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Stormwater control measures (SCMs) are effective and sustainable complementary means of managing stormwater in cities. Unlike underground drainage systems, they require space on the city surface, and therefore must be included in initial sketches of urban planning and design. These initial sketches are often made by architects and urban planners, who are usually not trained in hydrology, and therefore require simple and robust tools to inform their initial plans with respect to stormwater management. There may be local guidelines for dimensioning SCMs, but their applicability is often limited with regard to the range of SCMs, and the methodology behind them may be oversimplified, including a lack of assessment of benefits on the urban hydrological cycle. We developed a methodology for estimating multiple performance indicators of a wide range of SCMs and applied it to Danish meteorological conditions. The methodology includes consulting expected end users, configuring an SWMM model for each SCM type and choosing applicable parameter ranges, running multiple simulations for each type covering the parameter space, and post-processing the results using python and PySWMM. The outputs can be used to draw general recommendations regarding effective application ranges for different SCMs, and to quickly assess the performance of case-specific configurations.

Stormwater control measures (SCMs) are effective and sustainable complementary means of managing stormwater in cities. Unlike underground drainage systems, they require space on the city surface, and therefore must be included in initial sketches of urban planning and design. These initial sketches are often made by architects and urban planners, who are usually not trained in hydrology, and therefore require simple and robust tools to inform their initial plans with respect to stormwater management. There may be local guidelines for dimensioning SCMs, but their applicability is often limited with regard to the range of SCMs, and the methodology behind them may be oversimplified, including a lack of assessment of benefits on the urban hydrological cycle. We developed a methodology for estimating multiple performance indicators of a wide range of SCMs and applied it to Danish meteorological conditions. The methodology includes consulting expected end users, configuring an SWMM model for each SCM type and choosing applicable parameter ranges, running multiple simulations for each type covering the parameter space, and post-processing the results using python and PySWMM. The outputs can be used to draw general recommendations regarding effective application ranges for different SCMs, and to quickly assess the performance of casespecific configurations.

Water is key to keeping urban areas safe and healthy for humans and hence safe sanitation and waste water treatment is promoted by the United Nations Sustainable Development Goals. We show that emissions from existing state-of-the-art water technologies are problematic from a Planetary Boundaries (PBs) perspective. The magnitude of the climate change impact in relation to the PB based normalization is much higher than for any other PB. The current paradigm for urban water management needs a radical change for society to be served while emissions are reduced to a level that complies with the Planetary Boundaries.

Infiltration-based stormwater control measures are often implemented in a dispersed manner across catchments, making it difficult to assess their combined effect. This study proposes a set of principles that can guide planners in distributing stormwater control measure volumes within a catchment while maintaining the same performance as that of a single large measure at the catchment outlet. The principles are tested by setting up seven different cases, which respect and violate the principles in different ways, and by simulating their performance using continuous simulations with 41 years of data. The results show that when the principles are followed, the system performance is maintained, on the contrary, when the principles are violated, the system performance deteriorates. The principles can be very useful for green field developers who want to implement distributed stormwater control measures in series and need to document their expected effect at an early screening level. Furthermore, the principles can be used to make better simplifications of stormwater control measures in sewer system models at the catchment level.

We present a method to assess and communicate the efficiency of stormwater control measures for retrofitting existing urban areas. The tool extends the Three Points Approach to quantitatively distinguish three rainfall domains: (A) rainwater resource utilisation, (B) urban stormwater drainage pipe design, and (C) pluvial flood mitigation. Methods for calculating efficiencies are defined recognizing that rainfall is both a valuable resource and a potential problem. Efficiencies are quantified in relation to rainfall volume, supplied potable water volume and volume of wastewater treated. A case study from Denmark is used to illustrate how the efficiency varies between the rainfall domains. The method provides a means for communicating some important quantitative aspects of stormwater control measures among engineers, planners and decision makers working with management of water resources, stormwater drainage and flood risks.

To improve our understanding of the impacts of feedback between the atmosphere and the terrestrial water cycle including groundwater and to improve the integration of water resource management modelling for climate adaption we have developed a dynamically coupled climate–hydrological modelling system. The OpenMI modelling interface is used to couple a comprehensive hydrological modelling system, MIKE SHE running on personal computers, and a regional climate modelling system, HIRHAM running on a high performance computing platform. The coupled model enables two-way interaction between the atmosphere and the groundwater via the land surface and can represent the lateral movement of water in both the surface and subsurface and their interactions, not normally accounted for in climate models. Meso-scale processes are important for climate in general and rainfall in particular. Hydrological impacts are assessed at the catchment scale, the most important scale for water management. Feedback between groundwater, the land surface and the atmosphere occurs across a range of scales. Recognising this, the coupling was developed to allow dynamic exchange of water and energy at the catchment scale embedded within a larger meso-scale modelling domain. We present the coupling methodology used and describe the challenges in representing the exchanges between models and across scales. The coupled model is applied to one-way and two-way coupled simulations for a managed groundwater-dominated catchment, the Skjern River, Denmark. These coupled model simulations are evaluated against field observations and then compared with uncoupled climate and hydrological model simulations. Exploratory simulations show significant differences, particularly in the summer for precipitation and evapotranspiration the coupled model including groundwater and the RCM where groundwater is neglected. However, the resulting differences in the net precipitation and the catchment runoff in this groundwater dominated catchment were small. The need for further decadal scale simulations to understand the differences and insensitivity is highlighted.

The city of Copenhagen currently pursues a very ambitious plan to make the city ‘cloudburst proof’ within the next 30 years. The cloudburst management plan has the potential to support the city’s aim to become more green, liveable, and sustainable. In this study, we assessed stormwater system designs using the Three Point Approach (3PA) as a framework, where an indicator value for each domain was calculated using state-of-the-art modelling techniques. We demonstrated the methodology on scenarios representing sequential enhancements of the cloudburst management plan for a district that has been appointed to become the first climate resilient neighbourhood in Copenhagen. The results show that if the cloudburst system is exploited to discharge runoff from selected areas that are disconnected from the combined sewer system, then the plan leads to multiple benefits. These include improved flood protection under a 100-years storm (i.e., compliance with the new demands in domain C of the 3PA), reduced surcharge to terrain under a 10-years storm (i.e., compliance with the service goal in domain B of the 3PA) and an improved yearly water balance (i.e., better performance in domain A of the 3PA).

Sustainable flood risk management has to be achieved since flood protection is a fundamental societal service that we must deliver. Based on the discourse within the fields of risk management and sustainable urban water management, we discuss the necessity of assessing the sustainability of flood risk management, and propose an evaluation framework for doing so. We argue that it is necessary to include quantitative sustainability measures in flood risk management in order to exclude unsustainable solutions. Furthermore, we use the concept of absolute sustainability to discuss the prospects of maintaining current service levels without compromising future generation’s entitlement of services. Discussions on the sustainability of different overall flood risk schemes must take place. Fundamental changes in the approaches will require fundamental changes in the mind-sets of practitioners as well as lawmakers, politicians and the general public, which inevitably will take some time. Right now, the importance lies in setting an agenda where sustainability is important and needs to be quantified and assessed when managing flood risk

We developed a new tool to address the needs of utility companies in the early planning and design phase of LID for retrofitting in existing urban areas, where a high degree of collaboration among stakeholders with different professional backgrounds is needed. The tool uses simplified methods to assist the user in quickly assessing two key overall performance indicators of a LID plan: 1. Return period for overflow, and 2. Impact on the annual water budget of the catchment. The tool currently allows combining three types of stormwater control measures (SCMs) commonly used in LID: permeable paving, bioretention units and local detention ponds. We present a case study to illustrate the usefulness of the tool in the context of climate change adaptation in Copenhagen and discuss further development plans including more SCMs, better user interface and assessing the uncertainties introduced by the simplifications in the tool.

Summary A series of numerical experiments has been designed to investigate how effective satellite estimates of radiometric surface temperatures and soil surface moisture are for calibrating a Soil–Vegetation–Atmosphere Transfer (SVAT) model. Multi–objective calibration based on error minimization of temperature and soil moisture model outputs is performed in a semi–arid environment. Model accuracy when calibrated using in situ versus satellite objectives is explored in detail. Observational meteorological datasets from the African Monsoon Multidisciplinary Analysis (AMMA) were used to force a column model during a growing season in Mali. Fourier Amplitude Sensitivity Test (FAST) revealed the most sensitive parameters to model outputs. Parameters found sensitive were subsequently optimized in a series of model calibrations to reveal trade-offs between model objectives. Our main findings are (1) the SVAT model performs well in the semi–arid environment, but underestimates peak growing season evapotranspiration and overestimates soil moisture, (2) most of the parameters important for flux estimates can be constrained using surface temperature and soil surface moisture with the three exceptions: root depth, the extinction coefficient and unstressed stomatal resistance, (3) flux simulations are improved when the model is calibrated using in situ surface temperature and soil surface moisture versus satellite estimates.

Summary Climate impact studies in hydrology have traditionally neglected the land–atmosphere feedback. Hydrological models are forced with output from climate models but neglecting this feedback may lead to an inaccurate estimation of evapotranspiration (ET). Two-way coupling of a hydrological model and a climate model can overcome this problem by linking the two models through a shared land–atmosphere process description. In this study we analyse the hydrological model MIKE SHE using a two-layer energy-based ET model for use in a coupling with a regional climate model (RCM). The value of coupling to MIKE SHE is that it makes it possible to include lateral transport of surface water and groundwater not generally treated in RCM’s and to represent human interventions like groundwater pumping, irrigation schemes, etc. for adaptation studies. The hydrological model is applied to the FIFE site to investigate the effects of model resolution and parameter scales. The area of interest corresponds to a RCM grid cell. The hydrological model is parameterized with effective parameters assessed directly from field data at the site and literature. Using only these observed data and literature estimates to parameterise the model, it is able to reproduce the observed ET, sensible heat flux and to some extent surface soil moisture content; over a whole growing season. Hydrological simulations carried out over a range of spatial grids from 240 m to 15 km show that, for this case, the areal average ET appears to be insensitive to model resolution. The model is able to reproduce some of the spatial variability within the area, but not the exact pattern. By running the hydrological model at the highest resolution with uniform atmospheric input we examined the effect of using coarser resolution climate forcing, for example from a RCM. The areal mean ET and soil moisture (SM) temporal variations are reproduced quite well, but the spatial variability in the hydrological response is substantially underestimated; mainly because of the uniform precipitation. Our results are therefore encouraging for using this type of energy-based model in a coupling between a regional climate model and a distributed hydrological model. As the FIFE area is a relatively homogeneous site, additional tests are needed at heterogeneous sites to validate whether our findings are in general valid.

Summary The development of sophisticated distributed hydrological models that characterize groundwater, surface water and atmospheric interactions, inevitably increases the amount of observational data required to force the model and evaluate simulations. The limitations of using traditional evaluation data and the benefits of including independent and spatially distributed observational constraints are illustrated here through a sensitivity analysis of a coupled surface-water/groundwater/atmosphere model simulated at the catchment scale. In the analyses, model performance based on objective functions using conventional stream flow and groundwater head observations are compared against objective functions that utilize spatially distributed satellite based surface temperature retrievals as the calibration variable. The advantage of incorporating remote sensing based observations into the model evaluation process is their spatially distributed information content, enabling an assessment of the capacity of the model to reproduce observed spatial patterns. Results indicate that employing spatially distributed model parameterizations has limited impact on improving model performance when evaluated against traditional model objectives of stream flow and groundwater head. Indeed, a spatially uniform parameterization produced almost identical model performance. In contrast, objective functions that incorporate remote sensing based surface temperatures, highlighted the comparatively poor reproduction of spatial patterns when using a spatially uniform parameterization. Although lumped observations such as stream discharge contain valuable information regarding the total catchment water budget, such traditional observations should be merged with independent data sets that incorporate spatial pattern information to strengthen the robustness of model performance and model parameter constraint.

Summary The Yucatan Peninsula is one of the world’s largest karstic aquifer systems. It is the sole freshwater source for human users and ecosystems. The region hosts internationally important groundwater-dependent ecosystems (GDEs) in the 5280 km2 Sian Ka’an Biosphere Reserve. The GDEs are threatened by increasing groundwater abstractions and risks of pollution. Hydrogeological exploration work is needed as basis for sound groundwater management. A multidisciplinary approach was used to study this data-scarce region. Geochemical data and phreatic surface measurements showed distinct hydrogeological units in the groundwater catchment of Sian Ka’an. The hilly southwestern areas had a low hydraulic permeability, likely caused by a geology containing gypsum, whereas the transition zone and flat areas in the east and north had a high permeability. In the latter areas, the fresh groundwater could be described by a Dupuit–Ghyben–Herzberg lens. Geophysical borehole logging and time-domain electromagnetic soundings identified a shallow, low-resistive and high-gamma-radiation layer present throughout the hilly area and transition zone. Its thickness was 3–8 m, apparent conductivity was 200–800 mS/m and natural gamma-radiation about 80 counts pr. second. The layer is proposed to be ejecta from the Chicxulub impact (Cretaceous/Paleogene boundary). Spatial estimates of recharge were calculated from MODIS imagery using the ‘triangle method’. Average recharge constituted 17% of mean annual precipitation in the study area. Recharge was greatest in the hilly area and towards Valladolid. Near the coast, average actual evapotranspiration exceeded annual precipitation. The multidisciplinary approach used in this study is applicable to other catchment-scale studies.

We present a prototype for a new software tool which enables quantification of impacts of water sensitive urban design (WSUD) plans in a simplifying manner. The tool is designed to fill a gap between the needs of utility companies for assessing WSUD performance and available urban drainage simulation tools. Emphasis is put on reducing complexity in order to help drainage engineers communicate their priorities to other stakeholders. The tool outputs include two key indicators: The first is the amount of runoff held back in stormwater control measures on event basis, presented graphically against three distinct decision domains. The second is the percentage of runoff managed locally on an annual basis, presented graphically as a water budget. The tool concept was tested on several smaller case studies in Denmark, and we plan to have it ready for full-scale testing ultimo 2015.

To support climate adaptation measures for water resources, we have developed and evaluated a dynamic coupling between a comprehensive distributed hydrological modelling system, MIKE SHE, and a regional climate modelling system, HIRHAM. The coupled model enables two-way interaction between the atmosphere and the groundwater via the soil and land surface and can represent the lateral movement of water in both the surface and subsurface and their interactions as well as human interventions. The coupled model is applied to one-way and two-way coupled simulations for a managed groundwater-dominated catchment, the Skjern River, Denmark. The 2500 km2 catchment model is embedded in a meso-scale (4000 km x 2800 km) climate modelling domain. By using the ERA Interim reanalysis as boundary conditions the coupling performance is evaluated against measurements of both climatic and hydrological variables, including local measurements of energy fluxes. The results presented here suggest that there may be important differences in the simulated water balances for this catchment created by introducing an alternative hydrological model into the RCM.

To overcome the challenge of designing good-looking open detention/retention areas in the urban landscape that can manage stormwater runoff from both the large, rare events and the frequent smaller events without looking empty and oversized a new approach referred to as Characteristic Rain Events (CRE) is proposed. The idea of the CRE is to demonstrate the water dynamics of a detention/retention area in a number of characteristic situations, in this way allowing the designer to work in a more tangible way with the design.Based on historical rain series single events are selected, representing the day-to-day domain, the design domain and the extreme domain as defined in the Three Point Approach (3PA). In this paper the ability of CRE to unfold the water dynamics of a detention/retention area is investigated by applying four CRE to a fictive rain garden including frequent, short event, a frequent long event, a seldom heavy event and a rare extreme event, and comparing resulting numbers for time with standing water, water depth, retention volume, overflow volume etc. The CRE approach is concluded to hold potential for improving the design process and thus the final design of detention-retention areas.

"LAR-potentiale” er et nyt værktøj, der kan bruges til at vurdere hydrologiske effekter af mulige LAR-løsninger, især i eksisterende byområder. Værktøjet er designet til at understøtte beslutninger i den indledende fase af LAR projekter, hvor der er mange faggrupper, organisationer og borgere involveret. Derfor er værktøjet enkelt og hurtigt at bruge, og resultaterne er nemme at kommunikere.