Leutnant, Dominik
Refine
Document Type
Has Fulltext
- no (5)
Is part of the Bibliography
- no (5)
Keywords
- R (1)
- SWMM (1)
- Stormwater Quality (1)
- model data management (1)
- urban drainage modelling (1)
Institute
The in-situ performance of large decentralised stormwater treatment systems is investigated by means of continuous turbidity measurements. Turbidity measurements are used as a surrogate to continuously estimate Total Suspended Solid (TSS) concentrations. TSS event loads are calculated at the inlet and outlet of two stormwater treatment systems, which both are installed at the outlet of catchments with high pollution potential. The event-specific performance is defined as ratio between TSS loads of inflow and outflow. Based on measurement data obtained, the overall TSS load retention efficiency is about 32 %.
Stormwater quality models are usually calibrated using observed pollutographs. As current models still rely on simplified model concepts for pollutant accumulation and wash-off, calibration results for continuous pollutant concentrations are highly uncertain. In this paper, we introduce an innovative calibration approach based on total suspended solids (TSS) event load distribution. The approach is applied on stormwater quality models for a flat roof and a parking lot for which reliable distributions are available. Exponential functions are employed for both TSS buildup and wash-off. Model parameters are calibrated by means of an evolutionary algorithm to minimize the distance between a parameterized lognormal distribution function and the cumulated distribution of simulated TSS event loads. Since TSS event load characteristics are probabilistically considered, the approach especially respects the stochasticity of TSS buildup and wash-off and, therefore, improves conventional stormwater quality calibration concepts. The results show that both experimental models were calibrated with high goodness-of-fit (Kolmogorov–Smirnov test statistic: 0.05). However, it is shown that events with high TSS event loads (>0.8 percentile) are generally underestimated. While this leads to a relative deviation of −28% of total TSS loads for the parking lot, the error is compensated for the flat roof (+5%). Calibrated model parameters generally tend to generate wash-off proportional to runoff, which is indicated by mass-volume curves. The approach itself is, in general, applicable and creates a new opportunity to calibrate stormwater quality models especially when calibration data is limited.
Results from a long-term stormwater quality monitoring program were used to derive total suspended solids (TSS) event load distributions at four small urban environments (flat roof, parking lot, residential catchment, high traffic street). Theoretical distribution functions were fitted to the empirical distribution functions obtained. Parameters of the theoretical distribution functions were optimized with respect to a likelihood function to get both optimized parameters and standard errors. Kolmogorov-Smirnov and Anderson-Darling test statistics were applied to assess the goodness-of-fit between empirical and theoretical distribution. The lognormal distribution function was found to be most expressive to approximate empirical TSS event load distributions at all sites. However, the goodness-of-fit of the statistical model strongly depends on the number of events available. Based on the results of a Monte-Carlo-based resampling strategy, around 40 events should be considered.
Der Behandlung von Niederschlagsabflüssen aus Trennsystemen kommt zur Zielerreichung eines wirksamen Gewässerschutzes eine wesentliche Rolle zu. Konventionelle, zentrale Anlagen behandeln den Abfluss vor der Einleitung in das Gewässer. Zunehmend an Bedeutung gewonnen haben dezentrale Anlagen, die den Abfluss am Entstehungsort behandeln. Unterschiedlich belastete Oberflächenabflüsse können somit den wasserrechtlichen Anforderungen entsprechend gezielt behandelt werden. Voraussetzung zur Anwendung ist der Nachweis der vergleichbaren Reinigungsleistung zu zentralen Anlagen. In-situ Gütemessungen der Zu- und Ablauffrachten einer Behandlungsanlage ermöglichen eine datenbasierte Bewertung der Anlagenwirksamkeit.
The stormwater management model SWMM of the US EPA is widely used to analyse, design or optimise urban drainage systems. To perform advanced analysis and visualisations of model data this technical note introduces the R package swmmr. It contains functions to read and write SWMM files, initiate simulations from the R console and to convert SWMM model files to and from GIS data. Additionally, model data can be transformed to produce high quality visualisations. In accordance with SWMM’s open source policy the package can be obtained through github.com or the Comprehensive R Archive Network (CRAN).
