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
|
Grading |
Total (maximum : 100) |
|
A |
>80 |
|
B |
60-79 |
|
C |
40-59 |
|
D |
20-39 |
|
E |
<20 |
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 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.