DEVELOPMENT OF HYDRODYNAMIC, WATER QUALITY AND EUTROPHICATION MODELS - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 153

Table (7-2): Calibration process parameters for water quality model
Calibration parameters run1

(default )

run2 run3

Reareation transfer coeff (m.d -1) 1 2 3

Decay rate BOD (d -1 ) 0.3 0.15 0.08

Decay rate COD (d -1 ) 0.05 0.025 0.01

Temp coeff. decay rate BOD 1.04 1.04 1.04

Temp coeff. decay rate COD 1.02 1.02 1.02

Calibration was done for two sets of model parameters values. It is important to note that the
temperature is an important water quality parameter that affects almost every water quality process.
Therefore the temperature coefficients for the decay rates of oxygen group parameters are also used in
the calibration process. Results of calibration of the oxygen group are shown in the following f igures
(7-26) to (7-28) :

1. Dissolved Oxygen

Figure (7-26): The calibrated result of dissolved Oxygen (DO).

It is noted that at the entrance of the main drain to the lake (LO4) the DO has the lowest values; in
general the DO measurements are close to the simulated results with an RME value of 11.78%.
2. BOD 5

Figure (7-27): The calibrated result of BOD5

The BOD values show a difference between simulated and observed values at locations near the drain
inlets to the lake, where the model over estimated the values of BOD. Although the trends are quite
similar, the values are simulated with a relative error of 48%. This could be due to the low velocity
distributions at these locations around the lake edges; but the overall MRE for all measurement
locations is within an acceptable range of 18.29%.