New conceptualization and quantification method of first-flush in urban catchments: A modelling study

Zan Gao; Qionghua Zhang; Jie Li; Yufei Wang; Mawuli Dzakpasu; Xiaochang C Wang

doi:10.1016/j.scitotenv.2023.162271

New conceptualization and quantification method of first-flush in urban catchments: A modelling study

Sci Total Environ. 2023 May 15:873:162271. doi: 10.1016/j.scitotenv.2023.162271. Epub 2023 Feb 17.

Authors

Zan Gao¹, Qionghua Zhang², Jie Li¹, Yufei Wang¹, Mawuli Dzakpasu³, Xiaochang C Wang⁴

Affiliations

¹ Key Lab of Northwest Water Resource, Environment and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an 710055, China.
² Key Lab of Northwest Water Resource, Environment and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an 710055, China; International Science & Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an University of Architecture and Technology, Xi'an 710055, China. Electronic address: qionghuazhang@126.com.
³ International Science & Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an University of Architecture and Technology, Xi'an 710055, China; School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
⁴ Key Lab of Northwest Water Resource, Environment and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an 710055, China; International Science & Technology Cooperation Center for Urban Alternative Water Resources Development, Xi'an University of Architecture and Technology, Xi'an 710055, China.

PMID: 36801410
DOI: 10.1016/j.scitotenv.2023.162271

Abstract

A major challenge for runoff pollution control lies in the quantification and identification of the first-flush. At present, there is a lack of reasonable theoretical methods to guide engineering practices. To remedy this deficiency, a novel method of cumulative pollutant mass vs. cumulative runoff volume (M(V)) curve simulation is proposed in this study. Subsequently, the first-flush phenomenon was redefined based on the M(V) curve simulation and demonstrate that the first-flush exists until the derivative of the simulated M(V) curve is equal to 1 (F_t' = 1). Consequently, a mathematical model for first-flush quantification was developed. The Root-Mean-Square-Deviation (RMSD) and Pearson's Correlation Coefficient (PCC), as objective functions, were used to evaluate the performance of the model and the Elementary-Effect (EE) method was used to analyze the sensitivity of the parameters. The results indicated the satisfactory accuracy of the M(V) curve simulation and first-flush quantitative mathematical model. The NSE values exceeding 0.8 and 0.938, respectively, were obtained by analyzing 19 rainfall-runoff data for Xi'an, Shaanxi Province, China. The wash-off coefficient "r" was demonstrably the most sensitive factor influencing the model performance. Therefore, interactions between "r" and the other model parameters should be focused on to highlight the overall sensitivities. Overall, this study posits a novel paradigm shift from the traditional dimensionless definition criterion to redefine and quantify first-flush, which has significant implications for urban water environment management.

Keywords: First-flush; M(V) curve; RMSD; Runoff pollution; Sensitivity analysis; Urban wash-off.