PhD Thesis Emmanuel Obeng Bekoe - Cranfield University

Change in streamflow (%)
118
80
60
40
20
0
-20
-40
-40 -20 0
Change in parameter (%)
20 40
CAY_apan CAY_Har FC1_apan FC1_Har
Figure 5.5 Comparison of cumulative streamflow using Apan (apan) and
Hargreaves (Har) methods for the most sensitive parameters
It is observed that the Hargreaves method increases the sensitivity of
cumulative simulated streamflow to changes in the crop coefficient and the field
capacity of the topsoils compared to using the A-pan method.
5.2.4 Results and Conclusion
As a rule, high sensitivity of a parameter is only desirable if that parameter can
be measured easily and has a very small range. Schultz (1995) suggested the
following scale for parameter sensitivity in ACRU:
• extremely sensitive (E): the percentage change in the output (∆O%) is
more than twice that of the input parameter being tested (∆I%), i.e ∆O%
> 2(∆I%)
• highly sensitive (H): the output change is more than the input change, but
by less than 200% , i.e. 2(∆I%) > ∆O% > ∆I%
• moderately sensitive (M): relative output changes less than the relative
input change, but by more than 50% of the input change, i.e. ∆I% > ∆O%
> 0.5(∆I%)
• slightly sensitive (S): output changes by between 10% and 50% of the
input change, i.e. 0.5(∆I%) > ∆O% > 0.1(∆I%)
Emmanuel Obeng Bekoe Phd Thesis Chapter 5 Hydrological modelling of Densu