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General background
The study of water resources requires an assembly of several scientific disciplines that examine components of the hydrological cycle and evaluate the degree to which human intervention can derive benefits for society. There is a rising need for more comprehensive inputs from different scientific disciplines as the pressure on limited water resources continues to escalate. Falkenmark, de Sherbinin, and Dompka (1996) pointed out that the world’s water supplies are continuing to dwindle because of resource depletion and pollution, whilst water demand is rising fast because population growth is coupled with rapid industrialisation, mechanisation and urbanisation. South Africa is one country where water demand in many areas has already exceeded the available water supplies and progressively larger volumes of water have to be transferred from those catchments where water is still available (Basson, 1998; Ashton and Haasbroek, 2000).
In addition to the inadequate state of the present water supplies, the South African Government is implementing the National Water Act (Republic of South Africa, 1998) where new approaches are being utilised in the development, operation and management of water resources. Of importance in the changes sweeping the water sector is the fact that while new legislation is coming into the water sector, the political climate is also going through extensive changes, affecting sectors that were dominated by inequalities.The water sector, with a previous legislation that linked water rights to land ownership has noted the need for extensive restructuring that, in many cases, has put pressure on practitioners in water resources management (WRM), to provide information that is more closely linked to the water sector changes to assist the decision-makers. Dent (2000) pointed out that in southern Africa the practice of water resources management has moved in step with the societal needs of the region over the past decades. These needs have passed through phases which placed more emphasis on « getting more water », University of Pretoria etd – Dube, R A (2006) than « using water more efficiently ». Dent (2000) points out that the dominant theme now is « allocating water equitably ».
Developments in the WRM field have focused on the development of an Integrated Water Resources Management (IWRM) approach (Walmsley et al., 2001). The concept of sustainability is identified as a key to the measurement of the successes of the implementation of the new South African Water Act. Wamsley et al. (2001) explore a number of indicators of sustainability in terms of the water resources managed by different organisations. In the Murray-Darling basin, a major catchment in Australia, the sustainability plan is « to promote and co-ordinate effective planning and management for the equitable, efficient and sustainable use of water, land and other environmental resources of the catchment ». The Fraser Basin Council of Canada had another interesting vision on sustainability in its charter which states that: « the basin is a place where social well being is supported by a vibrant economy and sustained by a healthy environment ». In the national water policy of South Africa, the term « resource quality » is used to summarise environmental sustainability where it is used to include the health of all parts of the water resource that make up an ecosystem, including plant and animal communities and their habitat (DWAF, 1997d).
In South Africa, most of the water used in water provision schemes comes from surface water resources. The consumption of water in South Africa exceeds 10 000 million cubic metres (m3) per annum, of which 90 % is derived from flowing rivers and storage dams. The mean annual runoff of the country as a whole was estimated in 1999 to be 60 000 million m3 (DWAF, 1999). Most urban settlements in South Africa have already exhausted their own catchment runoff yields and are now relying on water transfers from adjacent catchments (Basson, 1998). The Pretoria-Witwatersrand-Vereeniging (PWV) area is a typical example of a case where there are already four schemes pumping water from other catchments. The four schemes pump a total of 840 million m3 per year into the Vaal River catchment. A number of projects to transfer more water from other catchments to the Vaal River are also under investigation. Additional transfer schemes under investigation include the Thukela, Umzimvubu, Caledon River and Phase 2 of the Lesotho Highlands Project (DWAF, 1999). The volume of these additional water transfers to the Vaal River is presently equivalent to 40 % of the natural inflow to the Vaal Dam, and is expected to reach 150 % of the natural flow in the early 2020s when University of Pretoria etd – Dube, R A (2006) further transfer schemes are completed (Basson, 1999; McKenzie, 2000). Against this background, the country has seen the use of a range of sophisticated water management tools to co-ordinate, manage, plan and serve the water requirements of a number of water using activities. Recent examples of extensive use of modelling tools in water management in South Africa include the Orange River Replanning Study (ORRS) (DWAF,1999) and the Thukela Water Project (DWAF, 2001a).
Section 1: Literature review and water resources modelling update
1 Introduction
1.1 General background
1.2 The growing “water problem” in southern Africa as it applies to modelling
1.3 Study objectives and methodologies
1.4 Layout of the thesis report
1.5 Water resource modelling trends
1.5.1 South African trends in water resources modelling
1.5.2 International trends in water resources modelling
2 Water resources planning and management
2.1 Water resources planning
2.2 Planning objectives in water resources.
2.3 The planning process in water resources management projects where models are used
2.4 Water quality, quantity and spatial representation in water resources planning
2.5 The planning model and its position in water resources decision making
2.6 Surface water resources models and the modelling problem
2.7 Social and economic factors in water resources modelling
3 Unique South African features in water resources modelling
3.1 Legislation and policies affecting water resources modelling.
3.2 Water resources stakeholders and institutions in water resources modelling.
3.3 Hydrological processes in South Africa in relation to water resources modelling .
3.4 Technology and the human factors in water resources modelling
4 Water resources model inputs and pre-processing
4.1 Data and information in water resources modelling
4.2 Data processing
4.3 Data storage and dissemination .
4.4 Implications of data sources in WRM models .
4.5 Summary of recommendations on model inputs and pre-processing
5 Model software selection and development
5.1 Policies and a framework in development and use of models
5.2 Topography, watercourses and climatic factors in South Africa
5.3 Water recourses institutional frameworks in South Africa
5.4 Socio-economic, political and trans-boundary issues
5.5 Recommendations on models and software
5.6 Routines, objects, tool integration and interfacing in modelling
5.7 User platforms and model packaging.
5.8 Guiding thoughts on model software selection and development
6 Verification, Calibration and Validation
6.1 Model Verification
6.2 Model Calibration / Validation
6.3 A summary of guidance on model verification, calibration and validation
7 Spatial data and stakeholder inputs in water resources modelling .
7.1 Geographical Information Systems (GIS)
7.2 Digital Elevation Models (DEMs).
7.3 Databases and data models in water resources modelling.
7.4 Stakeholder factors in water resources modelling .
7.5 Summary of recommendations on spatial data and stakeholder inputs .
8 Development and use of a water systems analysis model
8.1 Introduction
8.2 Why the model HYDRO25 was developed
8.3 The general model structure
8.4 An overview of all modules
9 Doring River catchment simulation, calibration and verification
9.1 Introduction
9.2 The study area
9.3 Water use activities in the Doring catchment
9.4 Simulation scenarios
9.5 Simulation stages.
10 Doring River model simulation results and analysis
10.1 Introduction
10.2 Simulation of historical irrigation patterns of development
10.3 Koue Bokkeveld irrigation development assessment without additional storage.
10.4 Aspoort irrigation potential with the proposed additional water supply
reservoir.
Section 4: Conclusions and Recommendations.
11 Conclusions
11.1 South Africa’s unique challenges in surface water resources modelling
11.2 Planning and the use of models in the water resources sector
11.3 The model development process.
11.4 Doring River system case study.
12 Recommendations
12.1 Modelling as a tool in planning
12.2 Development of water resources models
12.3 HYDRO25, further development and use
12.4 Towards a preferred water resources modelling scenario in
South Africa
References
Appendix A1: HYDRO25 model development case study
1 HYDRO25 model modules and interfaces
Appendix A2: Application of the HYDRO25 model in the Doring River case studY
References
