PhD Thesis Emmanuel Obeng Bekoe - Cranfield University

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(see Table 4.2) had some data however; Nsawam and Koforidua were chosen
because they were the most readily available and had longer duration. As
explained in Section 4.1, these represent the data which could be accessed
from archives. The data from the remaining rainfall stations at Aburi, Adeiso,
Bunso, Kibi, Oyoko, Suhum and Tafo were unavailable due to poor filing and
archiving from the meteorological data collecting agencies.
Table 4.2: Rainfall stations in the Densu Basin
Station Period of Data No of
Years
Station Period of
Data
Asuboi 1955 – 1971 16 Nsawam 1928 – date >70
Aburi 1936 – 1971 35 Oyoko 1949 – 1971 30
Adeiso 1953 – 1971 18 Suhum 1939 – 1976 37
Bunso 1928 – 1978 50 Tafo 1939 – 1998 59
Kibi 1926 – 1978 52 Accra 1965.–- date >33
Koforidua 1953 – date >45
No of Years
Prior to using these data in the modelling, a data screening procedure
consisting of three principal steps (Dahmen and Hall, 1990) was followed:
- Initial screening of the data for accuracy and verifying totals for the
hydrological year or seasons. This was done by tabulating daily totals
and visual examination to detect whether the observations have been
consistently or accidentally credited to the wrong day, whether they
show gross errors (e.g. from weekly readings instead of daily ones) or
whether they contain misplaced decimal points (Dahmen and Hall,
1990). Also noting ‘no observation’ instead of ‘observation =0’ and
missing data.
- Plotting these totals (Figure 4.1) according to the annual time step and
detecting any trends or discontinuities by visual examination (Dahmen
and Hall, 1990).
- Testing the time series for the absence of a trend with Spearman’s
Rank Correlation coefficient, Rsp method (equation 4.1) and testing the
trend for the Null hypothesis, Ho:Rsp = 0 (there is no trend) against the
Emmanuel Obeng Bekoe Phd Thesis Chapter 4 Data Availability, Model setup & Analysis