0 100 200 300 400 500 600 700 MURRAY-DARLING BASIN COMMISSION Risks to Shared Water Resources

Impact of the 2003 Alpine Bushfires on Streamflow: Broadscale water yield assessment

December 2007

Prepared by SKM for the Victorian Department of Sustainability and Environment, and the Murray-Darling Basin Commission. Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Published by Murray-Darling Basin Commission Postal Address GPO Box 409, Canberra ACT 2601 Office location Level 4, 51 Allara Street, Canberra City Australian Capital Territory

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This report may be cited as: Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

MDBC Publication No. 21/08

ISBN 978 1 921257 61 2

This project was funded by the Department of Sustainability and Environment, the Murray-Darling Basin Commission and the Gippsland Lakes Taskforce.

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Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Contents

Executive Summary 1

1. Introduction 4

2. Study Catchments 5

3. Modelling Framework 7

4. Streamflow Response Functions for Regrowth Forests 9 4.1 Introduction 9 4.2 Ash Species 11 4.3 Mixed Species 12 4.4 Snowgum 13 4.5 Summary 14 4.6 Adjustment for Catchment Rainfall 15 5. Inputs to BISY Model 22 5.1 Source of Data 22 5.2 Vegetation Type 22 5.3 Forest Age 23 5.4 Fire severity 26 5.5 Mean Annual Rainfall 26 5.6 Gridding Input Data 29 6. Assessment of Forest Response 30 6.1 Response Categories 30 6.2 Results 34 6.3 Conclusions 35 7. Results 38 7.1 Catchment Characteristics 38 7.2 No fire response 39 7.3 Fire Response 42 7.4 Spatial Variation of Results 53 7.5 Sensitivity of Results 57 8. Conclusions 58

9. References 59

PAGE i Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Appendix A Rules for Estimating Forest Age 61 A.1 Nominal age of Ash forest stands based on stand height and growth stage61 A.2 Nominal age of Mixed Eucalypt, Snowgum and other Native Tree forest stands based on stand height and growth stage 61 A.3 Nominal age of forest stands in NSW based on growth stage descriptions62 Appendix B Check of Bias in Inputs 63 B.1 Northern Catchments 63 B.2 Southern Catchments 65 Appendix C BISY Documentation 67 C.1 Description 67 C.2 Inputs 67 C.3 Outputs 70 Appendix D Results at catchment outlet 71 D.1 Northern Catchments 72 D.2 Southern Catchments 79 Appendix E Estimated change in streamflow over time (subject to average climatic conditions) 84 E.1 Northern Catchments 84 E.2 Southern Catchments 87 Appendix F Cumulative streamflow response 90 F.1 Northern Catchments 90 F.2 Southern Catchments 93 Appendix G Spatial Inputs and Outputs 95

PAGE ii

Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Executive Summary

The 2003 bushfires were the most extensive fires seen in Victoria since 1939, burning over a million hectares of National Park and reserves, State Forests and grazing land. As a part of the Department of Sustainability and Environment’s Bushfire Recovery Program, a project was established to predict the magnitude and duration of changes to water quality and quantity available to downstream users as a result of the 2003 alpine bushfire. This document comprises Task 1 of the project and involves a broad scale assessment of the water yield impacts over the whole burnt area of Victoria and selected parts of NSW that drain into the River Murray or Victoria (the Snowy River).

As water use by a forest changes as the forest ages, the streamflow in forested catchments is also affected by the ageing of the forest. Typically, streamflow increases immediately following the destruction of mature forest due to the reduction in interception and water use. The streamflow then decreases as the forest regrows and increases water use. Streamflow response functions for particular forest types were applied to the bushfire affected area to predict the change in streamflow given known tree species and response pattern (“regrowth”, “recovery” or “partial recovery”).

A new model, the Bushfire Impact on Streamflow Yield (BISY) model, was developed to estimate the change in streamflow. The key focus of the modelling approach was the estimation of long term changes in streamflow as a result of the 2003 bushfires. The modelling approach incorporated the streamflow response functions, which allowed changes in water use to be simulated over time. Given the hydrologic response of a species type to fire (ie regrowth, recovery or partial regrowth/recovery), the streamflow response curve modelled by BISY varies. The streamflow response curves for mortality of a species are based upon recorded streamflow data.

High resolution digital imagery of the bushfire affected region, taken two years after the 2003 bushfires, was visually interpreted to gain an understanding of general forest response. Particular combinations of forest type and fire severity were determined as either “regrowth”, “recovery” or “partial recovery” depending on the results of the image interpretation.

Uncertainties regarding the response of Mixed Eucalypt species to fire severity 2 were encountered during the digital imagery interpretation. A ‘Best Estimate’ of response was adopted which assumed that 60% of the forest responded as per the regrowth scenario, and 40% recovered. However, to reflect the uncertainty in the response, upper and lower bounds were also estimated, which assumed that the Mixed Eucalypt and Snowgum response was entirely regrowth or entirely recovered.

The study area was divided into 12 catchments, in order to ensure that all the significant tributaries within the study region were modeled. Additionally, it was imperative to monitor the impact of the bushfires on locations of importance to water resource management.

The results indicate that the typical streamflow response following a fire consists of an initial increase followed by a long-term reduction, rejoining the streamflow response for a no-fire scenario after approximately 100 years. The initial increase in streamflow for the River Murray was predicted to be 1,120 GL and 250 GL for the Gippsland Lakes.

PAGE 1 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

The modelled reductions in streamflow were presented relative to the average streamflow up to 2003 (ie: pre-fire). This allowed the changes due to the bushfire to be expressed as a percentage of mean annual flow and convey the expected change in a form relevant to water resource managers. The magnitude of the maximum reduction was a function of the species type and the fire severity across the catchment.

The maximum reduction in streamflow for the Best Estimate was 692 GL for the River Murray and 155 GL for the Gippsland Lakes, compared to 2003 mean annual flow. The maximum reduction predicted for each catchment is presented in the table below. At all locations, the maximum reduction occurs around 20 to 25 years after the fire.

„ Summary of the estimated maximum reduction in streamflow, relative to 2003 (pre-fire) mean annual flow (MAF) for average climatic conditions

Maximum reduction in streamflow Catchment GL % MAF

Buffalo -26 -5.9 Corryong -26 -16 Dartmouth -320 -20 Kiewa -20 -3 Mitta Mitta (d/s of Dartmouth) -29 -1 Ovens -65 -12 Upper Murray -170 -26

Northern Catchments Other Northern -36 - River Murray (d/s of -692 -10 confluence with Ovens) Dargo -51 -29 Tambo -31 -27 Wongungurra -58 -20 Other Southern -15 - Gippsland Lakes -155 -5 Buchan -74 -53

Southern Catchments Snowy -230 -31 Note: The impact to the Gippsland Lakes includes only the eastern rivers flowing into the Lakes. The western rivers (ie the Thomson Macalister system) have been excluded, as these were not affected by the bushfires.

If there had not been a bushfire in 2003, or any other disturbance to the forest, then the modelling estimated that there would have been a net increase in streamflow over the next 150 years due to the natural aging of the forest. In order to determine the impact of the bushfires on streamflows, the maximum reductions in streamflows were also calculated as the maximum difference between the fire and no fire scenarios. Compared to the anticipated streamflow assuming no fire had occurred, streamflow under the Best Estimate fire scenario was 859 GL less for the River Murray and 195 GL less for Gippsland Lakes. This larger estimate is because there would have been an increase in flows over time as a result of natural forest aging. These responses are presented in the change in streamflow plots below for the Murray and Gippsland Lakes. PAGE 2 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

2000 25 20 1000 15 10 5 0 0 859GL Reduction relative to no-fire scenario -5 -10 Change in Streamflow Change in Streamflow No-fire response tion Mean Annual Flow (%) of -1000 692GL Reduction relative to 2003 conditions (pre-fire) -15 r Lower Bound relative to 2003 (pre-fire) (GL) to 2003 (pre-fire) relative

-20 opo Best Estimate r P Upper Bound -25 -2000 2000 2020 2040 2060 2080 2100 2120 2140 Year

„ Change in streamflow relative to 2003 (pre-fire) for the Murray River downstream of the confluence with the Ovens River

400

10

200 5 nnual Flow(%) A 0 0 195GL Reduction relative to no-fire scenario -5

Change in Streamflow in Streamflow Change -200 155GL Reduction relative to 2003 conditions (pre-fire) No-fire response Lower Bound relative to 2003 (pre-fire) (GL) (pre-fire) 2003 to relative Best Estimate -10 Proportion of Mean Upper Bound -400 2000 2020 2040 2060 2080 2100 2120 2140 Year „ Change in streamflow relative to 2003 (pre-fire) for the Gippsland Lakes

The modelling assumed mean annual climate inputs for every year in the simulation. The actual recorded streamflow over this period will vary due to climate variability and the influence of other factors affecting streamflow such as climate change, future logging or other bushfires.

Information on the within year changes in streamflow were estimated as part of Task 4 of the Bushfires Recovery Program and are reported in a companion document.

PAGE 3 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

1. Introduction

The Department of Sustainability and Environment’s Bushfire Program includes a project aimed at studying the impact of the 2003 Victorian fires on the quality and quantity of water supply for downstream users. Task 1 of this project involves a broad-scale assessment of water yield impacts over the whole burnt area in Victoria and selected parts of NSW, the results of which are presented in terms of annual changes in streamflow. This broadscale assessment will be subsequently refined to capture within-year impacts as part of Task 4.

This report outlines the modelling approach and empirical grounds on which the bushfire impacts on streamflow is assessed. A new model - the Bushfire Impact on Streamflow Yield (BISY) model - was developed to estimate the change in flow. The modelling approach is based on the key principles of the ForestImpact model, which was developed to estimate catchment average impacts of forest management (Munday et al, 2000). For this project, the model has been significantly re-worked in order to enable the impact of the bushfires to be simulated in a spatially explicit way.

The study area was sub-divided into 12 catchments, as described in Section 2. For each of these catchments an annual streamflow response, under both no-fire and fire scenarios, was produced at the catchment outlet, as well as spatially explicit data sets showing change in streamflow across the catchment.

The report is structured in six subsequent sections. Section 2 outlines the reasoning behind the catchment delineation. Section 3 provides a summary of the modelling approach and details the features of the new modelling approach. Section 4 introduces the concept of streamflow response functions, which provide the basis of the model. This section also discusses the key outcomes from research into the impact of forest age on catchment yield and presents the modelling approach to scaling the streamflow response functions for rainfall. Section 5 outlines the way in which the model inputs are generated and the data sets on which they are based. Section 6 details the interpretation of high resolution imagery that provides the basis for the modelling assumptions. Section 7 contains a discussion of the final modelling results for all catchments and the sensitivity of these results to different factors. Finally, Section 8 reaches conclusions based on the study results.

PAGE 4 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

2. Study Catchments

The 2003 bushfires were the most extensive fires seen in Victoria since 1939, burning over a million hectares of National Park and reserves, State forests and grazing land. The burnt region incorporates large areas which drain into a number of key water storages including Hume and Dartmouth Dams and also the Gippsland Lakes.

The study area was divided into fourteen catchments, which includes two ‘catchments’ that combine other small isolated areas affected by the bushfire (referred to as the Other Northern and Other Southern catchments). These fourteen catchments provide the basis for reporting on the outputs from the modelling. The catchments were chosen in order to ensure that all the significant tributaries within the study region are modelled. The basic units used in the catchment delineation were the subcatchments used in the Sustainable Diversions Limits Project1 (Voorwinde et al, 2003).

Another key criteria in the catchment delineation was that the study be able to show the impact of the bushfires on locations of importance to water resource management, for example Dartmouth Dam was selected as the downstream end of one of the catchments. The catchment boundaries were chosen to maximise the percentage area burnt within each area. The resulting catchments are shown in Figure 2-1 and their details are shown in Table 2-1.

„ Table 2-1 Study Catchments

Catchment Name Area (km2) % of Area Burnt Buffalo 1140 34 Corryong 485 76 Dartmouth 3579 90 Kiewa 421 90 Mitta Mitta d/s Dartmouth Dam 652 91 Ovens 1237 62 Upper Murray 2400 82 Northern Catchments Other Northern 807 87 Buchan 849 77 Dargo 533 90 Snowy 9563 32 Tambo 893 67 Southern

Catchments Wongungurra 730 62 Other Southern 251 99 It can be seen in Figure 2-1 that there are some residual burnt out areas which do not form part of the individual catchments. These residual areas are modelled to allow the total impact of the fires on the flows to the River Murray and also the Gippsland Lakes to be estimated. The results for these areas are presented grouped together as "Other Northern" and "Other Southern".

1 As part of this project, each of the Victorian drainage basins were divided into sub-catchments at a spatial scale that is practical for use by water authorities and for which the SDL parameters would be estimated. A total of 1,584 catchments were defined for Victoria.

PAGE 5 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 2-1

PAGE 6 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

3. Modelling Framework

The basis of the broadscale modelling approach is the use of streamflow response curves, which simulate the changes in water use of forests with age. The development of these curves is detailed in Section 4 and is predominantly based on empirical data, although some interpolation has been required.

The modelling tool is based upon the ForestImpact model (Munday et al, 2000) which was originally developed to model the impact of forestry management on streamflow in NSW. It has since been used to simulate management of forestry in the Otways in Victoria (Daamen et al, 2001) and to predict the impact of land use change across a large portion of Victoria and part of South Australia (Daamen et al, 2003). As such, ForestImpact has been used in the context of water yield impacts of land use over areas of similar magnitude to the burnt out area, which is the subject of the current study.

The main limitation of the ForestImpact model with regards to this study is that it is not spatially explicit. Hence, a single representative catchment rainfall over the entire catchment is used and variation in results cannot be seen across the catchment.

For the purposes of this project a new model, Bushfire Impact on Streamflow Yield (BISY) has been developed from the key principles in the ForestImpact model. BISY provides a broad scale assessment of the impact of bushfires on streamflow assuming average annual climatic conditions.

The BISY model has the advantage of spatially varying inputs. It uses a 1 km grid with each grid cell assigned an average for each of the following inputs (see Section 5 for details):

1) Vegetation type 2) Pre-fire forest age 3) Fire severity 4) Mean annual rainfall As a general rule, each grid cell was allocated the input characteristics that are most dominant in the cell. For example a cell with 51% grass and 49% forest would be allocated as a grass grid cell. A check has been made for each catchment to ensure that the assignment of single representative values for each grid has not introduced a bias in the percentage representation of each vegetation type. The methodology for this check is described in Section 5.6. In some cases, grid cells cross catchment boundaries. Where this occurs it is assumed that the grid falls into the catchment in which the majority lies. This approach means that all grid cells will only be counted as part of one catchment and avoids the risk of accounting for cells more than once.

Information on forest age prior to the fire is required as input to the BISY model, and the model then calculates forest age after a fire based on the user-defined hydrologic response to fire. For example, if a vegetation type is defined as regrowth, its hydrologic age is set to zero. For the purposes of this project, forests affected by fires of relatively low severity (ie fire severity ≥3, refer to Table 5-2), were assumed to retain their original age category, as they were expected to regrow a canopy within one year and therefore not have an impact on forest water use and streamflow. Using the defined PAGE 7 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment vegetation type, hydrologic response and calculated post-fire age, BISY then assigns each cell a streamflow response curve. Adjustment is made for rainfall (see Section 4 for details). Further information on the operating assumptions of BISY is provided in Appendix C.

The key focus of this modelling approach is the estimation of long term changes in streamflow resulting from the 2003 fires. The model only simulates the impact of forest regrowth as it is assumed that the regrowth of grassland will occur over a short time span (ie less than one year) and therefore will not impact on the average annual streamflow response.

BISY uses average rainfall data. In reality the yield response of a catchment to bushfires will be dependent on the variability of climate over the modelled period, though the impacts here are assessed on the basis of constant (average) rainfall over the simulation period. Similarly, the changes modelled are only those caused by the 2003 bushfires and do not take into account other exogenous influences such as climate change, future logging, or other bushfires.

PAGE 8 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

4. Streamflow Response Functions for Regrowth Forests

4.1 Introduction The water use of a growing eucalypt forest changes as the forest ages and this also affects streamflow in forested catchments. The link between eucalypt forest age and streamflow is now well described within the literature concerned with Australian forest hydrology. Typically, streamflow increases immediately following the destruction of mature forest by fire or harvest (due to the reduction in forest water use), and then, from year 2 to 20, streamflow decreases as the forest grows back. Typically, eucalypt forest evapotranspiration is at a maximum and streamflow at a minimum between forest ages of 20 and 30 years. After this time streamflow slowly increases again as the forest reaches maturity.

The understanding of the effects of forest age on streamflow in Australia is underpinned by the studies of the Ash forests of the Maroondah catchments in the central highlands of Victoria following the 1939 fires. The Maroondah catchments are characterised by high rainfall (1200-2500 mm per annum), and a cool climate. They are heavily forested, the dominant species type being Eucalyptus regnans or Mountain Ash. The forests also include some Alpine Ash, which is a botanically similar species. These forests will be referred to as Ash forest. Based upon a relatively long series of streamflow data, Langford (1976) developed relationships linking streamflow from Ash catchments to forest age. Kuczera (1985) built upon this by fitting an equation that describes mean annual streamflow as a function of forest age for an Ash forest. The ‘Kuczera curve’ combines the observed hydrologic responses of eight large (14-900 km2) basins to regeneration after wildfires in 1939. The curve is described below in Equation 4-1 and Figure 4-1. Note that this curve does not predict an increase in streamflow after the fire as would be normally expected. This increase is evident in later studies (refer to Section 4.2 and Watson et al., 1999).

(1 ( −− ttD 0 )) Change in Streamflow= ( 0,0min max ( −− 0 )ettDL ) Equation 4-1

Where: Lmax= the maximum reduction in yield= 615 (for MAR = 2000 mm/year) D= decay parameter indicating the rate of change in streamflow = 0.039 (for MAR 2000 mm/year)

to= time at which change in streamflow becomes negative = 2 years (for MAR 2000 mm/year) t= time in years MAR = Mean Annual Rainfall

PAGE 9 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 4-1 Streamflow response function for mountain Ash in the Maroondah catchment with an average annual rainfall of 2000 mm/year (after Kuczera, 1985)

The following sections outline the basic streamflow response curves adopted in the modelling. These streamflow response curves were deemed to be appropriate as a result of visual interpretation of digital imagery of the bushfire area. This imagery was captured 2 years after the bushfire, and provided an ideal opportunity to observe the actual forest response to the fire.

As different species have different sensitivities to fire, a fire that results in mortality in one species may only scorch another. This was observed through the image interpretation in Section 6. In a regrowth scenario, the basic streamflow response ultimately re-sets the forest age to zero. As Ash is a fire sensitive species, the hydrologic response to fires of a high severity will be equivalent to the death of most trees. The Kuczera relationship is therefore appropriate when fire results in a regrowth scenario.

The Kuczera relationship was assumed to also hold for a recovery fire response. In this situation, the forest is considered to continue development as though there was no fire. Hence, any deviation from the Kuczera curve is relatively insignificant in the long term, and the forest ultimately follows the same streamflow response function for the remainder of the forest life.

Note that the effects of fire on tree species other than Ash are not yet fully understood. Thus, the approach adopted here is somewhat pragmatic and based upon a consensus between technical experts. This has been deemed acceptable for this broadscale assessment, where the methods suggested are proposed as an upper and lower limiting response. However, it is recommended that, in particular, the mortality of Mixed Eucalypt and Snowgum species and their scorched hydrologic response should be further investigated through research and monitoring. This could include remote sensing (as per work by Peter Black, Department of Sustainability and Environment , in early 2005), field validation, as well as continued field monitoring and physically based modelling. This refined

PAGE 10 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment understanding of the mortality of these species and their scorched response should then be incorporated into the later stages of the project.

These curves have been derived from the consideration of recorded streamflow and therefore relate to a specific climate. Section 4.6 discusses the adjustment of these curves for mean annual rainfall.

4.2 Ash Species Watson et al (1999) developed an alternative forest age-streamflow relationship to the Kuczera curve. This was also based on data from the Maroondah catchments. The function has four terms to provide a flexible means of interpolating and extrapolating streamflow response to forest regeneration. The functional form of the relationship is shown below in Equation 4-2 and in Figure 4-2.

⎛ −t ⎞ ⎜ ⎟ ⎜ ⎟ e ⎝ tP ⎠ ET= ()cp −− ETETET D AGEe t P

⎛ ⎞ ⎛ −t ⎞ ⎜ ⎟ ⎜ ⎟ ⎛ ⎜ ⎟ ⎞ 2 ⎜ tD ⎟ ()−++ ETETET ⎜ −1⎟ + eET ⎝ ⎠ −1 + ET Equation 4-2 c D M ⎛ −t ⎞ D M ⎜ ⎟ ⎜ ⎟ ⎜ ⎜ ⎟ ⎟ ⎝1 + e⎝ tc ⎠ ⎠ ⎝ ⎠

Where: ETP = Peak evapotranspiration (mm/year)

ETC = Climax evapotranspiration (mm/year)

ETD = Decline Evapotranspiration (mm/year)

ETM = Minimum evapotranspiration (mm/year) T = forest age (years)

tp = time to peak evapotranspiration (years)

tc= time to climax evapotranspiration (years)

tD= time to mdecline evapotranspiration (years)

The curve has four terms and was designed to provide a flexible, controllable means of interpolating long term patterns of variables such as Leaf Area Index, water yield and evapotranspiration. The first term starts at zero, rises rapidly to a peak and declines more gradually back to zero. It represents a peak in estimated evapotranspiration. The second term is one half a sigmoid curve (Zurada, 1992) which starts from zero, rises, and steadies at a constant value. It represents the long term climax evapotranspiration. The third term is a simple exponential decline. It represents the decline from peak evapotranspiration to climax evapotranspiration, which is represented too quickly by the peak evapotranspiration term alone. The final term is a constant, representing the minimum evapotranspiration. The size of the peak, climax, decline and minimum can easily be changed by changing the ET constants. The time to peak, climax and decline can also be changed easily using the t constants. (Watson et al, 1999)

The limitation of this equation is that it was fitted subjectively to the data set and it has a large number of parameters. When the equation is fitted to different data sets the best fit can require some parameters to have arbitrary or inconsistent values.

PAGE 11 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

The two Kuczera and Watson et al curves are compared in Figure 4-2. It can be seen that the Watson form of the streamflow response function is similar to the Kuczera curve except that it predicts a sharp increase in streamflow above the mature forest value in the initial years.

An advantage of the Watson et al curve is that the seven parameters mean that it is flexible and able to be transparently applied to data from different forest types. For this reason the Watson et al curve was selected as the functional form for describing streamflow responses in this project.

Kuczera (1985) and Watson et al (1999) both present functions that can be used to characterise the streamflow response caused by the aging of Ash forests in the same water supply catchments. The parameter values input to Equation 4-2 are given in Table 4-1.

„ Figure 4-2 Streamflow response curve for Ash in the Maroondah catchment (rainfall 2000 mm/year) as derived by Kuczera (1985) and Watson et al (1999)

4.3 Mixed Species In 1999 Sinclair Knight Merz undertook a study for the Ecologically Sustainable Forest Management (ESFM) group looking at the management options for State Forests in NSW (SKM, 1999). As part of this project, two streamflow response curves were developed for Mixed Eucalypt species, one representing conditions in a Northern Forests region and one for a Southern Forests region. The curve for the northern region was developed using results obtained from the Karuah catchments (Cornish and Vertessy, 1998) which have a mean annual rainfall of 1600 mm. The curve for the Southern region was developed using results obtained from the Yambulla/ Wallagaraugh catchments (Cornish, 1991, 1993, 1997) which have a mean annual rainfall of 1000 mm. These curves were based on the effects of logging of mixed Eucalypts, and are therefore appropriate for developing a curve for the effect of a fire resulting in mortality of mixed Eucalypts.

The work undertaken on the ESFM project was refined as part of the Otways Forest Hydrology Project (SKM, 2000) which included an examination of the impact of Mixed Eucalypt forest on streamflow in

PAGE 12 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Victoria. The streamflow response curve adopted for Mixed Eucalypt in the Otways was based on the curve developed for the Southern NSW. This curve was chosen because, although the rainfall in the study catchments is higher than the calibration catchments in Southern NSW, it was anticipated that the shallow soil depths in the Otways would mean that the streamflow response is similar. In addition, the lower temperatures in the Otways would also slow growth rates. As a result, the maximum yield decrease relative to a mature forest was not changed but the time taken to reach the maximum decrease was extended to make it consistent with Mountain Ash.

For this bushfire project, the streamflow response curve developed for the Southern region of NSW will be used as this area adjoins the bushfire study area. This curve is shown in Figure 4-3 and the parameters for this curve is shown in Table 4-1. The mean annual rainfall used for the development of this curve was 1000 mm/year. It can be seen that the streamflow response curve for Mixed Species is slightly different to that for Ash; in particular, the magnitude of the initial increase and subsequent reduction in streamflow is less severe.

„ Figure 4-3 Streamflow response curve for Mixed Species eucalypt forest developed for Southern NSW (SKM, 1999).

4.4 Snowgum A literature search for information on the water use of Snowgums found that there have been very few relevant studies. The Leaf Area Index of plants (and hence plant water use) is known to be closely related to plant water use, information documented in Watson (1999) indicated that the Leaf Area Index of Snowgum is constant at 2.5 after the first five to ten years of growth. In the absence of more accurate data, Peel et al (2000) used the evapotranspiration response function presented as Equation 4-2, to simulate the water use of Snowgum based on Leaf Area Index. Sinclair Knight Merz have fitted Equation 4-2 by eye to the results presented by Peel et al (2000). The resulting curve is shown in PAGE 13 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Figure 4-4 for a catchment with a mean annual rainfall of 2475 mm and the parameter values are given in Table 4-1.

„ Figure 4-4 Streamflow response function for Snowgums by Peel et al (2000).

If more detailed information about the evapotranspiration of Snowgums becomes available this curve could be revised. It is significant to note, however, that the evapotranspiration of the forest is less than half of the annual precipitation. As this is due to the cold climate in which Snowgums grow and their low Leaf Area Index, this result is unlikely to change. However, the effect of understorey species on the water use of a Snowgum forest is still uncertain. Another noteworthy feature of the Peel et al Snowgum curve is that streamflow with respect to mature forest becomes negative after only three years of the tree being planted. This representation suggests that the regrowth of Snowgums is very vigorous.

4.5 Summary The streamflow response functions of various species have been characterised using the relationship shown in Equation 4-2. The form of this curve was chosen for its capacity to simulate a variety of vegetation species. Parameters used to adjust this curve for each of the dominant vegetation types are shown in Table 4-1. A fire that results in a regrowth forest will reset the forest age to zero and these curves can be used to estimate streamflow as a function of the forest age that is equal to the number of years since the fire. Additionally, these response functions also describe the forest response for situations where the forest recovers.

PAGE 14 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Table 4-1 Parameters used to characterise streamflow response curves for Ash, Mixed Species Eucalypt and Snowgum forest

Mixed Species Ash Snowgum Eucalypt Associated Rainfall (mm/year) 2000 1000 2475

ETP (mm/year) 1500 795 1200

tp (year) 34 16.1 5.5

ETc (mm/year) 800 843 925

tc (year) 6 6.8 1.2

ETd (mm/year) 400 -439.7 220

td (year) 60 17.1 100

ETm (mm/year) 300 403.5 250

4.6 Adjustment for Catchment Rainfall 4.6.1 Overview The streamflow response functions for each vegetation type described in the section above describe the effect of forest age on streamflow for a particular rainfall. BISY enables catchments with a range of average annual rainfalls to be modelled by adjusting the curves for rainfall using a relationship developed between rainfall and evaporation for forest and grassland. The approach used is described below.

4.6.2 Forest and Grassland Evapotranspiration A relationship between mean annual rainfall and runoff for forest and grassland was described by Holmes and Sinclair (1986). They examined rainfall/runoff relationships for 19 large catchments in Victoria with with varied vegetation types and mean annual rainfalls ranging between 500 mm and 2,500 mm. They demonstrated a significant difference between the evapotranspiration of grass and eucalypt forest and developed a set of curves to model the mean annual evapotranspiration against mean annual rainfall for forest and grassland. The analysis considered the dominant contributors to the water balance (i.e. rainfall and evapotranspiration) and did not consider other detailed catchment characteristics such as slope and soil which may also influence catchment runoff. This research was supported by Cornish (1989) following analysis of independent data sets.

This early work and other studies were the starting point for a study by Zhang et al (1999). Zhang et al (1999) developed a semi-empirical relationship between mean annual rainfall and evapotranspiration. This relationship is shown in Equation 4-3.

E 1+ w 0 ET P = −1 Equation 4-3 P E ⎛ E ⎞ 1 w 0 ++ ⎜ 0 ⎟ P ⎝ P ⎠

Where: ET = actual annual evapotranspiration (mm/year)

PAGE 15 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

P = precipitation (mm/year)

E0 = potential evapotranspiration (mm/year) w = plant available water coefficient, this represents the ability of plants to access water stored in the root zone for transpiration (-). Zhang et al (1999) suggest that w should range between 0.5 (short grass) and 2 (forest). For bare soil, w represents the water in the soil that can be evaporated, it is expected that this is around 0.1.

Zhang et al (1999) refined Equation 4-3 by replacing E0 with a constant Ez using a large number of data sets from across the world:

Ez 1+ w ET P Equation 4-4 = −1 P E ⎛ E ⎞ 1 w z ++ ⎜ z ⎟ P ⎝ P ⎠

Where: ET = actual annual evapotranspiration (mm/year) P = precipitation (mm/year)

Ez = 1410 (mm/year) for trees and 1100 (mm/year) for grass. w = plant available water coefficient.

Equation 4-4 is used to estimate average annual evapotranspiration of forest and grassland as a function of rainfall (Figure 4-5). These functions are used to adjust the streamflow response (as described below). Note also that it would be possible to use any other similar functions (for example, Vertessy & Bessard, 1999) for the purposes of this adjustment.

PAGE 16 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 4-5 Evapotranspiration versus rainfall for forest and grassland (after Zhang et al., 1999)

4.6.3 Rainfall Transposition Factor The stream flow response functions are applied to any catchment by scaling or transposing the function using the difference between the generalised evapotranspiration curves for forest and grassland (above). It is assumed that:

1) The grassland curve (Figure 4-5) is the minimum evapotranspiration for any land use, and 2) The forest curve (Figure 4-5) represents evapotranspiration of a mature eucalypt forest. The scaling factor is the ratio of the difference between the forest and grass curves at the rainfall of the catchment in question to the difference between the forest and grass curves at the rainfall associated with the response function. For example, let us consider how the Mountain Ash stream flow response function (fitted to data for a catchment with a rainfall of 2000 mm/year) is used in a catchment with a mean annual rainfall of 1500 mm. The response function is multiplied by a transposition factor. The required factor is explained with reference Figure 4-6 and is the difference between the grass and forest curves at a rainfall of 1500 mm/year (y) divided by the difference between the grass and forest curves at a rainfall of 2000 mm/year (x).

PAGE 17 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 4-6 Forest evapotranspiration versus rainfall for forest and grassland (after Zhang et al., 1999). The differences shown as x and y are used to scale the function fitted to a catchment with a rainfall of 2000 mm (x) for use in another catchment with a rainfall of 1500 mm (y)

4.6.4 Limits to the Transposed Streamflow Response Function There are two constraints or bounds to the streamflow response functions that limit the maximum and minimum evapotranspiration of a forest and these constraints are detailed below.

The difference between the grassland curve and the forest curve for a given rainfall gives the maximum possible increase in streamflow when a mature eucalypt forest is harvested or burnt. Using the example in Figure 4-6, the maximum possible increase in streamflow when a mature forest in the study catchment is harvested or burnt would be y and the scaled streamflow response function is limited to this value.

The second constraint is rainfall itself, it is assumed that the forest evapotranspiration is not able to exceed the mean annual rainfall of a given catchment. This means that any calculated increase in forest evapotranspiration that exceeds rainfall is truncated.

4.6.5 Example of Rainfall Adjustment Figure 4-7 shows a plot of the streamflow response functions for Mountain Ash, Mixed Eucalypt and Snowgum species scaled to a common mean annual rainfall of 2000 mm/year using the methodology detailed above. It can be seen in Figure 4-7 that Mountain Ash and Mixed Eucalypt species have a similar minimum streamflow (peak evapotranspiration). In contrast, the scaled Snowgum curve has a significantly lower peak evapotranspiration, this difference is consistent with the observations of Watson et al (see Section 4.4) who attributed the low water use of Snowgums to the cold climate in which they grow and their low Leaf Area Index.

PAGE 18 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

600 Mountain Ash

400 Mixed Species Eucalypt Snow Gum

200

0 0 20406080100120

-200 mature forest (mm/year)

-400 with respect to in streamflow Chnage

-600 Forest Age (years)

„ Figure 4-7 Plot of streamflow response functions scaled for a mean annual rainfall of 2000 mm/year.

Figure 4-7 also shows that the regrowth of Snowgums is considerably faster than that of mountain Ash and Mixed Eucalypt species. It is hoped that this is indicative of the typical effect of fire on Snowgums i.e. the trees are not killed, the leaves are only burnt off. Figure 4-7 also shows that the increase in streamflow to that of a mature forest is much faster for Mixed Eucalypt species than that of Mountain Ash. This can be attributed to the long life span of Mountain Ash which are known to not mature for 300 years. Mixed species eucalypt species are made up of a variety of vegetation types, some of which have shorter lifespan and as such the streamflow response curve will return to a mature forest level at a faster rate.

Figure 4-8, Figure 4-9 and Figure 4-10 show the scaled and bounded streamflow response curves for Mountain Ash, Mixed Eucalypt species and Snowgums respectively.

PAGE 19 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

600

400

200

0 0 20 40 60 80 100 120

-200 1000 mm 1200 mm -400 1400 mm 1600 mm

Streamflow with respect to a mature forest (mm/year) forest mature a to respect with Streamflow 1800 mm -600 2000 mm 2200 mm 2400 mm -800 Forest Age (years)

„ Figure 4-8 Mountain Ash streamflow response curve scaled by mean annual rainfall

600

400

200

0 0 20 40 60 80 100 120

-200 1000 mm 1200 mm -400 1400 mm 1600 mm 1800 mm Streamflow Streamflow withto respect a mature forest (mm/year) 2000 mm -600 2200 mm 2400 mm

-800 Forest Age (years)

„ Figure 4-9 Mixed Eucalypt streamflow response curve scaled by mean annual rainfall

PAGE 20 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

400

300 1400 mm 1600 mm 1800 mm 200 2000 mm 2200 mm 2400 mm 100

0 0 20406080100120

-100 Streamflow with respect to a mature forest (mm/year) forest mature a to respect with Streamflow -200

-300 Forest Age (years)

„ Figure 4-10 Snowgum streamflow response curve scaled by mean annual rainfall

It can be seen in Figure 4-8 and Figure 4-9 that for low rainfalls both Mountain Ash and Mixed Eucalypt species streamflow response functions are significantly truncated, as discussed in Section 4.6.4. This reflects the high water use of these forest types. If water use was unconstrained the functions would estimate a water use larger than rainfall. The impact of this constraint on Snowgums is considerably less due to the lower evapotranspiration rate.

Figure 4-9 shows that the increase in streamflow (in the first two years) for Mixed Eucalypt forest is truncated by the maximum difference in evapotranspiration as explained in Section 4.6.4.

PAGE 21 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

5. Inputs to BISY Model

5.1 Source of Data The basic modelling framework is described in Section 3 and the key inputs for the simulation and the source data are shown in Table 5-1.

„ Table 5-1: Data sets used

Input Source Dataset and description Vegetation Parks & Forest State Forest Resource Inventory 2002 (Sfri02)- Stewardship Victoria, vegetation before the fire – State Forest areas DSE, Victoria Sveg100- vegetation of all areas Dept. Environment & FE_all_ext – vegetation mapping Conservation, NSW Oldgrwth_finl – Eden CRA Old Growth and Eden_map4 – vegetation mapping Forest age Parks & Forest Sfri02- vegetation before the fire – State Forest areas Stewardship Victoria DSE, Victoria Sveg100- vegetation of all areas Dept. Environment & newgstage – Eden CRA Growth Stage Conservation, NSW t_ss_25m – Southern CRA Growth Stage Fire severity Parks & Forest Fsev03 - fire severity classification Stewardship Victoria Dept. Environment & Kosci_Fire_NBR (k0501, k0504, k0203, k0206) Conservation, NSW Preliminary fire index grids Mean annual Bureau of Meteorology Grided rainfall data rainfall Note: CRA Comprehensive Regional Assessment which provide the framework for Regional Forest Agreements.

5.2 Vegetation Type The vegetation in the study area was categorised into four key classes as follows:

„ Mountain Ash

„ Snowgum

„ Mixed Eucalypt

„ Non-tree (modelled as grassland) Figure 5-1 shows the distribution of these vegetation types across the study area.

The development of the streamflow response curves for each of these vegetation types is detailed in Section 4.

The vegetation classifications were based on species data and forest names as provided with the source data sets. Where possible, vegetation types were matched across the Victorian / NSW border for consistency. An outline of the classes is provided below:

„ the “Mountain Ash” class includes all forests dominated by Eucalyptus regnans (commonly known as Mountain Ash) and E. delegatensis (Alpine Ash);

PAGE 22 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ “Snowgum” areas are dominated by Eucalyptus pauciflora;

„ “Mixed Eucalypt Species” are forests dominated by all other Eucalypt species present in the study area;

„ Areas under plantations of Eucalyptus globulus were assigned to the Blue Gum class, which is treated as “Mixed Species” (refer to comment below);

„ Other native trees include a range of mixed non-eucalypt native tree species; and

„ Pine plantations occurring in the study area are predominately growing the species Pinus radiata. Areas designated other native and blue gum were classed as Mixed Species Eucalypt by BISY, as they are considered to have a similar streamflow response. This assumption was considered acceptable as these types cover a small portion of the study area: other native is only 4% of Snowy and blue gum covers only 1% of Kiewa, Buffalo, Buchan and Ovens, 4% of Tambo, 2% of Dartmouth and 6% of Mitta Mitta. This was considered a reasonable assumption given the lack of other information on the streamflow response of these species.

Areas covered by pine plantations were assumed by BISY to not contribute to any changes in yield (ie. "Non-tree"). Again, this assumption was considered acceptable as pine plantations cover a very small portion of the study area, being present only in Buffalo and Ovens as 2% and 3% of the vegetated area respectively.

5.3 Forest Age Forest age before the fire was generated for the Victorian component of the study area by interpreting a series of attributes including the year in which the forest was most recently regenerated, height of forest and growth stage using a set of rules provided by Parks and Forest Stewardship, Victoria. In NSW, broad growth stage descriptions were assigned ages based on the rules applied in Victoria. These rules are provided for Ash, Mixed Eucalypts, Snowgum and other native trees and for all NSW forest types in Appendix A. Non tree areas were given age zero to indicate that forest cover was not present. Pine plantations were attributed as 7 years old. As it was assumed that pine plantations do not contribute to water yield changes, the age of the plantation is not important for the model. However, it was necessary to provide an age greater than zero to differentiate from non tree areas. Figure 5-2 shows how pre-fire vegetation age varies across the study area.

PAGE 23 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 5-1

PAGE 24 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 5-2

PAGE 25 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Fire severity Fire severity for the study area was mapped according to the classified data set provided for Victoria. This data includes a number of classes outlined in Table 5-2. These classes were simplified for the model input grids to classes 1, 2 and fire severity ≥3. This simplification was deemed acceptable as vegetation subject to fire severity ≥3 is assumed to recover within a year and therefore does not impact on average annual streamflow response.

„ Table 5-2 Fire Severity Classes

Fire severity Description 1 Forest Crown Burn (most severe) 2 Forest – Severe Crown Scorch 3 Forest – Moderate Crown Scorch 4 Forest – Light Crown Scorch 5 Treeless – Burnt 6 Treeless – Unclassified

Fire severity was mapped in NSW based upon a reclassification of the fire severity index grids. The fire severity grids provided by Dept. Environment & Conservation, NSW, are the result of the application of the following band ratio to Landsat TM imagey captured following the bush fires:

Normalised Difference Fire Index = (TM Band 4 – TM Band 7) / (TM Band 4 + TM Band 7)

The reclassification was generated to be compatible with the simplified fire severity classes mapped in Victoria and was based upon the best fit of class values for the region of overlap between the Victorian and NSW data sets. An analysis of the correlation between the reclassified NSW grid and the Victorian fire severity data for the region of overlap, indicates that there was an overall 73% accuracy for three classes (1, 2, fire severity ≥3). There is a 92% correlation between the total areas for the simplified two class classification (1, fire severity ≥2).

Figure 5-3 shows how fire severity varies across the study area.

5.4 Mean Annual Rainfall Mean annual rainfall data was obtained using gridded data from the Bureau of Meteorology (BOM, 2000). The mean annual rainfall for the study area (Refer Figure 5-4) shows that there is a significant rainfall gradient with mean annual rainfalls varying from greater than 2250 mm/yr to less than 750 mm/yr, and includes the highest rainfall areas in Victoria.

PAGE 26 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 5-3

PAGE 27 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 5-4

PAGE 28 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Gridding Input Data A 1 km grid was developed for the whole study area and the model was applied to each grid cell. The source data sets were processed as described in Sections 5.2 – 5.5 and were converted to grid datasets using standard GIS processing (ArcInfo). This process of assigning each grid cell to an input data attribute results in the predominant data value occurring in the grid cell being assigned to the cell. As the rainfall source data is a gridded data set, this is a reliable process. However for spatially complex data, such as vegetation type and fire severity, this can result in a bias towards attributes with more consolidated extents. For example, fire severity Class 1 is sparsely distributed and therefore may not be the dominant class in a representative number of grid cells despite compromising a significant proportion of the entire catchment area. A detailed and complex data analysis methodology was undertaken to identify and correct and / or minimise any such bias in the model input data.

Fire severity and vegetation type have the greatest impact on streamflow response, as these factors strongly influence the overall shape of the adopted streamflow response curve. Therefore a check on the proportions of fire severity and vegetation type was undertaken to ensure that the model inputs were consistent with the data provided at a catchment scale.

The initial step in the analysis was to define the actual proportions of each vegetation type and fire severity in each catchment. This was compared with the initial number of grid cells representing each Vegetation / fire severity class. A set of rules for the correction of cell input values were then developed based upon an analysis of the actual catchment proportions versus the observed grid values for fire severity and vegetation type. If a specific fire severity and vegetation type combination was over-represented then the appropriate number of cells of that combination were selected to be re- attributed to a combination which was under-represented.

The selection of cells to be re-attributed was done on the basis of the percentage cover of each vegetation type / fire severity class within each 1 km2 cell. The cells to be re-attributed were selected as having the highest percentage cover of the particular class that was under-represented. This process was restricted to cells in which a direct swap between classes was possible, and therefore cells had to have a significant proportion of the under-represented class to be attributed. If a cell was re-attributed from the non-tree class, the age value was updated for the cell using the mean age of the new vegetation class occurring within that catchment.

Biases were observed in all catchments, and approximately 1 to 4% of cells in each catchment were re-attributed as a result of the analysis. The results of this analysis are presented for each catchment in Appendix B.

PAGE 29 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

6. Assessment of Forest Response

In February 2005, 2 years after the alpine bushfire, high resolution imagery of the area of Victoria affected by the fires was captured for the Department of Sustainability and Environment (DSE). These images provide significant detail of the ground level, in some cases allowing individual tree stands to be seen.

A workshop discussing the visual interpretation of the digital imagery was undertaken with members of the wider project team, including Peter Black, Cain Trist, Greg Day and Pat Lane, and the SKM team. As a result of this meeting, agreement was obtained on the classification of particular classes of vegetation, and their apparent response to fire. Additionally, appropriate terms to describe the fire response were considered, and it was decided that ‘regrowth’ (ie: the forest is hydrologically equivalent to a regenerating forest) or ‘recovered’ (ie the existing forest recovers) responses were to be used.

With this in mind, a sampling strategy for the study area (Victoria) was devised, which ensured that a range of samples within each forest type and fire severity were considered. The imagery was interpreted visually to gain an understanding of the general response patterns, and to ensure that realistic assumptions of forest response were incorporated into the modelling task. This section outlines the image interpretation process undertaken.

6.1 Response Categories A large proportion of the Victorian area burnt by the 2003 Alpine fires was covered by the high resolution imagery (Figure 6-1). This imagery has a resolution of 0.65 m and includes an infrared band, which is used to highlight growing vegetation.

These images, combined with the fire severity, forest type and forest age datasets, were visually sampled to determine the specific forest response to known fire intensities.

A sampling strategy was determined to choose a random sample of sites for various combinations of fire severity and forest type, as outlined in Table 6-1.

„ Table 6-1 Image sampling strategy

Forest type Fire severity Number of Sites Mountain Ash 1 15 Mountain Ash 2 15 Mountain Ash 3 15 Mixed Species / Snowgum 1 30 Mixed Species / Snowgum 2 36 Mixed Species / Snowgum 3 20

PAGE 30 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 6-1 Area covered by the high resolution imagery

The samples were chosen by selecting all the areas that met the forest type and fire severity criteria across the study area. A random number generator was used to choose a sub-set of these for visual interpretation. This resulted in an even spread of samples across the study area.

The imagery was then visually examined and the following criteria assessed:

„ Recovery of canopy;

„ Percentage canopy cover;

„ Presence of epicormic growth;

„ Presence of stags (indication of mortality);

„ Percentage cover of understorey; and

„ Heterogeneity of landuse. These criteria were used to classify the sample area as either ‘regrowth’, ‘partial recovery’ or ‘recovered, to determine the forest response to fire. These classifications are described below.

PAGE 31 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

6.1.1 Regrowth A sample was interpreted as ‘regrowth’ when the forest had very little or no canopy cover and visible stags. It was assumed that forest in this state, even though individual trees may be showing some epicormic growth and may not be dead, would follow a regrowth model of water usage. Figure 6-2 displays examples of regrowth forest samples, as identified in the data set.

Mixed Eucalypt, Fire Severity 2 Infrared Image Visible Image

Ash, fire severity 1 Infrared Image Visible Image

„ Figure 6-2 Regrowth forest samples

PAGE 32 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

6.1.2 Recovered A sample was interpreted as ‘recovered’ when the canopy cover was dense and similar to the pre-fire canopy cover and no stags were evident. It was assumed that forest in this state would follow a model of water usage similar to a pre-existing forest. Figure 6-3 displays recovered forest samples, as identified in the high resolution imagery.

Mixed Eucalypt, fire severity 3 Infrared Image Visible Image

Ash, fire severity 3 Infrared Image Visible Image

„ Figure 6-3 Recovered forest samples

6.1.3 Partially recovered A sample was interpreted as ‘partially recovered’ when canopy cover was evident but was less than the pre-fire canopy cover, and stags and epicormic regrowth were evident. The implications for water

PAGE 33 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment usage are not straightforward but it was assumed that they could be modelled as a combination of the regrowth and recovery responses. Figure 6-4 displays sample images indicating partially recovered forest.

Mixed Eucalypt, fire severity 2 Infrared Image Visible Image

Ash, fire severity 2 Infrared Image Visible Image

„ Figure 6-4 Partially recovered forest samples

6.2 Results The results from the high resolution image interpretation were analysed to determine the most common result from the combinations of forest type and fire severity.

Table 6-2 below summarises the results of the analysis. For Mountain Ash forests burnt by a fire of severity level 1, the majority of the samples indicated a regrowth scenario. This implies that the

PAGE 34 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

following such an intense fire, the hydrologic response of the forest is equivalent to a completely new regrowth forest. Fire severity 2 displayed similar trends, with a regrowth scenario identified. Fire severity 3 did not have as severe an impact on the forest, and the Mountain Ash was able to recover.

For Mixed Species and Snowgum forest, the response to fire was not so clear cut. Fire severity 1 was observed to result in a regrowth response. Fire severity 2 was observed to result in partial recovery of the forest. Some areas of the forest displayed recovery of the canopy, while other areas were completely burnt. After further investigation into the response to this fire severity, it was determined that modelling of the response should reflect the partial recovery of the forest by combining the regrowth and recovery reponses. Consequently, the response scenario of Mixed Species/Snowgum to a fire severity 2 was defined as 60% regrowth and 40% recovery of the forest based upon the balance of results from the interpretation of the imagery. Full recovery of the forest was observed for fire severity 3.

„ Table 6-2 Image interpretation results

Forest type Fire Recovered Partial Regrowth severity Recovery Mountain Ash 1 1 2 12 Mountain Ash 2 4 4 3 Mountain Ash 3 10 1 1 Mixed Species / Snowgum 1 2 4 16 Mixed Species / Snowgum 2 10 10 14 Mixed Species / Snowgum 3 7 5 5

The impact of forest age was examined for fire severity 1. The results indicated that there was no identifiable difference in the forest response.

6.3 Conclusions The availability of high resolution imagery of the alpine bushfire area provided a unique opportunity to observe the forest response to fire, which allowed for an accurate understanding of the overall hydrologic response to fire. The results of the image interpretation are summarised in Table 6-3. The following definitions apply to the response scenarios:

„ Regrowth: In the imagery, the forest had very little or no canopy cover and visible stags. It was assumed that forest in this state, even though individual trees may be showing some epicormic growth and may not be dead, would follow a regrowth model of water usage (that is, the forest would effectively need to regrow as a completely new forest).

„ Recovered: The imagery showed dense canopy cover, similar to the pre-fire canopy cover. No stags were evident. It was assumed that forest in this state would follow a model of water usage similar to a pre-existing forest (that is, the forest would effectively recover to a state similar to that prior to the fire).

„ Partial recovery: Canopy cover was evident in the imagery, but was less than the pre-fire canopy cover. Stags and epicormic regrowth were evident. The implications for water usage are not

PAGE 35 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

straightforward but it was assumed that they could be modelled as a combination of the regrowth and recovery responses.

„ Table 6-3 Assumed post-fire response based upon image interpretation

Fire Severity Tree Species 1 2 3 Mountain Ash Regrowth Regrowth Recovered

60% Regrowth / Mixed Eucalypt Regrowth Recovered 40% Recovered

60% Regrowth / Snowgum Regrowth Recovered 40% Recovered

For each catchment, the results using the fire response assumptions in Table 6-3 have been regarded as the ‘Best Estimate’ of change to streamflow. The responses to fire severities 1 and 3 were easily identified from the digital imagery. However, the partial recovery observed as a result of fire severity 2 was not as clear. Hence, for comparison, upper and lower bounds have also been considered. These show the impact on streamflow resulting from either 100% regrowth of the forest or 100% recovery of the forest in response to a fire with severity 2, and provide bounds on the likely forest response. Thus, three modelling scenarios were considered for each catchment. These are summarised in Table 6-4.

PAGE 36 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Table 6-4 Modelling scenarios

Modelling Fire Mountain Ash Mixed Species Snowgum scenario Severity 1 Regrowth Regrowth Regrowth Lower Bound 2 Regrowth Recovery Recovery 3 Recovery Recovery Recovery 1 Regrowth Regrowth Regrowth Best Estimate 2 Regrowth Partial recovery Partial recovery 3 Recovery Recovery Recovery 1 Regrowth Regrowth Regrowth Upper Bound 2 Regrowth Regrowth Regrowth 3 Recovery Recovery Recovery Note: The various scenarios differ in the Mixed Species and Snowgum response to fire severity 2. Partial recovery was modelled as 60% regrowth / 40% recovered based on the interpretation of the 2005 imagery.

PAGE 37 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

7. Results

7.1 Catchment Characteristics Table 7-1 provides a summary of the key characteristics for all catchments and is referred to in the following sections to explain the variation in the streamflow response curves shown.

„ Table 7-1 Summary of catchment characteristics

Catchment Mean Mean Annual Flow Ash % of % of Vegetated % of Fire Severity Annual Vegetated Area Area (% of Area) Rainfall Area Burnt (mm/year) ML/year mm/year ≤ 20 ≥ 100 1 2 years years Northern Catchments Buffalo 1380 439,000 385 5 5 91 34 1 14 Corryong 1440 204,000 421 20 5 86 76 1 27 Dartmouth 1340 1,590,000 445 12 8 75 90 6 47 Kiewa 2040 595,000 1,410 35 20 61 90 10 32 Mitta Mitta 1410 267,000 410 20 6 85 91 3 33 Ovens 1490 554,000 448 10 9 83 62 1 27 Upper Murray 1310 666,000 277 8 6 69 82 11 33 Other Northern 1540 - - 4 2 92 87 5 22 Southern Catchments Buchan 1170 140,000 165 9 6 38 77 23 29 Dargo 1530 177,000 333 6 6 78 90 6 41 Snowy 800 750,000 78 1 13 36 32 3 10 Tambo 910 114,000 127 8 10 79 67 6 28 Wongungurra 1520 293,000 401 18 2 84 62 5 32 Other 1260 - - 20 1 84 99 5 33 Southern

For the Victorian catchments mean annual flow was derived from the Sustainable Diversion Limits (SDL) project, which was based on 165 selected sites with more than 10 years of record (SKM, 2003). Where SDL catchments corresponded with the catchments defined for this project, then mean annual flow was taken directly from the SDL project.

Where SDL catchments did not coincide, mean annual flows had to be calculated using several SDL catchments. For the catchments, which extended partially into NSW (Snowy and Upper Murray), no SDL data was available and therefore a different method was used. Flow data was collected from gauges throughout these catchments and a relationship was derived between mean annual flow and catchment area. This relationship was used to determine the mean annual flow for the catchment areas defined in this project.

For each catchment a summary of the distribution of vegetation type, pre-fire vegetation age and fire severity, has been generated and is included with the catchment outlet streamflow response curves in Appendix D. Figure 7-1 is an example for the Dargo catchment.

PAGE 38 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Figure 7-1 shows that for Dargo, the majority of vegetation (91%) is Mixed Eucalypt, 78% of vegetation in the catchment is greater than 70 years old and 41% of the catchment was affected by fire severity 2, a severe scorch.

100 100 50

80 80 40

60 60 30 Catchment (%) f 40 40 20 tion o tion r 20 20 10 opo r 0 0 0 P Cumulative (%) of Catchment Proportion Proportion of Catchment (%) Catchment of Proportion 0 40 80 120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Treed Not Light Scorch Light Severe Scorch Mixed Eucalypt

Moderate Scorch Moderate „ Figure 7-1 Dargo: Catchment characteristics

7.2 No fire response In order to assess the change in streamflow due to the bushfires two scenarios were modelled:

1) Change in streamflow assuming no fire had occurred and that forest ageing occurs without further forest disturbance; 2) Change in streamflow allowing for the effects of the 2003 fire and no other forest disturbance. The difference in streamflow between these two scenarios reflects the impact of the 2003 bushfires, and other exogenous influences such as climate change, future logging, or other bushfires not accounted for.

For each catchment, a no-fire streamflow response curve, showing change in streamflow relative to 2003 (pre-fire) mean annual flow, was generated at the outlet (refer Appendix D). Figure 7-2 is an example curve for Dargo.

Considering Figure 7-2, it can be seen that there is a gradual increase in streamflow towards a level that is indicative of mature forest water use. For Dargo, long term streamflow is 23,000 ML or 13% higher than 2003 mean annual flow (MAF).

Table 7-2 summarises the estimated long-term increase in streamflow, assuming no fire, for all catchments.

PAGE 39 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

120000 No-fire response 60

80000 40

40000 20

0 0 Change in Streamflow Streamflow in Change (ML) to 2003 (pre-fire) relative Proportion of Mean Annual Flow (%) Flow Annual Mean of Proportion -20 -40000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

„ Figure 7-2 No fire streamflow response curve for Dargo

„ Table 7-2 Summary of estimated long-term increase in streamflow, relative to 2003 (pre-fire) mean annual flow (MAF), assuming no fire and average climatic conditions

Estimated long term increase for no fire Catchment scenario (>100 years following fire) ML mm % MAF Buffalo 30,000 26 7 Corryong 30,000 61 15 Dartmouth 150,000 42 9 Kiewa 48,000 114 8 Mitta Mitta (downstream of Dartmouth) 35,000 54 13 Ovens 50,000 40 9 Upper Murray 114,000 47 17

Northern Catchments Other Northern 21,000 26 - River Murray (downstream of confluence with Ovens) 478,000 - - Dargo 23,000 43 13 Tambo 17,000 19 15 Wongungurra 46,000 63 16 Other Southern 13,000 59 - Gippsland Lakes 99,000 - - Buchan 39,000 46 28

Southern Catchments Snowy 124,000 13 16 Note: The impact to the Gippsland Lakes includes only the eastern rivers flowing into the Lakes. The western rivers (ie the Thomson Macalister system) have been excluded, as these were not affected by the bushfires.

Comparing Table 7-1 and Table 7-2, it can be seen that the estimated long-term increase in streamflow under a no fire scenario varies with species type and age distribution. Catchments with a young age distribution tend to have a larger estimated increase as the current water use of a young tree is high and can be expected to decline significantly thus increasing streamflow. This is particularly true of Ash, which undergoes a natural thinning process as it matures, resulting in higher streamflows as it gets older. However, Ash also matures more slowly and so takes longer to reach a stable streamflow value. PAGE 40 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Streamflow values are compared in mm, to remove the effect of area. Considering Table 7-2, Kiewa has the highest estimated increase in streamflow, 114 mm. However, this is a small percentage of its mean annual flow, which is very high compared to the other catchments. This large increase in streamflow can be explained by Kiewa's characteristics: the forests in the Kiewa catchment are relatively young, with 39% of trees less than 100 years and 20% less than 20 years, and it also has a high proportion of Ash (35%, refer Table 7-1). In terms of mean annual flow, Buchan has the largest estimated increase at 28%. In absolute terms this increase is of a similar magnitude to other catchments with young vegetation and a fair proportion of Ash, for example Upper Murray, Dargo and Dartmouth (refer Table 7-1). However, as Buchan has a comparatively low mean annual flow, these changes represent a higher proportion of the mean annual flow.

Considering the study area as a whole, and assuming there had been no-fire, it is estimated that in the long-term, streamflow will be 478 GL higher than 2003 mean annual flow to the Murray River and 99 GL higher to the Gippsland Lakes.

It is important to note that although these figures are significant, streamflow is naturally highly variable. Figure 7-3 shows annual streamflow variation for the Dargo catchment.

Considering Figure 7-3, it can be seen that streamflow commonly varies between 50,000 and 250,000 ML/year, with the current average being 177,000 ML/year (refer Table 7-1). Therefore, it would be difficult to detect an increase of 23,000 ML/year within the natural streamflow variation.

500000

450000

400000

350000

300000 Estimated Average in 2100 Average in 2003

250000

200000 Annual Streamflow (ML)Annual Streamflow

150000

100000

50000

0 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Year

„ Figure 7-3 Dargo Annual Streamflow

PAGE 41 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

7.3 Fire Response This section discusses the anticipated change in streamflow resulting from the fire. The results can then be compared to either the ‘no fire’ scenario or pre-fire mean streamflow to determine the net impact of the fire. For each catchment, a post-fire streamflow response curve, showing change in streamflow relative to 2003 (pre-fire) mean annual flow, was generated at the outlet (refer Appendix D). Figure 7-4 is an example curve for Dargo.

Considering Figure 7-4, it can be seen that there is an immediate increase in streamflow following the fire. Streamflow then declines, reaching a minimum value approximately 25 years after the fire. After reaching this minimum, streamflow begins to gradually increase until it rejoins streamflow under the no-fire scenario. This pattern of change in streamflow over time is summarised in 20 year intervals and plotted for each catchment in Appendix E. An example table and plot for Dargo is included as Table 7-3 and Figure 7-4.

PAGE 42 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

120000 No-fire response 60 Lower Bound 80000 Best Estimate 40 Upper Bound 40000 20

0 0

-40000 -20

Change in Streamflow Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -40 relative to (pre-fire) (ML) relative 2003 -80000 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery Proportion of Mean Annual Flow Flow Annual (%) Proportion of Mean c Best Estimate - 60% forest regrowth, 40% forest recovery -60 c Upper Bound - 100% forest regrowth -120000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year „ Figure 7-4 Dargo: Change in streamflow relative to 2003 (pre-fire) for fire and no-fire scenarios

„ Table 7-3 Estimated change in streamflow for Dargo catchment (subject to average climatic conditions)

Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 9 38 58 2020 5 -1 -28 -46 2040 9 3 -20 -35 2060 11 7 -4 -11 2080 12 10 6 3 2100 13 12 10 9 2120 13 12 12 11 2140 13 13 12 12 2160 13 13 13 13 2180 13 13 13 13 2200 13 13 13 13

The change in streamflow allowing for the effects of fire was modelled using three scenarios, as outlined in Section 3.

For each catchment, a post-fire streamflow response curve, showing change in streamflow relative to 2003 (pre-fire) mean annual flow, was generated at the outlet (Appendix D). Figure 7-4 is an example curve for Dargo. The no-fire response is also shown for comparison.

The key points in this streamflow response pattern over time are discussed in the following Sections. These are:

1) the initial increase (Section 7.3.1),

PAGE 43 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

2) the maximum reduction in streamflow (Section 7.3.2), The long-term increase resulting from the no fire scenario is previously discussed in Section 7.2.

7.3.1 Initial Increase In contrast to the no fire scenario, the fire scenarios (Lower Bound, Best Estimate and Upper Bound) show a large increase in streamflow in the initial years (Figure 7-4). This increase is typical following a fire as the fire reduces leaf area, immediately reducing interception and evapotranspiration. Streamflow increases to a value typical of grassland water use. For Dargo, the maximum likely streamflow (from the Best Estimate scenario) immediately after the fire is 68,000 ML or 38% higher than the mean pre-fire streamflow.

Table 7-4 summarises the estimated initial increase in streamflow for all catchments for the Best Estimate case.

The magnitude of the initial increase in streamflow is dependent on the difference between the pre-fire forest evapotranspiration and a grassland evapotranspiration rate at the catchment average rainfall. The pre-fire forest evapotranspiration rate is dependent on the growth stage of the forest. A young growing forest has a higher evapotranspiration rate than a maturing forest and hence lower streamflow. The initial increase in streamflow will therefore be higher for a young forest than a maturing one. Similarly, as regenerating Ash tends to have a higher evapotranspiration rate than other species, a young Ash forest is likely to have a lower pre-fire streamflow value and therefore the initial increase in streamflow following the fire will be greater.

Considering Table 7-4, it can be seen that Buchan has the largest immediate increase in terms of mean annual flow, although in absolute terms this is of a similar magnitude to other catchments. Kiewa has the largest absolute increase (154 mm, Table 7-4). This is reflective of the high proportion of burnt catchment, the high proportion of Ash and the young age distribution within the catchment (refer Table 7-1).

Considering the study area as a whole, the estimated initial increase in streamflow in the year following the fire, compared to 2003 levels, is 1,116 GL for the River Murray, and 250 GL for the Gippsland Lakes. Based on mean annual flows in the Murray and Gippsland Lakes of 6,746 GL/yr and 2,830 GL/yr respectively, this accounts for 16% and 9% of the flow into these areas.

PAGE 44 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Table 7-4 Summary of the estimated initial increase in streamflow resulting from 2003 fire subject to average climatic conditions for the Best Estimate case

Maximum increase in flow relative to 2003 (pre-fire) mean annual flow (MAF) in year Catchment following fire ML mm % MAF Buffalo 41,000 36 9 Corryong 41,000 85 20 Dartmouth 492,000 137 31 Kiewa 66,000 154 11 Mitta Mitta (downstream of Dartmouth) 56,000 86 21 Ovens 106,000 86 19 Upper Murray 268,000 112 40 Other Northern 46,000 - -

Northern Catchments River Murray (downstream of confluence with Ovens) 1,116,000 - 16 Dargo 68,000 127 38 Tambo 56,000 62 49 Wongungurra 99,000 136 34 Other Southern 27,000 105 - Gippsland Lakes 250,000 - 9 Buchan 120,000 141 85

Southern Catchments Snowy 260,000 27 35 Note: The impact to the Gippsland Lakes includes only the eastern rivers flowing into the Lakes. The western rivers (ie the Thomson Macalister system) have been excluded, as these were not affected by the bushfires.

7.3.2 Maximum reduction in streamflow relative to 2003 (pre-fire) From Figure 7-4, it can be seen that the initial increase in streamflow quickly declines until about ten years after the fire, when streamflow under the fire scenario drops below that of the no-fire scenario. This decline continues, until the fire scenario streamflow reaches a minimum around 2020, after which streamflow begins to increase. For Dargo, the minimum streamflow is 3,000 ML or 1.7% below 2003 mean annual flow for the Lower Bound; 51,000 ML or 29% below 2003 mean annual flow for the Best Estimate; and 84,000ML or 47% below the mean annual flow for the Upper Bound. This decline in streamflow after an initial increase is again typical following a fire as the forest begins to regenerate. A regenerating forest utilises more water than a maturing forest, therefore reducing streamflow. After approximately 100 years, the fire scenario curve rejoins the no-fire scenario, indicating that forest regrowth after the fire is reaching maturity.

Table 7-5 summarises the maximum reduction in streamflow, relative to 2003 (pre-fire) mean annual flow, for all catchments for each of the three modelling scenarios.

PAGE 45 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Table 7-5 Summary of the estimated maximum reduction in streamflow, relative to 2003 (pre-fire) mean annual flow (MAF) for average climatic conditions

Maximum reduction in streamflow Catchment Lower Bound Best Estimate Upper Bound ML mm % MAF Year ML mm % MAF Year ML mm % MAF Year Buffalo +4,000 3 +1 2013 -26,000 -22 -5.9 2022 -47,000 -41 -11 2022 Corryong -5,000 -11 -3 2021 -26,000 -53 -16 2022 -39,000 -80 -19 2022 Dartmouth -65,000 -18.1 -4 2022 -320,000 -89 -20 2024 -492,000 -137 -31 2024 Kiewa -10,000 -24 -2 2019 -20,000 -49 -3 2020 -27,000 -65 -5 2020 Mitta Mitta (d/s of Dartmouth) -800 -1 -0.3 2017 -29,000 -44 -1 2022 -47,000 -73 -18 2022 Ovens +900 0.7 0.2 2022 -65,000 -52 -12 2022 -109,000 -88 -20 2024 Upper Murray -50,000 -21 -7 2022 -170,000 -71 -26 2021 -252,000 -105 -38 2024

Northern Catchments Other Northern -6,000 -7 - - -36,000 -45 - - -57,000 -71 - - River Murray (d/s of -131,000 - -2 2021 -692,000 - -10 2022 -1,070,000 - -16 2024 confluence with Ovens) Dargo -3,000 -6 -2 2017 -51,000 -96 -29 2024 -84,000 -158 -47 2024 Tambo -9,000 -11 -8 2017 -31,000 -35 -27 2022 -46,000 -52 -41 2022 Wongungurra -19,000 -26 -7 2025 -58,000 -80 -20 2025 -84,000 -115 -29 2025 Other Southern +600 2 - - -15,000 -59 - - -23,000 -91 - - Gippsland Lakes -30,000 - -1 2022 -155,000 - -5 2024 -237,000 - -8 2024 Buchan -40,000 -48 -29 2022 -74,000 -87 -53 2024 -97,000 -114 -69 2024

Southern Catchments Snowy -142,000 -15 -19 2014 -230,000 -24 -31 2018 -292,000 -31 -39 2020 Note 1: Negative numbers indicate that minimum streamflow is below 2003 mean annual flow, positive numbers indicate the minimum streamflow is above 2003 mean annual flow. Note 2: The impact to the Gippsland Lakes includes only the eastern rivers flowing into the Lakes. The western rivers (ie the Thomson Macalister system) have been excluded, as these were not affected by the bushfires.

PAGE 46 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Table 7-6 shows the proportions of vegetation type affected by fire severity 1 and 2 for each catchment. It can be seen that Buchan could be expected to have the largest maximum reduction in streamflow as it has the greatest proportion of Ash affected by fire severity 1 or 2 combined with Mixed Species and Snowgum affected by fire severity 1 and 2. This is confirmed by Table 7-5, which shows Buchan has the largest decrease in terms of percentage of mean annual flow for all modelled scenarios.

„ Table 7-6 Proportions of vegetation type affected by fire severity 1 or 2 by catchment

Ash affected by Mixed species or Mixed species or fire severity 1 or 2 Snowgum affected Snowgum affected by Catchment (proportion of by fire severity 1 fire severity 1 or 2 vegetated area (proportion of (proportion of (%)) vegetated area (%)) vegetated area (%)) Buffalo 0.9 0.9 13.5 Corryong 6.6 0.6 21.1 Dartmouth 5.0 6.2 48.1 Kiewa 11.9 8.6 29.9 Mitta Mitta 2.7 1.4 15.8 Ovens 4.1 1.0 23.9 Upper Murray 1.7 5.4 23.4 Northern Catchments Other Northern 0.0 0.5 3.4 Buchan 6.0 20.3 47.6 Dargo 1.9 5.9 45.9 Snowy 0.1 2.9 12.2 Tambo 2.4 6.1 35.7 Southern

Catchments Wongungurra 10.5 3.7 26.3 Other Southern 9.2 3.3 29.2

Considering the study area as a whole, for the Best Estimate case, the maximum predicted reduction in streamflow, compared to 2003 levels is 692 GL for the River Murray and 155 GL for the Gippsland Lakes. These changes are displayed in Figure 7-5 and Figure 7-6.

PAGE 47 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

2000000 Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. 25 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery 20 c Best Estimate - 60% forest regrowth, 40% forest recovery 1000000 c Upper Bound - 100% forest regrowth 15 10

5 Flow (%) nnual A 0 0 -5 Mean Mean f -10

Change in Streamflow Change in Streamflow -1000000 No-fire response -15 Lower Bound relative to 2003 (pre-fire) (ML) (pre-fire) to 2003 relative -20 Best Estimate Proportion o Proportion Upper Bound -25 -2000000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

„ Figure 7-5 Change in streamflow relative to 2003 (pre-fire) for the Murray River downstream of the confluence with the Ovens River

400000 Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: 10 c Lower Bound - 100% forest recovery c Best Estimate - 60% forest regrowth, 40% forest recovery 200000 c Upper Bound - 100% forest regrowth 5 nnual Flow (%) A 0 0

-5 Change in Streamflow in Streamflow Change No-fire response tionMean of

-200000 r Lower Bound relative to 2003 (pre-fire) (ML) opo

Best Estimate -10 r P Upper Bound -400000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

„ Figure 7-6 Change in streamflow relative to 2003 (pre-fire) for the Gippsland Lakes

7.3.3 Maximum reduction relative to no fire scenario If there had not been a bushfire in 2003, or any other disturbance to the forest, then the modelling estimated that there would have been a net increase in streamflow over the next 150 years due to the natural aging of the forest. In order to determine the impact of the bushfires on streamflows, the maximum reductions in streamflows were also calculated as the maximum difference between the fire and no fire scenarios. For example, some catchments have relatively large reductions in streamflow in terms of percentage of mean annual flow; however, a decrease of a slightly greater magnitude is expected relative to a no-fire scenario. This is because in the absence of fire, some increase in flows would have been expected due to the natural aging of the forest. Table 7-7 summarises the difference in streamflow between the fire and no-fire scenarios for all catchments.

PAGE 48 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

The difference between the streamflow response functions under the fire and no-fire scenarios at the catchment outlet have been generated for all catchments and are included in Appendix D. An example curve for the Dargo catchment is included in Figure 7-7.

120000 Lower Bound 60 Best Estimate 80000 Upper Bound 40

40000 20

0 0

-40000 -20 Fire Severity 1 results in a Regrowth scenario for all forest types. Difference in Streamflow Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -40 -80000 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery Proportion of Mean Annual Flow (%) betweenfire and no-fireresponse (ML) c Best Estimate - 60% forest regrowth, 40% forest recovery -60 c Upper Bound - 100% forest regrowth -120000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

„ Figure 7-7 Dargo: Difference in streamflow between fire and no-fire scenarios Figure 7-7 shows the difference between streamflow under the no-fire scenario compared to the fire- scenario for the three scenarios for Dargo. As described for Table 7-5, negative numbers indicate that the streamflow is less than the flow expected had there been no fire, while positive numbers indicate the streamflow is greater than the no fire streamflow.

Initially, it can be seen that for the Best Estimate case the streamflow under the fire scenario is approximately 68,000 ML greater than under the no-fire scenario, or 38% of mean annual flow. Streamflow then declines, reaching a minimum value of -62,000 ML or 35% of mean annual flow below the no-fire scenario.

Table 7-7 summarises the key results from the difference between the fire and no-fire response curves for all catchments. Note that as the maximum positive difference between the fire and no-fire scenarios is equal to the increase in flow that occurs immediately after the fire, given in Table 7-5, this has not been included. Table 7-7 therefore gives the maximum negative difference between the fire and no-fire scenarios. It should be noted that the timing of the maximum difference between the fire and no fire scenarios is later than that relative to the 2003 pre-fire conditions (ie: compare the year of maximum reduction relative to streamflow in Table 7-5 to the year of maximum difference between fire and no fire scenario in Table 7-7).

PAGE 49 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Table 7-7 Summary of estimated difference in streamflow between fire and no-fire scenarios subject to average climatic conditions

Maximum reduction in streamflow Lower Bound Best Estimate Upper Bound Catchment ML mm % Year ML mm % Year ML mm % Year MAF MAF MAF Buffalo -6,000 -5 -1 2031 -37,000 -33 -9 2027 -58,000 -51 -13 2027 Corryong -12,000 -24 -6 2036 -32,000 -66 -16 2029 -46,000 -94 -22 2028 Dartmouth -114,000 -32 -7 2034 -368,000 -103 -23 2028 -540,000 -151 -34 2027 Kiewa -20,000 -47 -3 2038 -30,000 -70 -5 2031 -36,000 -86 -6 2031 Mitta Mitta (d/s of Dartmouth) -17,000 -26 -6 2035 -45,000 -69 -17 2029 -63,000 -97 -24 2029 Ovens -22,000 -18 -4 2037 -87,000 -70 -16 2027 -130,000 -106 -24 2027 Upper Murray -91,000 -38 -14 2029 -215,000 -90 -32 2027 -298,000 -124 -45 2027

Northern Catchments Other Northern -14,000 -17 -45,000 -56 -66,000 -82 River Murray (d/s of -296,000 - -4 2031 -859,000 - -13 2027 -1,237,000 - -18 2027 confluence with Ovens) Dargo -12,000 -22 -7 2030 -62,000 -116 -35 2027 -95,000 -178 -54 2026 Tambo -15,000 -17 -13 2036 -37,000 -42 -33 2031 -52,000 -58 -46 2031 Wongungurra -41,000 -56 -14 2032 -79,000 -108 -27 2028 -105,000 -144 -36 2027 Other Southern -600 -2 -17,000 -69 -25,000 -101 Gippsland Lakes -69,000 - 2 2032 -195,000 - -7 2027 -277,000 - -10 2027 Buchan -52,000 -61 -37 2028 -86,000 -101 -61 2027 -109,000 -128 -78 2027

Soutthern Catchments Snowy -69,000 -7 -9 2034 -168,000 -18 -22 2029 -233,000 -24 -31 2031 Note: The impact to the Gippsland Lakes includes only the eastern rivers flowing into the Lakes. The western rivers (ie the Thomson Macalister system) have been excluded, as these were not affected by the bushfires.

PAGE 50 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

The magnitude of the reduction in streamflow as a forest begins to regenerate is dependent on the hydrologic response of a tree to a fire. This response varies with fire severity, vegetation type and pre-fire age distribution. This project considered three possible hydrologic responses; regrowth, recovered and partial recovery (as described in Section 6.3). The combination of these responses as per Table 6-3 has been considered the Best Estimate of streamflow response. For the Best Estimate and Upper Bounds, the Other Northern catchments (combines NSW and Victorian catchments) has the largest negative difference in absolute terms, although Buchan has the greatest difference in terms of mean annual flow. These large differences can be explained by the high proportion of Ash burnt by fire severity 1 or 2 in these catchments (refer Table 7-6).

In cases of regrowth, the hydrologic response resets the tree age to zero. This has the biggest impact on streamflow. Therefore, for the Best Estimate scenario, catchments with large proportions of Mountain Ash affected by fire severity 1 or 2, and Mixed Eucalypts or Snowgum affected by fire severity 1 or 2 can be expected to have the largest reduction in streamflow (and the greatest difference between the fire and no fire scenarios) as these combinations are all assumed to result in at least partial regrowth of the forest.

The Lower Bound case assumes that Mixed Species and Snowgums affected by fire severity 2 will recover. Consequently, under this condition, the greatest change to streamflow will occur in catchments with high proportions of Mountain Ash affected by fire severity 1 or 2, and Mixed Species or Snowgum affected by fire severity 1. Conversely, the Upper Bound scenario assumes all Mixed Species or Snowgum affected by fire severity 2 will result in regrowth. Hence, the greatest impact to streamflow under these conditions will occur in catchments with large proportions of Mountain Ash affected by fire severity 1 or 2, and Mixed Eucalypts or Snowgum affected by fire severity 1 or 2.

For the Lower Bound case, Buchan has the largest reduction in streamflow in both absolute terms and in terms of mean annual flow (refer Table 7-7). As previously discussed, Buchan has the highest proportion of all the catchments burnt by fire severity 1 (refer Table 7-1) and the highest proportion of Ash affected by fire severity 1 or 2 combined with Mixed Eucalypts and Snowgum affected by fire severity 1 (refer Table 7-6). Therefore, a large reduction in streamflow under the fire scenario is expected resulting in a large difference to the no-fire scenario.

In megalitres, Dartmouth has the largest difference in streamflow. This is a function of the size of the catchment and the proportion burnt (90%, Table 7-1).

Considering the whole study area, under the Best Estimate case, the fire is expected to decrease streamflow compared to the no-fire scenario by 859 GL for the River Murray and 195 GL for the Gippsland Lakes. These changes are displayed in Figure 7-8 and Figure 7-9.

PAGE 51 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

2000000 Lower Bound 25 Best Estimate 20 Upper Bound 1000000 15 low low f 10

5 nnual Flow (%) A 0 0 -5 Mean f -10 erence in Stream f f Fire Severity 1 results in a Regrowth scenario for all forest types.

Di -1000000 Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -15 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery -20 c Best Estimate - 60% forest regrowth, 40% forest recovery o Proportion between fire and no-fire response (ML) response no-fire and fire between -25 c Upper Bound - 100% forest regrowth -2000000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year „ Figure 7-8 Expected differences in streamflow between fire and no-fire scenarios for the Murray River downstream of the confluence with the Ovens River

400000 Lower Bound Best Estimate 10 Upper Bound 200000 5 eamflow eamflow nnual Flow (%) nnual r A 0 0 ence in in St ence r -5 Fire Severity 1 results in a Regrowth scenario for all forest types. tionMean of

-200000 r Diffe Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo

c Lower Bound - 100% forest recovery -10 r c Best Estimate - 60% forest regrowth, 40% forest recovery P between fire and no-fire response (ML) c Upper Bound - 100% forest regrowth -400000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

„ Figure 7-9 Expected differences in streamflow between fire and no-fire scenarios for the Gippsland Lakes

Summing the annual difference in streamflow over the entire period provides an indication of the cumulative impacts of the bushfire. Cumulative impacts for the Murray River and Gippsland Lakes are shown in Figure 7-10 and Figure 7-11, while all other catchments are provided in Appendix F. These plots show the long term changes that are likely to occur after a fire, and that the overall impact to the catchments is expected to be quite significant.

PAGE 52 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

20000

0

-20000

-40000

-60000 Lower Bound Best Estimate Cumulative difference in streamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -80000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year „ Figure 7-10 Expected cumulative difference in streamflow between fire and no-fire scenarios for the Murray River downstream of the confluence with the Ovens River

4000

0

-4000

-8000

-12000 Lower Bound Best Estimate Cumulative difference in streamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -16000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

„ Figure 7-11 Expected cumulative differences in streamflow between fire and no-fire scenarios for the Gippsland Lakes catchments

7.4 Spatial Variation of Results The results presented in Sections 6-1 to 6-4 are at the catchment outlet and show the spatial variation in streamflow across the catchment. Spatial variation in inputs and outputs for each catchment is shown in Appendix G. The output grids reflect the predicted difference in streamflow between the fire and no fire scenarios, for the Best Estimate case, at years 0, 25 and 100. Year 0 typically reflects the largest positive difference between the fire and no-fire scenarios, year 25 the largest negative difference and year 100 where the fire and no fire scenarios coincide. Figure 7-12 to Figure 7-14 show these output results for the whole study area.

PAGE 53 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Figure 7-12

PAGE 54 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

„ Figure 7-13

PAGE 55 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Figure 7-14

PAGE 56 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Sensitivity of Results A number of key assumptions have been made in this analysis which may impact on the results. The sensitivity of the results to these assumptions has been discussed in the previous sections, through the inclusion of Lower and Upper Bound modelling scenarios. Based on the interpretation of the high resolution imagery, these Upper and Lower Bounds are not considered likely forest responses. However, they have been included to provide limits on the Best Estimate case. This Best Estimate case was based on the visual interpretation of the digital imagery; however, only a limited number of samples were considered. These were determined to be a reasonable indication of the magnitude of the impacts over the bushfire affected area.

Looking beyond this project, the digital imagery provides a great resource for a number of other applications, and full analysis of the data would allow this resource to be fully utilised.

PAGE 57 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment 8. Conclusions

This report has summarised the approach used in the broad scale assessment of the impact of the 2003 Alpine bushfires on streamflow yield and the results for the defined catchments.

The modelling tool used was the Broad scale Impact on Streamflow Yield (BISY) model. BISY uses streamflow response curves, which simulate the changes in water use with forest age, to model changes in streamflow under different scenarios.

BISY has advantages over the ForestImpact model, (which has been used in previous studies to assess the impact of forest management on streamflow yield), in that it incorporates spatial variability in inputs and produces spatially variable outputs. BISY also enables the user to define the hydrologic response of a species to fire. Therefore, the fire sensitivity and different responses of each species can be accommodated.

Given the hydrologic response of a species type to fire (ie regrowth, recovered or partial regrowth/recovery), the streamflow response curve, defined by BISY varies. The streamflow response curves for mortality of a species are based upon recorded streamflow data. Although there is some uncertainty in the exact parameterisation of these curves, the adopted approach and response curves are well supported by the literature. There is also uncertainty as to the hydrologic response of Mixed Species and Snowgum to high severity fires. The assumptions adopted to cope with these uncertainties were based on the interpretation of digital imagery of the bushfire affected area.

The results indicate that the typical streamflow response following a fire consists of an initial increase followed by a long-term reduction, rejoining the streamflow response for a no-fire scenario after approximately 100 years. The initial increase in streamflow, compared to mean annual flow pre 2003, for the River Murray was predicted to be 1,116 GL and 250 GL for the Gippsland Lakes. The maximum reduction in streamflow for the Best Estimate was 692 GL for the River Murray by 2022 and 155 GL for the Gippsland Lakes by 2024, compared to mean annual flow pre 2003. However, compared to anticipated streamflow assuming no fire had occurred, streamflow under the Best Estimate fire scenario was 859 GL less for the River Murray and 195 GL less for Gippsland Lakes, both occurring by 2027. The differences between these different baselines (ie no fire or mean annual flow pre 2003) is discussed in more detail in Section 7 and the Executive Summary.

For all catchments, the magnitude of the maximum reduction was impacted on by the species type and the fire severity across the catchment. The assumptions made for this study were appropriate for broad scale assessment of the 2003 bushfires impact on water yield and enabled the presentation of the expected direction and magnitude of average annual streamflow changes. Task 4 of the project examines the within-year impacts of the fire on streamflows.

PAGE 58 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment 9. References

Bureau of Meteorology (BOM) 2000, Climatic Atlas of Australian Rainfall, Bureau of Meteorology, Melbourne.

Cornish, P. M. & Vertessey, R. A. 1998., Wateruse by a regenerating eucalypt forest in eastern Australia. Environmental Forest Science. Extended abstract volume of IUFRO Division 8 Conference Proceedings, 19-23 October 1998, Kyoto, Japan pp95-96.

Cornish, P. M. 1989., The effect of radiata plantation establishment and management on wateryields and water quality- a review. Forestry Commission of NSW, Technical Paper No. 49, 53pp.

Cornish, P. M. 1991., Water yields in southeast forests. Report to the Tantawangalo Technical Committee. Forestry Committee of NSW unpublished report. Forestry Commission of NSW, Sydney. April 1991, 28 pp.

Cornish, P. M. 1993., The effects of logging and forest regeneration on water yields in a moist eucalypt forest in New South Wales, Australia, Journal of Hydrology. 150, 301-322.

Cornish, P. M. 1997 Water Yields in the Wallagaraugh River Catchment- a preliminary assessment. Unpublished report prepared for the State Forest of NSW.

Daamen, C.C., Clifton, C., Hill, P.I., Ryan, H., Nathan, R.J. (2003) Modelling the impact of landuse change on regional hydrology. 28th International Hydrology and Water Resources Symposium, 10 - 14 November 2003, Wollongong, NSW

Daamen, C.C., Hill, P.I., Munday, S.C., Nathan, R.J., Cornish, P.M. (2001) Assessment of the Impact of Forest Logging on Water Quantity in the Otway Ranges, MODSIM November 2001.

Holmes, J. W. and Sinclair, J. A., 1986 Streamflow from some afforested catchments in Victoria. Hydrology and Water Resources Symposium, Griffith University, Brisbane, 25-27 November 1986, oo 214-218.

Kuczera, G. A. 1985., Prediction of water yield reductions following a bushfire in Ash- Mixed Species Eucalypt Forest. Melbourne Metropolitan Board of Works, Water Supply Catchment Hydrology Research, Rep. No. MMBW-W-0014

Langford, K. J., 1976. Change in yield of water following a bushfire in a forest of Eucalyptus reganas. Journal of Hydrology, 29: 87-114.

Munday, S., Nathan, R., Daamen, C. and Cornish, P., 2001. Development and Application of an Operations Model to Assess the Impact of Plantation Forestry on Water Yields. ModSim 2001, International Congress on Modelling and Simulation. ANU, Australia.

Peel, M., Watson, F., Vertessy, R., Lau, A., Watson, I., Sutton. M. & Rhodes, B., 2000., Predicting the water yield impacts of forest disturbance in the Maroondah and Thomson catchments using the Macaque model. CRC for Catchment Hydrology Technical Report 00/14.

PAGE 59 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Sinclair Knight Merz, 1999 ESFM Project Water Quality and Quantity for the Upper and Lower North East, Southern RFA Regions, report to the Department of Urban Affairs and Planning, NSW.

Sinclair Knight Merz, 2000 Impact of Logging Practices on Water Yield and Quality in the Otway Forests Final report to Vic Gov.

Sinclair Knight Merz, 2003 Sustainable Diversions Limit Project: Estimation of Sustainable Diversion Limit Parameters over Winterfill Periods in Victorian Catchments Final report to the Department of Sustainability and Environment.

Vertessy, R. A & Bessard, Y., 1999, Anticipating the negative hydrologic effects of plantation expansion: results from a GIS based analysis on the Murrumbidgee basin. Croke, J. & Lane, P. (eds) Forest management for water quality and quantity. Proceeding of the second forest erosion workshop. May 1999. Cooperative Research Centre for Catchment Hydrology, Report, No. 99/6 Monash University, Victoria 69pp

Voorwinde, L, Nathan, R & Hansen, W 2003, "Estimation of the sustainable winter diversions in ungauged Victorian catchments’ in the 28th International Hydrology and Water Resources Symposium, 10-14 November 2003, Wollongong, NSW. The Institution of Engineers, Australia.

Watson, F. G. R., Vertessy, R. A., McMahon, T. A., Rhodes, B. G. & Watson, I. S, 1999, The Hydrologic Impacts of Forestry. CRC for Catchment Hydrology, Rep. 99/1.

Zhang, L., Dawes, W. R & Walker, G. R., 1999, Predicting the effect of vegetation changes on catchment average water balance. Cooperative Research Centre for Catchment Hydrology, Technical Report, No. 99/12, Monash University, Victoria, Australia. 35pp

Zurada, J.M.1992, Introduction to artificial neural systems. West Pub. Co., St. Paul, USA, 683 pp.

PAGE 60 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment Appendix A Rules for Estimating Forest Age

A.1 Nominal age of Ash forest stands based on stand height and growth stage

Growth Stage Stand Nominal Age Nominal Year of Height (m) (2002) Origin Regenerating N/A 9 1993 Early Mature N/A 28 1974 Regrowth < 25 28 1974 Regrowth 25 44 1958 Regrowth 31 55 1947 Regrowth 34 55 1947 Regrowth 35 - 45 56 1946 Regrowth > 45 63 1939 Early Mature N/A 69 1933 Mature N/A 74 1928 Late Mature N/A 124 1878 Senescent N/A 124 1878 Unevenaged N/A 124 1878

A.2 Nominal age of Mixed Eucalypt, Snowgum and other Native Tree forest stands based on stand height and growth stage

Growth Stage Stand Nominal Age Nominal Year of Height (m) (2002) Origin Undefined 0 3 1999 Regenerating N/A 9 1993 Early Mature 18 16 1984 Early Mature 21 17 1985 Regrowth < 25 34 1968 Regrowth 25 48 1954 Early Mature 25 56 1946 Regrowth > 30 64 1938 Early Mature > 25 89 1913 Mature N/A 104 1898 Non-regrowth < 28m N/A 104 1898 Late Mature N/A 124 1878 Senescent N/A 124 1878 Unevenaged N/A 124 1878

PAGE 61 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

A.3 Nominal age of forest stands in NSW based on growth stage descriptions

Growth stage Nominal age (years) Old growth 120 Old forest 120 Rainforest 120 Mature 100 Young forest 20 Recently disturbed 5

PAGE 62 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment Appendix B Check of Bias in Inputs

B.1 Northern Catchments Buffalo Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 58 40 50 Ash 1 1 0 0 Ash 2 10 9 10 Ash 3 or less severe 44 35 44 Mixed Eucalypt 1 10 1 10 Mixed Eucalypt 2 134 162 143 Mixed Eucalypt 3 or less severe 868 882 868 Snowgum 1 0 0 0 Snowgum 2 1 0 0 Snowgum 3 or less severe 12 8 12

Corryong Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 33 27 27 Ash 1 2 0 0 Ash 2 28 34 32 Ash 3 or less severe 61 53 62 Mixed Eucalypt 1 5 0 3 Mixed Eucalypt 2 89 100 91 Mixed Eucalypt 3 or less severe 246 252 250 Snowgum 1 0 0 0 Snowgum 2 10 5 9 Snowgum 3 or less severe 13 16 13

Dartmouth Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 669 659 655 Ash 1 11 1 10 Ash 2 170 177 170 Ash 3 or less severe 210 171 205 Mixed Eucalypt 1 185 82 184 Mixed Eucalypt 2 1239 1624 1332 Mixed Eucalypt 3 or less severe 814 621 769 Snowgum 1 37 20 37 Snowgum 2 169 189 169 Snowgum 3 or less severe 78 38 51

PAGE 63 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Mitta Mitta Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 626 622 622 Ash 1 1 0 0 Ash 2 33 32 34 Ash 3 or less severe 92 94 97 Mixed Eucalypt 1 15 8 16 Mixed Eucalypt 2 171 190 175 Mixed Eucalypt 3 or less severe 290 287 289 Snowgum 1 2 2 2 Snowgum 2 7 3 3 Snowgum 3 or less severe 5 4 4

Ovens Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 162 147 149 Ash 1 3 0 1 Ash 2 50 65 50 Ash 3 or less severe 64 40 64 Mixed Eucalypt 1 11 1 9 Mixed Eucalypt 2 240 285 263 Mixed Eucalypt 3 or less severe 682 682 682 Snowgum 1 5 1 4 Snowgum 2 21 22 21 Snowgum 3 or less severe 6 1 1

Upper Murray Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 1739 1723 1719 Ash 1 4 0 0 Ash 2 64 64 64 Ash 3 or less severe 108 107 107 Mixed Eucalypt 1 193 150 193 Mixed Eucalypt 2 625 692 630 Mixed Eucalypt 3 or less severe 946 977 975 Snowgum 1 17 6 13 Snowgum 2 53 50 49 Snowgum 3 or less severe 33 14 36

Kiewa Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 30 31 31 Ash 1 5 1 5 Ash 2 45 45 45 Ash 3 or less severe 98 98 98 Mixed Eucalypt 1 0 0 0 Mixed Eucalypt 2 28 23 25 Mixed Eucalypt 3 or less severe 95 86 89 Snowgum 1 36 30 36 Snowgum 2 57 83 65 Snowgum 3 or less severe 27 24 27

PAGE 64 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Other North Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 5252 5251 5249 Ash 1 0 0 0 Ash 2 4 1 2 Ash 3 or less severe 29 30 30 Mixed Eucalypt 1 26 21 25 Mixed Eucalypt 2 170 152 171 Mixed Eucalypt 3 or less severe 489 520 494 Snowgum 1 2 1 2 Snowgum 2 6 3 6 Snowgum 3 or less severe 16 15 15

B.2 Southern Catchments Buchan Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 3 10 10 Ash 1 37 30 37 Ash 2 14 9 12 Ash 3 or less severe 25 17 25 Mixed Eucalypt 1 160 163 160 Mixed Eucalypt 2 204 220 207 Mixed Eucalypt 3 or less severe 341 342 335 Snowgum 1 8 5 6 Snowgum 2 16 16 16 Snowgum 3 or less severe 9 5 9

Dargo Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 3 0 3 Ash 1 3 0 3 Ash 2 7 5 7 Ash 3 or less severe 19 9 19 Mixed Eucalypt 1 31 15 31 Mixed Eucalypt 2 207 265 207 Mixed Eucalypt 3 or less severe 243 221 243 Snowgum 1 0 0 0 Snowgum 2 4 2 4 Snowgum 3 or less severe 10 10 10

PAGE 65 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Snowy Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 3514 3986 3922 Ash 1 2 2 2 Ash 2 11 7 9 Ash 3 or less severe 64 38 58 Mixed Eucalypt 1 238 202 236 Mixed Eucalypt 2 725 718 736 Mixed Eucalypt 3 or less severe 3797 3538 3424 Snowgum 1 29 16 25 Snowgum 2 92 66 85 Snowgum 3 or less severe 388 287 363

Tambo Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 89 88 88 Ash 1 8 4 6 Ash 2 13 4 13 Ash 3 or less severe 34 22 34 Mixed Eucalypt 1 46 31 46 Mixed Eucalypt 2 221 290 225 Mixed Eucalypt 3 or less severe 365 347 364 Snowgum 1 2 1 2 Snowgum 2 9 1 9 Snowgum 3 or less severe 4 2 4 Wongungurra Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 5 5 4 Ash 1 9 4 9 Ash 2 69 81 68 Ash 3 or less severe 58 38 54 Mixed Eucalypt 1 25 12 25 Mixed Eucalypt 2 142 171 152 Mixed Eucalypt 3 or less severe 400 404 400 Snowgum 1 3 0 2 Snowgum 2 14 12 13 Snowgum 3 or less severe 7 4 4

Other South Actual Uncorrected Corrected Vegetation Type Fire Severity Number Number Number Grassland 4 6 6 Ash 1 3 3 3 Ash 2 19 19 19 Ash 3 or less severe 25 21 25 Mixed Eucalypt 1 8 9 8 Mixed Eucalypt 2 61 59 61 Mixed Eucalypt 3 or less severe 118 122 117 Snowgum 1 0 0 0 Snowgum 2 1 1 1 Snowgum 3 or less severe 1 0 0

PAGE 66 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment Appendix C BISY Documentation

C.1 Description The Bushfire Impact on Streamflow Yield (BISY) model provides a broadscale assessment of the impact of bushfires on streamflow assuming average annual climatic conditions. It has been developed to investigate the effects of the 2003 bushfires in Victoria.

BISY assumes that there are 3 possible hydrologic responses for a forest affected by fire and the selection of the response depends on both the forest type and forest age:

Response Description Individual trees may or may not be killed, however the overall forest response will be Regrowth Forest hydrologically similar to a regrowth forest. The fire has no effect on the water use of the forest. In the long term, the Recovered Forest hydrological conditions are equivalent to those likely if the original forest recovered completely. 60% of the forest is considered to be consistent with a regrowth scenario. In the long 60% regrowth forest term, the water use of this component is equivalent to that observed in a forest 40% recovered forest made up of new trees. The remaining 40% of the forest is not significantly affected by the fire, and the hydrology is similar to that of a recovered forest.

The BISY model uses a 1 km grid, with each grid cell assigned a 1 km2 average for each of the following inputs:

„ Vegetation type

„ Forest age

„ Mean annual rainfall Each cell is then assigned a time series of streamflow response from the date of the fire according to its vegetation type, fire severity, and rainfall.

C.2 Inputs BISY requires the following inputs:

1) Response Parameters File: Parameters of stream flow response functions 2) No. Rows in input matrix files 3) No. Columns in input matrix files 4) Annual Rainfall file 5) Vegetation Type File 6) Forest Age File 7) Fire Severity File 8) Response Parameters to Fire File These are described below.

PAGE 67 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

C.2.1 Response parameters File The parameters of the streamflow response function are entered in this file for five forest types (see Table below). For each forest type seven parameters are required (as described by Watson et al., 1999) and also the annual rainfall that is associated with the function. These functions are adjusted for actual rainfall in each 1 km2 .

Row Number Vegetation Type Description Also ‘BISY Vegetation Type Number’ 1 Ash 2 Mixed Eucalypt 3 Snowgum 4 Pine Plantation 5 Blue Gum Plantation 6 Grassland

Note that BISY version 7 allows for up to 20 different vegetation types in the response parameters file. Only parameters for the first five types (above) are defined as default. The user can manually input the rest. Note that a fire in grassland results in effectively no change in streamflow quantity, therefore grassland is effectively ignored in the BISY model (zero streamflow response).

C.2.2 Rainfall File This file provides input for average annual rainfall in each 1 km2 grid square.

C.2.3 Vegetation Type File This file maps the vegetation type distribution for each 1 km2 grid square.

Currently, BISY uses a different vegetation type numbering system to the input files (refer to the Table below). BISY simplifies the input vegetation types into either BISY type 1,2,3 or 6. BISY types 4 and 5 both relate to plantation forest, which is not used in the input files.

PAGE 68 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Input Vegetation Type No. Vegetation Type Description BISY Vegetation Type No. 1 Undefined 6 2 Snowgum 3 3 Mixed Eucalypt 2 4 Ash 1 5 Blue Gum 2 6 Not Treed 6 7 Other Native Trees 2 8 Pinus 6 9 Other Trees (not native) 6

C.2.4 Forest Age File This file maps the pre-fire forest age distribution for each 1 km2 grid square.

C.2.5 Fire Severity File This file maps fire severity across the catchment for each 1 km2 grid square. The following codes are used:

Fire Severity Fire Severity Code Forest - Crown Burnt 1 Forest - Severe Crown Scorch 2 Forest - Moderate Crown Scorch 3 Forest - Light Crown Scorch 4 Treeless – Burnt 5 Treeless – Unclassified 6 Unclassified 7

C.2.6 Response Parameters to Fire File This file defines the hydrologic response to fire, i.e. (1) killed, (2) scorched or (3) (no effect) for each vegetation type subjected to each different fire severity - see table below. A streamflow response curve for each of the hydrologic scenarios can then be derived for each vegetation type, using the factors in the response parameter file.

PAGE 69 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Column No. Description 1 Row No. 1 Ash Currently only the first three lines of 2 Mixed Eucalypt this file are read. These correspond to 3 Snowgum BISY vegetation types 1-3. Input vegetation types are allocated a BISY vegetation type as per the Table above. Note that BISY veg type 6 (grassland) is effectively ignored and therefore is not allocated a row in the response parameters to fire file. Similarly, BISY veg types 4 and 5 are not found in the input file and are therefore not allocated a row. 2 Critical Age A different streamflow response curve may be assigned for trees less than and greater than the critical age. 3 If a tree is scorched (hydrologic response 2), number of years the linear response function applies before the tree rejoins the water use of a forest unaffected by fire. 4-11 Indicate which hydrologic 1 Reset to forest age to zero response to use for the 7 2 Linear response function difference fire severities for trees less than the critical age. 3 No effect of fire 12-19 Indicate which hydrologic 1 Reset to forest age to zero response to use for the 7 2 Linear response function difference fire severities for trees greater than the critical age. 3 No effect C.3 Outputs The following output files are generated:

1) Outfile.dat – The outfile contains 2 sets of output. The first assumes that no fire has occurred, the second assumes a fire of severity as defined in the fire severity input file. Each set of output contains the following:

„ Streamflow Response Functions – note these are numbered according to BISY vegetation type (as per the Response parameter file)

„ All Input files

„ Grid age at start, 25, 50 and 200 years

„ Rainfall adjustment factor

„ Maximum flow reduction

„ Streamflow Response change in flow with respect to grassland 2) Outgrids 1-4.dat – These files list the change in streamflow after 0, 25, 50 and 100 years in matrix form across the catchment, assuming no fire at the start of the model run. 3) Outgrids 5-8.dat - These files list the change in streamflow after 0, 25, 50 and 100 years in matrix form across the catchment, assuming the fire occurred at the start of the model run.

PAGE 70 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment Appendix D Results at catchment outlet

The following Figures depict:

1) Change in streamflow compared to 2003 mean annual flow under a fire and no-fire scenario for the Best Estimate, as well as the Lower and Upper Bounds at the catchment outlet; 2) Difference in streamflow between a fire and no-fire scenario for the Best Estimate, as well as the Lower and Upper Bounds at the catchment outlet; 3) A snapshot of catchment characteristics.

PAGE 71 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Northern Catchments D.1.1 Buffalo 80000 No-fire response Lower Bound 15 Best Estimate 40000 Upper Bound 10

5 nnual(%) Flow A 0 0

-5

Change in Streamflow -40000 Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -10

relative to 2003 (pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery c Best Estimate - 60% forest regrowth, 40% forest recovery -15 Proportion of Mean c Upper Bound - 100% forest regrowth -80000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

80000 Lower Bound 15 Best Estimate Upper Bound 40000 10

5 nnual Flow (%) A 0 0

-5

Fire Severity 1 results in a Regrowth scenario for all forest types.

Difference in Streamflow in Streamflow Difference -40000 Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -10 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery c Best Estimate - 60% forest regrowth, 40% forest recovery of Mean Proportion between fire and no-fire response (ML) -15 c Upper Bound - 100% forest regrowth -80000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 100 100 80

80 80 60 60 60 40 40 40

Cumulative 20 20 20

0

Proportion of Catchment (%) 0 0 Proportion of Catchment (%) Proportion of Catchment (%) 0 40 80 120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Mixed Eucalypt

Moderate Scorch Moderate

PAGE 72 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.1.2 Corryong

60000 No-fire response Lower Bound 25 Best Estimate 40000 Upper Bound 20 15

20000 10 nnual Flow(%) A 5

0 0

-5

Change in Streamflow Fire Severity 1 results in a Regrowth scenario for all forest types. -20000 Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -10 relative to 2003 (pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery c Best Estimate - 60% forest regrowth, 40% forest recovery -15 Proportion of Mean c Upper Bound - 100% forest regrowth -40000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

80000 Lower Bound Best Estimate 30 Upper Bound 40000 20

10 nnual (%) Flow A 0 0

-10

-40000 Fire Severity 1 results in a Regrowth scenario for all forest types. Difference in Streamflow -20 Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery

-30 Proportion ofMean c between fire and no-fire response (ML) Best Estimate - 60% forest regrowth, 40% forest recovery c Upper Bound - 100% forest regrowth -80000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 80 100 40

80 60 30 60 40 20 40

20 Cumulative 10 20

0

Proportion of Catchment (%) 0 0 Proportion of Catchment (%) Proportion of Catchment(%) 0 40 80 120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Mixed Eucalypt

Moderate Scorch

PAGE 73 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.1.3 Dartmouth 800000 50 No-fire response 40 Lower Bound Best Estimate 30 400000 Upper Bound 20 10 0 0 -10 -20 Change in Streamflow

Fire Severity 1 results in a Regrowth scenario for all forest types. tionof Mean Annual Flow (%)

-400000 r Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -30 relative to 2003 (pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery r -40 P c Best Estimate - 60% forest regrowth, 40% forest recovery c Upper Bound - 100% forest regrowth -800000 -50 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

800000 50 Lower Bound Best Estimate 40 Upper Bound 30 400000 20

eamflow eamflow 10 r 0 0 -10 ence in St ence r -20

Fire Severity 1 results in a Regrowth scenario for all forest types. tionMeanof Annual Flow(%)

Diffe -400000 r Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -30 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery r -40 P between fire and no-fire response (ML) response no-fire and fire between c Best Estimate - 60% forest regrowth, 40% forest recovery c Upper Bound - 100% forest regrowth -800000 -50 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 80 100 50

60 80 40 60 30 40 40 20

20 Cumulative 20 10

0

Proportion of Catchment (%) Catchment of Proportion 0 0 Proportion of Catchment (%) Proportion of Catchment (%) 04080120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Severe Mixed Eucalypt Mixed

Moderate Scorch Moderate

PAGE 74 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.1.4 Kiewa 80000 No-fire response Lower Bound Best Estimate 20 Upper Bound 40000 10 nnual(%) Flow A 0

0 -10

Change in Streamflow Streamflow in Change Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. relative to 2003(pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: -20 c Lower Bound - 100% forest recovery c Best Estimate - 60% forest regrowth, 40% forest recovery Proportion of Mean c Upper Bound - 100% forest regrowth -40000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

80000 Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery 20 c Best Estimate - 60% forest regrowth, 40% forest recovery c Upper Bound - 100% forest regrowth 40000 10 nnual Flow(%) A 0

0 -10 Difference in Streamflow Lower Bound -20 Best Estimate Proportion of Mean

between fire and no-fire response (ML) response no-fire and fire between Upper Bound -40000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 40 100 40

80 30 30 60 20 20 40

10 Cumulative 10 20

0

Proportion of CatchmentProportion of (%) 0 0 Proportion of Catchment (%) Proportion of Catchment(%) 0 40 80 120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Mixed Eucalypt

Moderate Scorch

PAGE 75 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.1.5 Mitta Mitta 80000 No-fire response Lower Bound Best Estimate 20 40000 Upper Bound 10 nnual(%) Flow A 0 0

-10

Change in Streamflow Streamflow in Change -40000 Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. relative to 2003(pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: -20 c Lower Bound - 100% forest recovery c Best Estimate - 60% forest regrowth, 40% forest recovery Proportion of Mean c Upper Bound - 100% forest regrowth -80000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

80000 Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery 20 c Best Estimate - 60% forest regrowth, 40% forest recovery 40000 c Upper Bound - 100% forest regrowth 10 nnual Flow(%) A 0 0

-10 -40000 Difference in Streamflow Lower Bound -20 Best Estimate Proportion of Mean

between fire and no-fire response (ML) response no-fire and fire between Upper Bound -80000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 80 100 40

80 60 30 60 40 20 40

20 Cumulative 10 20

0

Proportion of CatchmentProportion of (%) 0 0 Proportion of Catchment (%) Proportion of Catchment(%) 0 40 80 120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Mixed Eucalypt

Moderate Scorch

PAGE 76 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.1.6 Ovens 200000 No-fire response Lower Bound 30 Best Estimate Upper Bound 20 100000

10

0 0

-10 Change in Streamflow

Fire Severity 1 results in a Regrowth scenario for all forest types. tionof Mean Annual Flow (%)

-100000 r Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -20

relative to 2003 (pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery r c Best Estimate - 60% forest regrowth, 40% forest recovery -30 P c Upper Bound - 100% forest regrowth -200000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

200000 Lower Bound 30 Best Estimate Upper Bound 20 100000

10 eamflow eamflow r 0 0

ence in St ence -10 r Fire Severity 1 results in a Regrowth scenario for all forest types. tionMeanof Annual Flow(%)

Diffe -100000 r Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -20 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests:

c opo Lower Bound - 100% forest recovery r

c Best Estimate - 60% forest regrowth, 40% forest recovery P between fire and no-fire response (ML) response no-fire and fire between -30 c Upper Bound - 100% forest regrowth -200000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 100 100 40

80 80 30 60 60 20 40 40

Cumulative 10 20 20

0

Proportion of Catchment (%) Catchment of Proportion 0 0 Proportion of Catchment (%) Proportion of Catchment (%) 04080120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Severe Mixed Eucalypt Mixed

Moderate Scorch Moderate

PAGE 77 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.1.7 Upper Murray 400000 No-fire response Lower Bound 60 Best Estimate Upper Bound 40 200000

20

0 0

-20 Change in Streamflow

Fire Severity 1 results in a Regrowth scenario for all forest types. tionof Mean Annual Flow (%)

-200000 r Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -40

relative to 2003 (pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery r c Best Estimate - 60% forest regrowth, 40% forest recovery -60 P c Upper Bound - 100% forest regrowth -400000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

400000 Lower Bound 60 Best Estimate Upper Bound 40 200000

20 eamflow eamflow r 0 0

ence in St ence -20 r

Fire Severity 1 results in a Regrowth scenario for all forest types. tionMeanof Annual Flow(%)

Diffe -200000 r Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -40

Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery r P

between fire and no-fire response (ML) response no-fire and fire between c Best Estimate - 60% forest regrowth, 40% forest recovery -60 c -400000 Upper Bound - 100% forest regrowth 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 100 100 40

80 80 30 60 60 20 40 40

Cumulative 10 20 20

0

Proportion of Catchment (%) Catchment of Proportion 0 0 Proportion of Catchment (%) Proportion of Catchment (%) 04080120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Severe Mixed Eucalypt Mixed

Moderate Scorch Moderate

PAGE 78 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.2 Southern Catchments D.2.1 Buchan 150000 Fire Severity 1 results in a Regrowth scenario for all forest types. 100 Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: 80 c Lower Bound - 100% forest recovery 100000 c Best Estimate - 60% forest regrowth, 40% forest recovery c Upper Bound - 100% forest regrowth 60

50000 40 20

0 0

-20

Change in Streamflow No-fire response tionof Mean Annual Flow(%) r -50000 Lower Bound relative to 2003 (pre-fire) (ML) -40 opo

Best Estimate r P Upper Bound -60 -100000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

200000 140 Lower Bound 120 Best Estimate 100 Upper Bound 80 100000 60 40 eamflow eamflow r 20 0 0 -20

ence in St -40 r Fire Severity 1 results in a Regrowth scenario for all forest types. -60 -100000 Flow (%) Annual Mean of tion Diffe Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -80 r Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests:

c opo Lower Bound - 100% forest recovery -100 r

c Best Estimate - 60% forest regrowth, 40% forest recovery P between fire and no-fire response (ML) response no-fire and fire between -120 c Upper Bound - 100% forest regrowth -200000 -140 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 100 100 30

80 80 20 60 60

40 40 10 Cumulative 20 20

0

Proportion of Catchment (%) Catchment of Proportion 0 0 Proportion of Catchment (%) Proportion of Catchment (%) 04080120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Severe Mixed Eucalypt

Moderate Scorch Moderate

PAGE 79 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.2.2 Dargo 120000 No-fire response 60 Lower Bound 80000 Best Estimate 40 Upper Bound 40000 20

0 0

-40000 -20 Change in Streamflow

Fire Severity 1 results in a Regrowth scenario for all forest types. tionof Mean Annual Flow (%) Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -40 r relative to 2003 (pre-fire) (ML) -80000 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery r P c Best Estimate - 60% forest regrowth, 40% forest recovery -60 c Upper Bound - 100% forest regrowth -120000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

120000 Lower Bound 60 Best Estimate 80000 Upper Bound 40

40000 20 eamflow eamflow r 0 0 ence in St ence r -40000 -20

Fire Severity 1 results in a Regrowth scenario for all forest types. tionMeanof Annual Flow(%) Diffe Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -40 r -80000 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery r P between fire and no-fire response (ML) response no-fire and fire between c Best Estimate - 60% forest regrowth, 40% forest recovery -60 c Upper Bound - 100% forest regrowth -120000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 100 100 50

80 80 40

60 60 30

40 40 20 Cumulative 20 20 10

0

Proportion of Catchment (%) Catchment of Proportion 0 0 Proportion of Catchment (%) Proportion of Catchment (%) 04080120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Severe Mixed Eucalypt Mixed

Moderate Scorch Moderate

PAGE 80 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.2.3 Snowy 400000 No-fire response 50 Lower Bound 40 Best Estimate Upper Bound 30 200000 20 10 0 0 -10 -20 Change in Streamflow

Fire Severity 1 results in a Regrowth scenario for all forest types. tionof Mean Annual Flow (%)

-200000 r Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -30

relative to 2003 (pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery -40 r c Best Estimate - 60% forest regrowth, 40% forest recovery P c Upper Bound - 100% forest regrowth -50 -400000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

400000 Lower Bound 50 Best Estimate 40 Upper Bound 30 200000 20 eamflow eamflow

r 10 0 0 -10 ence in St ence r -20 Fire Severity 1 results in a Regrowth scenario for all forest types. tionMeanof Annual Flow(%)

Diffe -200000 r Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -30 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests:

c opo Lower Bound - 100% forest recovery -40 r c Best Estimate - 60% forest regrowth, 40% forest recovery P between fire and no-fire response (ML) response no-fire and fire between c Upper Bound - 100% forest regrowth -50 -400000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 100 100 80

80 80 60 60 60 40 40 40

Cumulative 20 20 20

0

Proportion of Catchment (%) Catchment of Proportion 0 0 Proportion of Catchment (%) Proportion of Catchment (%) 04080120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Severe Mixed Eucalypt Mixed

Moderate Scorch Moderate

PAGE 81 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.2.4 Tambo 80000 No-fire response Lower Bound 60 Best Estimate Upper Bound 40 40000

20 nnual(%) Flow A 0 0

-20

Change in Streamflow Streamflow in Change -40000 Fire Severity 1 results in a Regrowth scenario for all forest types. Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -40

relative to 2003(pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery c Best Estimate - 60% forest regrowth, 40% forest recovery -60 Proportion of Mean c Upper Bound - 100% forest regrowth -80000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

80000 Lower Bound 60 Best Estimate Upper Bound 40 40000

20 nnual Flow(%) A 0 0

-20

-40000 Fire Severity 1 results in a Regrowth scenario for all forest types. Difference in Streamflow Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -40 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: c Lower Bound - 100% forest recovery

c Best Estimate - 60% forest regrowth, 40% forest recovery Proportion of Mean between fire and no-fire response (ML) response no-fire and fire between -60 c Upper Bound - 100% forest regrowth -80000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 100 100 40

80 80 30 60 60 20 40 40

Cumulative 10 20 20

0

Proportion of CatchmentProportion of (%) 0 0 Proportion of Catchment (%) Proportion of Catchment(%) 0 40 80 120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Mixed Eucalypt

Moderate Scorch

PAGE 82 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

D.2.5 Wongungurra 150000 No-fire response 50 Lower Bound 40 Best Estimate 100000 Upper Bound 30

20 50000 10

0 0

-10 Change in Streamflow

Fire Severity 1 results in a Regrowth scenario for all forest types. tionof Mean Annual Flow (%) -50000 Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. r relative to 2003 (pre-fire) (ML) Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests:

-20 opo c Lower Bound - 100% forest recovery r c Best Estimate - 60% forest regrowth, 40% forest recovery P c Upper Bound - 100% forest regrowth -30 -100000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

150000 50 Lower Bound Best Estimate 40 100000 Upper Bound 30 20 50000

eamflow eamflow 10 r 0 0 -10 ence in St ence r -50000 -20

Fire Severity 1 results in a Regrowth scenario for all forest types. tionMeanof Annual Flow(%) Diffe Fire Severity 2 results in a Regrowth scenario for Mountain Ash forest. -30 r -100000 Post-fire response assumptions for Fire Severity 2 for Mixed Eucalypt and Snowgum forests: opo c Lower Bound - 100% forest recovery r

-40 P

between fire and no-fire response (ML) response no-fire and fire between c Best Estimate - 60% forest regrowth, 40% forest recovery c Upper Bound - 100% forest regrowth -150000 -50 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

Vegetation Type Pre-Fire Vegetation Age Fire Severity 80 100 40

80 60 30 60 40 20 40

20 Cumulative 10 20

0

Proportion of Catchment (%) Catchment of Proportion 0 0 Proportion of Catchment (%) Proportion of Catchment (%) 04080120 Ash

Age (years) Burnt Treeless Un-burnt Snowgum Not Treed Light Scorch Severe Scorch Severe Mixed Eucalypt Mixed

Moderate Scorch Moderate

PAGE 83 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment Appendix E Estimated change in streamflow over time (subject to average climatic conditions)

E.1 Northern Catchments Buffalo Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 2 9 14 2020 2 1 -6 -10 2040 4 3 -3 -7 2060 6 5 2 0 2080 6 6 5 4 2100 7 6 6 5 2120 7 6 6 6 2140 7 7 7 7 2160 7 7 7 7 2180 7 7 7 7 2200 7 7 7 7 Average Impact 6 5 4 3

Corryong Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 9 20 27 2020 2 -3 -12 -19 2040 7 1 -7 -13 2060 10 5 1 -2 2080 12 9 7 6 2100 13 11 10 9 2120 14 12 12 11 2140 14 14 14 13 2160 15 15 15 15 2180 15 15 15 15 2200 15 15 15 15 Average Impact 11 9 7 5

PAGE 84 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Dartmouth Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 12 31 44 2020 2 -4 -20 -30 2040 5 -2 -16 -25 2060 7 2 -6 -11 2080 9 5 1 -1 2100 9 6 5 4 2120 9 7 7 6 2140 9 9 8 8 2160 9 9 9 9 2180 9 9 9 9 2200 9 9 9 9 Average Impact 8 5 1 -1

Kiewa Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 8 11 13 2020 1 -2 -3 -5 2040 3 0 -1 -2 2060 5 2 1 0 2080 6 4 3 3 2100 7 5 5 4 2120 7 6 6 5 2140 8 7 7 7 2160 8 8 8 8 2180 8 8 8 8 2200 8 8 8 8 Average Impact 6 5 4 4

PAGE 85 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Mitta Mitta Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 9 21 29 2020 5 0 -11 -18 2040 8 2 -7 -14 2060 10 5 1 -3 2080 12 9 7 5 2100 13 10 10 9 2120 13 11 11 11 2140 13 12 12 12 2160 13 13 13 13 2180 13 13 13 13 2200 13 13 13 13 Average Impact 11 9 6 5

Ovens Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 7 19 27 2020 3 0 -11 -19 2040 6 2 -8 -14 2060 7 4 -1 -4 2080 8 6 4 3 2100 9 7 6 6 2120 9 8 7 7 2140 9 8 8 8 2160 9 9 9 9 2180 9 9 9 9 2200 9 9 9 9 Average Impact 7 6 4 2

PAGE 86 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Upper Murray Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 18 40 55 2020 5 -7 -25 -37 2040 11 -1 -17 -28 2060 14 7 -1 -7 2080 16 12 8 6 2100 17 14 13 12 2120 17 15 15 14 2140 17 16 16 16 2160 17 17 17 17 2180 17 17 17 17 2200 17 17 17 17 Average Impact 14 11 7 4

E.2 Southern Catchments Buchan Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 56 85 105 2020 6 -28 -52 -68 2040 14 -21 -43 -57 2060 20 -1 -12 -19 2080 24 12 8 5 2100 26 19 17 16 2120 27 23 22 21 2140 28 26 25 25 2160 28 28 28 28 2180 28 28 28 28 2200 28 28 28 28 Average Impact 22 12 6 3

PAGE 87 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Dargo Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 9 38 58 2020 5 -1 -28 -46 2040 9 3 -20 -35 2060 11 7 -4 -11 2080 12 10 6 3 2100 13 12 10 9 2120 13 12 12 11 2140 13 13 12 12 2160 13 13 13 13 2180 13 13 13 13 2200 13 13 13 13 Average Impact 11 9 4 0

Snowy Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 14 35 48 2020 -9 -18 -30 -39 2040 0 -9 -21 -29 2060 9 4 -4 -9 2080 14 11 8 5 2100 15 14 13 12 2120 16 15 15 14 2140 16 16 16 16 2160 16 17 17 17 2180 16 17 17 17 2200 16 17 17 17 Average Impact 10 8 5 2

PAGE 88 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Tambo Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 20 49 68 2020 4 -8 -28 -41 2040 9 -4 -23 -36 2060 11 3 -9 -16 2080 13 8 3 0 2100 14 11 9 8 2120 14 12 11 11 2140 14 14 13 13 2160 15 15 15 15 2180 15 15 15 15 2200 15 15 15 15 Average Impact 12 8 3 -1

Wongungurra Year Change in streamflow with respect to 2003 (pre-fire) as a percentage of mean annual flow (%) No Disturbance Lower Bound Best Estimate Upper Bound 2003 (immediately after fire) 0 21 34 43 2020 5 -6 -18 -27 2040 10 -3 -14 -21 2060 12 2 -3 -6 2080 15 7 5 3 2100 15 10 9 9 2120 16 12 12 11 2140 16 14 14 14 2160 16 16 16 16 2180 16 16 16 16 2200 16 16 16 16 Average Impact 13 8 6 4

PAGE 89 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment Appendix F Cumulative streamflow response

F.1 Northern Catchments F.1.1 Buffalo 1000

0

-1000

-2000 Lower Bound Best Estimate Cumulative differenceinstreamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -3000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

F.1.2 Corryong 1000

0

-1000

-2000 Lower Bound Best Estimate Cumulative differenceinstreamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -3000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

PAGE 90 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

F.1.3 Dartmouth 10000 low f 0 eam r

ence in st -10000 r e f f

-20000 Lower Bound Best Estimate Cumulative di Cumulative

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -30000 20002020204020602080210021202140216021802200 Year

F.1.4 Kiewa 1000

0

-1000

-2000 Lower Bound Best Estimate Cumulative differenceinstreamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -3000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

PAGE 91 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

F.1.5 Mitta Mitta 1000

0

-1000

-2000

-3000 Lower Bound Best Estimate Cumulative differenceinstreamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -4000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

F.1.6 Ovens 2000

0

-2000

-4000

-6000 Lower Bound Best Estimate Cumulative difference in streamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -8000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

PAGE 92 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

F.1.7 Upper Murray 4000 low f 0 eam r

-4000 ence in st r e f f -8000

-12000 Lower Bound Best Estimate Cumulative di Cumulative

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -16000 20002020204020602080210021202140216021802200 Year

F.2 Southern Catchments F.2.1 Buchan 2000

0

-2000

-4000 Lower Bound Best Estimate Cumulative difference in streamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -6000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

PAGE 93 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

F.2.2 Dargo 1000

0

-1000

-2000

-3000

Lower Bound -4000 Best Estimate Cumulative differenceinstreamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -5000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

F.2.3 Snowy 4000 low f 0 eam r

ence in st -4000 r e f f

-8000 Lower Bound Best Estimate Cumulative di Cumulative

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -12000 20002020204020602080210021202140216021802200 Year

PAGE 94 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

F.2.4 Tambo 1000

0

-1000

-2000 Lower Bound Best Estimate Cumulative differenceinstreamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -3000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

F.2.5 Wongungurra 2000

0

-2000

-4000 Lower Bound Best Estimate Cumulative difference in streamflow

between fire and no-fire response (GL) response no-fire and fire between Upper Bound -6000 2000 2020 2040 2060 2080 2100 2120 2140 2160 2180 2200 Year

PAGE 95 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

Appendix G - Spacial inputs and outputs

G

PAGE 96 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 97 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 98 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 99 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 100 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 101 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 102 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 103 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 104 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 105 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

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PAGE 107 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 108 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 109 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 110 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 111 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

PAGE 112 Impact of the 2003 Alpine Bushfires on Streamflow - Broadscale water yield assessment

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