|
Perspectives of GIS modelling in hydrology
Focus on GIS Modelling In Hydrology Modeling draws to greater or lesser degree upon the geographic tradition that hydrology, catchment and fluvial system interact closely and casually in time and space. The elements of hydrological modeling predate GIS by more than a century. Geographic Information Systems (GISs) are highly specialised database management systems for spatially distributed data. Chow et al. (1988) offered a taxonomy of hydrological models based on the randomness (deterministic/ stochastic), spatial variation (lumped/ distributed; space independent/space dependent) and time variation (steady flow/ unsteady flow; time independent/time correlated) – thereby drawing the attention to the pivotal position of the spatial dimension explored the several possible applications of linking GIS with the hydrological models:
 Fig. 1: A Conceptual Structure for GIS Applications in Hydrology However relate these set of assumptions as a spectrum of significant role of GIS, with full linkage to modeling being seen as the ultimate expression of GIS contribution, but according to him these set of assumptions would be misleading the value of GIS not necessarily determined by the extent to which it is in control of the processes concerned, the role of GIS can be detrimental. Further Maffini (1997) argues that the database has been replaced by GIS as the integrating core of corporate information handling, which will further upgrade by network computing capability. GIS integrates different elements like automated mapping (AM), facilities management (FM), remote sensing, land information systems (LIS) and spatial statistics, also at the same time it serve as an input to the management information systems (MIF) in the corporate domain and modeling / control systems in the research domain (see Figure 1). As the corporate sector emphasizes the database as the key to the management information systems , in the same way Maidment (1993) tries to focus on the data model which is the key to the GIS modeling in hydrology concluding " It is probably true that the factor most limiting hydrologic modeling is not the ability to characterize hydrologic processes mathematically, or to solve the resulting equations, but rather the ability to specify values of the model parameters representing the flow environment accurately. GIS will help overcome that limitation." Application Domains of DEM In Hydrology Digital Elevation Models are used in number of sub-domains in hydrology. Varied hydrological applications can be driven by different users accessing the same pool of information. As a result the structure of the database that supports the GIS, quality of the data and the way in which the database is managed lie at the heart of development of many GIS applications. The DEMs have proved to be very efficient in extracting the hydrological data from the DEM by analysing different topographical attributes (elevation, slope, aspect, relief, curvatures) for modeling purposes. There are number of models developed in past which has been useful individually and combined applications in various combinations. DEMs have potentially proved to be a valuable tool for the topographic parameterization of hydrological models especially for drainage analysis, hillslope hydrology, watersheds, groundwater flow and contaminant transport etc. Discussion Most of the hydrological models are mathematical based,where they integrate existing knowledge into a logical framework of rules and relationships. GIS technology has been integrated with these several surface /subsurface hydrological models now for more than a decade understanding the utility and signifiocance of topographic attributes of the terrain for various hydrological applications. The reason of adopting GIS technology is because it allows the spatial information to be displaced in integrative ways that are readily comprehensible and visual. The spatial information collected are further subjected to continous GIS analysis. Further summarising the review of the historical models developed in past years and their significance with computing compatibility and suitability with GIS , discussing the different types of modeling – deterministic and stochastic approach to accomplish a complete linkage between GIS and hydrological models would require GIS to have time dependent data structures so that the evolution through time spatial distribution of hydrologic phenomena could be observed. The GIS techniques have the potential for widespread application to resource evaluation, planning and management. Finally modeling provides the opportunity for realistic representing the three – dimesional nature of natural landscapes in hydrologic modeling under the constraints of maintaining physical rigour , simplifying the governing equations that must be solved and reducing the computational requirements. Looking into the future of infornation technology is a high risk activity for possible evaluation of priorities of GIS in hydrology. Technologically, the effective acquistion and manipulation of high resolution spatial data will become commonplace to every individual for assessing the development factors in an area. Further increase in efficiency and limitless access to information may lead to real detriment and GIS will be strengthened but progressively subsumed to modeling management and operational control systems. References
Page 2 of 2
| Previous | |