An information base for a decision support system for management of the Mhlathuze River
Effective integrated catchment management is dependant on suitable information describing the physical, social and economic conditions in the catchment. It also depends on knowledge of the processes controlling the environmental systems in the catchment. This thesis describes the development of an information base (IB) for a computer-based decision support system (DSS) to support the effective management of the Mhlathuze River system. The IB has been developed to contain most of the available data, which are analysed and processed by models, for utilization by catchment managers. The DSS and accompanying IB was developed during the formulation and implementation of the new Water Act (1998) in South Africa. It attempts to support the implementation of this Water Act, which stipulates the integrated management of water resources on a catchment basis. The database was designed to contain all hydrologically relevant data and information on the Mhlathuze River catchment. Extensive data collection has identified information on rainfall, evaporation, flow measurements, the soil type map of the area, 1:50 000 topographical maps and 1:500 000 maps, 1991 census data, lithology and groundwater, national, regional and local boundaries, pollution and water quality monitoring points, water consumption and details of water users, etc. The database is still growing with the identification and collection of more data and the creation of additional information about the Mhlathuze River catchment from various models. A structure was developed in the IB to give access to the megabytes of information on the database in a structured manner. The operating environment of Arcview 3 (running on Windows 95) was used to develop a user - database interaction system. The Windows concept of interactive icons was used to customise the user interface by incorporating buttons and tools to the IB. Scripts, written in Avenue, were attached to these buttons and tools, to add to the functionality of the IB. A Digital Elevation Model (DEM) was developed from 100-metre elevation contours which originated from 1:500 000 maps. These were supplemented by digitized contours from the 1:50000 maps. The DEM has a horizontal resolution of 125 metre by 125 metre per cell, and covers the whole extent of the Mhlathuze River catchment, stretching 120 km in the east-west direction, and 60 km in the north-south direction. A land use model for the catchment was developed from satellite imagery (7 bands from the Landsat TM satellite). Two different techniques, involving supervised and unsupervised classification methods were applied to identify the land cover classes. The supervised classification method used the maximum likelihood technique, while the unsupervised classification method applied a cluster analysis technique of classification. For the hydrological run-off modelling of the Mhlathuze River system, the HYdrological Modelling System (HYMAS), utilising the Variable Time Interval (VTT) model, was chosen to simulate short duration hydrological events in a distributed manner. The model was used in an Instream Flow Requirements (IFR) study to identify the ecological reserve of the river. Information derived from the DEM and land use model were used during the hydrological simulations. Output from the simulations was compared to the few observed flow measurements which are available for the catchment.
Hydrology--Thesis and dissertations., Hydrology--Kwa-Zulu Natal--Mhlathuze River.
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