PhD Thesis Emmanuel Obeng Bekoe - Cranfield University

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Table 5.4 Performance statistics for weekly lumped
simulations at Manhia
Weekly Calibration Weekly Validation
Period (01/03/68-28/02/1970) Period (01/03/1970-31/12/1972)
All Months
All Water Period
Months Years
01/03/1971- 01/031972-
Period Period 31/12/72 31/12/72
RMS (mm) 6.67 3.20 1.88 1.40
PBIAS (%) -4.35 -69.27 -13.71 9.69
NSE 0.83 -0.70 0.54 0.70
PME -ve -ve 0.37 0.43
The weekly calibrated streamflow had an improved NSE of 0.83 (compared to
the daily simulation) which is good and a PBIAS of overestimation of 4.35%.
The weekly RMS error was 6.67 mm indicating that the standard deviation of
the model prediction error was high.
With the ‘best’ calibrated values established and the model achieving a low
PBAIS and a very good NSE according to Henrikson et al. (2003) the model
was run for the validation period. Figures 5.10 and 5.11 show the simulated
daily streamflow and weekly streamflow for the validation period with the
corresponding performance appraisal statistics shown in Tables 5.2 and 5.3
respectively.
From the performance statistics of both the daily (Table 5.3) and weekly (Table
5.4) simulations during the validation period, it is apparent that the validation
period had NSEs of -0.51 (daily) and -0.70 (weekly) which were poor according
to the acceptance criteria. However, the year of 1972 has very good statistics
with NSE as high as 0.70 for the weekly and 0.58 for the daily. In the weekly
simulations the year 1970 had an improved PME of 0.37 to 0.43 for the weekly
flows for 1971 and 72 water years, respectively as against 0.13 and 0.18 for the
daily flows respectively.
Emmanuel Obeng Bekoe Phd Thesis Chapter 5 Hydrological modelling of Densu