Stormwater Pollutant Process Analysis with Long-Term Online Monitoring Data at Micro-Scale Sites

Dominik Leutnant,Dirk Muschalla,Mathias Uhl

doi:10.3390/w8070299

Dominik Leutnant, Dirk Muschalla + Show 1 more

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https://doi.org/10.3390/w8070299

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Abstract

Stormwater runoff quality was measured with online turbidity sensors at four common types of small urban subcatchments: (i) a flat roof; (ii) a parking lot; (iii) a residential catchment; and (iv) a high-traffic street. Samples were taken to estimate site-specific correlations between total suspended solids (TSS) and turbidity. Continuous TSS time series were derived from online turbidity measurements and were used to estimate event loads and event mean concentrations. Rainfall runoff event characteristics were subjected to correlation analysis to TSS loads. Significant correlations were found for rainfall intensities at sites with high imperviousness and decrease with increasing catchment size. Antecedent dry weather periods are only correlated at the parking lot site. Intra-event TSS load distributions were studied with M (V)-curves. M (V)-curves are grouped at runoff quantiles and statistically described with boxplots. All sites show, in general, a more pronounced first-flush effect. While wash-off of the flat roof tends to be source-limited, the parking lot and high-traffic street sites show a more transport-limited behavior. Wash-off process of the residential catchment appears to be influenced by a composition of different subcatchments.

Highlights

Stormwater runoff from urban environments is a significant source of pollutants which impacts the quality of receiving waters
Current stormwater quality model concepts are based upon empirical equations or simple regression functions to replicate the complex nature of pollutant accumulation and wash-off
Stormwater runoff and quality was continuously monitored at four microscale experimental sites: (i) a 50 m2 flat roof FR; (ii) a parking lot PL with approx. 2350 m2 ; (iii) a 9.4 ha residential catchment RC in a suburb of Muenster, Germany; and (iv) a high-traffic HT

Summary

Introduction

Stormwater runoff from urban environments is a significant source of pollutants which impacts the quality of receiving waters. Current stormwater quality model concepts are based upon empirical equations or simple regression functions to replicate the complex nature of pollutant accumulation and wash-off. These approaches offer a set of parameters for model calibration, quality models often show poor performance when simulating long-term conditions [1,2]. Improving quality models is crucial to produce more reliable model results. In this respect, in-depth knowledge of processes is a key requirement which demands measurement data. Online turbidity measurements have been successfully used for intra-event analyses in larger catchments [6,7]

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