Evaluation of a small hssf constructed wetland in treating parking lot stormwater runoff using swmm

Abstract

Stormwater management modelling (SWMM) is a dynamic hydrologic simulation model developed by the Environmental Protection Agency for urban areas. In this study, the objective was to evaluate and simulate the performance of an HSSF (horizontal subsurface flow) constructed wetland (HW) with long-term monitored data in treating urban runoff utilizing SWMM. HW was constructed beside a 424 m2 combined road and parking lot land uses in 2009 with a design rainfall of 5 mm. The facility was manually monitored with a total of 20 storm events from May 2010 until September 2016 to obtain hydrologic, hydraulic and water quality data. Monitored data were used for calibrating and verifying hydraulic parameters such as sub-catchment area, sub-catchment width, and depression storage and water quality parameters such as build-up and wash-off coefficients. Based on the results, the calculated relative errors between the uncalibrated and calibrated parameters were within the accepted ranges (<30%). 0.68–0.98 Nash–Sutcliffe model efficiency coefficient values were computed inciting that the observed and simulated results have a good fit. The volume and TSS loads reduction were also better performed in SWMM (55%–92%) than the observed values. Generally, the simulated results had higher reduction efficiency which suggests that the SWMM model maximized the capability of the facility.