GIS@development August 2002: "GIS and simulation models for Water Resources Management A case study of the Kelantan River, Malaysia"

Water resources are at the heart of sustainable development in many regions of the world. Water of sufficient quantity and quality is an essential resource for agriculture, industry, and tourism, but also for everyday life in cities and villages. A growing population and a growing economy not only lead to increasing demand for water, they also cause increasing pollution that may threaten the very water resources this growth depends on and thus threaten the sustainability of development (Brookfield and Byron, 1993).

Water resources are distributed in time and space, and their availability may vary greatly from time to time and place to place. This variability causes problems: not enough or too much, drought or flood, and not of the right quality, i.e., polluted: these are the main issues to be addressed.

Spatial Problems and Spatial Solutions
The basic unit in water resources management is the river basin or hydrographic catchment, and the network of draining channels, the river network that collects and conveys surface water. River reaches, dams and reservoirs, diversion and pumping stations, water works and secondary distribution networks are all spatially distributed elements of this system. Underneath, we find the unsaturated and saturated zones of groundwater aquifers, usually contributing considerable quantities of high quality water with quite different, much slower storage and flow characteristics.

The elements of water resources management are distributed in space. Their location, surrounding, and spatial relationships are critical for the resulting flow characteristics and the quality, of the water resources and thus their availability for different types of use. River basin management has obvious spatial dimensions, since it is focused on a spatial unit, the hydrological catchment, in the first place. Consequently, geographic information systems are one of the tools that can be used for their analysis. This makes the use of GIS, and its integration with traditional water resources models, and obvious strategy for the development of river basin management systems (Maidment 1996, Fedra and Jamieson, 1996).

While the GIS is used to capture, analyse, and display spatial data, the models provide the tools for complex and dynamic analysis. Input for spatially distributes models, as well as their output, can be treated as map overlays and topical maps (Fedra,1994) . The familiar format of maps supports the understanding of model results, but provides also a convenient interface to spatially referenced data. And expert systems, simulation and optimisation models add the possibility for complex, and dynamic analysis to the GIS. One major challenge in building effective river basin information systems is the integration of dynamic models with the capabilities of GIS. The GIS can provide a common framework of reference for the various tools and models addressing a range of problems in river basin management, supply distributed data to the models, and assist in the visualisation of spatial model results in the form of topical maps. In a multi-media framework, it can also provide a common interface to the various functions of an integrated river basin information and decision support system. This interface has to translate the data and model functionality available into information that can directly support decision making processes (Fedra, 1995).

Functions and Tools
WaterWare, which is an object oriented information and decision support system for river basin management, organises the data describing a river basin in terms of spatial objects: they include elements such as monitoring stations and their associated time series of measurements, sub-catchments and irrigation districts, the river network with it nodes and connecting reaches, as well as the various simulations models and their scenarios (Fedra and Jamieson, 1996a,b, Jamieson and Fedra 1996a,b). With all objects geo-referenced and the models spatially distributed, the embedded GIS is a central component.

The embedded GIS
The map layers used in WaterWare either provide background for spatial reference and orientation, or direct data input for the simulation models. Examples for the latter are the digital elevation model (DEM), land use maps, and the river network. The embedded GIS offers tools for layer selection and stacking, zooming, color editing, a four window mode for map comparison, 3D display of the DEM with any map draped over the elevation data, and read-back functions for locations, distances, or areas.

Fig. 1: Mutiple GIS windows support they direct comparison of several map layers

Fig. 2: 3D display of the Kelantan river basin, seen from the East, the sea coast

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