Rijkswaterstaat

Seas are polluted with macro- (>5 mm) and microplastics (<5 mm). However, few studies account for both types when modeling water quality, thus limiting our understanding of the origin (e.g., basins) and sources of plastics. In this work, we model riverine macro- and microplastic exports to seas to identify their main sources in over ten thousand basins. We estimate that rivers export approximately 0.5 million tons of plastics per year worldwide. Microplastics are dominant in almost 40% of the basins in Europe, North America and Oceania, because of sewage effluents. Approximately 80% of the global population live in river basins where macroplastics are dominant because of mismanaged solid waste. These basins include many African and Asian rivers. In 10% of the basins, macro- and microplastics in seas (as mass) are equally important because of high sewage effluents and mismanaged solid waste production. Our results could be useful to prioritize reduction policies for plastics.

For a tidal channel with water of homogeneous density, an approximate analytical expression is derived for the tidally averaged transport of coarse sediment in terms of the amplitudes and phases of the tidal-current constituents. Transport is in the form of bed load and the rate of transport is proportional to some power of the local current speed. It is assumed that the tidal current is dominated by the M2 constituent. From the analytical expression it follows that the interactions of M2 and M0 (= Eulerian mean current) and of M2 and any of its even overtides, M4, M8etc., constitute the major contribution to the tidally averaged sediment transport. A combination of the M2 tidal current and a fundamental constituent in the diurnal, semidiurnal or subsequent period bands results in a tidally averaged transport that fluctuates with the corresponding beat frequency. Therefore, for the long-term mean bed-load transport only the contributions of M2 and M0 and of M2 and its even overtides are of interest. Application to the main channel of the Ems estuary showed good agreement with transport pathways derived from the grain-size distribution pattern. The tidally averaged sediment transport is largely the result of the interaction of the M2 and M0 tidal current constituents.

Abstract One critical problem confronting mankind today is how to manage the intensifying competition for water between expanding urban centres, traditional agricultural activities and in‐stream water uses dictated by environmental concerns. In the agricultural sector, the dwindling number of economically attractive sites for large‐scale irrigation and drainage projects limits the prospects of increasing the gross cultivated area. Therefore, the required increase in agricultural production will necessarily rely largely on a more accurate estimation of crop water requirements on the one hand, and on major improvements in the construction, operation, management and performance of existing irrigation and drainage systems, on the other. The failings of present systems and the inability to sustainably exploit surface and groundwater resources can be attributed essentially to poor planning, design, system management and development. This is partly due to the inability of engineers, planners and managers to adequately quantify the effects of irrigation and drainage projects on water resources and to use these effects as guidelines for improving technology, design and management. To take full advantage of investments in agriculture, a major effort is required to modernize irrigation and drainage systems and to further develop appropriate management strategies compatible with the financial and socio‐economic trends, and the environment. This calls for a holistic approach to irrigation and drainage management and monitoring so as to increase food production, conserve water, prevent soil salinization and waterlogging, and to protect the environment. All this requires, among others, enhanced research and a variety of tools such as water control and regulation equipment, remote sensing, geographic information systems, decision support systems and models, as well as field survey and evaluation techniques. To tackle this challenge, we need to focus on the following issues: affordability with respect to the application of new technologies; procedures for integrated planning and management of irrigation and drainage systems; analysis to identify causes and effects constraining irrigation and drainage system performance; evapotranspiration and related calculation methods; estimation of crop water requirements; technologies for the design, construction and modernization of irrigation and drainage systems; strategies to improve irrigation and drainage system efficiency; environmental impacts of irrigation and drainage and measures for creating and maintaining sustainability; institutional strengthening, proper financial assessment, capacity building, training and education. Copyright © 2002 John Wiley &amp; Sons, Ltd.

In order to investigate potential links between marlne pollution and fish diseases, an ep~zootiological study was conducted in The Netherlands during 1983-89. This study concentrated on grossly identifiable diseases of flounder Platichthys flesus. Flounder were found to be affected by the viral skin disease lymphocystis and by skin ulcers probably of bacterial origin. Overall prevalences of these 2 diseases in fish 2 2 yr old were 14.3%r and 2.8% respectively. Also notable was t h e presence of neoplastic nodules in the livers of 1.0% of the population, prevalences rising steeply with a g e and locally attaining values of up to 3 0 % in 6+ yr old fish. Most of the samples were collected in September when flounder are resident in inshore feeding arcas. Using data from 9 sites, spatial and temporal (year-to-year) variation in disease occurrence was analysed statistically using log-linear models which incorporated possible effects of length, a g e and sex. Year-toyear variation showed little correspondence among the 3 diseases, but their spatial distributions showed striking similarities. Lymphocystis and skin ulcers were associated in individual fish. The observed variation in disease prevalence showed no significant correlation with condition factor of the fish or with concentrations of contaminants in sediments or tissues. However, disease preval e n c e ~ at different sites showed a strong positive correlation with fishing activity (possibly indicating an effect of damage by fishing gear) and appeared also to be positively related to salinity. When only strictly marine sites were considered, a relationship with pollution could not be ruled out. Additional data collected in February-April at offshore sites indicated that disease preval e n c e ~ were generally higher at this time of the year, which corresponds to the spawning period of the populations studied. This trend was particularly pronounced for liver neoplasms, and might be partly related to a low condition factor resulting from spawning activities. In view of the different aetiologies of the 3 diseases, the similarities in spatial patterns indicate the existence of 1 general underlying mechanism of disease causation, perhaps acting through immunosuppressive effects. However, age-related migration appeared to explaln some aspects of the spatial pattern of liver neoplasms, whereas it was less important in the case of epidermal diseases, which develop more rapidly. On the basis of the findings of this study, the possible contribution of pollution to disease prevalence cannot be adequately assessed due to the interfering effects of other factors (salinity, fishing activity, migration and spawning). Disease causation appears to be con~plex, and it may be that effects of pollution interact with those of other factors to produce observed, spatial patterns.

This study was a part of a research program concerning the pollution of the Venice Lagoon, in the north of Italy. The purpose was to evaluate the contamination due to polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F), a class of pollutants arising mainly from combustion and chemical manufacture. Six selected stations of the lagoon were investigated by analysis of surface sediment samples using gas chromatography−mass spectrometry (GC−MS). Principal Component Analysis and Regularized Discriminant Analysis, two chemometric approaches, were applied to the data set of the lagoon and to source-related samples from the literature. The results showed a moderate contamination due to PCDD/F in the investigated areas, and the levels within the lagoon were substantially higher than in the open sea. The investigation of the homologue profiles and the comparison with published PCDD/F data indicated different dioxin sources within the lagoon and some similarities of these with two environmental sources. Samples collected near Marghera Harbour and some samples collected at Sacca Sessola were similar to samples contaminated from ethylene dichloride production effluents while the profiles of most of the other samples were similar to those of gasoline and diesel engine emissions.

In this paper, we review and analyze the cyclic morphodynamics and sand-bypassing processes at the Ameland Inlet, The Netherlands. The inlet is located between the islands of Terschelling and Ameland in the Dutch Wadden Sea. The bypassing rate and sand storage have a periodicity of 50 to 60 years in connection with the migration of the channels in the inlet and the transformation of the gorge between a one-channel and a two-channel system. These developments modulate the volumes of the shoal and bypassing bars and produce an attenuating sand wave toward the downdrift coast. An aggregate model is developed to describe the inlet morphology at this intermediate timescale. The model is based on a modified equilibrium-volume approach, which allows erosion and accretion of the shoal and bars to occur about their long-term equilibrium. The model results depict observed morphologic behaviors of the inlet and corroborate the measured modulation of the downdrift coastline. The simulation of the effect of the 1979 and 1980 sand mining operations in the ebb tidal delta reproduces the reported rapid recovery of the sandpits and illustrates the capabilities of the model as an inlet planning and management tool.

Several studies have reported a low inducibility of hepatic cytochrome P4501A (CYP1A) activity in European flounder (Platichthys flesus) following exposure to mixtures of polychlorinated biphenyls (PCBs). Here we report on mechanistic studies toward understanding this low CYP1A inducibility of flounder, involving molecular characterization of the Ah receptor (AhR) pathway as well as inhibition of the CYP1A catalytic activity by PCB congeners. Hepatic cytosolk AhR levels in flounder were determined using hydroxylapatite, protamine sulfate adsorption analysis, or velocity sedimentation on sucrose gradients. AhR levels in flounder (˜2–7 fmol/mg protein) were much lower than observed generally in rodents (˜50–300 fmol/mg protein). Molecular characterization of the flounder AhR was provided by first-strand cDNA synthesis and amplification of flounder hepatic poly(A)+ RNA using RT-PCR. A 690-bp product was found, similar in size to a Fundulus AhR cDNA. The specificity of the 690-bp band was established by Southern blotting and hybridization with a degenerate AhR oligonucleotide. The deduced amino acid sequence of the flounder AhR fragment was 59–60% identical to mammalian AhR sequences. Although the AhR is present in flounder cytosol, we were unable to demonstrate detectable amounts of inducibk TCDD-AhR-DRE complex in gel-retardation assays. High induction levels of CYP1A protein and associated EROD activity have been previously found in flounder following exposure to 2,3,7,8-tetrachlorod-ibenzo-p-dioxin (TCDD). In contrast, the induction of CYP1A catalytic activity by PCB mixtures remains unexpectedly low. Therefore, we further characterized the inhibitory potential of PCB congeners on CYP1A activity in flounder and compared this with inhibitory effects of PCB congeners on rat CYP1A activity. Analysis in vitro demonstrated that 3,3',4,4'-tetraCB, 3,3',4,4',5-pentaCB, 2,2',4,4',5,5'-hexaCB, 3,3',4,4',5,5'-hexaCB, and the commercial PCB mixture Clophen A50 are potent competitive inhibitors of hepatic microsomal CYP1A catalytic activity in flounder and rat The Km for ethoxyresonifin (0.095 μM) in flounder is strikingly close to Ki's found for the tested PCBs. This emphasizes the possible involvement of PCB congeners in inhibition of EROD activity in PHAH exposed fish. Finally, our data indicate that flounder CYP1A is more efficient in metabolizing ethoxyresonifin than that of rat CYP1A.

The exposure to and effects of estrogenic compounds in male breams from Dutch freshwater locations were investigated. Ovotestis was observed infrequently (maximum frequency 16%). However, plasma vitellogenin (VTG) concentration was elevated highly at some locations. Estrogenic activities in male bream plasma, liver, and in gastrointestinal content were measured in the estrogen-responsive chemical-activated luciferase gene expression (ER-CALUX) assay. Plasma concentrations of vitellogenin correlated very well with the estrogenic activities in gastrointestinal content. The ER-CALUX activity in gastrointestinal content thus could provide a biomarker for recent exposure to estrogenic compounds, and the gastrointestinal content was chosen as investigative matrix for the toxicity identification and evaluation ([TIE]; bioassay-directed fractionation) of estrogenic compounds in bream. The approach consisted of a reversed-phase high-performance liquid chromatography fractionation of gastrointestinal content extract, directed by ER-CALUX and followed by gas chromatography analysis. The estrogenic hormones 17beta-estradiol and its metabolite estrone were identified as major contributors to the activity at all locations (except the reference location), independent of the presence or absence of a known source of estrogenic activity, such as a sewage treatment plant. Chemical screening showed the presence of other pollutants, such as a lower chlorinated dioxin and the disinfectants clorophene and triclosan. However, these compounds did not have high estrogenic potencies and their concentrations were not high enough to contribute significantly to the observed estrogenic activity.

The Wave Overtopping Simulator was developed in 2006 and destructive tests on dikes have been performed in February and March of 2007 and 2008. The tests show the behaviour of various inner slopes of dikes, embankments or levees under simulation of wave overtopping, up to a mean overtopping discharge of 125 l/s per m. This paper focuses on the improvements of the Wave Overtopping Simulator after the 2007 tests and summarizes the results of the tests performed early 2008, ending with preliminary conclusions.

Macroplastic pollution in and around rivers negatively impacts human livelihood, and aquatic ecosystems. Monitoring data are crucial for better understanding and quantifying this problem, and for the design of effective intervention strategies. However, current monitoring efforts are often of short duration, or study single river compartments. We present a “Roadmap” to overcome the challenges related to the design and implementation of long-term riverine macroplastic monitoring strategies. This “Roadmap” can help accelerating the process of achieving structural monitoring through providing a stepwise approach, which links monitoring goals and research questions to the data and methods required to answer them. We identify four monitoring goals: 1) policy, 2) knowledge development, 3) operations, and 4) solutions. Linked to these, we provide a non-exhaustive list of 12 globally common research questions that are important to answer to reach these goals. The “Roadmap” takes these questions and links them to development levels of monitoring methods for each river compartment: 1) method development, 2) baseline assessment, and 3) long-term monitoring. At each level, specific questions can only be answered if the level is achieved for specific river compartments. For questions at higher levels, the previous levels need to be achieved first. This creates a clear stepwise approach to solve open challenges. With the “Roadmap”, we provide a new tool to support decision-making and planning of specific projects by policy makers. The “Roadmap” is a clear and stepwise, yet flexible framework that allows to add and remove elements based on new insights, available resources, and other relevant changes.

Summary: The enhanced use of protective materials and chemicals during the COVID-19 pandemic has probably increased river pollution, but the effects of country-specific measures on multiple pollutants in rivers worldwide are not well documented. Here, we use an updated, spatially explicit water quality model to estimate the effects of the increased use of hand soap (triclosan), personal protective equipment and packaging materials (plastics), painkillers (diclofenac), and reduced transportation (microplastics from car tires) on river pollution in 10,226 sub-basins worldwide. Model results indicate that, globally, COVID-19 measures increased river pollution with macroplastics by 56%, triclosan by 33%, and diclofenac by 50%. Notably, only microplastics from car tires decreased. We identified priority sub-basins and pollutants across the globe for which water pollution control strategies should consider the impacts of COVID-19 measures. For these sub-basins, our results can inform the development of strategies for ameliorating the impacts of measures taken during the COVID-19 pandemic. Science for society: Globally, river pollution is a growing concern, given its potential impacts on ecosystems. COVID-19 has likely compounded this pollution via an increased use of products such as masks, hand sanitizers, and painkillers. However, we do not have a clear understanding of pollutant types, at which locations pollution might have increased, or the extent of any increase. This hinders the development of pollution control strategies in the worst-affected river basins. Countries encouraged or enforced varying strategies to combat the pandemic; therefore, assessing the impact of these differing COVID-19 measures on river pollution requires models that capture country-specific strategies.

Riverine macroplastic pollution (>0.5 cm) negatively impacts ecosystems and human livelihoods. Monitoring data are crucial for understanding this issue and for the design of effective interventions strategies. Macroplastic pollution floating on the river surface and plastic deposited on riverbanks are studied relatively often. Data on riverine plastics in the water column remain scarce. In this study, we utilized trawl nets at different depths to sample plastic pollution in the water column at the entry point of the river Rhine to the Netherlands. We show that plastic concentrations in the water column increased during higher discharge. Moreover, the results indicate that the vertical distribution of macroplastic pollution changes during different flow conditions. Significantly higher concentrations of macroplastic can be seen near the riverbed during low discharge conditions, while no significant differences in concentration are observed between the bottom, middle, and surface samples during high discharge conditions. Taking into account the recurrence time of low discharge conditions the transport of plastic during low discharge conditions is substantial. These findings provide first insights into the key role of hydrology in explaining macroplastic transport in the water column. These insights can be used to improve future monitoring and intervention strategies.

Abstract The history of water management in The Netherlands shows how the original natural landscape was transformed into a man‐made landscape and has led to a never‐ending struggle with the water. Water comes from all directions into the lowlands: over land via rivers (floods), from the sea side (surges), from above (excessive rainfall) and from the subsoil (seepage). Human intervention is continuously needed to be able to survive with effective solutions. History has shown that since men started intervening in nature, in particular in the alluvial water‐saturated soft soils where Dutch society has settled and developed, the need for these measures will never stop. Any one measure leads to counter and correcting measures later on. This is clearly visible today and it will definitively continue in the future. It sets the mind of Dutch society in its continuous struggle for life and can be a lesson learned for others, living and developing in areas with similar water‐related characteristics. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Abstract Information about sediment transport in the Common Meuse, an armoured gravel‐bed river, can be obtained by the determination of the relationship between sediment transport and discharge and integrating the relationship with respect to time, or by computing the differences between series of measured bed‐levels along the Common Meuse and integrating these differences. For three periods of 9, 8 and 17 years sediment transport computations are made with two series of relationships between sediment transport ( Q b ) and discharge ( Q ) in which the condition of the armour layer is taken into account. These sediment‐transport–discharge ( Q b &amp;#38; sol ; Q ) relationships are determined by local bed‐load transport measurements in the Common Meuse. At the beginning and the end of the first period (1978–1987) and at the end of the second period (1987–1995) bed levels have been measured by soundings. By the analysis of the measured bed levels at the beginning and the end of the two periods the sediment transport along the Common Meuse is estimated. The same analysis was carried out for the combined period (1978–1995). The yearly mean sediment transport computed by these two methods are compared. The necessity of carrying out bed‐load transport measurements at several locations in a cross‐section and over the entire range of discharges is clearly shown. Attention is paid to the advantages and disadvantages of the two methods and the need for applying more than one method to compute sediment transport. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Abstract An accurate means of predicting erosion rates is essential to improve the predictive capability of breach models. During breach growth, erosion rates are often determined with empirical equations. The predictive capability of empirical equations is governed by the range for which they have been validated and the accuracy with which empirical coefficients can be established. Most empirical equations thereby do not account for the impact of material texture, moisture content, and compaction energy on the erosion rates. The method presented in this paper acknowledges the impact of these parameters by accounting for the process of dilation during erosion. The paper shows how, given high surface shear stresses, the erosion rate can be quantified by applying the principles of soil mechanics. Key is thereby to identify that stress balance situation for which the dilatency induced inflow gives a maximum averaged shear resistance. The effectiveness of the model in predicting erosion rates is indicated by means of three validation test cases. A sensitivity analysis of the method is also provided to show that the predictions lie within the range of inaccuracy of the input parameters.

Anthropogenic litter is omnipresent in terrestrial and freshwater systems, and can have major economic and ecological impacts. Monitoring and modelling of anthropogenic litter comes with large uncertainties due to the wide variety of litter characteristics, including size, mass, and item type. It is unclear as to what the effect of sample set size is on the reliability and representativeness of litter item statistics. Reliable item statistics are needed to (1) improve monitoring strategies, (2) parameterize litter in transport models, and (3) convert litter counts to mass for stock and flux calculations. In this paper we quantify sample set size requirement for riverbank litter characterization, using a database of more than 14,000 macrolitter items (&gt;0.5 cm), sampled for one year at eight riverbank locations along the Dutch Rhine, IJssel and Meuse rivers. We use this database to perform a Monte Carlo based bootstrap analysis on the item statistics, to determine the relation between sample size and variability in the mean and median values. Based on this, we present sample set size requirements, corresponding to selected uncertainty and confidence levels. Optima between sampling effort and information gain is suggested (depending on the acceptable uncertainty level), which is a function of litter type heterogeneity. We found that the heterogeneity of the characteristics of litter items varies between different litter categories, and demonstrate that the minimum required sample set size depends on the heterogeneity of the litter category. More items of heterogeneous litter categories need to be sampled than of heterogeneous item categories to reach the same uncertainty level in item statistics. For example, to describe the mean mass the heterogeneous category soft fragments (&gt;2.5cm) with 90% confidence, 990 items were needed, while only 39 items were needed for the uniform category metal bottle caps. Finally, we use the heterogeneity within litter categories to assess the sample size requirements for each river system. All data collected for this study are freely available, and may form the basis of an open access global database which can be used by scientists, practitioners, and policymakers to improve future monitoring strategies and modelling efforts.

The objective of this paper is to describe the hydraulic climate of the Southern North-Sea by statistical models and physical laws for wave heights, wind setup, wave periods and wind speed. The focus is on the selection and calibration of parametric physical models for the use in the description of the joint probability distribution of hydraulic loads. For the validation and calibration of these models, observations have been used. An application is presented about the Rotterdam harbour extension.

Anthropogenic litter is omnipresent in terrestrial and freshwater systems, and can have major economic and ecological impacts. Monitoring and modelling of anthropogenic litter comes with large uncertainties due to the wide variety of litter characteristics, including size, mass, and item type. It is unclear as to what the effect of sample set size is on the reliability and representativeness of litter item statistics. Reliable item statistics are needed to (1) improve monitoring strategies, (2) parameterize litter in transport models, and (3) convert litter counts to mass for stock and flux calculations. In this paper we quantify sample set size requirement for riverbank litter characterization, using a database of more than 14,000 macrolitter items (&gt;0.5 cm), sampled for one year at eight riverbank locations along the Dutch Rhine, IJssel and Meuse rivers. We use this database to perform a Monte Carlo based bootstrap analysis on the item statistics, to determine the relation between sample size and variability in the mean and median values. Based on this, we present sample set size requirements, corresponding to selected uncertainty and confidence levels. Optima between sampling effort and information gain is suggested (depending on the acceptable uncertainty level), which is a function of litter type heterogeneity. We found that the heterogeneity of the characteristics of litter items varies between different litter categories, and demonstrate that the minimum required sample set size depends on the heterogeneity of the litter category. More items of heterogeneous litter categories need to be sampled than of heterogeneous item categories to reach the same uncertainty level in item statistics. For example, to describe the mean mass the heterogeneous category soft fragments (&gt;2.5cm) with 90% confidence, 990 items were needed, while only 39 items were needed for the uniform category metal bottle caps. Finally, we use the heterogeneity within litter categories to assess the sample size requirements for each river system. All data collected for this study are freely available, and may form the basis of an open access global database which can be used by scientists, practitioners, and policymakers to improve future monitoring strategies and modelling efforts.

In environmental studies attention increasingly focuses on identification of spatial extremes: locations with observations that are apparently higher than either a preset background threshold or neighbouring observations. We consider various procedures for identifying values and locations of these extremes: extreme value theory, conditionally simulated fields and disjunctive kriging. In a recent research project we studied the distribution of nine environmental pollutants (heavy metals, polyaromatic hydrocarbons and mineral oil) in a large industrial estate in the southern Netherlands. This area is interesting as it is influenced by three contaminating processes: inundation by the river Meuse, anthropogenic heightening with contaminated materials and local industrial activities. Concentrations are measured. In this paper the peaks over threshold method was useful for finding extremes for spatially uncorrelated variables, whereas conditional simulations applied in particular to areas with spatial dependence.

Abstract The two objectives of the present study are first, measuring sorption coefficients (Kp) of PAH in lake sediments. Secondly, comparing the Kp's of PAH in two lake sediments in order to establish if normalization on organic carbon content (OC) of the sediments lead to equal Kp's. The OC of both sediments could not explain the measured differences in Kp's. In the sediment with the highest OC the lowest Kp's were measured.