1.1 Hydropower project planning stages
Hydropower project planning stages is divided into three main categories:-
1. Reconnaissance
- It is first stage of project planning.
- It is mainly based on secondary data from maps, aerial photographs and visual inspection.
- This is done mainly for license acquisition purpose.
Objective:
- To identify the suitable project for the stated purpose.
- To provide preliminary cost figure of the project.
Major steps are:-
- Data collection
- Desk studies
- Field work and design
- Estimation
- Environmental and social studies
- Economic assessment
- Report
2. Prefeasibility
- In prefeasibility study the review of the study made in reconnaissance studies is further studied in detail from precise instrument, data series of long time and field survey data.
Objective:
- Establish the need and justification for the project.
- Formulate the plan for developing the project.
- Determine the technical, economic and environmental practicability of the project.
- Make recommendation for further action.
Major steps are:-
- Data collection
- Desk studies
- Field work and design
- Estimation
- Environmental and social studies
- Economic assessment
- Report
3. Feasibility
- In this level pf study the detailed study of the project is carried out in order to determine the technical, economic and environmental feasibility of the project.
Objective:
- To carry out detail design of the project.
- To direct project towards construction.
Major steps are:
- Data collection
- Desk studies
- Field work and design
- Estimation
- Environmental and social studies
- Economic assessment
- Report
1.2 Hydrological data processing
a. Mass curve:
- It is a graph of cumulative values of a water quantity (runoff) against time.
- Also known as Ripple curve.
- It is and integral curve of a hydrograph.
Characteristics:
- It is continuously rising curve.
- The slope at any point on the curve represent the inflow rate.
- If the curve rises sharply, it indicates the high rate of inflow within that period.
- If the curve is horizontal, the flow is zero.
- If the curve is convex, it indicates flood.
Uses:
- It helps in designing the size of the storage required for hydro-electric power plant.
- Check the consistency of many kinds of hydrologic data.
b. Flow Duration Curve (FDC):
- It is the plot of discharge versus percentage of time exceedance of discharge.
Characteristics:
- The slope of flow duration curve depends upon the interval of the data.
- FDC is a decreasing curve.
- Chronological sequence is disturbed in flow duration curve.
- With the increase in storage, the flow duration curve becomes flatter.
- Area under flow duration curve gives flow volume.
Use:
- It is useful in planning and designing of water resource projects.
- It helps in the design of drainage system and in the flood control studies.
1.3 Reservoir planning and regulation
Reservoir:
- When a barrier is constructed across the river, the pool of water formed on the upstream side of the barrier is called reservoir.
Classification of reservoir:
1. Flood control reservoir
- Main purpose of the reservoir is to temporarily store the flood water and release slowly at a safe rate.
- Gates and spillways are used for flood control.
2. Storage or conservation reservoir
- Used to maintain minimum supplies of water for irrigation, hydropower and industries.
- Used to store excess water.
3. Distribution reservoir
- Small capacity reservoir used to fulfill the water supply requirement of a particular city.
- Made of masonry or cement concrete.
4. Multipurpose reservoir
- Reservoir planned and designed for more than one purpose.
- Used to protect from flood, irrigation, water supply and hydroelectric purpose.
Site selection for reservoir:
- Should be located in area with maximum inflow and minimum percolation.
- Site should be accessible by road.
- Site should be located at narrow opening of the basin.
- Construction materials for the dam should be available locally.
- Site should have sufficient water depth.
- Site should be free from objectional minerals.
Regulation of reservoir:
- It is defined as the rational distribution of river flow in time and space among different fields of water resource system.
Need of reservoir regulation:
- The hydroelectric plant will not operate with efficiency if it is operated be low certain head.
- To prevent the excessive siting in the reservoir.
Useful life of reservoir:
- It is impossible to completely stop the flow of sediments of water into reservoir. A dead storage is made available to accommodate the volume of sediments.
- The useful life of reservoir is said to exist till the storage is reduced to 20% of designed capacity.
1.4 Environmental study policy based on type and size
- In order to check whether the proposed project has significant effect on the environment and whether such effect could be avoided or mitigated by any means or not, various studies are carried out at different stages of project planning which is known as Environmental Assessment (EA).
- There are two types of environmental study policy:
- IEE (Initial Environmental Examination)
- EIA (Environmental Impact Assessment)
| IEE | EIA |
| Conducted for small scale project. | Conducted for large scale project. |
| Scoping is not required. | Scoping is required. |
| Environmental auditing not required. | Environmental auditing is required. |
| Deals with simple and easily predictable impact. | Deals with unknown impact. |
| Approved by concerned authority within 21 days. | Reviewed by concerned body and approved by MOEST. |
Process of EIA/IEE:
- Environmental screening:
- Process determine whether EIA or IEE is required or not.
- Scoping:
- Purpose of scoping is to gather and identify the matters which should be covered in environmental information submitted to concerned authority.
- Involvement of relevant authorities, affected groups.
- Identification of relevant or significant issues to examined.
- TOR (Terms of Reference):
- Provides basic guideline to conduct project specific EIA or IEE.
- EIA/IEE Report:
- For IEE it is review by MOEn(Ministry of energy) and approved.
- EIA is review by MOEn and approved by MOEST (Ministry of Environment, Science and Technology).
1.5 Climate change and ecology:
River Engineering:
- In Himalayan area discharge of river is low and velocity is also low but in plain area discharge is high and velocity is low. So, this leads to sedimentation of structure and to prevent this various river training structure like guide bank is required.
Social cost:
- Hydropower projects becomes barrier to aquatic life.
- Due to large hydraulic structure it changes the flow regime of river.
- Hydropower project may affect particular social group of the community.
Population displacement:
- Destroys forest, wildlife habitat, agricultural land area by flooding.
Change in lifestyle:
- Pollution
- Health issue
Global worry:
- Global warming due to deforestation
- Destroy vegetation and agriculture
Clean energy alternatives:
- Solar energy
- Wind energy
- Geothermal energy
References:
- Hydropower Development: Engineering & Policy Perspectives – John S. Gulliver & Roger E. A. Arndt
- Renewable Energy Systems: Hydropower and Beyond – Godfrey Boyle