EFFECTS OF REAERATION COEFFICIENT ON RIVER WATER DISSOLVED OXYGEN, DINACHAL RIVER, IRAN

The main aim of this paper is to evaluate the effects of reaeration coefficient on the river water dissolved oxygen, case study Dinachal River, IRAN. To achieve this goal, water quality samples were collected along a reach of 2 kilometers of the river in September 2013. Electrical Conductivity, pH, Dissolve Oxygen, Biochemical Oxygen Demand, Nitrate and Phosphorus are the main quality parameters which were measured in laboratory, using the above mentioned collected water samples. Streeter-Phelps model has been used to simulate dissolved oxygen in the river analytically and to improve the output of the model; advection, dispersion and decay rate terms were included to the basic form of the Streeter-Phelps equation. Also, dissolved oxygen concentration in the river has been simulated involving FTCS, QUICKEST, Upstream and Lax-Wendroff numerical methods. The reaeration coefficient has been estimated using four empirical equations including; Oconnor-Dobbins, Langbein-Durum, Boulton and Ling et al. The results show that Up-stream numerical method containing Boulton reaeration Coefficient equation has the most accurate results, with the amounts of Pearson correlation coefficient and Mean Absolute Errors equal to 0.995 and 0.033, respectively. Generally speaking, numerical methods in contrast to analytical solution of the Streeter-Phelps equation showed more accurate results, which is due to existing of the empirical coefficients in the Streeter-Phelps equation.