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GIS and Visualisation Capabilities for Interlinking of Indian Rivers
 Dr. M. Krishnaveni Visiting Faculty mveni70@yahoo.co.in J. Prakashvel MS Scholar pra_vel@yahoo.com Dr. M. Kaarmegam Director karmegam@annauniv.edu Centre for Water Resources, Anna University, Chennai – 600 025 Tamil Nadu, India Ph/Fax: 2235 1075 Introduction India is blessed with abundant water resources, which are unevenly distributed in space and time. When one part of the country is reeling under severe water scarcity, floods damage another part. India experiences extremes of climate within the 329 M ha of geographical area. Mean annual rainfall varies from 100 mm in western Rajasthan to over 11000 mm at Cherrapunji in Meghalaya (Indian Water Resources Society, 1994). Flood prone areas of 40 M ha and Drought prone areas of 51 M ha are being affected in India. Some rivers are perennially dry and some rivers discharge huge quantum of water to the sea every year. This necessitates the surplus and deficits to be redistributed for the betterment of the whole country through the massive task of Interlinking of rivers. Interlinking of rivers involves multidisciplinary data on hydrological, environmental, agricultural, socio-economic and political aspects. Moreover, these data will be derived from various sources such as toposheets, remote sensing imagery, aerial photographs, paper maps and field data. For decision making on such complicated project issues, the related data and information should be stored at one place in digital form for easy retrieval, updation and analysis for effective planning and execution purposes. GIS, a powerful spatial technology, provides the scientific environment to store and analyse multidisciplinary data for solving such real world problems. GIS combines spatial database management, statistical analysis and cartographic modelling capabilities within computer hardware and software configuration. The objective of the paper is to explore the capabilities of GIS that will be very useful in solving the various issues of interlinking in order to expedite the process of interlinking. National Perspective Plan Ministry of Water Resources and Central Water Commission formulated a National Perspective Plan (NPP) for Water Resources Development in 1980, which is undertaken by National Water Development Agency (NWDA). The NPP comprises of two components, Himalayan Rivers Development and Peninsular Rivers Development. There are 14 link canals in Himalayan component and 16 link canals in Peninsular component (Fig.1). Himalayan Rivers Development envisages construction of storage reservoirs on the principal tributaries of Ganga and the Brahmaputra Rivers in India, Nepal and Bhutan along with interlinking canal systems to transfer surplus flows of the eastern tributaries of the Ganga to the west apart from linking of the main Brahmaputra and its tributaries with Ganga and Ganga with Mahanadi. Peninsular Rivers component consists of diversion of surplus from Mahanadi to Godavari system and to a further transfer of the surplus from Godavari to Krishna, Krishna to Cauvery, and Cauvery to Vaigai Rivers. It also comprises of diversion of west flowing rivers towards eastern side and building storages at potential sites in these basins. The three stages of the above water resource project are:
Functionalities of GIS Digital Mapping Digital mapping is the most elegant and compact method of displaying the spatial data. Graphical representation of natural resources, utilities and facilities smoothen the progress of decision-making. Maps that are difficult to make manually such as 3-D maps or stereoscopic maps can be created. Statistical analyses of attribute data can be performed and mapping can be done accordingly. Mapping of resources can be done at different scales (Small, Medium or Large), which depends on the level of study (National, Regional or Local). National level planning (Small Scale Mapping) is needed for sustainable water resources development of the Country, whereas local level planning (Large Scale Mapping) is needed for the benefit of the villages’ enroute the river link. Overlay Analysis Using the overlay technique, various thematic layers can be overlaid and specific information can be derived from it. For example, layer consisting of proposed canal of any particular stretch can be overlaid over the Land use map, of that region. From the resulting layer, one can get the information of land uses that are affected based on which the problems of deforestation, land acquisition, resettlement and impact on environment can be analysed. The strategies can be framed to solve the above issues within the stipulated time and proceed with the works. Drought prone area can be identified and planning of alignment can be made so as to benefit the deficit areas. Interpolation Spatial variation of any water related aspect such as rainfall, surface water, etc could be interpolated using GIS. Various interpolation techniques used are Natural neighbourhood, krigging, etc. which are provided by GIS. For instance, spatial variation of seasonal rainfall can be interpolated over a region to get an overview of rainfall deficit and excess regions. Figure 2 shows rainfall distribution map of Palar basin.  Figure 2. Spatial Distribution of Northeast Monsoon Rainfall in Palar basin Digital Elevation Model (DEM) It is a quantitative model of part of earth’s surface in the digital form. One of the most sophisticated GIS capabilities which is very much useful in hydrologic modelling is digital representation of topography of the catchment. Techniques used in the computer descriptions of topography are called Digital Elevation Models (DEM). Three principal methods for structuring a network of elevation data are square-grid networks, contour – based networks and Triangular irrerugular networks. They can be used to automate the delineation of drainage pattern, stream networks, and water sheds. Digital Elevation Model of the region through which the canal passes can be created. This will help the engineers to study the three-dimensional topography of the region through which the canal passes. Automatic calculation of earthwork quantities for cutting and filling can be done. The fundamental requirement for canal alignment is topography of the region. The topography can be studied in detail if digital elevation model is constructed for the project areas using GIS software. Three dimensional view of the topography can be prepared using GIS which will be very useful for planning the canal alignment and construction of various hydraulic and irrigation structures enroute of the canal alignment. Planning shall be made so as to use the existing reservoirs and anicuts to the maximum extent. Moreover, the project involves construction of various irrigation and hydraulic structures along the canal. Tunnels, Canal alignment and cross drainage works. Figure 3 shows the digital elevation model of Cauvery – Vaigai – Gundar Link.  Figure 3 DEM in a VRML Browser Visualisation (Virtual GIS) Visualisation is a form of communication, which is universal and which has the ability to form an abstraction of the real world into graphical representation. Once a project proposal is developed, it is necessary to communicate the effects of proposed changes to other agencies and public review groups to facilitate decision-making. Some of the changes in the environment can be modelled and visualised using GIS. Visualisation provides additional insights to results, which would otherwise be displayed as text or numbers. The virtual GIS are making a revolution in 3D analysis. Multimedia technologies are enhancing the use of GIS as decision making tool. It is possible to visualise the landscape of project site in a virtual manner. This is very economical and less frightening than a ride in an aeroplane. The natural existing system can be virtually viewed in the desktop. Using GIS and Virtual Reality Modelling Language (VRML), one can view the entire link as if the walkthrough of entire stretch. The required information about the project can be seen in advance. Visualisation technique combined with GIS will really be a boon for planners. Impacts during the droughts such as the depletion of ground water level, greater accumulation of silt leading to rising of river bed and saline intrusion in the coastal areas and impacts due floods such as inundation problems can be modelled and visualised in the computer system. As visualisation will project various benefits to the people with visual impact, it will greatly enhance the process of getting National political consensus. The contours of regions through which the link canal passes will be digitised along with river and other physical features using MapInfo GIS software. A fly through the model of above contours can be developed using Virtual GIS module “PAVAN” of MapInfo that can be viewed using VRML browser. Third dimension of terrain and other geographic features can be visualised to get the real picture of the topography. By simulating the project in the system using virtual GIS, degradation of land if any can be evaluated and necessary measures can be taken to prevent the degradation. There will be a change in the regime of rivers due to abstraction and addition in the river. This aspect can be modelled and critically assessed and their impacts due to change in the quantum of water in rivers can be studied using Virtual GIS.
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