| |
CRC PUBLICATIONS |
The Hydrologic Impacts of Forestry on the Maroondah Catchments
Fred Watson,
Rob Vertessy,
Tom McMahon,
Bruce Rhodes,
Ian Watson
Publication Type:
Technical Report
This is a publication of the initial CRC for Catchment Hydrology
CRC Program:
Forest Hydrology (Previous CRC)
|
Publication Keywords:
Forestry
Hydrology
Water Yields
Tree Felling
Modelling (Hydrological)
Catchment Areas
Flow Rates
Stream Flow
Growth
Forest Products Industry
Biological Impact
Transpiration
Soil/Water Systems
|
Abstract / Summary:
Abstract
The effects of various forest treatments on forest water yield, low flow duration, and a range of other key forest hydrological variables were examined for the Maroondah experimental catchments in Victoria, Australia. The work follows more than three decades of hydrological data collection, analysis, and publication in Victoria's Mountain Ash forests, and attempts to synthesise some key data sets into a number of continuous descriptions of changes in hydrological variables in the decades immediately following forest regeneration.
The primary analysis was a rigorous statistical quantification of the effect of treatment on water yield in three catchment groups: Myrtle, Monda and Coranderrk, the latter including Picaninny and Slip. Regressions of water yield data at treated catchments versus that at control catchments were formed. The chosen method used monthly data, driven by often short pre-treatment records, and involved accounting for heteroscedasticity, non-normality, and serial correlation in the data using log transformations, sinusoid regression terms, and a lag-one auto-regressive (AR1) model. Statistically significant treatment effects were observed in all cases. Both Myrtle and Picaninny responded to clearfelling with initial increases in yield in the 2-3 years following treatment, followed by more gradual decreases to significantly lower than pre-treatment values. It was uncertain whether a recovery back up to pre-treatment levels had commenced in either catchment (by 12 years of age for Myrtle, and 25 years of age for
Picaninny). Water Yield at Monda responded similarly to clearfelling in the first few years, but at the time when decreased water yield would be expected, teh data were strongly affected by two Psyllid insect infestations causing dieback, and further periods of increased water yield. The three Monda catchments were initially regenerated at different seedling densities, but the infestations obscured any differences in water yield which may have resulted from this.
The data from all the subject catchments were able to be aligned along a single regeneration curve using a simple water balance model, which eliminated the influence of differences between the control catchments in comparisons between the paired catchment studies. A general evapotranspiration curve was fitted to the model results, and when subtracted from a mean precipitations value, was found to predict similar long term water yield patterns to the regionally-based Kuczera curve. Differences between the two curves centred on the inclusion of an initial increase in water yield, and a delayed recovery after water yield decline. Further analysis is required before the second of these differences, in particular, may be considered significant.
Results from secondary analyses were as follows. An analysis of changes in low flow duration (LFD) revealed that temporal patterns of LFD differed from water yield patterns only in the driest catchment (Picaninny), where low flows declined more than did overall yield. Declines in soil moisture were observed in Picaninny in the decade following forest clearing, matching our expectations based on water yield data. Forest growth at Picaninny appears to be peaking near the time of maximum water yield decline predicted by the general water yield curve, as would be expected. The growth data from Monda, however, clearly reveal the adverse effects of insect infestation on forest growth. Precipitation interception data at these two catchments essentially matches the growth data, which is also as expected because interception is largely controlled by leaf area index (LAI), itself an indicator of growth.
This report is available for downloading below. Printed copies may be purchased from the Centre Office.
 |
1 Download(s) |
|
|
|
|
|
|
|
|
Centre Office:
CRC for Catchment Hydrology
Dept of Civil Engineering
Building 60
Monash University Vic 3800
Tel: +61 3 9905 2704
Fax: +61 3 9905 5033
|
|
|
