Planning of Hydropower Projects

Hydropower studies are done in stages so that money is spent in steps and weak projects are dropped early. Each stage gives more detail and less uncertainty (cost accuracy about ±30-40% at reconnaissance, ±20-25% at pre-feasibility, ±10-15% at feasibility).

1. Reconnaissance study

Purpose: to identify possible sites and find if the project is worth further study.

• Desk study: topographic maps (1:25,000/1:50,000), satellite images, geological maps.
• Rapid site visit: access, river and valley shape, rough geology.
• Hydrology: use of nearby station data and regional methods (e.g. WECS-DHM method, MIP) to get mean flow.
• Rough layout, installed capacity, energy and rough cost estimate.
• Quick check of environment and social issues; ranking of sites.

2. Pre-feasibility study

Purpose: to compare layout options and choose the best one.

• Topographic survey of the headworks and powerhouse areas (1:2,000-1:5,000), river cross-sections.
• Hydrology: at least 1 year of gauging if possible; flow duration curve, floods (design flood 100 yr), sediment.
• Geology: surface mapping, geophysical survey (seismic refraction/resistivity), a few drill holes.
• Alternative layouts and capacities; selection of the best.
• Cost estimate (±20-25%), preliminary economic analysis (B/C, IRR), preliminary environment study (scoping).
• Access road and transmission line options.

3. Feasibility study

Purpose: to prove the technical, economic and environmental viability so that the investor and lender can decide.

• Detailed topographic survey (1:500-1:1000 for structures).
• Hydrology: long term flow series, FDC, 100-year and 1000-year flood, GLOF, sediment load.
• Geology: detailed mapping, drilling at all structures, tunnel and test adits, construction material survey and laboratory tests.
• Optimisation of capacity; layout design of headworks, desander, canal/tunnel, forebay, penstock and powerhouse; selection of turbines and equipment.
• Bill of quantities and cost estimate (±10-15%), construction schedule and plan.
• Financial and economic analysis (NPV, B/C, IRR, sensitivity).
• Complete IEE/EIA, resettlement plan, and risk assessment.

Minimum checklist

Hydropower plants are classified in several ways. Three common ways are given below.

1. Based on head

Low-head plants use large flow and often a weir or barrage; high-head plants use small flow, long penstocks or tunnels. Some books use 30 m and 100 m as the limits.

2. Based on turbine characteristics

• Impulse turbine plants (Pelton, Turgo, cross-flow): The water jet strikes buckets at atmospheric pressure. Used for high head and low discharge. The runner is above tail water.
• Reaction turbine plants (Francis, Kaplan, propeller): Water flows through the runner under pressure and the runner is completely filled; they have a draft tube. Used for medium to low head and large discharge.

Specific speed increases from Pelton to Francis to Kaplan.

3. Based on load characteristics

• Base load plant: Runs continuously at high load factor. RoR plants and large thermal plants do this. They give firm energy.
• Peak load plant: Runs only for the peak hours (few hours a day). Has pondage or a reservoir; large installed capacity but low load factor. Examples: peaking RoR, storage and pumped storage.
• Intermediate (load following) plant: Follows the daily load change.
• Pumped storage plant: Takes energy off-peak to pump water up and generates in peak hours.

Selection depends on the head, discharge, system load shape and economy.

Based on hydraulic characteristics (how water is brought to the turbine), hydropower schemes are:

1. Run-of-river (RoR) scheme

• Uses river flow directly without significant storage; a small weir diverts the water. Output follows the river flow.
• Variants: RoR with daily pondage (peaking RoR).

2. Storage (reservoir) scheme

• A dam stores monsoon flow and releases it as needed. Gives firm power and can regulate the river seasonally or annually.

3. Diversion (canal/tunnel) scheme

• Water is diverted from a weir by a canal or tunnel along the river to a powerhouse downstream, so that the head is gained over the length of the river.
• Types: free-flow canal, pressure tunnel.

4. Dam-toe (dam-based) scheme

• Powerhouse is at the foot of the dam, and the head comes from the dam height.

5. Pumped storage scheme

• Two reservoirs; water is pumped up in off-peak time and used in peak time.

6. Tidal scheme (also considered)

• Uses the rise and fall of the sea; not suited for Nepal.

 Diversion RoR          Storage dam-toe
 weir--canal--forebay   reservoir | dam
              | penstock          |__ PH
              PH

Run-of-river (RoR) plant

A small weir or barrage raises the river level and diverts the flow into the intake. The plant uses the flow as it comes; no significant storage exists. Hence the output changes with river flow; it is high in the monsoon and low in winter. Pondage (storage for less than a day) is not provided.

 River --> [Weir] --> Intake --> Desander
                                    |
                     Headrace tunnel/canal
                                    |
                    Forebay/surge --> Penstock
                                    |
                      Powerhouse --> Tailrace --> River

Peaking run-of-river (PRoR) plant

It has a small reservoir or pond near the headworks that stores water for a few hours (daily regulation). In the lean period, water is stored in off-peak hours and used for 4-6 hours in the peak hours, so the installed capacity is larger than that of the RoR plant. Example: Kaligandaki A, Upper Tamakoshi.

 Off-peak: Q stored in pond (small turbine use)
 Peak:     Q_river + Q_stored --> turbine (full power)

Storage (ST) plant

A high dam creates a reservoir to hold monsoon flow for seasonal or annual use. It gives firm energy through the year and permits the largest installed capacity and best regulation. Example: Kulekhani I.

      Reservoir
  ____/~~~~~~~\____
 |    Dam        |  --> Intake --> Tunnel/Penstock --> PH

Suitability in Nepal

• RoR: Cheap and quick but gives little dry-season energy; Nepal has surplus in monsoon and deficit in winter, so too many RoR plants lead to spill energy and an imbalance.
• PRoR: Best for the near term; it meets the evening peak. Many projects are of this type.
• Storage: Best for the long term because it gives dry-season energy, flood control and irrigation; but it needs high cost, long time, land and resettlement. Prefer a mix with priority to storage and PRoR projects.

Layouts of a run-of-river plant

A RoR plant has: a diversion weir/barrage, intake, gravel trap, settling basin (desander), headrace (canal or tunnel), forebay or surge tank, penstock, powerhouse and tailrace. Two common layouts:

(a) With a free-flow headrace canal

 Plan
                          Forebay
 Weir/Intake--Desander--=========+
 ~~~~ River ~~~~~~~~~~~~~~~~~     | Penstock
                                  v
                            Powerhouse-->Tailrace-->River

(b) With a pressure tunnel

 Section
 Weir   Intake   Headrace tunnel (pressure)
 ___|~~~|======================+ Surge tank
                               | Penstock
                               PH  --> Tailrace

• In (a), water flows with a free surface in the canal at a gentle slope, then drops in a penstock from the forebay. It is cheap in gentle terrain.
• In (b), water flows under pressure through a tunnel, suitable in steep, rocky or landslide-prone terrain. It needs a surge tank.

Importance of storage over RoR plants

• Gives firm power in the dry season, while RoR depends on river flow.
• Regulates flow, so it increases installed capacity and energy and the plant factor.
• Can supply peak load and respond to demand and the grid.
• Multipurpose: flood control, irrigation, water supply, fishing, tourism.
• Reduces the need for imports of power in the dry season.
• Less spill of the monsoon surplus.
• But it needs high capital, a long time, and resettlement/environment issues.

Three common RoR layouts are given with plan and section sketches.

Alternative 1: Headrace canal (free surface flow)

Plan
 River ~~~~~\       Canal ___________
 Weir|Intake=Desander==============\ Forebay
                                    \ Penstock
                                     PH-->River
Section
 weir  canal (gentle slope)  forebay
 ____    _________________   |
     \__/                 \__| penstock
                              \_PH

Suitable for gentle valley slopes; low cost; open canal can be damaged by landslides.

Alternative 2: Headrace tunnel (pressure) with surge tank

Plan
 Weir/Intake -> Desander -> Tunnel ==== Surge tank
                                          |
                                        Penstock
                                          |
                                          PH -> Tailrace
Section
 Intake======= tunnel =======(ST)
                              \ penstock
                               \_PH

Used for steep, rocky terrain and long bends; safe from landslide; high cost.

Alternative 3: Dam-toe/short penstock (low head)

Plan
 ~~~ River ~~~~ Barrage + Powerhouse in line ~~~~
Section
  U/S  |barrage|  D/S
 ~~~~~~|  PH   |~~~~
       |intake |

Powerhouse is placed at the barrage; no canal or tunnel; for low-head, high-discharge rivers in the Terai.

In each layout, the intake, desander, headworks, waterway, powerhouse and tailrace are labelled, and the layout is chosen from topography, geology and cost.

(i) Alignment with pressure tunnel

Plan (contours 1000-1400 m)
        ____________
 ~~ River ~~ Weir/Intake/Desander
              \
               \== Headrace tunnel ===+ Surge tank
                                      |
                              Penstock (steep)
                                      |
                                  PH -> Tailrace -> River
Section
 FSL
  ~~|intake|=============== HGL =======(ST)
                      tunnel             \ penstock
                                          \__PH

Salient features: Weir/barrage, intake with trash rack and gate, gravel trap, settling basin, headrace pressure tunnel (circular, lined), surge tank, penstock (steel, surface or buried), powerhouse (surface or underground), switchyard, tailrace and transmission line. The tunnel flows full under pressure; HGL stays above the crown. Shorter than the canal, safe from slides, used in steep valleys.

(ii) Alignment with free-surface flow

Plan
 ~~ River ~~ Weir/Intake/Desander
                 \_______ Open canal / free-flow tunnel
                         \______ Forebay
                                   \ Penstock
                                    PH -> River
Section
 ___weir__intake___ canal (S = 1:1000)______forebay
                                              \ penstock
                                               \_PH

Salient features: Weir, intake, desander, free flow canal (or tunnel flowing partly full with slope 1:1000), spillway at forebay, forebay with trash rack, penstock, powerhouse and tailrace. Cheaper, but the head is lost to the slope, and the canal needs bends and cross-drainage works; needs gentle terrain.

Importance of storage projects in Nepal

• Nepal gets about 80% of its flow in June-October, so run-of-river plants give little power in winter when demand is at its highest. Storage plants hold the monsoon flow and release it in the dry season, giving firm energy.
• Supply peak load and help in stability and frequency control of the grid.
• Reduce the spill of monsoon surplus and dry-season import from India.
• Are multipurpose: flood control, irrigation (Terai), drinking water, fish, tourism.
• Allow a larger installed capacity and more total energy per cubic metre of water.
• Help export of firm power at better prices.
• Give a long life asset. The limits are large cost, a long construction time, resettlement and sediment problems.

General layout of a pumped storage plant

   Upper reservoir
     ~~~~~~~~~
        |  Penstock / tunnel
        |
     [Powerhouse: reversible pump-turbine
      and motor-generator]
        |
     ~~~~~~~~~
   Lower reservoir / river

• Generation (peak): water flows down through the turbine from the upper to the lower reservoir.
• Pumping (off-peak): surplus cheap energy turns the unit as a pump to lift water back.

A pumped storage power plant has two reservoirs at different levels. In off-peak hours (night or monsoon surplus) the reversible pump-turbine uses cheap surplus electricity to pump water from the lower to the upper reservoir. In peak hours the water is released back through the turbine to generate power. The cycle efficiency is about 70-80%.

Benefits to Nepal

• Peak power: It meets the evening peak with stored energy.
• Use of monsoon surplus: Nepal has surplus RoR energy in the wet season, which would otherwise be spilled, and this can be stored.
• Grid stability: Gives fast frequency control and spinning reserve.
• Dry season support: Reduces the import from India and improves energy security.
• Needs less water than a storage dam, because the same water is reused, and can be built on a hill near the load centre.
• Supports intermittent sources such as solar and wind.
• Lower environmental effect than a large dam.

A diversion-type storage plant has a dam that creates a reservoir, but the water is taken out from the reservoir by a tunnel or canal and carried to a powerhouse located away from the dam, often in another valley or far downstream. This gives extra head over the dam height.

Plan
      Reservoir
   ~~~~~~~~~~~~|Dam|--Spillway
   ~~~~~~~~~~~~|   |
   Intake ---->+   |
        \
         \== Headrace tunnel ==+ Surge tank
                               |  Penstock
                               PH --> Tailrace --> River
Section
 FSL ~~~~|dam
    Intake\______ tunnel _______(ST)
                                  \ penstock
                                   \__PH

Principal characteristics

• A dam stores water for seasonal regulation, so firm power is available throughout the year.
• The head is the sum of dam head and the drop gained along the river course through the tunnel; the powerhouse is not at the dam.
• Main components: dam with spillway and bottom outlet, intake with trash rack and gates, headrace tunnel, surge tank, penstock, powerhouse, tailrace and switchyard.
• The tunnel runs under pressure, so the river bend between dam and powerhouse is bypassed. The river reach between them has reduced flow (environmental flow is required).
• Needs high capital cost and a long construction time, but gives large capacity and good peaking.
• Examples: Kulekhani I (Nepal) with a dam at Indrasarobar and a powerhouse downstream; Kali Gandaki 'A' type of layout where the head is gained through a tunnel.

The stages of the hydropower development cycle are:

1. Reconnaissance (identification) study: find possible sites and rank them.
2. Pre-feasibility study: compare layout options and choose the best.
3. Feasibility study: prove technical, economic and environmental viability.
4. Detailed engineering design: final design, drawings and tender documents.
5. Construction and commissioning: build, test and hand over.
6. Operation and maintenance: run the plant and monitor its performance.

Before these, a river basin master plan may be done; the first four stages are the planning stages, in which investment decisions are made.

Hydropower development cycle

 Master plan / Reconnaissance
            |
     Pre-feasibility study  --> drop? (stop)
            |
      Feasibility study     --> drop? (stop)
            |
   Detailed engineering design
            |
   Tender, contract, financing
            |
   Construction, commissioning
            |
   Operation and maintenance

Each stage is a decision gate: the project goes ahead only when the results are favourable, and the cost accuracy improves from about ±30% to ±5-10%.

Studies in the detailed engineering design stage

• Surveys: Very detailed topographic survey (1:200-1:500) of all structure sites, and alignment survey of access roads and transmission line.
• Geotechnical investigation: Additional boreholes and test adits at dam/weir, tunnel, powerhouse and slopes; in-situ and laboratory tests (rock mechanics, soil properties); construction material survey (borrow, quarry).
• Hydrology update: Final flood, sediment and low-flow analysis; check of design discharge and installed capacity.
• Hydraulic model tests: Physical or numerical model of the spillway, intake, desander, and energy dissipator.
• Structural and hydraulic design: Final design of weir, intake, tunnel, penstock, surge tank, powerhouse and tailrace; stability and stress analysis; support and lining design.
• Electro-mechanical and hydro-mechanical design: Turbine and generator selection, transformers, gates, governor and control, and transmission line.
• Environmental management plan and resettlement plan.
• Quantities, drawings, specification, tender documents and final cost estimate and construction schedule.

Phases of the hydropower development cycle

1. Reconnaissance: Desk study and site visit to identify and rank the sites; rough cost and energy.
2. Pre-feasibility: Survey, hydrology and geology at a moderate level; compare alternative layouts; select the best.
3. Feasibility: Detailed investigation, design optimisation, cost (±10-15%), economic and financial analysis, IEE/EIA.
4. Detailed design and tendering: Final drawings, specification, tender documents, contract.
5. Construction and commissioning: Build and test the plant.
6. Operation and maintenance: Run, maintain and monitor.

Layout of RoR plant with headrace canal

Plan
 River~~~~~  Weir             Canal
 ~~~~~~~~~~~|Intake=Desander===========\
 ~~~~~~~~~~~                            \ Forebay
                                          \ Penstock
                                            PH -> Tailrace
                                               -> River
Section along waterway
 weir  intake desander    canal (slope 1:1000)  forebay
 __|~~~|__ __ ___________________________________|
                                               \ penstock
                                                  \__PH

Main components: diversion weir with undersluice, intake with trash rack, gravel trap, settling basin (desander), headrace canal with cross-drainage works, forebay with spillway and trash rack, penstock, powerhouse, tailrace and switchyard. The canal is laid along the contour at a small slope so that most of the gross head is kept for the penstock.

Hydropower development cycle (flow chart)

 Reconnaissance study
        |
 Pre-feasibility study
        |
 Feasibility study
        |
 Detailed design + tender
        |
 Construction + commissioning
        |
 Operation + maintenance

• Reconnaissance: identify and rank sites using maps and site visits.
• Pre-feasibility: survey, hydrology and geology; alternatives compared.
• Feasibility: complete design, cost, benefits and environment study; decide on investment.
• Detailed design: drawings, specifications, tender.
• Construction: diversion, dam, waterways, powerhouse, equipment; commissioning.
• Operation: generation, maintenance, monitoring.

Layout of a storage hydel plant with powerhouse

Plan
        Reservoir
   ~~~~~~~~~~~~~~~~~~
   ~~~~~~~~~~~~|Dam|----Spillway
        Intake +   |
               |   |
               Penstock
               |
               PH -> Tailrace -> River
Section
  FSL~~~~~~~~~|
  MOL  intake |  Dam (gravity/earthfill)
  ~~~~~~~~~~~~|\
              | \__penstock
                  \__PH --> tailrace

Components: dam, spillway with gates, bottom outlet / diversion tunnel, intake tower with trash rack and gates, penstock (through or around the dam), surface powerhouse at the dam toe, tailrace, switchyard. The reservoir is divided into dead storage (below MOL) and live storage (between MOL and FSL).

Phases of the hydropower development cycle

Reconnaissance, pre-feasibility, feasibility, detailed design and tender, construction and commissioning, operation and maintenance.

Factors in the pre-feasibility study

• Topography: map and survey of headworks, waterway and powerhouse; choose the layout alternatives.
• Hydrology: mean flow, flow duration curve, floods and sediment from available data and short-term gauging.
• Geology: surface mapping and geophysics for dam, tunnel and powerhouse sites; landslide and fault risk.
• Alternatives: capacity, head, and type of scheme (RoR, PRoR, storage); choose the best one.
• Access and transmission: road and line routes, distance to the grid and market.
• Cost and economics: rough cost (±20-25%), energy and B/C, IRR.
• Environment and society: screening of protected areas, land, settlement, and fish.

Additional factors in the feasibility study

• Accurate and detailed survey, drilling, tests, and material surveys.
• Long-term hydrology, 100- and 1000-year floods, sediment and GLOF.
• Optimisation of the installed capacity, final layout and equipment selection.
• Detailed quantity and cost estimate (±10-15%) and construction schedule.
• Financial analysis (NPV, IRR, B/C, sensitivity), financing plan, and the power market (PPA).
• IEE/EIA, resettlement, risk and legal clearances.

Stages of hydropower development

1. Reconnaissance study
2. Pre-feasibility study
3. Feasibility study
4. Detailed engineering design and tender
5. Construction and commissioning
6. Operation and maintenance

Working principle of a peaking run-of-river (PRoR) plant

A PRoR plant has a weir plus a small reservoir (pond) at the headworks that can store the river flow for several hours. In the dry season the river flow is small. During the off-peak hours the turbines run at low load or stop, and the water is stored in the pond. In peak hours (usually 4-6 hours in the morning and evening) the stored water plus the inflow runs the turbines at full load. In the wet season, when flow is large, it behaves as an ordinary RoR plant. So the installed capacity is larger than for a pure RoR plant, and the energy has a higher value because it is supplied at peak time. Examples are Kaligandaki A and Upper Tamakoshi.

General arrangement of components

 River --> Weir + Undersluice --> Intake --> Gravel trap
                  |                              |
              Pond (daily)                    Desander
                                                 |
                                       Headrace tunnel
                                                 |
                                            Surge tank
                                                 |
                                             Penstock
                                                 |
                         Powerhouse --> Tailrace --> River

 Section
 FSL ~~~~~|weir          intake====tunnel====(ST)
 MDDL ~~~~|pond                                 \ penstock
                                                  \__PH

Fluctuating pond level between FSL and MDDL gives the daily storage.

Pre-feasibility selects the best option and decides if detailed study is worthwhile; feasibility confirms the selected option in full detail so that the investment decision can be made.

Site-specific hydrological investigations

• Collect all available rainfall and runoff records (DHM) and the catchment characteristics.
• Install a staff gauge or automatic gauge at the headworks; measure discharge by current meter or salt dilution regularly; develop the rating curve.
• Derive the mean monthly flow, flow duration curve and low flow using correlation with a nearby gauged basin or the WECS/MIP method.
• Estimate floods (return periods 2-1000 years), by frequency analysis or empirical methods, and check for GLOF/snow melt.
• Measure suspended sediment concentration; estimate the sediment load and the particle size.
• Record the high flood marks and the tail water level at the powerhouse.

Topographical investigations

• Topographic mapping with contours at the headworks, along the waterway and at the powerhouse.
• River cross-sections and longitudinal profile (for the stage-discharge and head).
• Reservoir area-capacity curve if the pond/reservoir exists.
• Alignment survey of the canal/tunnel, penstock, access road and transmission line.
• Benchmark control (GPS/total station), and the location of boreholes and test pits.

Site-specific investigations in the pre-feasibility study are done only at a moderate level to select the best layout.

Hydrological investigations

• Collect rainfall, flow, and climate data from DHM stations in or near the basin.
• Set up a gauge at the headworks and measure discharge across seasons (current meter, floats, salt dilution).
• Estimate mean monthly flows and the flow duration curve by regional methods (WECS/DHM, MIP) and correlation with a nearby station.
• Estimate flood flows of different return periods (frequency analysis, regional formula), and check for GLOF and landslide dam outburst.
• Sample suspended sediment to estimate load and plan the desander.

Geological investigations

• Review regional geology maps and satellite images; do detailed surface mapping of the sites for the weir, intake, tunnel alignment, powerhouse and slope stability.
• Find structures: faults, folds, shear zones, joint sets, and landslides.
• Geophysical survey (seismic refraction, resistivity) to find overburden thickness and rock quality.
• A few boreholes and test pits at the headworks and powerhouse; identify construction materials (quarry, borrow, sand).
• Seismic hazard check.

Topographical investigations

• Topographic map (1:5,000 to 1:2,000) with contours of the project area.
• River cross-sections and profile at the weir and powerhouse.
• Alignment of the waterway and access road options.
• Benchmarks and control points for later detailed survey.

Stages of hydropower planning

1. Reconnaissance (identification)
2. Pre-feasibility
3. Feasibility
4. Detailed engineering design and tender

Field investigations at each stage

Reconnaissance

• Site visit for access, river and valley form, rough geology.
• Spot discharge measurement; use of regional hydrology; collecting maps.
• Identify environmental and social constraints.

Pre-feasibility

• Topographic survey of key areas; river cross-sections.
• Hydrology: install a gauge, measure flows, estimate FDC, floods and sediment.
• Geology: surface mapping, geophysics and a few boreholes.
• Survey of access road and transmission line corridors; preliminary IEE scoping.

Feasibility

• Detailed topographic survey (1:1000 or larger) at all structure sites.
• Hydrology: at least one year of gauging, sediment sampling, flood and low-flow analysis.
• Geology/geotechnics: drilling at weir, intake, desander, tunnel portals, penstock and powerhouse; test adits; laboratory and in-situ rock/soil tests; material surveys.
• Socio-environmental baseline survey and IEE/EIA field work, land and settlement survey.

Detailed design

• Very detailed survey and extra drilling and tests of the exact foundation of structures.
• Hydraulic model tests (spillway, intake, desander).
• Final hydrological check, and survey for construction camps, roads and transmission line.
• Environmental monitoring programme set-up.

As team leader of a feasibility study for a small hydropower project, I would organise the work in the following steps.

1. Mobilisation and planning: Review the pre-feasibility report and terms of reference; form a team (hydrologist, geologist, civil/structural, hydraulic, electro-mechanical, survey, environment, social, economist, cost engineer); prepare the work plan, schedule and budget; collect maps and data.
2. Surveys: Topographic survey at 1:500-1:1000 of headworks, waterway, powerhouse; river cross-sections; alignment survey of access road and transmission line.
3. Hydrological study: Install/read the gauge, discharge measurements, long-term flow series by correlation, FDC, design flood, sediment load, environmental flow.
4. Geological and geotechnical study: Mapping, geophysics, core drilling, test pits, rock/soil tests, and construction materials survey; assess slope stability.
5. Selection of the project parameters: Optimise design discharge and installed capacity (energy vs. cost), fix the intake, waterway type, powerhouse position and the tailrace level.
6. Preliminary design: Weir/intake, desander, headrace, forebay, penstock, powerhouse, tailrace, access, and switchyard; hydraulic and structural calculations; turbine selection (type, number, rating).
7. Transmission and market: Line route to the grid, substation, and a check with NEA about the PPA/tariff.
8. Environmental and social: IEE (up to 50 MW) with baseline data, impact and mitigation, resettlement and land acquisition plan.
9. Quantities, cost and schedule: Bill of quantities, unit rates, project cost (±10-15%), construction schedule and implementation plan.
10. Economic and financial analysis: Energy and revenue, B/C, NPV, IRR, payback, sensitivity to cost, flow and tariff; financing plan.
11. Report: Main report, drawings, annexes; present to the client; revise by comments.

A 10 MW project in a remote area must be studied in a staged way, with the study depth increased only when the results are positive, so that money is not wasted. The stages before construction are:

1. Reconnaissance (identification): Desk study with maps, satellite images and DHM data; site visit; estimate flow, head, capacity (about 10 MW), rough layout and cost. Choose a run-of-river layout with the simplest civil structures to save cost.
2. Pre-feasibility: Moderate survey, gauging for a season, geological mapping, compare 2-3 layouts and capacities, access road and the transmission link to the nearest grid or load, a rough cost (±20-25%) and benefit-cost; decide whether to continue.
3. Feasibility: Detailed survey, long-term hydrology and floods, drilling at the main structures, optimisation of installed capacity, preliminary design and equipment, cost (±10-15%), financial analysis, and IEE (1-50 MW needs IEE). Prepare for PPA and financing.
4. Licensing and agreements: Survey licence from DoED before the study (the exclusive right), then IEE approval, PPA with NEA, financial closure, and generation licence.
5. Detailed design and tender: Final drawings, specifications, bill of quantities and tender documents.
6. Pre-construction: Land acquisition, access road, camps, contractor selection.

Cost-effective measures for a remote area

• Use standard modular equipment and local materials, and keep layout simple (short waterway).
• Optimise capacity for the lowest cost per kW and consider a connection to a local mini-grid if the grid is far.
• Share the access road with the community, and use local labour.
• Phase the study so that costly drilling is done only in the feasibility stage.

A 300 MW reservoir project is a large project; the steps from planning to commissioning are:

1. Basin master plan and identification: Choose the dam site by desk study, topographic maps and satellite images (reconnaissance).
2. Pre-feasibility study: Hydrology, geology, topography; compare dam sites, dam type, heights, and capacities; storage-yield curves; preliminary environment/resettlement study.
3. Feasibility study: Detailed survey, drilling, hydrology and sediment, optimisation of dam height and installed capacity, design of dam, spillway, intake, tunnel and powerhouse, cost, EIA, resettlement plan, financial analysis.
4. Licence, EIA approval, PPA and financing: Survey and generation licences, EIA approval, power purchase agreement, and finance (government, banks, development partners).
5. Detailed design and tender: Final design and drawings, hydraulic model tests, and tender documents; select the contractors (civil, hydro-mechanical, electro-mechanical, transmission).
6. Pre-construction work: Land acquisition, resettlement, access road, camp, power supply, diversion arrangements.
7. Construction: River diversion, foundation treatment, dam, spillway, intake, tunnel, powerhouse, installation of turbines and generators, transmission line.
8. Reservoir impounding, testing and commissioning: Fill reservoir in stages with monitoring, test machines, synchronise and run the plant.
9. Operation and monitoring: Maintenance, dam safety, sediment and environmental monitoring.