A novel water quality module of the SWMM model for assessing Low Impact Development (LID) in Urban watersheds

Authors: BAEK, SANG-SOO - Ulsan National Institute Of Science And Technology (UNIST); LIGARAY, MAYZONEE - Ulsan National Institute Of Science And Technology (UNIST); PYO, JONGCHEOL - Ulsan National Institute Of Science And Technology (UNIST); PARK, JONG-PYO - Hecorea, Inc; KANG, JOO-HYON - Dongguk University; Pachepsky, Yakov; CHUN, JONG AHN - Apec Climate Center (APCC); CHO, KYUNGHWA - Ulsan National Institute Of Science And Technology (UNIST)

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2020
Publication Date: 5/3/2020
Citation: Baek, S., Ligaray, M., Pyo, J., Park, J., Kang, J., Pachepsky, Y.A., Chun, J., Cho, K. 2020. A novel water quality module of the SWMM model for assessing Low Impact Development (LID) in Urban watersheds. Journal of Hydrology. 586:124886. https://doi.org/10.1016/j.jhydrol.2020.124886.
DOI: https://doi.org/10.1016/j.jhydrol.2020.124886

Interpretive Summary: The Low Impact Development (LID) practices have the potential to provide better hydrologic functioning of urban areas as well as improve the environmental, economic, social and cultural conditions. We developed the new LID model component to simulate the quality of water received from the LID installations. The tools provided two times better accuracy of predictions of total nitrogen, chemical oxygen demand, and total phosphorus compared with the existing module in the currently used the storm water management model (SWMM. The modified SWMM model can be applied to other LID such as rain gardens and bioretention in addition to the green roof. It is concluded that SWMM model amended with the water quality module from our work can be a useful tool to provide effective strategies for better urban water management.

Technical Abstract: The rapid increase of impervious area and climate change greatly affect the hydrological, environmental, and ecological system at the local, regional, and global scales. These phenomena can increase the peak flow and surface runoff carrying anthropogenic pollutants, thereby severely deteriorating the water quality of the surface waters. Low-impact development (LID) practices have been proposed as a promising urban management methodology to mitigate these environmental issues. Numerical models have been increasingly utilized as an analyzing tool for evaluating the LID performance. However, LID-associated numerical models are oversimplified in terms of water quality simulation by only considering the dilution effect by rainfall in LIDs. This study resolved this challenge by modifying the water quality module of LID in the storm water management model (SWMM). We evaluated the module performance for simulating total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) of the LID facilities. Using the developed model, we conducted the LID scenario analysis under the climate change scenarios. The scenario analysis was applied in the urban area which focused on flow rate and TSS. The modified module provided accurate results for pollutant simulations, yielding an average value of Root mean square error-observation Standard Deviation Ratio (RSR) of 0.52, while the original module showed an unacceptable performance, with an RSR value of 1.11. Scenario analysis showed that the hydrological outputs were sensitive to the volume of rainfall while the water quality results were sensitive to the temporal distribution of rainfall. Based on these statements, the modified water quality module in LID developed in this study will be useful in designing LID facilities and in formulating guidelines for LID installation.