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AVSWAT- a Spatial Decision Support System for Land and water management and its application for watershed management in Bankura district of West Bengal
Debapriya Dutta NRDMS Division, Department of Science and Technology Technology Bhavan New Delhi- 110016. India. Tel:91-011-6962819(Ext. 202/262), Fax:91-011-6516076 psa@alpha.nic.in Abstract
Decision Support Systems (DSS) are defined as computer-based information systems designed to support decision makers interactively in thinking and making decisions about relatively unstructured problems. Spatial Decision Support Systems (SDSS) , which are the integration of DSS and GIS was initiated by Densham and Goodchild ( 1988) are emerging as efficient tools for managing natural resources like land and water. AVSWAT ( Arc View- SWAT) , a user- friendly PC based SDSS tool has been developed at the Black Land Research Center , Temple, Texas, USA integrating Soil and Water Analysis Tool (SWAT) and Arc View GIS version 3.0a software along with Spatial Analyst version 1.1 extension. SWAT is a continuous time river basin or watershed scale model operating on daily time step. In the present study, the tool was applied in digitally delineating watersheds in a block of Bankura district of West Bengal and then it was used for estimating potential water ,silt and crop yield from each of them. This would be helpful in prioritising the watersheds and presenting the results spatially for the district level decision makers. Key Words: Spatial Decision Support System, AVSWAT, Watershed Management. Decision Support Systems (DSS) are defined as computer -based information systems designed to support decision makers interactively in thinking and making decisions about relatively unstructured problems. Traditionally, DSSs have three major components, a database, a model base and a user interface as depicted in Fig. 1a. An extension of the DSS concept, Spatial Decision Support Systems (SDSS), which are the integration of DSS and GIS (Fig. 1b) was initiated by Densham and Goodchild ( 1988).  GIS is a general purpose technology for handling geographic data in digital form, with the ability to preprocess data into a form suitable for analysis, to support analysis and modelling directly, and to post-process results (Goodchild, 1993). A significant capability of the SDSS is the ability to use spatial analysis and display tools with the sectoral models and that would form the model base of SDSSs. The modeling capability allows the user of the SDSS to simulate changes in objects and attributes. The database component of the SDSS can supply input data for the models. After the models are run, the resulting output can be written to the database for later display via the user interface , in tabular, chart or map form. For planning purposes, this ability to dynamically change information, forecast and perform sensitivity analysis is essential. Both GIS and DSS have been widely used in natural resources management. Watkins and Mckinney (1995) presented a review on DSS in water resources; and Goodchild et al. (1996) described a comprehensive study of GIS in water resources and environmental engineering. Singh and Fiorentino (1996) gave a comprehensive review of GIS in hydrology. In summary, SDSS provide unique advantages for land and water resources management in the following aspects: 
for land and water management, the following considerations were made :
Based on the above considerations, the Soil and Water Assessment Tool (SWAT) model was selected. The SWAT model is a combination of the SWRRB, GLEAMS and ROTO models and hence it is able to model both the hydrology and water quality of a watershed (Arnold et al., 1995). The model is reported to be able to operate on both a raster and sub-watershed (hydrologic response unit) basis (Arnold et al., 1995).In addition, the model is linked to GIS packages like GRASS (Geographic Resources Analysis Support System) via the SWAT-GRASS interface (Srinivasan and Arnold, 1993) and ARC-View through the SWAT-ARC View interface (Diluzio et al, 1997), thus easing the task of data input and output display.
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