Vries, P. de; Tien, N.S.H. ; Tulp, I. ; Griffioen, A.B. - \ 2014
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C058/13) - 52
    zoet water - aquatische ecologie - vissen - monitoring - ijsselmeer - randmeren - rivieren - inventarisaties - fresh water - aquatic ecology - fishes - monitoring - lake ijssel - randmeren - rivers - inventories
    De visstand bemonsteringen die in opdracht van RWS Waterdienst plaatsvinden maken deel uit van een uitgebreider programma: de Monitoring van de Waterstaatkundige Toestand des Lands (MWTL). In de loop der tijd is uit pragmatische overwegingen de uitvoering en financiering van de visstand bemonsteringen verdeeld over RWS en Min EZ, waarbij grofweg RWS de vismonitoring in de rivieren en delta uitvoert en Min EZ de vismonitoring in het IJsselmeer en Markermeer
    Bouwstenen voor de grensoverschrijdende Vecht : een half-natuurlijke laaglandrivier tussen Emlichheim en Hardenberg
    Maas, G.J. ; Woestenburg, M. - \ 2014
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2491) - 22
    rivieren - natuurontwikkeling - kaderrichtlijn water - waterbeheer - hoogwaterbeheersing - ecologisch herstel - overijssel - duitsland - grensgebieden - rivers - nature development - water framework directive - water management - flood control - ecological restoration - overijssel - germany - frontier areas
    De Duits-Nederlandse rivier de Vecht wordt over de volle lengte weer zoveel mogelijk teruggebracht in een natuurlijke staat. In de studie naar de Vecht tussen Emlichheim en Hardenberg is onderzocht wat de effecten zijn van de verschillende bouwstenen op de rivier, en ook welke gevolgen de maatregelen hebben voor de randvoorwaarden die gesteld zijn. Om de Vecht om te vormen tot een half-natuurlijke rivier is een integrale aanpak nodig. Herstel van de Vecht vraagt om ingrijpende maatregelen.
    Bausteine für die grenzüberschreitende Vechte : ein lebendigen Flachlandfluss zwischen Emlichheim und Hardenberg
    Maas, G.J. ; Woestenburg, M. - \ 2014
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2492) - 22
    rivieren - natuurontwikkeling - kaderrichtlijn water - waterbeheer - hoogwaterbeheersing - ecologisch herstel - grensgebieden - duitsland - overijssel - rivers - nature development - water framework directive - water management - flood control - ecological restoration - frontier areas - germany - overijssel
    De Duits-Nederlandse rivier de Vecht wordt over de volle lengte weer zoveel mogelijk teruggebracht in een natuurlijke staat. In de studie naar de Vecht tussen Emlichheim en Hardenberg is onderzocht wat de effecten zijn van de verschillende bouwstenen op de rivier, en ook welke gevolgen de maatregelen hebben voor de randvoorwaarden die gesteld zijn. Om de Vecht om te vormen tot een half-natuurlijke rivier is een integrale aanpak nodig. Herstel van de Vecht vraagt om ingrijpende maatregelen.
    Toestand vis en visserij in de zoete Rijkswateren. Deel II: Methoden
    Overzee, H.M.J. van; Boois, I.J. de; Graaf, M. de; Goudswaard, P.C. ; Keeken, O.A. van; Kuijs, E.K.M. ; Lohman, M. ; Os-Koomen, E. van; Westerink, H.J. ; Wiegerinck, J.A.M. - \ 2013
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C059/13) - 48
    zoet water - aquatische ecologie - vissen - monitoring - ijsselmeer - randmeren - rivieren - inventarisaties - fresh water - aquatic ecology - fishes - monitoring - lake ijssel - randmeren - rivers - inventories
    Het rapport “Toestand Vis en Visserij in de Zoete Rijkswateren” bestaat uit drie delen. Dit rapport (Deel II) is een achtergronddocument waarin de gebruikte monitoringsmethodieken in de verschillende vismonitoringen in de zoete Rijkswateren in detail worden beschreven. Het omvat de volgende bemonsteringen: - Open water monitoring IJssel- en Markermeer - Oeverbemonstering IJssel- en Markermeer - Bemonstering zeldzame vis IJssel- en Markermeer - Overige gegevens van vis in het IJssel-en Markermeer - Bemonstering diadrome vis Kornwerderzand - Actieve monitoring grote rivieren en delta - Passieve monitoring grote rivieren en delta - Zalmsteekmonitoring grote rivieren.
    Field experiment on alternate bar development in a straight sand-bed stream
    Eekhout, J.P.C. ; Hoitink, A.J.F. ; Mosselman, E. - \ 2013
    Water Resources Research 49 (2013). - ISSN 0043-1397 - p. 8357 - 8369.
    sediment - channels - instability - patterns - meanders - growth - rivers
    Alternate bars in rivers and streams develop as a result of differences in length scales involved in the adjustment of flow and sediment transport to irregularities of the bed. The amount of field evidence supporting theoretical insights is highly limited. Here, we present results from a large-scale field experiment in a 600 m long straight reach. Over a period of almost 3 years, the channel was allowed to evolve autogenously from initially flat bed conditions, subject to discharge variation. Alternate bars developed within 8 months from the start of the experiment. The initial stages of bar development included bar growth, both in wavelength and amplitude, and bar migration. The latter was too limited to classify the bars as being migrating bars; therefore, we classify the bars as nonmigrating bars. Toward the end of the experiment, the regular alternate bar pattern evolved into an irregular pattern and bar amplitude started to decrease. From the start of the experiment we observed a declining channel slope, from 1.8 m km-1 initially to 0.9 m km-1 halfway the experiment, after which it stabilized. We applied two bar theories to establish their predictive capacity. Both bar theories predicted the development of alternate bars under the constructed channel conditions. In response to the declining channel slope, both theories predicted a decreasing likelihood for the development of alternate bars. Our study shows that under field conditions, the applied bar theories may predict the initial stages of bed development.
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