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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.
Dynamic Adaptive Policy Pathways (DAPP)
Dynamic Adaptive Policy Pathways (DAPP) is a DMDU approach that explicitly includes decision making over time. The essence is proactive and dynamic planning in response to how the future actually unfolds. DAPP explores alternative sequences of decisions (adaptation pathways) for multiple futures and illuminates the path dependency of alternative strategies. It opens the decision space and helps to overcome policy paralysis due to deep uncertainty. There are different routes that can achieve the objectives under changing conditions (like ‘different roads leading to Rome’). Policy actions have an uncertain design life and might fail sooner or later to continue achieving objectives as the operating conditions change (i.e. they reach an adaptation tipping point (ATP)). Similarly, opportunity tipping points may occur. Multiple pathways are typically visualized in a metro map or decision tree, with time or changing conditions on one of the axes. DAPP supports the design of a dynamic adaptive strategy that includes initial actions, long-term options, and adaptation signals to identify when to implement the long-term options or revisit decisions.
Dynamic Adaptive Policy Pathways (DAPP) : from theory to practice
Decision making by flood risk managers is challenged by uncertainty and changing climate risk profiles that have elements of deep uncertainty. Flood risk managers at a regional level in New Zealand requested better understanding and tools for decision making under conditions of uncertainty and changing conditions. A game was used to catalyze a process of new knowledge transfer and its uptake in technical assessments and decision making processes. The understanding enabled DAPP to be used to develop a long-term plan that can accommodate changes in flood frequency from climate change (as projected in three climate change scenarios) over at least 100 years. Use of “new” economic tools with DAPP facilitated decision making to consider the sensitivity of alternative policies to a range of climate change scenarios, to discount rate, decision review date, and costs and losses, thus addressing deep uncertainty by considering the long-term effects of initial decisions to changing conditions. The risk of path-dependent decisions and the role that current frameworks and practices play in blinding actors to the range of possible outcomes that could evolve in the future, was reduced. A series of interventions to raise and increase awareness through new information and its framing, experimentation, and leadership enabled the uptake of DAPP.
Pan-European calculation of hydrologic stress metrics in rivers : a first assessment with potential connections to ecological status
The hydrologic regime of a river is one of the factors determining its ecological status. This paper tries to indicate the present hydrologic stress occurring across European rivers on the basis of model integration. This results in a pan-European assessment at the resolution of the functional elementary catchment (FEC), based on simulated daily time-series of river flows from the model PCR-GLOBWB. To estimate proxies of the present hydrologic stress, two datasets of river flow were simulated under the same climate, one from a hypothetic least disturbed condition scenario and the second from the anthropogenic scenario with the actual water management occurring. Indicators describing the rivers’ hydrologic regime were calculated with the indicators of hydrologic alteration (IHA) software package and the river total mean flow and the relative baseflow magnitude over the total flow were used to express the deviations between the two scenarios as proxy metrics of rivers’ hydrologic alteration or hydrologic stress. The alteration results on Europe’s FEC-level background showed that Southern Europe is more hydrologically stressed than the rest of Europe, with greater potential for hydrology to be clearly associated with river segments of unreached good ecological status and high basin management needs.
Investments under non-stationarity : economic evaluation of adaptation pathways
Investment decisions about capital-intensive, long-lived infrastructure are challenging due to uncertainty about their future performance, particularly if the performance is sensitive to climate change. Such investments, like those made for water infrastructure, are rarely evaluated over their total operational lifetime, during which socio-economic and environmental changes can cause potential lock-ins and reduced options for future choices that lead to high costs to transfer to other options. We propose an economic evaluation framework to explore adaptation pathways, or sequences of strategic investments options, that can be implemented if needed due to changing conditions. A novel feature is the inclusion of “transfer costs” associated with a switch to alternative pathways to allow adaptive decision-making and to minimize the cost of adjustment over time. Implementing a pathway-driven approach represents a break with most institutional decision-making processes and can significantly improve decision-making under uncertainty compared to the conventional single-investment perspective. We present a case study on flood risk management in the Netherlands to show the longterm socio-economic consequences of short-term decisions by going beyond the project cycle horizon.
User guide to SUB-CR : a MODFLOW package for land subsidence and aquifer system compaction that includes creep
This document is the user guide of SUB-CR, version 1.0. SUB-CR is a MODFLOW-2005 based land subsidence package developed by Deltares1 that includes consolidation by creep. The package was developed to allow the modelling of land subsidence with a more comprehensive and more complete process representation of soft-sediment deformation than existing regional-scale hydrogeological models of land subsidence which do not consider creep. Creep and secondary consolidation are important in geotechnical applications involving soft-sediment (silt, clay, peat) consolidation. There is no obvious reason why creep would be irrelevant or insignificant when these sediments consolidate and cause land subsidence driven by groundwater use and groundwater management.
The benefits of spatial resolution increase in global simulations of the hydrological cycle evaluated for the Rhine and Mississippi basins
To study the global hydrological cycle and its response to a changing climate, we rely on global climate models (GCMs) and global hydrological models (GHMs). The spatial resolution of these models is restricted by computational resources and therefore limits the processes and level of detail that can be resolved. Increase in computer power therefore permits increase in resolution, but it is an open question where this resolution is invested best: in the GCM or GHM. In this study, we evaluated the benefits of increased resolution, without modifying the representation of physical processes in the models. By doing so, we can evaluate the benefits of resolution alone. We assess and compare the benefits of an increased resolution for a GCM and a GHM for two basins with long observational records: the Rhine and Mississippi basins. Increasing the resolution of a GCM (1.125 to 0.25) results in an improved precipitation budget over the Rhine basin, attributed to a more realistic large-scale circulation. These improvements with increased resolution are not found for the Mississippi basin, possibly because precipitation is strongly dependent on the representation of still unresolved convective processes. Increasing the resolution of the GCM improved the simulations of the monthly-averaged discharge for the Rhine, but did not improve the representation of extreme streamflow events. For the Mississippi basin, no substantial differences in precipitation and discharge were found with the higher-resolution GCM and GHM. Increasing the resolution of parameters describing vegetation and orography in the high-resolution GHM (from 0.5 to 0.05) shows no significant differences in discharge for both basins. A straightforward resolution increase in the GHM is thus most likely not the best method to improve discharge predictions, which emphasizes the need for better representation of processes and improved parameterizations that go hand in hand with resolution increase in a GHM.