Hydel Power Assessment for Small Catchments in Himalayan Region using GIS & RS Techniques
Anit Ghose, VP, Webstar Infotech (P) Ltd; Nov 2003

Introduction

Indian power sector has an installed capacity of 86000 MW. Out of which 25% is hydro power and remaining are thermal, nuclear and gas-based projects. Power shortages in our country are estimated as 9% of total energy and 18 % of peak capacity requirements. Thermal based power projects have environmental repercussions related to emission of suspended particles and gases. While, large hydro power plants could lead to degradation and erosion of soil, loss of forests, wild life habitat and bio-diversity and most important is the resettlement of people.

To promote the environmentally sound energy investments as well as to help in mitigating the acute shortfall in power supply, the Government of India is promoting development of country's renewable energy resources and had made it a priority thrust area under India's National Environmental action plan. As there is vast potential for development of Small Hydro Power projects, enormous funds shall be required to tap this potential. Considering the large requirement of funds, it may not be possible alone by Government to provide adequate finances.

To mobilize additional resources for the small hydro power, private sector participation has to be encouraged. In many states, private sector has been invited to tap the hydro power resources for captive use as well for commercial purpose. Private sector participation in renewable energy has also increased significantly in recent years as Government of India has opened the power sector to private sector participation.

The run-of-river schemes are existing mainly in hilly areas of Jammu and Kashmir, Himachal Pradesh, Uttar Pradesh, West Bengal and North Eastern States of our country. A significant number of potential sites have been identified for development by private developers (table 2). The categories of sites identified in Himachal Pradesh have been shown in table 3. The schemes allotted to private sector, especially in Uttar Pradesh and Himachal Pradesh, has limited hydrological data. These projects if planned and designed scientifically, based on regional hydrology, may be less affected by risk and provide excellent opportunity for development.

Advance Action for Capacity Addition in the 10th plan and beyond:

Government will take immediate steps to tie up funding, execution agencies and convey investment decision for schemes already accorded techno economic clearance of CEA. As far as Central Sector is concerned, NHPC would take up Chamera Stage II (300 MW), Parbati Stage-II (800 MW), HP and Kol Dam (800MW) in HP; Teesta Stage V(510 MW) in Sikkim, Loktak Downstream (90 MW) in Manipur and NEEPCO will take up Tuivai (210 MW) in Mizoram, Lower Kopili (150MW) in Assam, Kameng (600 MW) and Ranganadi Stage II (160 MW) in Arunachal Pradesh (after the consent of the State Govt. has been obtained). In addition THDC would take action to start activities on Tehri Stage II (1000 MW) and Koteshwar (400 MW) in UP. Similarly NJPC would also take up Rampur Project (535 MW) in HP. These projects would require budgetary support of about Rs. 2000 crores in the 9th Plan.

As a long term strategy efforts will be made to ensure that DPRs which are under various stages of processing for accord of TEC by CEA are finalized and cleared so that a start could be made on these projects in the next one or two years. Survey and investigation of the potential hydro sites on an advanced scientific basis would be essential requirement for the future. The progress on this front has been dismal given the funds constraint and outdated technology.

The funding agencies like World Bank and ADB have shown their interest towards funding the survey and investigation activities for hydroelectric projects. Concerted efforts would be made towards availing the funds quickly. This would not only help in preparation of the bankable DPRs for large hydroelectric projects but would also being in advanced technology by involving reputed international consultants. The Central organizations like CWC, Brahamputra Board, NEEPCO and NHPC, besides SEBs would be provided with Funding support from the proposed Power Development Fund for the Purpose of carrying out survey and investigations and preparation of bankable DPRs.

Development of Small Hydro Power projects and thrust areas:

Small hydropower development is one of the thrust areas of power generation from renewable in the Ministry of Non-conventional Energy Sources (MNES). Ministry of Non-conventional Energy Sources is encouraging development of small hydro projects in the State sector as well as through private sector participation in various States. In 1989, when the subject of small hydro up to 3 MW station capacity was given to the Ministry of Non-conventional Energy Sources, the total installed capacity of such projects was only 63 MW. In just 10 years, this capacity has increased 3 fold. Among the major initiatives taken in this regard includes identification of potential sites and their feasibility studies, R&D-cum-demonstration projects with new and innovative approach and technical and financial support to set up grid-connected as well as decentralized small hydro projects.

From 1989 to 1993, the thrust of the programme was on setting up of demonstration projects in various States to regenerate interest of State Governments/ SEBs to set up SHP projects. For this purpose capital subsidy of up to 50% of the cost of project subject to a maximum of Rs. 2.50 crores per MW was provided.

During 1993-94, keeping in view the over all policy of Government of India to encourage private sector participation in the field of power generation, the thrust of SHP programme was also shifted to encourage private sector for setting up of commercial SHP projects. All the States were requested to announce suitable policies for private sector participation in the field of SHP. For this purpose guidelines were issued by MNES to the States in September, 1993. So far 13 potential States have announced their policies for private sector participation in SHP sector. During the 9th Plan (1997-2002) again the thrust of SHP Programme is to promote commercialization in the SHP sector. The main thrust areas / activities for the 9th Plan are as follows:
1. Nation-wise small hydro resource assessment
2. Encouragement to commercial SHP projects
3. Renovation and modernization of old SHP projects
4. Special incentives to North-Eastern States to exploit small hydro potential
5. Development and up-gradation of water mills
6. Industry based research and development

Some Recent Developments:

o 150 MW Kopili Hydro Electric Project – Assam – commissioned.
o 16 MW Gas Based Power Project – Tripura – commissioned – power shared by Tripura & Mizoram.
o 405 MW Ranganadi (Arunachal Pradesh) & 75 MW Doyang (Nagaland) Hydro Electric Projects – under implementation.
o Also funded a large number of micro-hydel and non-conventional energy schemes

Utility of Regional flow Duration Models:

Flow duration curve is a simple graphical depiction of variability of water flow at a location without any reference to the sequence in which this flow would be available. Flow duration curve for the site for which adequate flow data is available can be directly developed. Flow for various levels of dependability for gauged site may be estimated from this curve. It is quite obvious that most of the prospective sites for hydro-power projects are likely to be ungauged. For such potential sites, there are either insignificant data or no flow data available for such analyses.

To derive: a flow duration curve for a location on a stream for which adequate flow data are not available, Regional flow duration curve may be used. Regional flow models are developed on the basis of data available for a few other gauged catchments in the same region or transposed from similar nearby region. Such models are employed to compute flow duration curves for ungauged catchments in that region. Availability of such regional flow duration models is of paramount significance in estimating the potential of hydro-power in remote hilly regions of the country.

Regional Flow Duration Model Developed Under UNDP-Study:

The regional flow duration models for hilly states have been developed by National Institute of Hydrology, Roorkee in association with Alternate Hydro Energy Centre (AHEC) under Zonal Plan Activity of UNDP-GEF Hilly Hydro Project - Ministry of Non-Conventional Energy Resources, Govt. of India. The yearly flow duration model provides the pattern of flow at an ungauged catchment. For the development of flow duration model, the physiographic characteristics of catchment like catchment area, perimeter, length of main channel, elevation of highest and lowest points, geology of area, hydro-geology of area, land use pattern. Climate and other parameters should have been taken into account. However the model developed under above study is based on catchment area of gauged site only. The main reason was non-availability of topo-graphical features for significant number of gauged catchments, availability of data for individual catchment for short length and paucity of time and resources in carrying out detailed study. It was decided to pool the available data together within a region to form a single data series by making them non-dimensional for obviating the need of relating the flow data of individual catchment with their physiographic characteristics. Only mean flow from a catchment, used for making the flow record non-dimensional, was related to catchment area

The flow duration models, under the above study, were developed for nine regions covering all thirteen states of Himalayan region. These models are expressed mathematically in the form of algebraic equations and graphically in the form of plots. The model data was verified with the actual measured data in case study. As the confidence limit is not very encouraging, so the flow duration obtained from above regional flow model may be used only for pre-feasibility studies. The installed capacity may be based on the actually measured discharge data.

Utility of Remote Sensing Data for Catchment Analysis:

Remote Sensing data available in the near infrared region (0.8 um - 1.1 um) provides clearly the contrast between land and water features and therefore is best suited for mapping perennial streams. IRS-LISS III-Geocoded False Colour Composites (FCCs) data may be used for identification of catchment boundary, drainage network; perennial streams, land use and vegetation cover for these projects. Digital Elevation model (DEM) of these catchments may be generated by digitizing the elevation contours and spot heights from topographic maps and using capabilities of ARC/INFO GIS module (ARC-TIN) with user defined azimuth, elevation and look angle. The catchment boundary, drainage network and location of major habitation may be overlaid on these DEMs for further analysis.

Objective of Present Study:

The objective of study in progress at this centre is to develop the modified regional flow duration model by collecting the discharge data of more gauged catchments with longer duration and relating more physiographic characteristics of gauged catchments with the mean flow. The database of Small Hydro Potential sites will also be updated with the availability of additional information about the catchments.

Data to be used for the Application:

To develop the modified regional flow duration model for ungauged catchments and to update the database of Small Hydro Potential Sites in North-Eastern States, following data are being collected by this centre for the gauged sites
• Physiographic characteristics of Catchments Name, Geographic location, catchments area, Altitude of gauging station, Mean & maximum altitude of catchments, Influence of ice/snow/glaciers, Catchments map/drawing. Stream network in catchments area, portion of catchments which is forest or under glacier, area of catchments covered by snow (mean of maximum snow cover)
• Meteorological Data Time-series of river flow data (daily or l0-daily), monthly precipitation, temperature, solarity, relative humidity and wind speed for all meteorological station with altitude of station
• Areal climatology Digital or paper maps of monthly/seasonal/annual precipitation, evaporation, temperature, snow cover, relative humidity, solarity, wind direction etc.
• Digital Terrain Model data (DTM) Digital Terrain Data for is being procured with different elevation posting in a grid data structure. Digital Terrain Models shall be used for computation of slope, channel length, area of catchments, head available for power generation and location of suitable sites for civil structures of small hydro power projects such as Diversion Weir, Feeder and Head Race Channel, Desilting Tank, Fore bay Tank, Power House Building etc.
• Repetitive satellite data for these catchments may be effectively used to locate the region of deforestation and impact of small hydro projects development on forest in the catchments. The sites in deforestation regions may be considered as potential sites for hydro power station to control the deforestation to a larger extent.
• Transmission Line Network Data It is proposed to integrate the existing 11 kV transmission line network with small Hydro Potential Sites. This information will have a bearing on priority of sites selected for development as for those sites which are close to existing transmission line network, expenditure on laying and maintenance of transmission line from small hydro project upto the existing network will be reduced considerably
• Other Data Geology, Hydro-Geology, Soil Cover and Land Use and other parameters are to be related with modified flow duration curves.

Conclusion:

Development of small hydro projects in remote places of hilly area will enhance the quality of life in these areas. Development of regional flow duration model and Small Hydro Potential Sites Database will enable to plan for Hydro-Power Development on a sound scientific basis. This will help in bringing the prosperity to the area in particular and region in general.

Development of Small Hydro Schemes will also help in reducing the migration from these areas and reduce the dependency on forest and fossil fuel products which are being used to meet the energy needs. The efficient Small Hydro Potential Sites in GIS environment will hasten the process of planning and implementation of small hydro projects for which private sector has shown a considerable interest.

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Also read "Geothermal Energy Resources in India and its Utilization" By D. Chandrasekharam, Indian Institute of Technology, Mumbai.

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