Author(s): Farhad Yazdandoost; Hamid Shamloo; Arash Adib
Linked Author(s): Farhad Yazdandoost
Keywords: Tidal rivers; Salinity distribution coefficient; Hydrodynamic modelingl; Numerical modeling; River quality model
Abstract: In the tidal rivers, determination of salinity concentration is a complex problem. Tidal surges have high salinity concentration. In mouth of tidal rivers, salinity concentration is equal to salinity concentration in the sea. In the upstream of the tidal rivers, fresh water in tidal rivers decreases salinity concentration. Two factors determine salinity concentration in rivers: 1- Convection: its causes are inertia and velocity of current. 2- Diffusion: its causes are molecular and momentum distribution. Distribution coefficient of ordinary rivers depends on velocity of current, hydraulic radius and Manning's coefficient. In addition to above factors, distribution coefficient of tidal rivers depends on domain of tidal surge, period of tidal surge and discharge of fresh water. In the present research, a hydrodynamic model was established for determination of velocity of current and water surface elevation. This model makes use of the Priessman method. This method is based on a four point finite difference scheme. For determination of salinity concentration, a diffusion-advection model was established. This model also makes use of the Priessman method. Manning's coefficient in hydrodynamic model and distribution coefficient in diffusion-advection model were determined by calibration of models. Karun River in Iran was selected for case study. This river is the most important tidal river in Iran. Selected reach of Karun River located between Ahwaz at the upstream and Khoramshar at the downstream was considered. Salinity concentration of intermediate stations was estimated utilizing the model.