Release process identification of non-instantaneous point source pollution in rivers via reverse flow and pollution routing

Abstract

Source identification is fundamental for managing sudden river water pollution; however, it is a challenging task. Although numerous studies have investigated this issue, most involve optimization or statistical models for instantaneous pollution and do not consider the reverse propagation and release processes. Herein, we propose an approach for identifying the release process of non-instantaneous point source pollution in rivers, based on reverse flow and pollution routing. The identification approach can trace the historical trajectory of pollutants and their release processes, providing the necessary information for treating accidental pollution. The effectiveness and efficiency of the proposed approach were tested and demonstrated using hypothetical and real-world river cases. The results indicated that the approach identified the release process with high accuracy, and second-round identification using the ensemble Kalman filter could generally improve the identification results from the reverse routing model. This approach was feasible in different cases of observation error, although the error considerably reduced its accuracy. The identification results were also found to be substantially influenced by release duration, with a shorter release time corresponding to an inferior identification result. Nevertheless, the approach worked well in real-world river cases and was generally not affected by the release location, pollutant diffusion, or river geomorphology. In addition, the new approach has advantages in computational efficiency and applicability over traditional methods.

Keywords: EnKF; Non-instantaneous point pollution; Release process; Reverse routing; Source identification.