Landscape Genesis Approach to Integrated Catchment Management: The Ben Chifley Catchment

Dhia Al Bakri

The University of Sydney, Orange, PO Box 883, Orange NSW 2800, Australia

Extended Abstract

The concept of integrated catchment management (ICM) is widely accepted as the most appropriate framework for undertaking sound natural resource assessments and management. This entails a holistic consideration of the biophysical systems, socio-economic factors and management process (DNR 1999, Savory 1999, Grayson et al. 2000). One of the main impediments to the successful implementation of the ICM has been the existence of a series of barriers to integration of R&D outcome. The R&D approaches adopted have varied in scope and emphasis, which produced incompatible, and some times irrelevant, outcomes. Other barriers are that most of the current approaches tend to be subjective, time consuming, costly and lack the ability to assess cause-effect relationship or predict potential implications of anthropogenic activities. The resultant solutions and management strategies have a tendency to focus on effects, rather than causes of the problems, and thus be of limited value in terms of achieving the goal of sustainability (Al Bakri 2001).

Resource degradation and related environmental problems result from interaction of two complex factors: 1) the intrinsic carrying capacity (inherent potential and vulnerability) of the biophysical system, and 2) impact of socio-economic development (anthropogenic activities). Conventional approaches to integrated catchment and resource management appear to focus on the second factor and largely ignored the inherent characteristics of the biophysical system. Consequently the root causes and magnitude of resource degradation have been either misunderstood or underestimated. It is imperative, therefore, that the inherent carrying capacity of the biophysical system is considered carefully in any integrated resource management effort. As biophysical resources underscore all socio-economic development, sustainability is untenable without securing the long-term health of the underlying natural biophysical system (Al Bakri 2001). The latter consists of essentially three independent causal factors (geology, climate and time) and several dependent factors (eg. soil, water, fauna, flora, topography, and other natural resources). The intrinsic properties of the dependent variables are ultimately controlled by the independent causal variables. Given that geological units encompass time factor and that changes in regional climate have a limited impact on the variation of other biophysical attributes at the catchment or on the local scale, geology and geomorphology remain the most critical factors in determining the intrinsic carrying capacity of any given landscape (Al Bakri 2001).

The landscape genesis (LG) approach, which is based on the geological and geomorphic genesis of the landscape, is rooted in concepts and case studies discussed in several articles published by the author and associate researchers (Al Bakri 1994, 1996, 2001, Al Bakri et al. 1997a&b, Al Bakri and Kittanah 1997, Al Bakri and Chowdhury 1999). The approach differs essentially from other integrated resource and catchment management approaches (e. g. Solntsev 1962, Wright 1973, Al Bakri 1975, Mitchell & Hollick 1993, Hooper 1995, Brierly et al. 1996, Grayson et al. 1997, DNR 1999). This approach determines the geological and geomorphic genesis of the landscape as a pre-requisite to: 1) assess the intrinsic biophysical characteristics and inherent carrying capacity of the natural ecosystems, 2) predict resource degradation due to anthropogenic activities, and 3) then undertake an integrated assessment to develop appropriate planning and management strategies.

The Ben Chifley Catchment is used as a case study to explain and validate aspects of the LG approach for sustainable catchment and resource management. The catchment (985 km²) exists upstream of Ben Chifley Reservoir, the main water supply for the country town of Bathurst, New South Wales. The catchment is located in cold-temperate region with an annual rainfall of 750-950 mm. Land clearing for agricultural purposes was started around 1850. According to the land use map of the catchment pastureland, soft wood plantation and native timber occupy more than 99% of the area, whereas cropping and horticultural land represents less than 1% of the catchment (Taylor 1994).

Despite the predominance of a non-cultivated land use system (pasture and timber), which has been ongoing for a relatively short period (approximately 150 years), the catchment suffers serious land and water degradation problems. Fertility decline, soil acidity, sodicity, soil structural decline, erosion, water logging, salinity, and weed infestation are some of the most common land degradation problems. Approximately 80% of the grazing land is improved pasture where superphosphate fertilizer is applied once every two years at the rate of 50 kg/acre to improve soil fertility. Lime is also applied regularly to moderate acidity and improve productivity. Considerable earthwork, gully filling, and fencing are employed to combat erosion. The Ben Chifley Reservoir and other catchment's waterways exhibit chronic algal blooms and degraded aquatic ecosystems together with serious water quality problems such as turbidity, siltation, and eutrophication. Given the need for high farming-input system and costly management practice coupled with modest productivity and low commodity prices, the land use in the catchment is becoming increasingly less sustainable, both ecologically and economically (T. Cox 1999, per. comm.).

The study demonstrated that lithological composition, tectonic and diagentic history, and landforming processes were paramount factors in shaping out the intrinsic properties and variation of the soil type, land use, land capability, erosion, slope and resource degradation within the catchment. The LG model proved to be a powerful tool to predict the inherent carrying capacity, resilience and sustainability of the different biophysical systems in the catchment. The intrinsic characteristics of other resources (e.g. water, fauna, flora, minerals), degree of degradation, and viability of socio-economic development were controlled ultimately by the geology, geomorphology, and related geoscientific processes.

As the catchment is dominated by parent material derived mostly from felsic-intermediate igneous rocks that have undergone low to moderate regional metamorphism, the study area has inherent genetic constraints which limited its carrying capacity for the development of intensive agricultural system. Although the existing land use was mostly restricted to fairly passive agricultural activity such as grazing and softwood plantation, the catchment has suffered serious land and water degradation. Judicious conservation measures and considerable chemical inputs are necessary to sustain this modest agricultural production system.

Although this new approach is still in the infancy, the Ben Chifley Catchment case study and recently published research (e. g. Al Bakri 2001) have demonstrated that the LG approach has several advantages over conventional approaches in terms of undertaking objective and cost-effective R&D within the context of ICM. Therefore, the LG approach would provide a sound basis for promoting the goal of sustainability efficiently and effectively because it:

• provides a rational basis and adopts a problem-solving methodology which ensure timely and cost-effective holistic catchment and resource management.
• offers a comprehensive yet flexible process to undertake an integrated multidisciplinary assessment. The process can be implemented within a single project or within a number of projects provided that the designated pathway was correctly followed.
• employs genetic (LG) models to understand the intrinsic properties and predict inherent carrying capacity and resilience of different landscape units under a range of land use scenarios.
• establishes a diagnostic basis to define root causes and cause-effect relationship which are essential for determining preferred land use and developing appropriate solutions to mitigate against anthropogenic impacts.
• offers the potential to develop global and quantitatively-based models and geoindicators that can be applied at different catchment scales, climatic regions and land use scenarios.

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Paper presented to: Australian Association of Natural Resource Management, NSW Branch Conference - Taking Charge of Change - November 23/24, 2001, Dubbo, NSW.