Hydrologic data network design i8 a fairly complicated problem where questions as to the number of gages required, time frequencies to be selected, and benefits/costs of monitoring still remain unresolved. These issues are intensified in case of water quality variables as they are more error-prone, costly, and time consuming to sample. The basic difficulty underlying the design and evaluation of monitoring systems is the lack of an objective criterion to assess: (a) the efficiency, and (b) cost-effectiveness of a network. A statistical procedure based on the entropy principle of information theory is proposed to address the evaluation of both factors. Efficiency is measured quantitatively in terms of the information produced by a network. Similarly, benefits of monitoring are described by informative measures for an objective evaluation of cost-effectiveness. The study presented demonstrates the applicability of the entropy method in assessing the efficiency and the benefits of an existing water quality monitoring network. The method is applied for temporal and spatial features of monitoring, handled as both separate and combined problems. The results are shown in the case of the highly polluted Porsuk River in Turkey. The strengths and shortcomings of the proposed methodology are discussed, with recommendations for future research on the application of the entropy principle in network design. (KEY TERMS: water quality monitoring; network design; network efficiency; benefits/costs of monitoring, information; entropy.)

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Planning of solid waste management (SWM) facilities in terrestrial as well as coastal areas addresses several situations, and requires considering numerous factors. This leads to large amounts of data and information that must be organized and analyzed. However, in many SWM systems, all of the relevant information cannot be managed properly due to insufficiencies in methods/tools and/or resources. To assist the solid waste decision making process, GIS-based decision support systems can be applied to deal with the multi-attribute and spatial nature of SWM systems. In this study, the application potential of GIS based decision support systems to functional elements of the SWM system are reviewed first. Then particular emphasis is given to landfill site selection. In this context, landfill siting process and key siting criteria were developed to incorporate the environmental, socio-political, engineering, and economic factors for an appropriate solution. To aid decision makers to determine landfill area requirements, an area estimation model, containing population projection and waste quantity forecasting modules, was developed in Visual Basic. Following the development of a graphical user interface, suitable areas for proposed landfill were determined in an IDRISI environment.

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