in rivers and streams

From spatial perspective, solutes enter surface waters through point sources (municipal treatment plants and industrial facilities) and nonpoint sources (agricultural runoff that enter a stream as overland flow, acid rain). Physical processes that play an important in determining the fate of solutes in surface water environment are :

  • Advection wich describes the downstream transport of solutes mass at the mean flow velocity
  • Diffusion may be a significant mixing process in waters with low flow velocities (lakes, groundwater) but the role of molecular diffusion is diminished in streams and rivers, as velocity variation becomes the dominant mixing mechanism.
  • Dispersion describes the spreading of the contaminant being produced by molecular diffusion and velocity variation caused by shear stress.

In the analysis below, we have assumed conservative conditions, sach that only physical processes af advection and dispersion are considered. The processes of sorption, oxidation/ reduction, volatilization, hydrolysis, biodegradation and other biochemical processes are neglected.

 Mathematical model for contaminant transport in rivers and streams (with analytical solutions)

 Application (excel spreadsheet calculator)