Sensitivity analysis of Qual2kw model in the modeling of water quality parameters of Sefidrud

Rivers are always one of the most important sources of water. In recent years, due to droughts and the entry of various pollutants, there have been many concerns about river quality conservation. Evaluation of the effective factors on the quality of river water quality management component is the first step of the rivers modeling. The aim of this paper is to evaluate the amount of Dissolved oxygen changes in the Sefidrud River by changing the parameters affecting it. To achieve this goal, after calibration and verification the results of simulation of water quality parameters using the Qual2kw model, the sensitivity analysis of this model was performed using YASAIw software. The data used in the present paper consists of the hydraulic data (depth, Velocity, Discharge), quality and pollutants input to a range of 110 kilometers in sefidrud River during December 2007, July, October and November 2008 and February, April, June and August 2011 at 12 sampling stations. The results showed that the minimum and maximum of normalized root mean square error (nRMSE) for calibration and validation phases for the pH parameter was 0.06 and 0.04 respectively, and for the total phosphorus parameter was 1.08 and 0.96, respectively. Also, the results of the sensitivity analysis of the model showed that the Dissolved oxygen in the Sefidrud River showed the highest sensitivity to the reaeration coefficient, the flow depth power and the decay rate of biochemical oxygen demand, respectively.