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RESULTS
Figure 2 shows the estimates of TP concentration for Clunie loch from all the three
scenarios applied to Lunan catchment compared with the default application.
The outputs from the first scenario suggest that taking into account the change into
winter/spring cereals distribution has some positive effect on estimating TP in loch
concentration, but the difference is not statistically significant at 95% confidence.
The outcome of the second scenario applied, demonstrates that model calibration
by inspecting and adjusting the export coefficients is required and has the potential
to result in a more accurate estimation of the total in-loch concentrations.
The descriptive statistics support the conclusion that the residuals of the second
scenario are better behaved compared with the default application. The mean of the
residuals is closer to zero and furthermore the standard deviation of the residuals is
smaller compared with the one of the control year. So, the notion that the scenario
application is more efficient is verified, since the high values of the residuals in the
case of the default application could mean that the independent variables used did
not explain satisfactory the variance of the dependent variable. It should be stated
though that the limited number of observations available diminishes the credibility of
the results.
Figure 2: Comparison of predicted range of Clunie loch mean TP
concentration with control year (all in µg/L)
The results of the third scenario, compared with the results of the default application
suggest that potential installation of buffer strip would have positive effect on holding
of TP to Clunie Loch. Specifically, minimum in loch TP concentration was estimated
to decrease from 22.9 to 13.2 µg/L, while the maximum was estimated to decrease
from 39.3 to 20.3 µg/L.
DISCUSSION
The conclusion that when the different proportions of winter and spring crops were
taken into consideration did not have any significant difference in the model outputs
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