A Review of Proposed Techniques for Modeling Longitudinal Dispersion Coefficient in Natural Channels

The World is facing a global climate change, while the world's population continues to grow. Therefore, providing sufficient water has become increasingly difficult in the last few decades. Artificially providing fresh water requires complex technology and economic investment. This is almost impossible, especially in underdeveloped countries. Due to these issues, water scarcity and/or stress is expected to rise dramatically in many regions in the world in the near future. Furthermore, current fresh water resources are vulnerable to pollutants (nuclear, biological, physical, and chemical). Conservation of fresh water resources has therefore become a critical issue. As is well known, the main fresh water sources are rivers and natural streams. Convective longitudinal dispersion is the most effective parameter in such sources. The longitudinal dispersion coefficient represents the rate of pollution and it is mostly used in water pollution modeling studies. Hence, learning the longitudinal dispersion mechanism in natural channels is vitally important to control water pollution. This paper's main purpose is to present a significant review and criticism on the literature related to both the longitudinal dispersion mechanism and the modeling techniques proposed for determining longitudinal dispersion coefficient in natural channels.