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Consequentieanalyse beoordelingssystematieken grond en bagger : gevolgen voor milieueffecten en toepasbaarheid
Het Besluit Bodemkwaliteit (Bbk), dat onder meer de grootschalige toepassingen van grond en bagger in oppervlaktewater regel wordt op korte termijn bijgesteld. Onderdeel hiervan is een herziening van het Milieuhygiënisch Toetsingskader (MHT) voor grootschalige bodemtoepassingen in diepe plassen. In deze systematiek verschuift de focus van de beoordeling van de samenstelling van de grond en baggerspecie naar de invloed op het waterlichaam waarin het wordt toegepast. De systematiek van het MHT is gebaseerd op beschikbaarheid van stoffen in plaats van het totaalgehalte in het Bbk.
Flow division dynamics in the Mekong Delta : application of a 1D-2D coupled model
The Mekong Delta constitutes a complicated multi-channel estuarine system, exchanging water with a delta-wide irrigation system. A 1D–2DH coupled numerical domain is calibrated and validated for water level and discharge during the dry season. This approach benefits from the simplicity of a 1D network within the estuarine and irrigation systems, while maintaining the interaction with the spatial tidal dynamics of the 2DH coastal domain. First, the role of the irrigation system on tidal dynamics is quantified; then, tidal propagation, freshwater budget, and the effect of offshore subtidal water level on discharge division are investigated. The results show that the complex irrigation system, in a friction-like manner, reduces the tidal amplitude up to 25%. The channels aggregate to 1% of the total water volume in the delta, while accommodating up to 10% of the tidal prism. Tidal amplitude reduces upstream, while subtidal water level is highly sensitive to upstream discharge, spring–neap cycles, and wind-generated oshore surge. Although cumulative discharge division within the estuarine network is consistent, temporal discharge division can be significantly sensitive to offshore wind-surge. During the dry season, it can reverse the expected subtidal discharge division within the time-scale of a few days and potentially influence salt intrusion.
De geschiedenis van het hydraulica laboratorium
Het boekje brengt meer dan een halve eeuw geschiedenis van de Wageningse hydraulica in beeld.
The shadow price of irrigation water in major groundwater depleting countries
In many semi‐arid regions with irrigation, the depletion rate of groundwater resources has increased substantially during the last decades. A possible reason for this is that the price that users pay for their water does not reflect its scarcity and value. An alternative way to assess the perceived value of water is calculating its shadow price, which is defined here as the marginal value produced, and relates to the efficiency gain from current reallocation. Here, we determine the shadow price of water used for irrigation for the most important groundwater depleting countries and for four staple crops and one cash crop. To quantify the shadow price, the relation between the output and water input is represented using production functions. We use globally available panel data on country‐specific crop yields and prices together with crop‐specific water consumption, calculated with the global hydrological model PCR‐GLOBWB, to parameterize the production function by country and crop with econometric analyses. Our results show that the variation of shadow prices for staple crops within several countries is high, indicating economically inefficient use of water resources, including non‐renewable groundwater. We also analyse the effects of re‐allocating irrigation water between crops, showing that changes in water allocation could either lead to an increase in the economic efficiency of water use or large reductions in irrigation water consumption. Our study thus provides a hydroeconomic basis to stimulate sustainable use of finite groundwater resources globally.
Paleo-hydrogeological reconstruction of the fresh-saline groundwater distribution in the Vietnamese Mekong Delta since the late Pleistocene
Present-day distribution of fresh-saline groundwater is highly heterogeneous in the Mekong Delta (MKD). Close to the coastline, fresh groundwater is found in aquifers up to 500 m below ground surface. To gain better insight into the fresh-saline groundwater evolution since the late Pleistocene, we simulated long-term groundwater flow and salt transport in a two-dimensional NW-SW cross-section over the MKD. To fully consider the regression and transgression phases of sea-level changes over the past 60 ka, variable-density groundwater flow and salt transport was simulated with SEAWAT to reproduce characteristics of the present-day distribution of freshsaline groundwater and its age. We simulated nine scenarios to evaluate the most important factors controlling freshening and salinization processes of the MKD groundwater system. We compared the final model stage with present day observations of groundwater salinity and age. New hydrological insights for the region: The sedimentation and erosion processes, related to sea-level changes over the last 60 ka, were important drivers of the fresh-saline distribution in the present MKD. The two-dimensional model indicates that most fresh groundwater in the MKD was recharged 60–12 ka before present, when the sea-level was at its lowest and the top sedimentary layers had a relatively high permeability. Due to deposition of a clayey top layer during the Holocene, at present, groundwater recharge of the deeper MKD groundwater system is very limited.
Long-term population dynamics of dreissenid mussels (Dreissena polymorpha and D. rostriformis) : a cross-system analysis
Dreissenid mussels (including the zebra mussel Dreissena polymorpha and the quagga mussel D. rostriformis) are among the world’s most notorious invasive species, with large and widespread ecological and economic effects. However, their long-term population dynamics are poorly known, even though these dynamics are critical to determining impacts and effective management. We gathered and analyzed 67 long-term (>10 yr) data sets on dreissenid populations from lakes and rivers across Europe and North America. We addressed five questions: (1) How do Dreissena populations change through time? (2) Specifically, do Dreissena populations decline substantially after an initial outbreak phase? (3) Do different measures of population performance (biomass or density of settled animals, veliger density, recruitment of young) follow the same patterns through time? (4) How do the numbers or biomass of zebra mussels or of both species combined change after the quagga mussel arrives? (5) How does body size change over time? We also considered whether current data on long-term dynamics of Dreissena populations are adequate for science and management. Individual Dreissena populations showed a wide range of temporal dynamics, but we could detect only two general patterns that applied across many populations: (1) Populations of both species increased rapidly in the first 1–2 yr after appearance, and (2) quagga mussels appeared later than zebra mussels and usually quickly caused large declines in zebra mussel populations. We found little evidence that combined Dreissena populations declined over the long term. Different measures of population performance were not congruent; the temporal dynamics of one life stage or population attribute cannot generally be accurately inferred from the dynamics of another. We found no consistent patterns in the long-term dynamics of body size. The long-term dynamics of Dreissena populations probably are driven by the ecological characteristics (e.g., predation, nutrient inputs, water temperature) and their temporal changes at individual sites rather than following a generalized time course that applies across many sites. Existing long-term data sets on dreissenid populations, although clearly valuable, are inadequate to meet research and management needs. Data sets could be improved by standardizing sampling designs and methods, routinely collecting more variables, and increasing support.
Uncertainty analysis in a large-scale water quality integrated catchment modelling study
Receiving water quality simulation in highly urbanised areas requires the integration of several processes occurring at different space-time scales. These integrated catchment models deliver results with a significant uncertainty level associated. Still, uncertainty analysis is seldom applied in practice and the relative contribution of the individual model elements is poorly understood. Often the available methods are applied to relatively small systems or individual sub-systems, due to limitations in organisational and computational resources. Consequently this work presents an uncertainty propagation and decomposition scheme of an integrated water quality modelling study for the evaluation of dissolved oxygen dynamics in a large-scale urbanised river catchment in the Netherlands. A forward propagation of the measured and elicited uncertainty input-parametric distributions was proposed and contrasted with monitoring data series. Prior ranges for river water quality-quantity parameters lead to high uncertainty in dissolved oxygen predictions, thus the need for formal calibration to adapt to the local dynamics is highlighted. After inferring the river process parameters with system measurements of flow and dissolved oxygen, the combined sewer overflow pollution loads became the dominant uncertainty source along with rainfall variability. As a result, insights gained in this paper can help in planning and directing further monitoring and modelling efforts in the system. When comparing these modelling results to existing national guidelines it is shown that the commonly used concentration-duration-frequency tables should not be the only metric used to select mitigation alternatives and may need to be adapted in order to cope with uncertainties.
Policy brief “Sustainable soil management”
Soil delivers numerous ecosystem services. However, soil degradation is a big issue in the EU. Good news is that soil degradation is not always irreversible: with an appropriate sustainable management of the soil it is possible to prevent the degradation process and remediate degraded land. By increasing soil fertility and soil health, sustainable soil management (SSM) offers multiple benefits. This policy brief gives good examples and recommendations for sustainable soil management.
Advancing global flood hazard simulations by improving comparability, benchmarking, and integration of global flood models
In recent years, a range of global flood models (GFMs) were developed, each utilizing different process descriptions as well as validation data sets and methods. To quantify the magnitude of these differences, studies assessed the performance of GFMs only on the continental and catchment level. Since the default model set-ups resulted in locally marked deviations, there is a clear need for further and especially more standardized research to not only maintain credibility, but also support the application of GFM products by end-users. Consequently, here we conceptually outline the basic requirements and challenges of a Global Flood Model Validation Framework for more standardized model validation and benchmarking. With the proposed framework we hope to encourage the much needed debate, research developments in this direction, and involvement of science with end-users. By means of the framework, it is possible to streamline the data sets used for input and validation as well as the validation approach itself. By subjecting GFMs to more thorough and standardized methods, we think their quality as well as acceptance will increase as a result, especially amongst endusers of their outputs. Otherwise GFMs may only serve a purely scientific purpose of continued ‘siloed’ model improvement but without practical use. Furthermore, we want to invite GFM developers to make their models more integratable which would allow for representation of more physical processes and even more detailed comparison on a model component basis. We think this is pivotal to not only improve the accuracy of model input data sets, but to focus on the core of each model, the process descriptions. Only if we know more about why GFMs deviate, are we able to improve them accordingly and develop a next generation of models, not only providing first-order estimates of flood extent but supporting the global disaster risk reduction community with more accurate and actionable information.
Klimaatverandering en weersextremen : toepassing van geokunststoffen bij waterkeringen en kustverdediging (deel 1)
Door klimaatverandering is het veilig en leefbaar houden van Nederland een grote uitdaging voorde komende decennia. Zeespiegelstijging en frequentere uitzonderlijke weersomstandigheden zullen significante effecten hebben op onze waterkeringen. De komende decennia zal er een enorme versterkingsoperatie moeten plaatsvinden. Voor het verkleinen van de impact hiervan lopen meerdere innovatie-trajecten. In verschillende POV-onderzoeksprogramma's staan geokunststoffen op de kaart, maar de toepassing is tot dusverre beperkt. terwijl het gebruik ervan kan resulteren in een substantieel betere, snellere en/of goedkopere aanleg van nieuwe waterkeringen, dijkversterkingen of kustverdediging. Dit artikel gaat in op de problematiek en de effecten van klimaatverandering en de potentiële rol die geokunststoffen kunnen spelen. Een vervolgartikel gaat uitgebreid in op verschillende toepassingen van geokunststoffen bij waterkeringen en kustverdediging.