DEVELOPMENT OF HYDRODYNAMIC, WATER QUALITY AND EUTROPHICATION MODELS - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 154

3. COD

Figure (7-28): The calibrated result of COD
The simulated COD results are very close to the measured values at most locations within the lake, but
with noticable different values and trends at locations LO9, LO10 and LO13, which could be due to
the inaccuracy of sampling analysis. This is because the trend of the model is in line with the trend of
measurements in general, and the MRE values is around 15.72 %.

Analysis of Results of the Calibrated Model

In general, we can conclude that the calibration of the oxygen group parameters shows that there is
close agreement between the simulated values and observed data, with an acceptable range of error
since the model performance is very much dependant on the sufficiency and accuracy of the measured
data. But since the modelling of water quality parameters is a complicated process that involves a
variety of uncertainties we can accept the relative errors at the investigated locations. Table (7-3)
shows the different values of RE and MRE for the modelled parameters at this level. The overall
calculated statistical parameters for the calibrated model are given in table (7-4) .

Table (7-3): Relative error for the calibrated model parameters
Location DO

(RE %)

COD
(RE %)

BOD
(RE %) Parameter

Lo4 17.32 41.18 42.69

Lo5 10.77 48.29 38.27

Lo6 9.36 10.13 40.81

Lo7 15.77 0.15 26.84

Lo8 4.74 0.92 24.90

Lo9 27.35 1.04 21.38

Lo10 35.00 11.77 6.02

Lo11 17.33 0.00 15.25

Lo12 34.72 7.50 6.84

Lo13 16.85 9.88 8.08

Lo14 4.61 3.80 2.08

Lo15 1.54 7.16 18.60

11.22 5.86 10.22

Lo16

Lo17 13.66 8.44 2.91

L018 7.31 15.00 2.83

Lo19 2.83 8.91 40.50

Lo20 8.14 6.04 6.88

Lo21 17.64 22.00 39.00

25.40 2.16 11.59

Lo23

Lo26 32.94 25.56 0.14

MRE 15.72% 11.79% 18.29%