Distribution-based calibration of a stormwater quality model

Dominik Leutnant*, Dirk Muschalla, Mathias Uhl

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


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-offand, 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-offproportional 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.

Original languageEnglish
Article number1027
Number of pages14
JournalWater (Switzerland)
Issue number8
Publication statusPublished - 3 Aug 2018


  • Annual TSS loads
  • Lognormal distribution
  • Model calibration
  • Probabilistic TSS event loads
  • Stormwater quality modelling
  • SWMM

ASJC Scopus subject areas

  • Biochemistry
  • Geography, Planning and Development
  • Aquatic Science
  • Water Science and Technology


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