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... model runs and data preparation was conducted on a 450 MHz PC with 256 MB of RAM and running Windows NT 4.0. (Figure 3.1), whereas the DEM for the Thomson was provided by DNRE. ...
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... A stream network is calculated and hillslopes are identified as the area upslope of each segment of the network (Figure 3.2). ...
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... requires forest type and forest age information in order to operate. Maps of forest type ( Figure 3.3) and age ( Figure 3.4) where provided by DNRE for Maroondah and for the Thomson. ...
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... requires forest type and forest age information in order to operate. Maps of forest type ( Figure 3.3) and age ( Figure 3.4) where provided by DNRE for Maroondah and for the Thomson. ...
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... relation between catchment area and the optimal ratio of hydraulic to surface gradient found in the Maroondah catchments is confirmed in the Thomson catchments ( Figure 6.3). In general, as catchment area increases the optimal ratio of the hydraulic to the surface gradient also increases, although the Thomson at Newlands required a surprisingly low value for this calibration variable. ...
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... shows the distribution of forest types as "seen" by the model. Note the altered spatial structure from the "true" species distribution given earlier in Figure 3.3. ...
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... result is not surprising, and largely reflects the data that were supplied to the model. Areas that are not ash-forested (Figure 3.3) were predicted to be minimally impacted, in absolute terms, by forest clearing. This is because LAI was assumed to be constant in the long term for non-ash forest types. ...
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... The water yield analysis for Thomson catchment was carried out in several studies (Mein et al. 1992;Peel et al. 2000;eWater CRC 2008). Mein et al. (1992) noted that streamflow entering the Thomson river was not generated uniformly over the catchment area, indicating the type and age of the forest to determine the difference in evapotranspiration and thus the water yield in the catchment. ...
... The catchment is largely uninhabited, entirely forested with different Ash-type (e.g., Eucalyptus regnans, Eucalyptus delegatensis, Eucalyptus nitens and Eucalyptus sieberi) and Mixed species. It receives an average annual precipitation of up to 2220 mm along upper Thomson river to about 1930 mm along the eastern slope of Mount Baw Baw (Peel et al. 2000), while northeastern part of the catchment receives much less around 1180 mm. Thus, the bulk of the runoff yield of the reservoir is generated from Mount Baw Baw and its slopes. ...
... Mein et al. (1992) also reported that the water yield of Alpine vegetation is 10 ML/ha/year, which does not depend on the age of the forest. On the other hand, based on Read Sturgess and Associates (1994) and Peel et al. (2000), there is an average 15% variation in the water yield between old (15.4 ML/ha/year) and re-growth Alpine forests (13.1 ML/ha/ year). A water yield of 11.9 ML/ha/year was assumed in the analysis for Scrub species, according to the data by Mein et al. (1992). ...
Bushfires in water supply catchments can adversely impact the reliability of water supply and thus threaten the wellbeing and prosperity of a city. Frequent fire events are looming to threaten water supply from the forested catchments of Victoria, Australia. Melbourne, the capital of Victoria, has to meet growing water demand due to population increase and economic development. In recent years, the state has confronted with severe drought conditions, resulting in a considerable reduction of the water supply yield of the catchments. These continued multi-year droughts culminated into the latest major bushfire in 2009 (Black Saturday). Thomson catchment, the largest water supply catchment supplying water in Melbourne is fully forested. This catchment is comprised of different Ash-type forests, Mixed species, Alpine vegetation, and Scrubs. The study noted that there is probability of occurrence of high danger fire events at 1 in 20-year return period for Thomson catchment. The objective of this study was to carry out a joint probability analysis for different percentages of catchment burning, if a 20-year fire event occurs at least once between 2010 and the given year, and determine the percent reductions in water yield from years 2030 to 2090. Based on the analysis carried out in the study, if 5% of the Ash-type forest is burnt once since 2010, the combined reduction of the total water yield would be 6.75% (16,968 ML/year) by 2090.
... Estimated values for water use for different land use and land cover types [48] were integrated into a GIS and assigned to five classes: very low, low, medium, high and very high. The rich forest was assumed to have very low water yield because it has a generally high leaf area, while the medium forest was valued to have low water yield [49][50][51][52][53][54]. Poor forest and planted forest were assessed to have medium water yield. The non-forest land was ranked to have very high-water yield. ...
Globally, planted forests are increasing, providing increased resources to forest industries and ecosystem services (ES) to local and wider communities. However, assessment of the impacts of plantations on ES has been limited. Planted forests have expanded rapidly in Vietnam over the last 20 years, with much of the planting undertaken by smallholder growers using exotic Acacia and Eucalyptus species. This study aimed to test a framework to assess changes in four ES due to an increase in Acacia plantations from 2005–2015 in central Vietnam: carbon sequestration, sediment retention, water yield and habitat. Quantitative and qualitative indicators for each service were derived from the literature. Results showed that the area of planted forests in Quảng Trị and Thừa Thiên-Huế Provinces increased from 130,930 hectares (ha) to 182,508 ha, mostly replacing non-forest areas (degraded lands, grasslands and agricultural lands) and poor forests. The framework demonstrated capacity to assess the effect of planted forests on wood flow, carbon stocks, sediment retention, streamflow and the extent of wildlife habitat. Apart from the wood supply and carbon sequestration, more research is required to translate biophysical indicators to benefit relevant indicators related to human welfare. The study also revealed that the area of rich forests decreased by 20% over the ten years, mostly through degradation to poorer quality natural forests. Therefore, at the landscape scale, improvement in ES due to conversion of non-forests to planted forests was offset by a reduction in some services as a result of degradation of native forest from rich to poorer condition. Assessment of changes in ES due to planted forests also needs to consider other landscape changes. These analyses can inform policymakers, forest owners and managers, environmental organizations and local communities of the benefits and impacts of planted forests and provide an improved basis for payments for ES and potential additional income for smallholder tree growers.
... In its early days, CRCCH researchers advocated mechanistic over empirical modelling approaches due to their potential superiority in management applications (Vertessy et al., 1996). Work included further development of TOPOG (Hatton et al., 1995;Vertessy et al., 1998;1993) and integrating empirical leaf conductance relationships into mechanistic hydrological models (Peel et al., 2000;Watson et al., 1998). However subsequent work placed heavier emphases on empirical approaches (Bradford et al., 2001;Vertessy, 1999;Vertessy and Bessard, 1999;Vertessy et al., 2000), doubtless related to the challenges in running mechanistic models and their onerous data requirements (Dawes et al., 1997). ...
IN the early to mid-1990s, Australia governments adopted significant forestry and water policy agendas. The forest policy stimulated plantation expansion, and articulated benefits to water resource degradation which became a focus of the water agenda. The prospect of changing water availability during a severe drought resulted in the National Water Initiative (NWI), which sought to protect the integrity of water entitlements from plantation expansion.
State government agendas provided additional complexity, notably in South Australia where forest water use became subject to regional regulation in 2004, reminiscent of South African experiences in 1972. Inconsistencies between assessments used to support/contest the sustainability of plantation developments resulted in the amendment of South Australian planning frameworks, to ensure competing policy issues were addressed in a balanced manner.
Mixed progress in implementing the interception clauses of the NWI have been relegated to unfinished business without critically evaluating its capacity to deliver the required policy and scientific outcomes. Here, national and jurisdictional forest water policies are analysed and weaknesses identified in the lack of a cohesive national policy agenda arising from jurisdictional independence under the Australian Constitution. Inefficiencies in implementation are traced to: competing agendas; the complexities of their inter/intra-jurisdictional administration; a lack of regard to relevant international precedents and a tendency for Australian water reform to be initiated as short-term responses to predictable disasters rather than long-term planning. Reforms under the NWI are found to have had little direct effect in progressing jurisdictional forest water management agendas.
Australian empirical hydrological assessment approaches used to support forest water decision-making are examined in the context of international systems and learnings from South Africa. An approach for evaluating and transparently integrating Australia’s limited forest hydrology datasets with modelled information is developed to improve confidence in decision-making.
A similar group of empirically-based models are subjected to a comprehensive Bayesian evaluation with South African and American approaches to identify an option with the greatest integrity to underpin current Australian forest water management. Systemic limitations in a widely used approach developed by a leading Australian research organisation are confirmed and revealed as being compounded by weak model structure, highlighting the challenges faced by water management agencies in securing research to support defensible decision-making.
Challenges associated with agency capacity limitations and the inevitability of using more complex modelling in supporting future Australian forest water management are addressed by noting South African learnings which identify the importance of growth in plantation water use; and exploring the feasibility of using simpler elements of a sophisticated Bayesian assessment to establish confidence in a plant growth model. Complexity introduced into the 3-PG plant process model is shown to improve the model’s ability to extract information from data providing greater confidence in its potential for future development as a water management tool than more exhaustive, integrated assessments focused on marginal improvements in performance.
Results are discussed in the context of water management and their implications for future research and policy developments.
... We used Macaque, a physically-based long term water balance model developed by Watson (1999) and summarised by Watson et al. (1999) and Peel et al. (2000). In Macaque, predictions of daily streamflow are sensitive to climate, vegetation water use, the amount of water stored within the soil, and the rate at which this water moves into and out of the soil and into the streams. ...
... An estimate of precipitation at each spatial unit is made using a method that relates total monthly precipitation at many stations to monthly totals (of daily) precipitation at two or three base stations with long and complete record lengths (Peel et al., 2000). An elevation-based lapse rate (-0.005 o C m -1 ) was used to calculate maximum and minimum temperatures at each spatial unit relative to a base station using the difference in elevation between the spatial unit and base station. ...
... For non-ash eucalypts (e.g. E. obliqua) and non-eucalypts, the development of long term LAI is assumed to have constant LAI, following a rapid initial increase from zero in the first 5 to 10 years following disturbance (Peel et al., 2000). ...
In February of 2009, after prolonged periods of hot and dry weather, wildfires spread across part of the state of Victoria, affecting more than 363 km2 of forests in the Melbourne water supply catchments. This has potential to alter long term water use (>100 years) of the forests and subsequent water yield from these catchments. Climate can have an important role in modifying the effects of fire on streamflow. One of the few ways to examine these is through a process-based modelling study. It is important that the combined effects of climate and wildfire on long term streamflow are included in simulations used by water managers for planning and decision making. We used a spatially explicit process-based model to explore relationships between climate and wildfire, and examine the combined influence of climate and wildfire on the post-fire streamflow response. Catchments were disaggregated into spatial units at which energy and water balances are simulated. Changes in land cover were expressed as changes in leaf area index (LAI) for the fire sensitive ash-type eucalypt species, and for the more fire-tolerant mixed eucalypt species forests. Catchment water balances were simulated for 100 years after wildfire to include most of the expected changes. We assumed post-fire mortality of vegetation from recent field studies, along with several climate scenarios to examine the response of post-fire catchment streamflow. Effects of climate variability were removed by creating a synthetic climate, with no inter-annual variability, and using this as an input to model.
... We used Macaque, a physically-based long term water balance model developed by Watson (1999) that predicts the streamflow of forested catchments. Summaries of the model are provided by Watson et al. (1999a), Peel et al. (2000) and Lane et al. (2010), and relevant parts are described only briefly here. Macaque is a distribution function model (DFM), operating in a similar way to RHESSys (Band et al., 1993) and TOPMODEL (Beven et al., 1995). ...
... An estimate of precipitation at each ESU for every day was made. A multiple linear regression (MLR) method (Peel et al., 2000) was used to relate total monthly precipitation at many stations in and around the catchment to monthly totals (of daily) precipitation at two or three base stations with long and complete record lengths. The location and elevation of each precipitation station is known, and a three dimensional spline was applied to interpolate the MLR coefficients across the entire catchment. ...
... For non-ash eucalypts (e.g. E. obliqua) and non-eucalypts, the development of long term LAI is less well understood, but based on observation, is assumed to have constant LAI, following a rapid initial increase from zero in the first 5-10 years following disturbance (Peel et al., 2000). Following the work of Roberts et al. (2001) a relationship between forest age and maximum leaf conductance is assumed to hold for all eucalypt species. ...
... Macaque is a physically-based forest hydrologic model that operates at a daily time step. It was originally developed by Watson (1999), with summaries and applications given by Watson et al. (1999Watson et al. ( , 2001 and Peel et al. (2000Peel et al. ( , 2001. It has been successfully applied to catchments up to 500 km 2 . ...
... A detailed climate sub-model is used to convert precipitation and temperature range inputs into required climate variables such as radiation and humidity for the estimation of evapotranspiration. Peel et al. (2000) developed a scheme whereby a precipitation surface is derived from multiple linear regression (MLR) analysis of monthly precipitation from stations in or near the catchment against a set of base precipitation stations. The regression analysis terms are then spatially interpolated by a 3-D spline and the daily surface precipitation is driven by the base stations with continuous records. ...
Disturbance of forested catchments by fire, logging, or other natural or human induced events that alter the evapotranspiration regime may be a substantial threat to domestic, environmental and industrial water supplies. This paper describes the physically-based modelling of the long term changes in water yield from two wildfire affected catchments in north-eastern Victoria, Australia, and of fire and climate change scenarios in Melbourne's principal water supply catchment. The effect of scale, data availability and quality, and of forest species parameterisation are explored. The modelling demonstrates the importance of precipitation inputs, with Nash and Sutcliffe Coefficients of Efficiency of predicted versus observed monthly flows increasing from 0.5 to 0.8 with a higher density of rainfall stations, and where forest types are well parameterised. Total predicted flow volumes for the calibrations were within 1% of the observed for the Mitta Mitta River catchment and <4% for the Thomson River, but almost −10% for the less well parameterised Tambo River. Despite the issues of data availability simulations demonstrated the potential for significant impacts to water supply in SE Australia from wildfire and climate change. For example, for the catchments modelled the moderate climate change impact on water yield was more pronounced than the worst fire scenario. Both modelled cases resulted in long term water yield declines exceeding 20%, with the climate change impact nearing 30%. A simulation using observed data for the first four post-fire years at the Mitta Mitta River catchment showed Macaque was able to accurately predict total flow.
... Several studies in Australia (e.g., Peel et al., 2000Peel et al., , 2003 rely on the Macaque model (Watson et al., 1999), a model with the unconventional characteristic that the two largest flows (precipitation and transpiration) are exogeneous: precipitation falls from and transpiration disappears into the sky, with no attempt to examine possible connectivity of feedback and rainfall recycling, which may be substantial (Brubaker et al., 1993;Burde and Zangvil, 2001;D'Almeida et al., 2006). Other researchers have commented on the significance of this feedback at various scales (e.g., Makarieva et al., 2006;Molen et al., 2006;Gordon et al., 2008). ...
Tree plantations have developed a reputation for excessive water use, with age commonly used as an explanatory variable to predict water loss – but many factors have the potential to affect plantation water use, and few of these alternatives have been considered. Changes in forest cover may be correlated with other environmental changes that may affect precipitation, transpiration, and runoff, indicating that more thorough investigation is required in both field and simulation studies. Several factors influencing water use by plantations are amenable to management control, so there is scope to design and manage forest plantations deliberately for water use efficiency. Research is needed to elucidate the relative contributions of forests and grasslands to atmospheric moisture; the influence of vegetation on the distribution of rainfall; the effect of air turbulence from plantation edges, firebreaks and streamlines; the potential to modify atmospheric coupling of forest plantations through plantation design, including the use of mixed species plantations, and by softening hard edges by thinning and pruning plantation edges.
... Watson et al (1999) indicated that the Leaf Area Index of Snowgum is constant at 2.5 after the fi rst fi ve to 10 years of growth. Peel et al (2000) developed a streamflow response curve for Snowgum based on Leaf Area Index (for a mean annual rainfall of 2475 mm). For this study, the relationship developed by Watson et al (1999) was fi tted by eye to the Peel et al (2000) results. ...
This paper reports on a broad-scale assessment of water yield impacts of the 2003 Alpine bushfires, which burnt over 1 million ha across northeastern Victoria and southern NSW, including catchments of a number of key water storages, such as Hume and Dartmouth Dams, and also the Gippsland Lakes. A new model - Bushfire Impact on Streamflow Yield (BISY) - was developed to estimate the change in streamflow. Streamflow response curves were derived for the different species, which were based upon recorded streamflows and transposed based upon the mean annual rainfall. The impact on streamflow was estimated for 12 catchments ranging in size from approximately 500 to 10,000 km2. For each catchment an annual streamflow response curve was produced at the catchment outlet, as well as spatially explicit data sets showing change in streamflow across the catchment. The results were aggregated to estimate the total change in mean annual streamflow for the River Murray and Gippsland Lakes.
... The Macaque model was originally developed by Watson (1999), with summaries given by Watson et al. (1999 and Peel et al. (2000Peel et al. ( ,2001. It was originally developed using the Tarsier framework and was written in C++. ...
... A precipitation surface is derived from multiple linear regression analysis of monthly precipitation from stations in or near the catchment against a set of base precipitation stations. The regression analysis terms are then spatially interpolated and the daily surface precipitation is driven by the base stations with continuous records (Peel et al., 2000). Observed temperature data is used to estimate lapse rates for distributing temperature to each ESU. ...
Disturbance of forested catchments by fire, logging, or other natural or human induced events that alter the evapotranspiration regime may be a substantial threat to domestic, environmental and industrial water supplies. While security of water supplies have always been of high importance in Australia, the recent long-lived drought, climate change predictions and two major "mega fire" events in 4 years that have burnt over 2 million ha of native forest in Victoria alone, have placed alarming uncertainty on the State's water resources. Furthermore, there are predictions of more frequent and intense wildfire under climate change (Howe et al., 2005). Physically-based models that can predict the hydrologic impact of forest disturbance and climatic inputs will be crucial for understanding changed water yields and for informing forest management options. One such model is Macaque (Watson, 1999), a physically based spatially distributed daily time step process model that was developed specifically to replicate the water yield variation over time observed in Victorian central highland catchments after the 1939 bushfires. This paper describes the modelling of the long term changes in water yield from two fire affected catchments, and of fire and climate change scenarios in Melbourne's principal water supply catchment (488km 2). The effect of scale, data availability and quality, and of species parameterisation is explored. For the two fire affected catchments, Mitta Mitta (1533 km 2) and Tambo (551 km 2) 250 year simulations were run with the changed vegetation conditions and with no disturbance. Macaque predicted a significant yield decrease, with a maximum annual change of 17% for the Mitta Mitta and a long-term decrease of 7%. These values were 20% and 7% for the Tambo. However there were some important uncertainties identified. The model calibrations although reasonable (Nash & Sutcliffe (E) = 0.5-0.6) demonstrated there were periods with significant discrepancies between observed and predicted flows in the calibration phase. It is likely that poor precipitation coverage over large, sparsely populated catchments is one cause. A second may have been the use of the model outside of its development range; i.e. into areas with drier forest types where the evapotranspiration characteristics are not well known. Subsequently, Macaque was calibrated for the Thomson catchment (488 km 2), which has a better coverage of rainfall stations, and a far smaller proportion of drier eucalypt species. The calibrations were much improved (E = 0.7-0.8), demonstrating Macaque to be an appropriate model for evaluating forest disturbance where input data is of high quality. Simulations of fire scenarios and of potential climate change scenarios were run. The latter were based on CSIRO projections of rainfall and temperature changes for the Melbourne region. There was no consideration of vegetation physiological responses to climate change. The simulations give an indication of the magnitude of yield responses that should be considered by catchment managers. Such predictions can be placed in the context of other disturbances or management decisions such as timber harvesting. The ability of Macaque to simulate spatially-distributed disturbance is important. The modelling has produced useful insights into potential yield responses to plausible disturbance scenarios. The research also demonstrates the decline in model performance when input parameters are problematic. 2953 AUTHORS COPY
... In addition, collection of long-term hydrological data (up to c. 30 years) from mountain ash catchments led to the development of empirical relationships between water yield and forest age. These became the basis for process models that incorporated the effects of topography (Vertessy et al. 1996;Peel et al. 2000). This trend of models begetting models, both descriptive and quantitative, was clearly evident in vertebrate and water studies, particularly those relevant to mountain ash forest (Lindenmayer, Cunningham & Donnelly 1994;Lindenmayer & Possingham 1995), but was largely absent from studies of tree regeneration. ...
Timber harvesting exemplifies many aspects of experimental manipulation in applied ecology. Evaluation of the research approaches used to assess ecological effects of harvesting thus has relevance to a diverse range of ecological questions that address large‐scale and human impacts on the environment.
We measured the frequency of approaches, and also design and statistical issues, in assessments of harvesting effects on three response variables (tree regeneration, vertebrates and water) in two major native forests of south‐east Australia. Our evaluation was based on 124 documents that contain unique, field‐based research and that represent the complete written record (published and unpublished) of relevant research prior to mid‐2002.
The dominant approach was contrasts between manipulated stands, nearly always involving mature and old‐growth stands as the reference or control. In studies of tree regeneration, focus on wood‐production objectives was apparent in the relatively frequent use of stocking standards, and in the use of between‐ and within‐stand contrasts without a control condition. Comparatively greater use of models in vertebrate and water studies suggested more frequent integration of generic principles and, in water studies, reflected strong collective knowledge based on the repeated use of BACI‐type designs (i.e. before–after, control–impact) or long‐term data sets.
Statistical issues such as poor reporting of experimental designs and of sample statistics were common. Explicit hypotheses were rare, and there was no evidence of definition of critical effect sizes, use of power analysis or use of non‐classical statistical approaches (e.g. Bayesian inference).
Lack of treatment replication was widespread in between‐stand contrasts and less frequent in within‐stand contrasts. Inappropriate interpretation of results from non‐replicated experimental designs remains an ongoing issue.
Synthesis and applications . The amount of information obtainable from stand‐level manipulations of forest would substantially increase through greater attention to data quality and experimental protocols. Studies require broader experimental contexts, including their potential place in meta‐replication frameworks. Increasingly, constraints of large‐scale manipulations necessitate the integration of data and the acknowledgement of uncertainty in formalized systems (e.g. Bayesian methods and adaptive management frameworks). Our evaluation suggests the alternative is a perpetuation of short‐term, isolated studies that repeat errors and have limited potential to refine knowledge on the ecological effects of timber harvesting and other similarly scaled disturbances.
