PhD Thesis Emmanuel Obeng Bekoe - Cranfield University

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Summary of the Causes of the Variable Model Performance in the Densu
Basin
The above detailed analysis of the performance of the ACRU model and the
data that was used within the model or against which the model outputs have
been calibrated or compared has identified a number of causes of the variable
model performance. Whilst it has not been possible to quantify the magnitude
of their contribution to the model performance, recognition of the detrimental
effects of the following issues is necessary:
1) the variable quality of the observed river flow data against which the
simulated flow data are calibrated and compared:
a. flow data recorded outside the limits of the rating curve are not
flagged;
b. suspect measurement readings, the causes of which could be non
reading and ‘cooking’ data, unadherence to times for reading data
and poor reading of measuring instruments;
2) the quality of the observed weather data e.g. rainfall and
evapotranspiration;
a. insufficient density of raingauges and pan evaporation stations
b. data quality auditing not strong
3) shortcomings within the numerical representation of processes within the
ACRU model;
a. groundwater processes
b. flow routing
4) shortcomings related to the incorporation of spatial variability within the
lumped and semi distributed simulations
a. Influence of soil parameters on ET:
b. Influence of manual calibration.
5) features within the Densu basin which were not considered within the
simulations above:
a. effects of control structures e.g. weirs
b. level of actual abstraction for irrigation not known.
Emmanuel Obeng Bekoe Phd Thesis Chapter 6 Discussion