Reliability Test of Mass Balance Model on Nitrogen Loads at The Rembangan River Jember

Abstract

The Mass balance model of nitrogen load was based on the continuity and momentum equations. Running the model was inserted the variable input into mathematical models based on differential equations by the finite difference method. Aims this study was to calibration, and validation the model. The coefficient of average monthly runoff (Cb) was defined as the ratio between the peak intensity of rainfall runoff to monthly. In this study, the average runoff coefficient monthly (Cb) was used to calculate the monthly average discharge. Calibration of the runoff coefficient of the monthly average (Cb) was do to find the best value of the runoff coefficient as output the model that was similar to the discharge measurement results in the field. The type of water flow in the river Rembangan Jember could determine with calculated the value of the Reynolds number. From the calculation, the Reynolds number is equal to 1929,821. Thus, the value was smaller than 2000, it was means the type of stream Rembangan including laminar flow. The result of running model was value of the nitrate concentration was 0.6549 mg/liter with calibrate of the reaction coefficient (K) and obtained a value of -1759 x 10-6. The minus sign means that the speed of reaction that occurs in the river Rembangan in July 2010 at a point 2 to decrease or reduction in the value of the reaction rate of 9.88 x 10-5/sec. This shows that the speed of the reactions in the river Rembangan tended to decline and approach the value zero.