INni.TRF.TI3N
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5.4.3.1 Statistical analysis of dry season results
The results of the analysis of variance for variation between blocks and treatments is shown in Appendix 5.10.
On the basis of cumulative infiltration at 1 minute there is no significant difference between the four blocks while there is a highly significant difference between treatments, that is the three forest types.
The average cumulative infiltration after 1 minute is shown for each block and for each treatment in Table 5.14.
The results of the analysis for significant differences between the individual forest types on the basis of cumulative infiltration after a period of 1 minute is shown in Appendix 5.11.
Table 5.14 Average cumulative infiltration after 1 minute by blocks and forest types.
Dry season, Kyetmauk-taung catchment (cm)
Forest Block No. Mean
type I II III IV (forest type)
Mixed deciduous 1.94 1.95 2.06 2.04 1.99
Man-made 1.78 1.38 1.69 1.65 1.75
plantation
Semi-indaing 1.36 1.42 1.38 1.51 1.42
On the basis of the cumulative infiltration after 1 minute there are highly significant differences between the mixed deciduous forest type
and the man-made plantation, between the mixed deciduous forest and the semi-indaing forest and between the man-made plantation and the semi- indaing forest. The results are summarized below.
Comparison Level of significant difference (cumulative infiltration)
Mixed deciduous and man-made plantation
** highly significant
Mixed deciduous and semi-indaing ** highly significant
Man-made plantation and semi-indaing ** highly significant
The results of the analysis of variance and the testing for
significant difference between forest types on the basis of sorptivity
are shown in Appendix 5.12 and summarized below.
Comparison Level of significant difference
(sorptivities)
Mixed deciduous and man-made plantation
* significant
Mixed deciduous and semi-indaing ** highly significant
Man-made plantation and semi-indaing ** highly significant
The results of the analysis of variance and the testing for
significant difference between forest types on the basis of hydraulic
conductivity are shown in Appendix 5.13 and summarized below.
Comparison Level of significant difference
(hydraulic conductivity)
Mixed deciduous and man-made plantation
** highly significant
Mixed deciduous and semi-indaing ** highly significant
Man-made plantation and semi-indaing ** highly significant
The results of the analysis of variance and the testing for
significant difference between forest types on the basis of the cumulative
infiltration at 1 minute are shown in Appendix 5 .,14 and summarized below.
This is a similar test as that shown in Appendix 5.11 but all plots (133)
have been lumped together as was done for the results shown in Appendices
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Comparison
Mixed deciduous and man-made plantation
Mixed deciduous and semi-indaing forest Man-made plantation and semi-indaing
Level of significant difference (infiltration at 1 minute) * significant
** highly significant ** highly significant
5.4.3.2 Statistical analysis of wet season results
The results are shown in Appendix ; Comparison
Mixed deciduous and man-made plantation Mixed deciduous and semi-indaing forest Man-made plantation and semi-indaing
.15 and summarized below.
Level of significant difference not significant
** highly significant ** highly significant
The analysis thus shows on the basis of cumulative infiltration after 1 minute, that there are highly significant differences between the mixed deciduous and the semi-indaing forest and between the man-made plantation and the semi-indaing forest but that there is no significant difference between the mixed deciduous forest and the man-made plantation.
5.4.3.3 Comparison of dry season and wet season results
The comparison is summarized on the basis of average cumulative infiltration in Table 5.15.
Table 5.15 Comparison of cumulative infiltration (average) in the dry and wet season
Forest type Cumulative infiltration (cm) 1 dry min. wet 60 dry min. wet Mixed deciduous 1.92 1.39 25.2 11.6 Plantations 1.73 1.40 22.1 11.6 Semi-indaing 1.54 1.15 19.5 9.4
5.4.4 Discussion
There is much less variability in the measured values of sorptivity and hydraulic conductivity within the measurements taken in the Kyetmauk- taung catchment than within the measurements taken in the Cotter catchment and the randomized block design for the sampling has enabled significant differences to be established on a statistical basis.
While in the dry season the infiltration characteristics of the man-made plantations are significantly different to those in the mixed deciduous forest, and are generally lower, they are higher than the semi-indaing forest.
The man-made plantations were established to rehabilitate eroding areas under banana plantations in 1969-70. Since that time it has been observed that the base flows of the small streams are higher and that small springs now flow later into the dry season than they did under the banana plantations. This field observation suggests that infiltrat ion of rainfall has increased as a consequence of the rehabilitation and is confirmed by the results of the study for the infiltration character istics on the brown volcanic soils are approaching the values for the black volcanic soils of the mixed deciduous forest.
The man-made plantations are located on land which was covered with mixed deciduous forest before it was cleared for banana plantations. While it deteriorated under its use for banana plantations the results of the study suggest that reafforestation has in the short period since 1969-70 restored the infiltration characteristics to values approaching those in the undisturbed and adjacent mixed deciduous forest.
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CHAPTER VI
THE DERIVATION OF RAINFALL INTENSITY-DURATION-FREQUENCY DIAGRAMS