Urban hydrology has so far lacked a suitable model for a precise long-term determination of evapotranspiration (ET) addressing shading and vegetation-specific dynamics. The proposed model “SWMM-UrbanEVA” is fully integrated into US EPA’s Stormwater Management Model (SWMM) and consists of two submodules. Submodule 1, “Shading”, considers the reduction in potential ET due to shading effects. Local variabilities of shading impacts can be addressed for both pervious and impervious catchments. Submodule 2, “Evapotranspiration”, allows the spatio-temporal differentiated ET simulation of vegetation and maps dependencies on vegetation, soil, and moisture conditions which are necessary for realistically modeling vegetation’s water balance. The model is tested for parameter sensitivities, validity, and plausibility of model behaviour and shows good model performance for both submodules. Depending on location and vegetation, remarkable improvements in total volume errors Vol (from Vol = 0.59 to −0.04% for coniferous) and modeling long-term dynamics, measured by the Nash–Sutcliffe model efficiency (NSE) (from NSE = 0.47 to 0.87 for coniferous) can be observed. The most sensitive model inputs to total ET are the shading factor K_S and the crop factor K_C. Both must be derived very carefully to minimize volume errors. Another focus must be set on the soil parameters since they define the soil volume available for ET. Process-oriented differentiation between ET fluxes interception evaporation, transpiration, and soil evaporation, using the leaf area index, behaves realistically but shows a lack in volume errors. Further investigations on process dynamics, validation, and parametrization are recommended.

Biofiltration has proved to be a useful system to treat combined sewer overflow (CSO). The study presented uses numerical simulation to detect the critical operating conditions of the filter. The multi-component reactive transport module CW2D was used for the simulation study. Single-event simulations of lab-scale-column experiments with varying boundary conditions regarding the throttle outflow rate were carried out. For the calibration of the CW2D model measurement results of four experiments in two lab-scale columns were used. The model was validated by simulating four events of two further columns filled with the same filter material. These columns were operating with higher throttle outflow rates than the columns used for calibration. For ammonium (NH4-N) a good fit between measured and simulated data could be achieved. However, the comparison of simulated and measured effluent concentrations of nitrate (NO3-N) showed that there is a need for further investigations mainly due to the uncertainties in the degradation process during dry periods between the loadings.

Blue–green infrastructures (BGI) play an important role in addressing contemporary challenges posed by urbanization, climate change, and demographic shifts. This study focuses on the parameterization of BGI within hydrological models, specifically emphasizing the Low Impact Development (LID) module of the Storm Water Management Model (SWMM), supplemented by the SWMM-UrbanEVA evapotranspiration model. Employing a systematic approach, a transferable framework is developed to categorize BGI types, leading to a comprehensive parameterization toolset. This toolset includes parameter estimates for predefined BGI types, encompassing both natural and technical systems with a specific emphasis on plant-specific parameterization. The justification of these parameter estimates is supported by an extensive literature review. Sensitivity analyses reveal the influence of plant-specific parameters, such as the crop factor (K_C), and soil storage capacity, on water balance and peak runoff. Additionally, this study presents practical guidelines to enhance the comprehension of model behavior and ensure the highest possible quality in model parameterization. While further research on validity and transferability of the toolset is required, the findings of this study provide useful support for the differentiated representation and analysis of hydrological processes in urban environments. As a result, this study serves as a valuable resource for researchers, practitioners, and decision makers, facilitating the implementation of sustainable water management practices in urban settings.

During the last decade, water sensitive urban design (WSUD) has become more and more accepted. However, there is not any simple tool or option available to evaluate the influence of these measures on the local water balance. To counteract the impact of new settlements, planners focus on mitigating increases in runoff through installation of infiltration systems. This leads to an increasing non-natural groundwater recharge and decreased evapotranspiration. Simple software tools which evaluate or simulate the effect of WSUD on the local water balance are still needed. The authors developed a tool named WABILA (Wasserbilanz) that could support planners for optimal WSUD. WABILA is an easy-to-use planning tool that is based on simplified regression functions for established measures and land covers. Results show that WSUD has to be site-specific, based on climate conditions and the natural water balance.