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Site evaluation for ranking study of potential hydro-power projects:
An Indian perspective using spatial technologies A. K. Chakraborti Water Resources Group, NRSA, Hyderabad, India chakraborti_ak@nrsa.gov.in Introduction As per the preliminary assessment made by the Central Electricity Authority (CEA), Government of India, the hydro-power potential of the country is 1,48,000 MW at 60% load factor. Out of this, 16% hydro-potential has been developed and 7% is under various stages of development. Potential sites are about 450 located in the river systems of Indus, Ganga, Brahmaputra rivers in central India, west flowing and east flowing rivers in Western Ghat and Eastern Ghat in southern India. In order to exploit the balance hydro-potential to the full extent, it is necessary to intensify technical planning (survey, investigation, design), financial planning (construction cost, funding source, return on investment) and programme implementation. Concept of Ranking Study All infrastructural development projects follow a set procedure of survey and investigation before taking up implementation (construction) programmes. These steps are: Pre-Feasibility Report ? Feasibility Report ? Detailed Project Report. Since balance potential hydro-power sites in the country are of the order of 450, it is realised that, at the Pre-Feasibility Report stage, a 'Ranking' or 'Order of Priority' should be evolved. Sole logic of the Ranking Study is in terms of best location(s) i.e., Indices in Ranking Study Using Spatial Technologies CEA has adopted ten major criteria for preliminary ranking of hydro-electric schemes. These criteria are technical and non-technical, involving : (i) Reconstruction and Rehabilitation (ii) Accessibility to Site (iii) Height of Dam (iv) Length of Tunnel / Channel (v) Hydro-power Potential (vi) Type of Scheme (Run-of-the River or Storage Development) (vii) Status of the Project (viii) Status of Upstream or Downstream Hydel Development (ix) Inter-State Aspects (x) International Aspects. While these criteria are important, a better appreciation of the physical and environmental settings, which can be addressed using spatial information technologies, can form another set of indices in the ranking study (Table 1). Ranking Order Ranking order considering best to worst scenarios based on the indices presented in Table 1 needs to be evolved. In essence, for each index, weightage has to be assigned based on spatial data based analysis of advantage(s) or constraint(s) which will influence the site suitability and ranking order. Table 1: Proposed Ranking Indices Using Spatial Technologies
CEA has adopted certain maximum and minimum value between number range from 6 to 15 for each of the ten criterias mentioned above. Basis to assign a value to a criteria specific to a hydro-power site has been given. Sum total of these numbers adds to hundred. A system of grading is shown in table 2. Site suitability and ranking order using spatial information technologies is well suited to adopt a similar weightage procedure, once a cluster of sites in a river basin is sufficiently analysed with all available spatial and attribute data. What Spatial Technologies Provide? Space technology using satellite and aerial remote sensing plays a very important role in terrain mapping and scientific assessment of the ground conditions at speed which no other survey method can provide. This technology is ideally suitable for inaccessible mountainous regions where majority of hydro-electric site are located. Image analysis of satellite digital data and creating spatial geo-reference information of the terrain, where potential hydro-electric schemes are located, using GIS tools, provide basis to address indices in the ranking study. Locational Physical settings of typical hydro-electric scheme consist of (i) dam site (ii) submergence are (at full reservoir level contour) of the run-of-the river pondage / storage reservoir, (iii) power tunnel /channel route, and (iv) power house site. With geometric rectification and co-registration of satellite data, precise locational geo-referenced layer incorporating these physical settings can be obtained. Mensuration of submergence area, dam and tunnel lengths are added information from this layer. Table 2
Landuse-Landcover Landuse-landcover information of the above-mentioned physical settings are of great interest in every stage of technical and financial planning. This information provides the social costs and environmental costs to the project. Key landuse-landcover information are : (i) agricultural lands (ii) forests and (iii) settlements vulnerable by the project. The extraction of these information from IRS-1C/1D LISS-III satellite-sensor data is an well-established operational tool. Since, ground-truth in these mountainous inaccessible terrains are not possible at this preliminary stage, image processing algorithm of "iso-data clustering" is performed for landuse classification and area information obtained within the reservoir submergence window. Infrastructural Infrastructural layer consists of (i) transportation network in and around the project site (ii) near-by townships (iii) lands available for resettlements (people, agriculture, afforestation) (iv) construction material sourcing. This layer needs to be prepared from all available map sources and to some extent from satellite data. Digital Elevation Digital elevation model (DEM) of the physical settings as mentioned above, can be prepared from (i) topographic maps (ii) fresh aerial photography (iii) IRS-1C/1D PAN stereo images. Environmental settings of landuse of the hydro-power site on to the DEM will constitute the digital terrain model (DTM). This helps the project site from different viewing angles and aspects for better appreciation of the advantages and constraints of technical planning. Case Study : Indus Basin Indus river system consists of 6 sub-basins (Indus main, Jhelum, Chenab, Ravi, Beas and Sutlej). Balance potential hydro-power sites in Indus river basin in Himachal Pradesh and Jammu & Kashmir are estimated to be 92 with a projected installed power generation capacity of 20512 MW. A rapid study (of 40 days) of 81 such potential hydro-power sites using IRS-1C/1D LISS-III satellite-sensor data of the year 2000 was conducted by NRSA on a request by CEA as inputs to the Preliminary Ranking Study Report. Locational, landuse-landcover and infrastructural layers are generated based on the procedures described earlier. With the limited information atpresent from spatial technology inputs, some of the ranking indices in Table 1 are addressed to assign ranking order. Table 3: Ranking Study of Potential Hydro-power Sites in Indus Basin Using Spatial Information Technologies
A: highest ranking order; E: lowest ranking order. Table 3 presents insight into the quantitative criteria of 3 good sites and 3 bad sites as a typical example. Sites (Wangtoo and Karcham) possess good power generation capacity, thus good return on investment, with low social and environmental costs and available infrastructure advantages. At Gangabal site, existing glacial moraine lakes are the source of water for hydro-power generation to be interconnected by power tunnel of 6.5 km length to the power house downstream, with no social and environmental cost and with minimal investment. In general, compared to run-of-the river schemes, storage schemes (for example, Bursar, Sonamarg, Chechesna) present serious social and environmental costs with constraints of resettlement, even though, there is attractiveness of power generation capacity. This type of objective ranking study will tilt in favour or against the decision about subsequent technical and financial planning and program implementation. Acknowledgement Ministry of Power, Government of India has taken the progressive step in initiating the process of balance hydro-power development in India with a 'Vision on Power on Demand by 2012". I like to thank Shri S. Prabhakaran, Special Secretary, Shri Anil Razdan, Joint Secretary, Shri Sailesh, Director, Ministry of Power, Govt. of India and Shri D.V. Khera, Ex-Chairman, Shri R.S. Chadha, Chief Engineer, CEA for giving the challenging responsibility to NRSA to apply spatial information technologies for the ranking study of hydro-power projects. Dr. R.R. Navalgund, Director, NRSA was the moving force to take up this challenging responsibility and a dedicated team of scientist-engineers in Water Resources Group helped me in implementing the task. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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