Evaluation of spatiotemporal variation of water quality in China: a study on the effectiveness of the River Chief System

Abstract

Abstract The River Chief System (RCS) is an institutional innovation launched to prevent and control water pollution. Its implementation has attracted much attention because it is a government-led effort to solve China's complex water problems. This study analyzed the characteristics and trends of four water quality (WQ) parameters, including pH, dissolved oxygen (DO), permanganate index (CODMn), and ammonia nitrogen (NH3-N), which were determined weekly from samples collected at 150 WQ monitoring stations in the Chinese rivers and lakes. The minimum WQ index (WQImin), Mann–Kendall test, wavelet analysis, and ArcGIS software were applied to evaluate the spatiotemporal variation of WQ before and after the implementation of the RCS, taking the main second-order basins and lakes in China as the research unit. The results demonstrated that CODMn and NH3-N were the main factors exceeding WQ. After the performance of the RCS, the WQ of each sub-basin and lake was improved, basically reaching the Class Ⅲ standard threshold; the WQImin values of sub-basins and lakes were above the ‘very bad’ level, where the proportion of ‘good’ was 68.09%, an increase of 52.38%. The spatial distribution of the trend coefficient of WQImin showed an upward trend, with the maximum trend coefficient being 4.99/a.