Assessing the water quality in urban river considering the influence of rainstorm flood: A case study of Handan city, China

Abstract

The water quality of urban rivers is subject to fluctuation caused by rainstorm flood. The uncertainty of flooding in a dynamic environment brings about changes in river quality, presenting a significant challenge. Water samples were collected at 7 sampling sites in Handan City of China from January 2020 to August 2023, and 9 water quality parameters (WT, pH, Cond, Do, COD, BOD, NH3-N, TP, and TP) were analyzed. Specifically, the spatial and temporal variation of water quality in the Qingzhang River was analyzed. In terms of season, the concentration of water quality parameters in spring and winter was found to be significantly higher than that in summer and autumn. Spatially, the concentration of water quality parameters was lower in the upstream compared to the downstream. Furthermore, it was discovered that the reservoir had a purifying effect on the water quality of the river. Additionally, a comparison of water quality during flood and non-flood periods revealed that the concentration of water quality parameters in the upstream, midstream, and downstream of the Qingzhang River were higher during non-flood periods. These findings indicated that, in comparison to the urbanization factor, the hydrological factor, which results in the runoff carrying nutrients into the Qingzhang River, plays a crucial role in the change of its water quality. Moreover, the autoregressive integrated moving average (ARIMA) method was employed to create a water pollution emergency prediction model for the different sections of the Qingzhang River, and an adaptive urban river water purification strategy was formulated based on its variation patterns. The research results contribute to the theoretical basis for the management of urban rivers and water resources.