Site evaluation for ranking study of potential hydro-power projects: An Indian perspective...

Site evaluation for ranking study of potential hydro-power projects: An Indian perspective using spatial technologies

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A. K. Chakraborti
Water Resources Group, NRSA, Hyderabad, India
[email protected]

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., “least socio-economic, environmental and infrastructural development costs and best return in hydro-power generation ensuring river basin-wise resource optimization”.Instead of random basis site selection, ranking study provides various alternative site scenarios based on certain objective criteria.

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

Spocial Costs submergence of lands
rehabilitation of settlements
– agriculture
– population
re-routing of roadways
Environment Costs forest vegetation
– area
– species
Disaster Sensitivity hydrology
– flash flood
– glacier lake outburst
geology
– landslide
– lineaments/tectonics,
– underlying rock instability
Infrastructural Advantage – accessibility to site
– transportation network
land availability for resettlements
construction material source
Fixing Design Parameters dam height & length, tunnelling length
assured water availability
installed power capacity
Financial Cost & Return construction cost
return on investment
– power tariff to be charged

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.

Site evaluation for ranking study of potential hydro-power projects: An Indian perspective using spatial technologies

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