Final Report

I. INTRODUCTION

1.1 General

Water is an inexhaustible commodity. As population and its economic activities go on

increasing so is the demand for water. To ensure a reliable water supply at the time of

needs, the proper and judicious use and management of water resources is required.

Hydropower generation and agriculture is major user of water resources in this

world .Hydropower plants, by their nature, require low operating cost and at the same

time provide great flexibility (especially reservoir based hydropower) in the use relative

to other sources of energy identified so far.

Benefits of water resources depends upon mainly on the three factors such as the physical

dimension of the system, the scale of development and the operating policies adopted for

the system.

Hydrological, geo-topographical factors have great influence on the physical dimension

of a reservoir. But with the advent of simulation techniques, not only optimal design is

achieved but also adverse effects are minimized and maximum benefits are accrued.

1.2 Problem Identification

Development of a country can be gauged by the amount of energy it consumes. Energy is

very important medium for the overall development of a nation .Hydropower is one of the

main sources of energy in Nepal. It accounts for nearly 90% of installed capacity and

95% of total generation of energy. Except for the firewood and Hydropower, Nepal has to

import all other types of energy paying scarce hard currencies while being extremely rich

in water resources. So, the proper utilization of its water resources is required for the

development.

In spite of potential resources of hydropower, Nepal has faced power crisis for several years

because most of the hydropower projects are based on the river run-off schemes except

Kulekhani-I (60 MW). To meet the power crises, storage scheme will be quite essential for the

country.

The predominant nature of hydroelectric source particularly, run of river type supply in

Integrated Power System(INPS) has exhibited that seasonal deficits of hydro energy is

bound to occur frequently along with seasonal surpluses. This has been the situation of

1

INPS even after the commissioning of Projects like Khimti, Mid Maryshandi

The estimated hydropower potential of Nepal is 83, 000 MW of which 114 projects

having 45,610 MW have been identified economically feasible However, to date, Nepal

has developed less than 1 percent of its vast hydropower potential. The total installed

capacity is about 680MW, of which 635 MW (93%) is generated by hydropower in the

integrated system. Peaking capacity as well as energy output of the power system drops in

the dry season of December to May due to the shortage of available runoff.

The peak power and energy demand is growing by about 11% annually, creating the

electricity shortage in Nepal. Demand has been exceeding supply every year. To meet the

significant difference between demand and supply, NEA had increased power cuts in the

country up to 18 hours a day in January 2009. Greater challenges of the NEA are bridging

the gap between supply and demand of electricity.

All the existing and future (scheduled to be commissioned by next five years)

hydropower plants are run-of-river types except Kulekhani power plant, Proposed Upper

Seti Hydropower Project and some of them are with daily regulating capacity. Therefore,

load shedding hours in the dry season depends on the availability of water in the

Kulekhani reservoir.

Figure 1.1: Contribution of energy in Nepal

1.3 Need of research

Due to limited power supply, optimum operation of water resources is

unavoidable. Latest estimates show, the demand for power in Nepal will be 1500 MW in

2015. Supply of this demand is only possible if more storage type hydropower projects are

constructed. [NEA, 2001]

2

Therefore, it is required that most of research be undertaken toward saving, storage,

management and water demand of water resources in this country. Ingredients include

analyzing various parameters such as population, economy, water use efficiency and etc.

[Siminovic, S.P, 2002].

Upper Seti Hydroelectric project with installed capacity of 127 MW has storage capacity of

374 million cubic meters [NEA, 2001]. In this study, simulation model was used for

system evaluation. Simulation model is a best way of using physical rules and a series

of operational rules try to simulate genuine phenomena and approach and accurate

scheme to predict the behavior of the system under a specific policy [Yeh W.W-G, 1985].

Input data of simulation model could be classified in three parts: fixed data, design data

and time series data. Fixed data are properties of system such as physical and economic

properties and relationship between them. Design data, in fact, are decision variables

which are determined in modeling process are reservoir capacity and plant generating

power capacity. Inflow to system is in the form of artificial data or time series data.

Simulation models can present efficiency and system performance in different

combination of reservoir, plant powers, reservoir storage, output etc. and in this

manner, they have good flexibility.

In the present study HEC-ResSim simulation model was used to evaluate performance of

Upper Seti storage dam operation and ability of the model to simulate of reservoir system

was studied.

1.4 Objectives of study:

The objective of reservoir simulation is to compute the plant capacity and the

corresponding maximum plant discharge, the reservoir drawdown pattern, the dry season

and the wet season energy and the total annual energy. The available inflow and the

reservoir live storage have to be fully utilized. The output data obtained from the

simulation are to evaluate the energy generations for two scenarios.

In view of the above factors the major objectives of the present study are as follows:

To compute plant capacity and the maximum plant discharge

To compute the dry and wet season energy

To compute the total energy generation

3

To develop a guide curve for computing the reservoir drawdown pattern

and operation of reservoir.

To compare the results obtained from HEC-Res Sim with the results obtained from

other models.

1.5 Scope of study:

This study is mainly focused on the development of reservoir operation model for

USHEP using HEC Res Sim. The study covers the following scope of works.

Literature reviews on Hydropower reservoir and its various aspects.

Review on present energy scenario of Nepal.

Study and collection of all relevant hydrological and topographical data of the

Upper Seti Basin.

Literature review on sediment studies on Upper Seti Basin.

Literature review on history of reservoir simulation.

Literature review on the operation of reservoir in Nepal and aborad.

Literature review on the operation of reservoir using HEC Res Sim models.

Recommend the model to be used for other reservoir operation under various

conditions.

1.6 Limitations:

Following limitations are set for the study:

Due to time and study limitations, sediment analysis for the reservoir has not been

performed.

Due to unavailability of required data seepage loss and hydraulic loss has been

neglected.

Input data used are collected from past study reports of NEA and JICA so that

comparisons of output could be effective and reliable.

If sediment analysis, seepage data and hydraulic loss data are used, the accuracy and

reliability of the results obtained would be increased.

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1.7 Organization of the Study

This thesis consists of seven chapters. Chapter 1 includes the introduction to the topic

with the need, objective, scope and limitations of the study. Chapter 2 reviews current

power production scenarios. Chapter 3 contains literature reviews .Chapter 4 contains

description of the site area and project. Chapter 5 contains the detailed model description,

research methodology and processes adopted to achieve the objective of the study.

Chapter 6 presents the results, its discussions and validation with tables and figures.

Finally, Chapter 7 presents the final conclusion of this study and recommendations for

further study.

The references and Annexes are incorporated at the end of this thesis while the

acknowledgements and abstract are given in the preface portion.

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II. HYDROPOWER AND ENERGY SITUATION IN NEPAL

2.1 Hydropower Potential

Nepal's water resource is considered to be abundant. The average annual precipitation is

about 1700mm (80% of which occurs during monsoon season from June to September).

The total annual average run-off from Nepal's 6000 rivers is over 200 billion m 3. [NEA,

2001]

Surface resources are distributed in the river system consisting of four major rivers (viz.

the Mahakali, the Karnali, the Gandaki and the Koshi), seven medium rivers and a large

number of small rivers.

Harnessing the water flowing from the Himalayas is Nepal’s development agenda for

increasing its national wealth. Water storage potential in Nepal is 88 billion m3. Nepal’s

theoretical hydropower potential is estimated at 83, 000 MW. At present altogether 114

projects having 45,610 MW capacity have been identified economically feasible The

country hopes to bring about development through three strategic consideration which

include building large-scale storage projects envisaged primarily for exporting energy,

medium scale projects for meeting national needs and small scale projects for serving

local communities. As such, four major storage projects are proposed as Indo-Nepal co-

operative initiatives. These are the Chisapani Karnali (10,800 MW), the Pancheswor

(7,200 MW), Budhi Gandaki (600 MW) and the Sapta Koshi high dam (3,600 MW)

which in total, would provide 22,200 MW installed capacity. Recent policy promotes

external and domestic private sector initiatives for hydropower development. Some of the

large projects with feasibility study completed are presented in table 2.1.

Table 2.1: Large Hydropower Projects with Feasibility Study

Project Name Capacity (MW)

Cost million USD

Year of Study Type

Karnali (Chisapani)

10,800 7 666 Updated in 2001

Storage

Pancheswor 6,480 2 980 1995 Storage

West Seti 750 1 098 1997 Storage

Arun-III 402 859 1991 Storage

Upper Tamakoshi 309 464 May 2005 PROR

Dudhkoshi 300 690 1998 Storage

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2.2 Energy Situation

Figure 2.1 shows the location map of power generation and transmission facilities in

Nepal. The power generating facilities in Nepal consists of hydro, diesel and solar power

plants but it is basically a hydropower-oriented system. The total installed capacity is

about 680 MW, which with 635 MW (93%) is generated by hydropower in the integrated

system.

Figure 2.1: Existing Power Stations and Distribution System

2.2.2 Available Energy and Peak Load Demand

NEA published total energy available and peak load demand in NEA annual report

2007/08 from 1999 to 2008. Figure 2.2 and Table 2.4 shows that the peak load demand

before 2001 was only 391 MW which is less than the total capacity of 398 MW including

IPP. Kaligandaki A Power plant was commissioned in 2001 and total capacity after it was

541 MW after the Kaligandaki A there was not any major power plant implemented in

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Nepal except small power plants developed by IPPs. Significant load shedding started

from year 2005 but energy have always been spilled during wet season

Figure 2.2: Available energy and total peak load demand

Table 2.2:Available energy and total peak load demand

Figure2.3:Monthly energy generation from Kulekhani I

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Figure2.4:Monthly energy generation from Marsyangdi

Figures 2.3 to 2.5 (Kulekhani I, Marsyangdi and Kaligandaki A) present the energy

generation from major power plants of Nepal. These figures show that Run of river plants

(Marsyangdi and Kaligandaki A) generated with lower capacity (up to 50% of the total

capacity) during the wet season but at the same time reservoir power plants (Kulekhani

A) also generated up to 50% of its total capacity.( Shrestha, 2007)

Figure 2.5: Monthly energy generation from Kaligandaki A

Figure 2.6 shows the system load curve of the peak load demand of the year in 2007

(December 31, 2007) and Figure 2.7 shows a typical system load curve in wet days. Both

figures show that the peak load demand is from 6 PM to 9 PM. Load demand at day time

is only about 60% of the peak demand.

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Figure 2.6:System load curve on 31 December 2007

Figure 2. 7:Typical system load curve in wet season.

Nepalese are already facing acute shortage of electricity whole year, if proper initiative is

not taken to develop more hydropower projects, it seems that the situation will be more

severe and power cut-off will be increased for more hours per week during dry period as

well as in wet season. Power and energy demand grew by 11.31% and 10.76%

respectively in the year 2008. The system demand of 721.73 MW recorded on December

31 2007 happened to the peak power demand observed in FY 2007/08. Likewise energy

demand over the year 2008 totalled 3490.12 GWh. As this amount of energy was not

available with the system the deficit amounting to 309.46 GWh had to be shedded to keep

the electricity service running. (Shrestha, 2007)

10

Figure 2.8:Energy and peak load demand forecast charts (NEA, 2000)

NEA made the power demand forecast for the further 18 years from 2009 to 2025 as

shown in figure 2.2 and Table 2.4. According to the forecast, the peak load is estimated to

be 1271.7 MW in 2013/14. The average annual growth rate for peak demand is estimated

to be about 10% for next 5 years. The further energy demand is also forecasted to be

5859.9 GWH in 2013.

Table 2.3: Energy and peak load demand forecast.

Source: NEA annual report, 2007/8

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Electricity generation should be increased by more than 10% per year to meet demand,

which is far high additional demand compare to additional generation rate at present.

[NEA,2001]

In February 2008 Government of Nepal formed a Committee for Solving the Load

Shedding Problem. The committee had prepared a report and recommended 25 points for

solving the load shedding problem. Some of them are development of Storage power

project like Upper Seti, speed up the construction of Upper Tama Koshi, Upper Trishuli

A, Upper Trishuli B, Kulekhani III and encourage IPPs for hydropower development.

They have also studied the energy production from existing and forthcoming hydropower

projects up to 2013/14. They have also developed energy and capacity balance per day of

the month from 2009/10 to 2013/14. Figure 2.9 and Table 2.6 presents the energy and

capacity balance per day of the month for year 2013/14. The figures show that capacity

will be surplused in wet season and deficit during the dry season. But the energy surplus

will be in every month.

Figure 2.9:Estimated Capacity and Energy balance in 2013/14

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Table 2.4:Estimated Capacity and Energy balance in 2013/14

Description Shrawan Bhadra Asoj Kartik Mangsir Paush

Jul/Aug Aug/Sep Sep/Oct Oct/Nov Nov/Dec December

Energy

Demand(MWh)16,264 16,093 15,715 13,974 15,806 16,136

Energy

Available(MWh)

28,129 28,129 28,129 28,129 21,199 19,983

Energy

Surplus(MWh)11,865 12,036 12,414 14,154 5,392 3,847

Peak demand(MWh) 1,073 1,065 1,090 1,090 1,161 1,208

Peak capacity(MW) 1,167 1,167 1,167 1,167 929 823

Av. Power

Deficit(MW)

(94) (102) (77) (77) 232 385

Description Magh Falgun Chaitra Baishakh Jesth Asar

Jan/Feb Feb/Mar Mar/Apr Apr/May May/Jun Jun/Jul

Energy

Demand(MWh)

16,466 16,136 15,806 15,477 16,384 17,231

Energy

Available(MWh)

17,830 17,474 16,085 16,735 21,880 26,729

Energy

Surplus(MWh)

1,364 1,338 279 1,258 5,496 9,498

Peak demand(MW) 1,197 1,162 1,124 1,107 1,134 1,157

Peak capacity(MW) 880 864 802 858 946 1,161

Av. Power

Deficit(MW)

317 298 321 249 188 (4)

III. LITERATURE REVIEW

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3.1 General

Determination of the optimum mode of operation for a reservoir has always been an

important task for water resources engineers for many years and yet no completely

satisfactory solution has been obtained in general and the problems have to be simplified

to fit each individual purpose as the problems are site specific and time specific.

Numerous methodologies such as Linear programming, Dynamic programming and

Simulation method are proposed as tools to optimize the reservoir operation. The

application of these techniques is reviewed below.

3.2 Reservoir operation problems

Reddy (1962) noted that it was customary for a long time to operate reservoir on the basis

of personal judgment by storing all inflows in the reservoir till it is required to release the

water to fulfill the target demand of different users. Such a method ignores the fact that

optimality is obtained only when the system operation takes into account that storage and

release can be apportioned among various system elements, purposes and operation time.

Optimum operation policy is sequential decision problem and consequently, systematic

approaches which model this sequential decision making are the appropriate ones to be

applied to solve the system operational problem.

Harboe et al.(1970) noted that in short operation the physical objective is to find

optimum hourly releases from a reservoir and in long term operation, the physical

objective is to find out monthly releases from the reservoir over an extended period such

as a critical period or the economic life of the project. Since the hydro plants are

connected with thermal, diesel or gas power station, the economic objective is the

minimization of the operational cost of the total power generation system while the

specific demand for energy is satisfied.

Harboe (1986) proposed a three stepped approach for establishing reservoir operational

rules. The three steps were optimization, simulation and multi objective analysis. The

method was applied to the real world system for low augmentation. First each reservoir

was sequentially optimized by dynamic programming. Then the results were taken as the

targets for standard operating rule on which simulation model was based .then several

simulation runs were performed with different targets when reservoir level was below a

certain critical level was also introduced. The alternative operating rules thus derived

were analyzed using multi objective analysis to select the acceptable solution to all.

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Lian (1976) summarized that vital in the reservoir operation policies is the existence of

the rule curves which provide an effective guide in the operation of the systems. It

explains the range of storage level in its period to enable maintain smooth transition

control of operation between periods. This envelope of defined corridor secures a basis

for system releases and storage regulation.

With the development of computer technology and system analysis, attempts have been

made to select the optimal reservoir operation with the requirement of providing the best

return from the system.

3.3 Review of simulation technique

Simulation is one of the earliest and perhaps the most widely used method for evaluating

alternative water resource system. A simulation model may be deterministic or stochastic

depending upon whether random components are involved or not. The reason for its

popularity lies in its mathematical simplicity and versatility.

Hall and Dracup (1970) defined simulation as reproducing the essence of a system

without reproducing the system itself. Simulation model is a creation of a model which is

a mathematical representation of the system under consideration. it enables the rational

assessment of the system behavior under various inputs and sets of system parameters.

However, the simulation does not ensure a systematic search over the decision space of

the controllable input data.

Simulation technique is an effective method for evaluating alternative configurations of

plant capacity, water use allocations, operating policies etc, they are not very effective

means for choosing the best configuration of capacity, target and policy. For this

optimization tools have been proven to be more effective. However, Loucks (1976)

pointed out that mathematical, computational, and data limitations restrict the use of

optimization models, while simulation models are far less restricted .hence they are better

suited for evaluating more precisely the alternatives defined by optimization models.

Thus, though simulation by definition doesn't ensure optimality and a local optimum may

be determined while the global optimum is bypassed in essentially what might be called a

trial and error approach, its importance in operational studies is unquestioned .In

particular, simulation being less stringent than an optimization model can be better

adopted to reflect peculiarities of the real system.

3.4 Reservoir Simulation

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3.4.1 Initial developments

In the 1930’s, interest grew in estimating more accurately the quantity of water passing

through a water power station. Until that time, calculations had been based on the

nominal head capacity combined with the technical efficiency of the turbines and

generators [Laurent J., 1936]. However, the efficiency of a turbine varies to a high degree

with the load, so that this approach needed to be improved by a more accurate

measurement of the flow passing through the turbines [Hartzell H., 1936]. These accurate

measurements were critical in order to maintain the stocked water in the reservoir at secure

levels and prevent flood events, since the natural flow had been replaced with a regulated

water discharge.

A few decades later in the early 70’s, many detailed studies were conducted in an

attempt to improve water resources systems, because of the enormous investments involved

in their design and operation. Programming techniques, such as linear and dynamic

programming, started to be used for optimum design and operation of water resource

systems. However, these techniques were based on steady inflow and water demands and

presented definite limitations when dealing with a natural stream flow with

stochastic properties [Charalampos Shaolikaris,2008].

The optimization of the operation of a reservoir based on the coupling of reservoir

simulation with hydrology was initiated in 1975. With this scheme, the first module is

a system model which simulates and evaluates the operation of a reservoir system on a

monthly basis for water supply, low flow regulation, power generation and recreation,

with storage and release constraints for flood control. The second module is a catchments

model which is usually meant for the simulation of short-time flow series meant to

reproduce flood periods [Beard L.R., 1975]. This coupled approach was initially

tested on the operational optimization of the dam’s complex in the Velika Morava

basin in the former Yugoslavia[Djordjevic B et.al] .It is nowadays the most common

program structure adopted in dam simulation software.

3.5 About the model

3.5.1 Introducing HEC Res Sim

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The U.S. Army Corp of Engineers - Hydrologic Engineering Center developed in 1973

the HEC-5 program for the simulation of flood control and conservation systems. It

was initially written for flood control operation of single flood events. The program was

later expanded to multi-events floods and included basic water supply and hydropower

analysis capabilities. Pumped-storage hydropower analysis capability was finally added in

1977.All versions were developed in FORTRAN and interfaced with the HEC-DSS

data storage system. [USACE-HEC, 2007]

HEC-5 recently evolved into the HEC-ResSim software with the addition of a graphical

user interface (GUI). Its hydropower simulation capabilities include analysis of run-of-

river generation, peak power generation, pumped storage and system power operation. To

simulate hydropower operation, the reservoir releases are determined to meet power

production goals which may vary on a monthly, daily, or hourly basis.

Additionally, the hydropower component takes into account the penstock capacity

and losses, as well as leakage parameters. [USACE-HEC, 2007]

The model allows the user to define alternatives and run simulations simultaneously to

compare results. Schematic elements in HEC-ResSim allow the representation of

watershed, reservoir network and simulation data visually in a geo-referenced context

that interacts with associated data. Additionally, HEC-ResSim is compatible with ArcGIS

shape files and AutoCAD drawing files, which can be used as a background layer and

facilitate the better representation of the physical system. Watershed boundaries,

reservoirs, channel networks, diversions, etc. can be superimposed over the shape file.

[USACE-HEC, 2007]

The HEC-ResSim program is divided into three modules(Fig.1) which are

respectively, the watershed setup, the reservoir network definition and the

simulation scenario management. [USACE-HEC, 2007]

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Figure 3.1 - Graphical illustration of the HEC-ResSim modules

• Watershed setup

The purpose of this module is to provide a common framework for watershed creation and

definition. A watershed is associated with a geographic region for which multiple

models and layers of information can be configured. A watershed may include all of the

streams, projects, e.g., reservoirs, levees, gage locations, impact areas, time-series locations,

and hydrologic and hydraulic data for a specific area. All of these details together, once

configured, form a watershed framework. [USACE-HEC, 2007]

• Reservoir network definition

The purpose of the Reservoir Network module is to isolate the development of the

reservoir model from the output analysis. This module facilitates the creation of the

network schematic, the description of the physical and operational elements of the

reservoir model, and the definition the management alternatives to be analyzed.

Reservoirs are further divided into multiple technical elements such the pool, the dam,

and one or more outlets. The criteria for reservoir release decisions are drawn from a set

of discrete pool heights, power production levels and release rules. Reservoirs are

connected to the river network as well diversions or junctions. After finalizing the

connection network schematic, physical and operational data for each network element

are defined. Management alternatives are created to compare results using different model

schematics, i.e. physical properties, operation sets, inflows, and/or initial conditions.

[USACE-HEC, 2007]

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• Simulation scenario management

The purpose of the Simulation module is to isolate the output analysis from the model

development process. Once the reservoir model is complete and the alternatives have

been defined, the Simulation module enables the model to test various river flow

hypotheses.

3.6 Review on past studies:

Feasibility Study of Upper Seti Storage Hydroelectric Project: NEA, 2001

NEA conducted detailed feasibility study on USHEP in 2001 which also includes the

reservoir simulation. It was envisaged to make a detail study of the power generation

possibility with respect to the available water resources and find the most suitable option

in terms of energy benefit. A tool was developed in –house for this purpose by NEA by

the Project Optimization Group in the form of a computer software named "Reservoir

Simulation Version 1.0" using C++ language.

The reservoir simulation has been carries out for the USHEP using the updated version

1.1 of the above mentioned software. Simulation was carried out for the three sets of

options depending on tail water level and the development concept. Two sets of

simulation are run for the Option A, one for the shaft powerhouse option (Alternate A1.1

and A1.2) and another for the Underground powerhouse option (Alternate A2.1 and

A2.2). One simulation was run for the Option B, toe development.

Design alternative of reservoir

During inception and feasibility study stage various alternatives for the project layout was

done by NEA. The study showed two options based on the findings of preliminary study

and site investigation.

Option A

In this alternative, different options for locations for the main intake and the powerhouse

are recognized. The four alternatives are based on two different powerhouse types

associated with two different location of the main intake and the resulting four different

alignments of the headrace tunnel. Intake No.1 and Intake No. 2 is 130 m and 300 m

upstream from the dam axis respectively. These are grouped as

Alternative A1.1 : Intake No.1 with Shaft Type Powerhouse

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Alternative A1.2 : Intake No.2 with Shaft Type Powerhouse

Alternative A2.1 : Intake No.1 with Underground Powerhouse

Alternative A2.2 : Intake No.2 with Underground Powerhouse

Option B

This option consists of only one alternative i.e toe development underground powerhouse.

This option is adopted during the feasibility study by NEA.

Alternative: B1 : Toe development

Option A and B both have 142 m high Roller Compacted Concrete dam with integrated

spillway and the river diversion structures. The dam is founded on bedrock of dolomite.

The head race tunnel is located at uphill side of the Seti River, which passes through the

dolomite and slate.

The economic and financial analysis conducted by NEA has shown that Option B is the

best alternative.

Simulated results obtained for Option B is shown in table 3.1.

Table 3.1: Simulated results obtained by NEA

Full Supply Level(FSL) (m) 425.00 m

Sediment Deposit Level (m) 399.56

Minimum Operating Level (MOL) (m) 410.96

Storage Volume at FSL (Mm^3) 333.71

Storage Volume at MOL (Mm^3) 237.00

Sediment Deposit Volume (Mm^3) 172.96

Weighted Average Head (m) 111.04

Discharge Utility Factor 0.68

Maximum Plant Discharge (m^3/s) 141.14

Minimum Plant Discharge (m^3/s) 124.21

Optimum Plant Capacity MW) 122.20

Plant Factor 0.555

Dry Season Energy (GWh) 171.93

Wet Season Energy (GWh) 422.43

Total Annual Energy(GWh) 594.36

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Upgrading Feasibility Study on the USHEP in Nepal

-JICA, Electric Power Development Co. Ltd, Nippon Koei Co. Ltd, 2007

JICA conducted the study in 2007 using the same input data as used by NEA in its

feasibility study. The study focused on sediment deposition pattern as well. The

simulation was carried out with the program named EPDC/KCC FLOW 500 MODEL.

The Reservoir is estimated to be filled with sediment in several decades, so the measures

against sedimentation shall be taken. A degree of importance for sediment management is

classified with the following two indices as shown.

Life of reservoir = Reservoir Capacity (CAP) /Average annual sediment inflow (MAS)

=331.7 MCM /(11.55 MCM/Year)

= 28.72 years

Turnover rate of reservoir = Reservoir Capacity (CAP) /Average annual inflow (MAR)

=331.7 MCM / 3,381 MCM

= 0.098

Average sediment deposit of the reservoir

=specific sediment yield X catchment area X trap efficiency

=6,244 X 1,502 X 0.85

=7.97 MCM / Year

Necessary number of years the reservoir will be filled with sediment is calculated as

270.3 MCM / 7.97 MCM / year

=34 years (in terms of effective capacity)

331.7 MCM / 7.97 MCM / year

=42 years (in terms of gross capacity)

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Numerical values of the above indices show that the reservoir will be filled with sediment

in a short period of year without sediment management and has relatively large turnover

rate.

A decrease in effective storage capacity of the Reservoir is as shown in Table 3.2:

Table 3.2: Storage capacity of reservoir

Years of Completion Effective Storage Capacity(MCM)

0 270.30

25 197.40

50 134.81

Sediment volume for different sill elevation is given in Table 3.3

Table 3.3: Sediment volume

Sediment flushing gate Sediment volume in Reservoir

sill elevation

After 108 yearsMaximum sediment volume

Volume

Years of completion(1,000 m^3)(1,000 m^3)

320.00 126,434 138,635 89330.00 162,952 169,943 89

The simulation results showed that sediment advances year by year without the yearly

sediment flushing operation. The cumulative and maximum sediment volumes after 108

years from completion, as well as the year in which the sediment volume peaks, are

shown in Table 3.4

Table 3.4: Sediment Volume in Reservoir

Frequency of sediment Sediment volume in Reservoir

flushing operation

After 108 yearsMaximum sediment volume

Volume

Years of completion(1,000 m^3)(1,000 m^3)

Every year 126,434 138,635 89Every 2 year 246,733 261,389 89Every 3 year 283,314 288,390 107

Table 3.5 shows other simulated results

Table3.5: Simulated results (JICA)

22

Full Supply Level(FSL) (m) 425.00 m

Sill Level of Flushing gates(m) 320

Minimum Operating Level (MOL) (m) 370

Weighted Average Head (m) 116.2

Optimum Plant Capacity MW) 126

Plant Factor 0.52

Dry Season Energy (GWh) 230.1

Wet Season Energy (GWh) 344

Total Annual Energy(GWh) 574.1

Conclusion drawn by JICA:

The project has a lot of sediment inflow to the Reservoir, and the sediment flushing

facilities are indispensable to maintenance of the effective Reservoir capacity.

It is recommended that the facilities be installed at EL.320.00 m considering the

topography of the Dam site.

Sediment flushing operation shall be carried out every year.

Assessment of Energy production from major Hydropower projects in Nepal-

(Shrestha, 2007)

The objective of this study was to assess the energy production from the major existing

hydropower plants and planned hydropower projects in next five years using nMAG

model. USHEP was also a part of the study and the study results are shown in Table 3.6.

Table3.6: Summary of the results (nMAG)

Total Energy Generated(GWh) 673.3

Maximum Discharge(m^3/s) 127.4

Maximum Power (MW) 132.698

Utility Factor 58.2

3.6.4 Some practical applications

23

In 2004, [Babazadeh et al, 2007]. for evaluation and reservoir management of Tigris and

Euphrates rivers system in Iraq HEC-ResSim 2.0 was used. First, multi-reservoir system of

these rivers where setup on HEC-ResSim. Model contains six main reservoirs, three off-

stream reservoirs and seven small reservoirs and many diversion dams for diverting

water from Tigris and Euphrates rivers. Priority in these multipurpose reservoir system

are water supply for agriculture demand then flood control, while, hydroelectric power

was also generated. HEC-ResSim 2.0 was used for simulation history events special flood

and drought periods.

USACE experts used HEC-ResSim for water resources simulation in Afghanistan.

Engineers of US Army Corps of Engineers and Afghani engineers created a team for

simulation of Kajakai reservoir and project development downstream plains. This

model simulates system operation for power generation, flood control, irrigation and

changes in power generation capacity, live storage and release structures [ Babazadeh et al,

2007].

Jhiroft dam simulation

Halil River is one of biggest river of Jazmourian basin and Kerman province, Iran. The

area of Halil river basin is 31462 km2. The starting point of this permanent river is

snow covered mountain near city of Baft and Rabor in Kerman province. Annual

volume of water carried by Halil River as measured by monitoring station in 42 years

time series is 515 MCM. Jiroft storage dam is the largest dam in this river basin that

started operation in 1992. Average annual inflow of dam reservoir over 42 years is 422

MCM and from initial operation up to 1995 is 536 MCM. First of all, operation

reservoir volume is 415 MCM at elevation 1184 meter from sea level and inactive

level is 1126 meters from sea level. This is an arched dam and average evaporation

from water surface is 2076 mm. Length of dam crest is 250 m and its height from river

bed is 125 m and crest width is 5 m. This dam has two Francis turbines with power

generation 32 MW. Main purpose of this dam construction is supply of downstream

agriculture water demand, flood control of Halil River and secondary is hydropower

generation. Due to drought in recent years, power station was not operated. [Babazadeh et

al, 2007].

72 months operation from 1999 to 2005, data of Jiroft Storage Dam (such as: inflow,

outflow, reservoir level, storage and power generation as daily data) have been

24

recorded by Jiroft Dam Operation Company. These data were used for validation and

estimation of model accuracy. [Babazadeh et al, 2007].

Study and evaluation of Jiroft storage dam in present conditions,

sedimentation condition and developing condition was performed using HEC-ResSim

Results of model validation showed that model was capable of simulation

with suitable accurate. For study of accuracy and validation of model, observed data

from April 1999 to March 2005 was used. Therefore, input data, output data and reservoir

and dam properties were supplied to the model and changes in computed volume of

reservoir were compared with observed data. Observed data input to model as history data

and reservoir storage were compared with observed data in observation periods. The value

of absolute error was 11% and root of mean square error was estimated 23 million cubic

meters. Therefore, model ability and efficiency are acceptable. [Babazadeh et al, 2007].

25

IV. DESCRIPTION OF SITE AREA AND THE PROJECT

4.1 Location

The Upper Seti (Damauli) Storage Hydroelectric Project has a capacity of 127 MW[NEA,

2001], the storage type scheme, and includes 1000 m long horse shoe headrace tunnel,

140 m high concrete gravity dam, two diversion tunnels of lengths 712 m and 881 m and an

underground powerhouse. [NEA, 2001]

The site is located in the upper part of the Seti River, a tributary of the Trishuli River

flowing in the central part of Nepal. The Seti River originates at the Annapurna (at an

elevation of 7,555 m above sea level) of the Himalayas and joins the Madi river 2 km

downstream from the proposed Dam site after flowing roughly from north to south. The

length of the Seti River from the origin to the Dam Site is about 120 km, and the

catchments area at the Dam site is 1,502 sq km. [NEA, 2001]

The Seti River basin belongs to a high mountain and a humid subtropical climate zone.

The NEA's report states that the average annual precipitation in the project basin is 2,973

mm, of which about 80% falls between June and September due to the influence of the

southwest monsoon. Records of temperature exceeding 36 Degree Celcius from April

through June as against a lower value of approximately 5 Degree Celcius from January

through February on average. [NEA, 2001]

4.2 Main Features of Upper Seti Storage Hydroelectric Project

River Name of River Seti River

Catchments Area 1502 km2

Annual Inflow 3,380 x 10^6 m^3

Reservoir Full Supply Level 425.0 m

Minimum Operating Level 370 m

Available Depth 55 m

Effective Storage Capacity 270.30 MCM

Dam Type Concrete Gravity Dam

Height x Crest Length 140.0 m, 170.0 m

Power House Type Underground

Size Wide 22mx High 42m length 90 m

26

Discharge Maximum 127.4 cumecs

Installed Capacity 127 MW

Turbine Type Vertical Shaft, Francis Turbine

Turbine Output x Number 65,100 KW x 2

Figure: 4.1: Location of the site

4.3 River System

The total length of the Seti River from the dam site to the source is about 120 km. Seti

river meets many medium and small tributaries upstream of the dam site. These are

described below.

Starting at dam site, the Seti River meets Jyamdi and Kyangdi River at 28 km upstream at

Khairenitar. The river gradient from dam site to this confluence is 1:280.The river

gradient is flatter and flows almost west to east. From Jyamdi and Seti River confluence

the river flows south to north and meets Saraudi River. The river has gradient 1:120 and

the length of the river reach is 7 km.

27

From Saraudi River and Seti River confluence, the Seti River meets Khudi River at Kotre.

The river reach is 3 km and gradient 1:120.Further Upstream Seti River meets Bijaypure

River. The river length is 12 km gradient 1:100.

At short distance, the Set River meets Phusre River. The river length is 2 km and gradient

1:90.From Phusre and Seti River confluence, the Seti River meets Yandi River at about

18 km upstream. The river flows almost north to south and has a gradient 1:70.

The river upstream of Yandi and Seti confluence, the river flows through Phokhara

valley.The Seti River flows through the Mahendra Pul. The highest gorge, that is, river

undercutting are seen at the Pokhara valley due to the Seti River. Upsream of Pokhara

valley, the river meets mardi River at Lahachowk. The river reach length is 7 km and

average gradient 1:53.

The Seti River upstream of Maridi and Seti confluence, the river gradient is steep ,more

than 1:27 upto Sadhu River confluence. The confluence height is about 2000 m above

mean sea level .the river length is 75 km. Above this the Seti River is very steep, the

gradient is more than 1:10,the remaining river length is 20 km up to the glacier tongue.

[NEA, 2001]

4.4 Meteorological and Hydrological Stations

Meteorological stations and gauging stations are arranged in the Seti River and

surrounding basin. The Department of Hydrology and Meteorology (DHM), a subordinate

organization of the Ministry of Environment, Science and Technology, carries out

meteorological observation and river discharge measurements and provides NEA with

those data. A few meteorological stations are also equipped with a thermometer. a

hygrometer, an anemometer and an evaporation pan, while the other stations are provided

with only a rain gauge.

Table 4.1: Rain Gauge Stations Near and at the Seti River Basin

Index.No. Station name Lat.-Long. ElevationYears of Records

Deg/Min m

613 Karki Neta 28 d 11'-84 d 45' 1720 1977-94

706 Damkauli 27d 41'-84d 13' 154 1971-95

726 Garakot 27d 52'-83d 48' 500 1980-96

802 Khudi Bazar 28d 27'-84d 22' 823 1957-97

803 Pokhara Hospital 28d 14'-84d 00' 866 1956-75

28

804 Pokhara Airport 28d 13'-84d 00' 827 1968-94

805 Shyangja 28d 06'-83d 53' 868 1973-94

806 Larke Samdo 28d 40'-84d 47' 3650 1978-94

807 Kuncha 28d 08'-84d 21' 855 1956-94

808 Bandipur 27d 56'-84d 32' 965 1956-95

810 Chapkot 27d 53'-83d 49' 460 1957-94

811 Male Patan 28d 13'-83d 57' 856 1966-94

813 Bhadaure Deurali 28d 16'-83d 49' 1600 1985-94

814 Lumle 28d 18'-83d 48' 1740 1969-94

815 Khairini Tar 28d 02'-84d 06' 500 1971-94

816 Chame 28d 33'-84d 14' 2680 1974-94

817 Damauli 27d 58'-84d 17' 358 1974-94

818 Lamachaur 28d 16'-83d 58' 1070 1972-94

820 Manag Bhot 28d 40'-84d 01' 3420 1975-94

821 Ghandruk 28d 23'-83d 48' 1960 1976-94

822 Khuldi 28d 26'-83d 5u0' 2440 1973-86

823 Gharedhanga 28d 12'-84d 37' 1120 1976-94

824 Slklesh 28d 22'-84d 06' 1820 1977-94

Source: NEA, 2001

4.5 Climate study

The total number of climate gauge stations is around 157 according to NEA.A few

climate gauging stations are equipped with precipitation gauge , temperature data,

humidity data, wind data and evaporation data.

The catchment lies in the High Himalayas and the Lesser Himalayas and the

physiographic characteristics of the Seti River influences the climate change with

variation of altitude. Therefore, the catchment area experiences severe cold, subtropical to

temperate climate. As in other parts of Nepal, the Seti River catchment also experiences

the effects of the southwest monsoon, which on an average lasts from June to the end of

September. The region receives rainfall approximately 80% of the annual rainfall during

this period. Rainfall intensifies vary throughout the basin with maximum intensity

occurring on the south facing slopes. During the monsoon period, relative humidity

reaches at their maximum, temperature are lower compared to the pre-monsoon period.

29

4.6 Stream Flow Data

The earliest data recorded for major rivers in Nepal is from 1962.The gauging stations in

the major rivers are equipped with discharge measurement, automatic water surface

record chart and the staff gauge. DHM provides records of the monthly flows for study

purpose. The locations of the gauging stations are shown below:

Table 4.2: Stream Flow data around the catchment area

Stream

GaugeRiver Name Location

Year of

Records

Latitude. /

Longitude

Drainage

Area(km^2)

406.5 Modi River Nayapool 1988-94 28d 13'-83d 42' 647

428 Mardi River Lahachowk 1974-90 28d 13'-83d 55' 160

430 Seti River Phoolbari 1964-84 28d 14'-84d 00' 582

N.A Seti River Damauli(Patan) Recent 500 m d/s of dam site 1505

438 Madi River Shisaghat 1978-90 28d 06'-84d 14' 858

439.3 Khudi River Khudi Bazar 1983-93 28d 17'-84d 21' 147

439.7 Marsyandi River Bimal Nagar 1987-93 27d 57'-84d 25' N.A

439.8 Marsyandi River Gopling Ghat 1973-86 27d 55'-84d 29' 3850

Source: NEA, 2001

4.7 Topographic Characteristic of the Basin

Seti River is one of the main tributaries of Sapta Gandaki River System. Annapurna

Himalayas is the main source of Seti River. The major source of the basin consists of

several peaks such as "Annapurna III(EL.7555 m), Annapurna Peak V(EL.7525 m)and

Machapuchre (EL.6999 m).The total area of Seti River basin up to site intake is 1502

km^2,in which 50 km^2 is covered with snow.

Table 4.3: Catchment Characteristic

Area(km^2) Upper Seti Intake

Total Area 1502

Area below 5000 m 1452

Area above 5000 m 1276

Source: NEA, 2001

30

Table 4.4: Major Lakes in the Seti River Basin

Lakes Lake Area(km^2) Catchment Area(km^2)

Phewa Lake 4.35 126.8

Begnas Lake 3.3 18.5

Rupa Lake 1.14 26.3

DipangLake 0.075 -

Maidi Lake 0.0125 -

Khasti Lake 0.100 -

Nyurehi Lake 0.0375 -

Total 9.185 171.6

Source: NEA, 2001

4.8 Evaporation

The evaporation data are available from the year 1977 to 1984 and shown in table 4.5.

The figure indicates that the evaporation occurs at the maximum rate during the dry

period of the pre-mansoon season.

Table 4.5: Monthly Evaporation Data

year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1977 N.A N.A N.A 3.5 5.8 7.1 5.7 6.2 4.7 3.5 2.6 1.3

1978 1.6 2.1 4.8 3.7 6.2 5 5.9 4.7 3.9 3.2 2.3 1.6

1979 1.7 2.8 4.7 5.6 6 6.6 3.9 4.5 3.9 3.4 2.4 1.6

1980 1.4 2.7 4.4 5.9 5.3 5.1 4.8 4.6 4.4 3.4 2.3 1.9

1981 2.2 2.5 4.5 5.2 6.1 5.6 4.9 4.4 4.7 3.4 2.4 1.8

1982 2.3 2.5 3.8 6.9 5.6 6 5.3 5.1 3.9 2.9 2.1 1.7

1983 1.9 2.5 4.2 4.1 5.6 6.8 6.2 5.3 5.9 3.5 2.4 1.5

1984 1.6 2.8 5.3 5.8 4.8 5 5.5 5.7 4.6 3 2 1.3

Days

Average

31

1.81

28

2.56

31

4.53

30

5.09

31

5.68

30

5.90

31

5.2

8

31

5.06

30

4.50

31

3.2

9

30

2.31

31

1.59

Evaporation

Mm/month

56 72 140 153 176 177 164 157 135 102 69 49

Reservoir

Evaporation(mm/mth)

39 50 98 107 123 124 114 110 95 71 49 34

Source: NEA, 2001

31

4.9 Probable Maximum Precipitation

Probable maximum precipitation (PMP) over the basin is used to determine the Probable

maximum flood. It is shown in table 4.6.

Table 4.6: Probable Maximum Precipitation

S.No Index No. Station PMP

1 706 Damkauli 1107

2 726 Garakot 1142

3 802 Khudi Bazar 844

4 803 Pokhara Hospital 867

5 804 Pokhara Airport 742

6 805 Shyangja 982

7 806 Larke Samdo 652

8 807 Kuncha 724

9 808 Bandipur 821

10 809 Chapkot 516

11 810 Male Patan 950

12 811 Bhadaure Deurali 920

13 813 Lumle 1005

14 814 Khairini Tar 856

15 815 Chame 668

16 816 Damauli 512

17 817 Lamachaur 1245

18 818 Manag Bhot 1063

19 820 Ghandruk 571

20 821 Khuldi 731

21 823 Gharedhanga 808

22 824 Siklesh 768

Source: NEA, 2001

32

4.10 Probable Maximum Flood (PMF)

The hourly flood hydrograph is given in the Table 4.7.

Table 4.7: Probable Maximum Flood

Time inHours

PMF Hydrographm^3/s

Dry season FloodHydrograph

123456789

1011121314151617181920212223242526272829303132333435363738394041424344

100.0100.0100.0100.0100.0100.0100.0111.2193.3330.9538.1812.6

1,148.11,538.51,977.52,457.82,970.43,506.44,057.54,615.45,170.05,707.06,215.26,681.47,099.57,463.67,768.28,008.58,180.68,281.08,306.78,255.48,126.57,931.27,692.77,429.37,152.26,869.96,589.76,317.26,055.25,804.05,563.35,332.5

10.010.010.010.010.010.010.010.010.010.010.215.521.829.337.646.856.566.777.287.898.3

108.6118.2127.1135.0142.0147.8152.3155.6157.5158.0157.0154.6150.9146.3141.3136.1130.7125.4120.2115.2110.4105.8101.4

33

45464748495051525354555657585960616263646566676869707172

5,111.44,899.44,696.24,501.44,314.74,135.73,964.23,799.83,642.23,491.13,346.33,207.53,074.52,947.02,848.82,707.62,595.32,487.72,384.52,285.62,190.82,099.92,012.81,929.41,849.31,772.61,699.11,628.6

97.293.289.385.682.178.775.472.369.366.463.761.058.556.153.751.549.447.345.443.541.739.938.336.735.233.732.331.0

Source: NEA, 2001

4.11 Temperature

The annual maximum air temperature occurs generally I month of May and ranges from

36 degree Celsius to 41 degree Celsius and slightly decrease in June. The Minimum

temperature occurs in December and January ranging from 1.5 degree Celsius to 7 degree

Celsius.

4.12 Humidity

The maximum and minimum monthly humidity are 100 % and 40%respectively.The

atmosphere is humid with average monthly relative humidity ranging from 77% to 100 %

in Janaury.April is the driest month with relative humidity at 40 %.

4.13 Wind Speed

The average monthly maximum wind speed at the dam site is 3.8 km/hr.

34

V. RESEARCH METHODOLOGY

5.1 Application of the model

HEC-ResSim uses an original rule-based approach to mimic the actual decision-making

process that reservoir operators must use to meet operating requirements for flood

control, power generation, water supply, and environmental quality. Parameters that may

influence flow requirements at a reservoir include time of year, hydrologic conditions,

water temperature, and simultaneous operations by other reservoirs in a system. The

reservoirs designated to meet the flow requirements may have multiple and/or conflicted

constraints on their operation. ResSim describes these flow requirements and constraints

for the operating zones of a reservoir using a separate set of prioritized rules for each

zone. Basic reservoir operating goals are defined by flexible at-site and downstream

control functions. As HEC-ResSim has evolved, advanced features such as multi-

reservoir system constraints, outlet prioritization, scripted state variables, and conditional

rule logic have made it possible to model more complex systems and operational

requirements. The graphical user interface makes HEC-ResSim easy to use and the

customizable plotting and reporting tools facilitate output analysis. [Charalampos

Shaulikaris, 2008]

HEC Res Sim model was used in reservoir simulation for water release for power

production and flood control with different operation policy. This model has three

main modules: Watershed Setup, Reservoir Network and Simulation. In this model we

can make different management in reservoir system by defining scenarios in a time

series data. Model input data are: reservoir properties (Volume-Area and Elevation

Curve, Operation levels, Operation rules and etc) control and operation points and time

series input file. The highest capability of this model was

defining of different operation rules in power plant generation flood control

conditions, creating scenarios for conditional operation, downstream control point,

reservoir system balance to imitate the hydrological condition and

installing of different structures in dam body, comparison of output with observed

data, defining of different operational level, different computational steps (15 min to a

day) and adjustment of output results . [Charalampos Shaulikaris, 2008]

5.2 ResSim Modules

ResSim offers three separate sets of functions called Modules that provide access to specific

35

types of data within a watershed. These modules are Watershed Setup, Reservoir Network,

and Simulation. Each module has a unique purpose and an associated set of functions

accessible through menus, toolbars, and schematic elements.

5.2.1. Watershed Setup Module

The purpose of the Watershed Setup module is to provide a common framework for

watershed creation and definition among different modeling applications. This module is

currently common to HECResSim, HEC-FIA, and the CWMS CAVI.

A watershed is associated with a geographic region for which multiple models and area

coverages can be configured. A watershed may include all of the streams, projects (e.g.,

reservoirs, levees), gauge locations, impact areas, time-series locations, and hydrologic and

hydraulic data for a specific area. All of these details together, once configured, form a

watershed framework.

When a new watershed is created, Res Sim generates a directory structure for all files

associated with the watershed.

In the Watershed Setup module, items are assembled, that describe a watershed’s physical

arrangement. Once a new watershed is created, it is possible to import maps from external

sources, specify the units of measure for viewing the watershed, add layers containing

additional information about the watershed, create a common stream alignment, and configure

elements. Projects can be added and time-series icons can be created within the Watershed

Setup module.

5.2.2. Reservoir Network Module

The purpose of the Reservoir Network module is to isolate the development of the reservoir

model from the output analysis. In the Reservoir Network module, river schematic is built,

physical and operational elements of reservoir model are described, and alternatives are

developed for analyzing. Using configurations that are created in the watershed Setup module

as a template, basis of a reservoir network is created. Routing reaches are and possibly other

network elements to complete the connectivity of your network schematic. Once the schematic

is complete, physical and operational data for each network element are defined. Also,

alternatives are created that specify the reservoir network, operation set(s), initial conditions,

and assignment of DSS pathnames (time-series mapping).

36

5.2.3. Simulation Module

The purpose of the Simulation module is to isolate output analysis from the model

development process. Once the reservoir model is complete and the alternatives have been

defined, the Simulation module is used to configure the simulation. The computations are

performed and results are viewed within the Simulation module. When you create a

simulation you must specify a simulation time window, a computation interval, and the

alternatives to be analyzed. Then, ResSim creates a directory structure within the rss folder of

the watershed that represents the “simulation”. Within this “simulation” tree will be a copy of

the watershed, including only those files needed by the selected alternatives. Also created in

the simulation is a DSS file called simulation. dss, which will ultimately contain all the DSS

records that represent the input and output for the selected alternatives. Additionally, elements

can be edited and saved for subsequent simulations.

Figure: 5.1: Procedural Flow Chart

37

5.3 Model development

The centerline (stream alignment) of the watershed model includes the river

system and the reservoir created by the construction of 140 m high concrete dam.

The current study is performed considering the one and only priority of the

project is the power production and no obligation for downstream release.

However, 10% of stream flow has been targeted as minimum downstream

release. Future development of the model can feature one or more reservoirs and

other water management issues.

5.3.1. Input Data for HEC Res Sim

The reservoir is the key component in the most hydropower projects. It is the reservoir

that makes it possible to store water in periods with a large inflow and less demand, and

release it in periods with less inflow and larger demand. In other words, the reservoir

works as a "buffer" to reduce the problems that show up when inflow and demand do not

occur at the same time.

Following data is provided for each reservoir module to run HEC Resevoir Simulation:

1. Topographic map of the study area.

An AUTOCAD drawing containing physical features of the study area such as stream

alignments, location of reservoir, area of the reservoir, contour, impact area etc was

imported as background map. Then required model was drawn on the basis of the

background map. River alignment, reservoir area, impact area, river junctions,

computational points are the required physical data.

2. Hydrological Data.

Major computational points are included as the inlet and outlet of the reservoir. The

input for the inlet is the average daily stream flow calculated from the data recorded from

1964 to 1999. Mean monthly flow at the dam site is shown in Table 12 at Annex -

III .Similarly Input of Daily Stream Flow is shown in Table 4.4.

The area volume curve of the reservoir has been adopted from the study

conducted by JICA in 2007.Other required data as evaporation data, climate

data have been extracted from the feasibility study report by NEA in 2001.

38

Table 5.1: Monthly Average Flow (MAF) -Evaporation Rate (ER)

Source: NEA, 2001

Table 5.2: Reservoir Volume and Elevation

S.N Month MAF(m3/s)ER (mm/month)

1 Jan 27.03 69.09

2 Feb 23.72 91.97

3 Mar 24.01 152

4 April 27.43 176

5 May 41.07 184.5

6 June 113.84 200.7

7 July 287.22 191

8 August 322.61 189.4

9 Sept 225.77 166

10 Oct 112.43 129.4

11 Nov 52.01 80.3

12 Dec 34.36 64.76

39

S.NHeight

(m) Area(km^2) Volume(MCM)

1 310 0.02 0

2 315 0.15 0.42

3 320 0.32 1.59

4 325 0.46 3.54

5 330 0.56 6.1

6 335 0.71 9.29

7 340 1.10 13.82

8 345 1.29 19.81

9 350 1.48 26.74

10 355 1.73 34.77

11 360 2.11 44.38

12 365 2.38 55.6

13 370 2.88 68.74

14 375 3.37 84.35

15 380 3.85 102.4

16 385 4.36 122.93

17 390 4.79 145.78

18 395 5.20 170.74

19 400 5.73 198.06

20 405 6.23 227.95

21 410 6.70 260.25

22 415 7.26 295.14

23 420 7.92 333.08

24 425 8.67 374.57

25 430 9.82 420.79

26 435 11.24 473.45

Source: NEA, 2001

3. Time-Step

40

A daily time-step HEC-ResSim model was developed for the study to simulate the

1964-1999 period-of-records. The monthly average generated daily records have

been taken .This average stream flow data accounts for nearly 45 % probability

of exceedence. (Annex-III, Table 11)

4. Guide curve

A guide curve suggests the level of water at the reservoir at any time of the year.

Rule curves are simply elevations at each reservoir that help guide the operation (i.e.

drafting or filling)

Rule curves specify the highest and the lowest elevation that a reservoir should be

operated to in order to stay within the planning objective.

Intermediate rule curves help determine which projects release water first when

energy is needed.

Flood Control

– defines the drawdown required to assure adequate space to store the

anticipated runoff without causing downstream flooding (Maximum Elevation).

Critical Rule Curve

– defines how deep a reservoir can be drafted in order to meet the firm energy requirements during the poorest water conditions on record (Minimum Elevation).

5.4 Modeling the dams complex

The modeling of the Upper Seti Hydro Electric Project dam using HEC-ResSim is carried

out in a three phase process: the Watershed network setup, the parameterization of the dam's

components and the simulation of the different operational scenarios.

5.4.1 The watershed network setup

The initial phase of the modeling concerns the tracing of the connected flow elements

of the river watercourse between Dhulegauda and the dam site. Apart from the main

course, the modeling includes the placement of stream junctions at the

segments gathering the water drained from the various watersheds nourishing the Seti

River. An inlet computational point (CP3) has been artificially placed at the upstream end of

41

the reservoir in order to simulate the total inflow to the reservoir. Similarly an outlet

computational point (CP4) is placed at the dam outlet to simulate the release. The stream

junction points of the watershed are as follows:

Jyagdi Khola junction

Pirun Khola junction

Wantan Khola junction

Bange Khola junction

Kumle Khola junction

Guhe(Kumle Khola tributary) junction

Kyangdi Khola junction

Figure 5.2: Representation of the watershed in HEC-ResSim

5.4.2. The parameterization of the study dam

42

Following the geographic placement of the HEC-ResSim elements including main stream

segments, inflow point, dams with their connections to the main river stream as well as

outflow point , the next step of the HEC-ResSim set-up is the definition of the technical

parameters defining for dam: the geometric properties of the pool, the capability of the

hydropower plant and the definition of the various management constraints regarding

the electric power production, the regime of released flow and the operation in

conditions of flooding.

5.4.3. Operational Parameters

River flow catchment (Km2) 1502

Maximum discharge (m3/sec) 127

Full Supply level (F.S.L) (m) 425

Minimum operation level (M.O.L) (m) 370

Volume in (F.S.L) 106 m^3 374.57

Volume in (M.O.L) 106 m^3 68.74

Reservoir surface in F.S.L (Km2) 8.67

Tailrace water level (m) 289

Upper spillway level 385.82

Elevation of crest dam (m) 430

Height of dam (m) 140

Number of Turbine units 2

Total installed power (MW) 127

As an illustration of how HEC-ResSim dam parameters have been set, the detailed

process followed for the Upper Seti Dam is presented as follows:

5.4.4 Definition of the pool parameters

For the reservoir characteristics, the minimum operating level is 370 m and upper crest

of the gate is maintained at 320 m. This defines the lowest elevation from which it is

possible to release water. Below this level the storage capacity of the reservoir is considered

to be equal to zero since the stored water cannot be used. When the upper operation level is

reached at 425 m the volume of the stored water is 374.57 million m3 and the area

covered with water is 8.67 km2. HEC-ResSim provides various models of relation

43

between pool area and water height.

Table 5.3: Gate Settings

Elevation Max capacity (cms)for gate settings(m)

(m) 1 5 9 12.5

310 0 0 0 0

315 910.26 678.47 678.47 678.47

320 1322.58 1175.15 1006.33 1006.33

325 1633.97 1517.11 1390.45 1269.3

330 1894.87 1795.07 1689.38 1591.16

335 2123.95 2035.41 1942.84 1858.07

340 2330.62 2250.23 2166.86 2091.19

345 2520.41 2446.26 2369.8 2300.81

350 2696.87 2627.71 2556.67 2492.86

355 2862.47 2797.41 2730.79 2671.14

360 3019 2957.39 2894.46 2838.25

365 3167.81 3109.14 3049.35 2996.05

370 3309.94 3253.83 3196.74 3145.94

375 3446.2 3392.35 3337.64 3289.01

380 3577.29 3525.44 3472.82 3426.11

385 3703.73 3653.68 3602.93 3557.93

390 3826 3777.57 3728.5 3685.04

395 3944.48 3897.52 3849.99 3807.91

400 4059.5 4013.89 3967.75 3926.93

405 4171.35 4126.98 4082.12 4042.46

410 4280.29 4237.05 4193.37 4154.77

415 4386.51 4344.33 4301.74 4264.12

420 4490.23 4449.03 4407.45 4370.74

425 4591.6 4551.32 4510.68 4474.82

430 4690.78 4651.36 4611.61 4576.54

435 4787.91 4749.3 4710.37 4676.04

44

Capacity (cms)

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Ele

v (m

)

300

320

340

360

380

400

420

440

1.00-Elevation 5.00-Elevation

9.00-Elevation 12.50-Elevation

Figure 5.3: Gate settings curve

Table 5.4: Reservoir pool parameter

Elevation(m) Storage Area(m) (m^3) (ha)310 0.00 2.00315 420,000.00 15.00320 1,590,000.00 32.00325 3,540,000.00 46.00330 6,100,000.00 56.00335 9,290,000.00 71.00340 13,820,000.00 110.00345 19,810,000.00 129.00350 26,740,000.00 148.00355 34,770,000.00 173.00360 44,380,000.00 211.00365 55,600,000.00 238.00370 68,740,000.00 288.00375 84,350,000.00 337.00380 102,400,000.00 385.00385 122,930,000.00 436.00390 145,780,000.00 479.00395 170,740,000.00 520.00400 198,060,000.00 573.00405 227,950,000.00 623.00410 260,250,000.00 670.00415 295,140,000.00 726.00420 333,080,000.00 792.00425 374,570,000.00 867.00430 420,790,000.00 982.00435 473,450,000.00 1124.00

45

Stor (m3)

0 1.0E8 2.0E8 3.0E8 4.0E8 5.0E8

Ele

v (m

)

300

320

340

360

380

400

420

440

Area (ha)

0 200 400 600 800 1000 1200E

lev

(m)

300

320

340

360

380

400

420

440

Storage Capacity

Area

Figure 5.3: Area Storage Graph

Table 5.5: Input (Daily Stream flow)

Month/Day Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1 29.74 25.02 23.60 25.48 32.49 48.63 242.01 354.45 290.23 151.22 66.02 40.46

2 29.51 24.33 23.27 25.00 31.26 49.59 228.53 349.36 276.70 148.65 64.62 40.04

3 29.36 24.05 23.14 25.09 33.15 55.71 239.71 469.73 278.41 168.18 61.53 39.42

4 28.99 24.25 23.64 24.08 32.92 55.69 230.83 344.67 266.15 173.72 62.94 38.84

5 28.75 24.04 23.65 24.61 34.11 55.01 239.03 353.71 266.06 171.04 63.12 38.57

6 28.48 24.23 23.82 23.97 34.01 61.43 240.45 332.13 275.48 153.64 57.97 37.68

7 28.33 23.74 23.74 23.86 34.01 59.98 253.02 335.08 251.19 144.33 56.41 37.32

8 29.07 24.20 23.36 24.23 33.06 57.87 251.37 336.09 254.49 140.02 56.20 37.18

9 28.44 23.89 23.49 25.43 36.11 79.97 252.45 306.33 250.73 137.18 54.54 36.77

10 27.91 23.78 23.27 25.44 36.90 75.18 270.84 327.93 255.33 132.28 52.69 37.28

11 27.44 24.08 23.08 25.72 35.55 72.85 285.14 350.20 248.72 130.82 53.85 36.25

12 27.24 23.54 24.70 25.83 36.00 82.58 274.15 354.08 251.56 125.12 53.44 36.06

13 27.06 23.52 24.88 26.29 35.89 97.10 260.62 338.63 248.38 143.43 52.39 35.77

14 26.94 23.63 23.79 27.55 38.12 94.37 295.79 331.14 312.37 118.70 51.64 35.75

15 27.80 24.05 23.65 26.89 42.91 99.99 288.25 304.23 225.28 109.87 50.85 34.48

16 27.45 23.60 23.62 27.39 48.99 104.59 296.06 300.60 216.40 105.08 50.38 34.04

17 27.16 23.54 23.86 27.92 46.66 120.75 305.69 303.37 217.19 98.42 49.29 33.48

18 26.72 23.78 23.99 27.44 45.44 141.52 323.13 341.21 205.19 97.42 48.97 32.96

19 26.27 23.07 24.25 27.66 42.02 131.92 304.02 307.04 208.29 93.86 47.70 32.50

20 26.16 23.24 23.87 28.38 40.89 132.76 303.64 302.26 202.61 91.77 47.20 32.01

21 26.01 23.24 24.29 27.47 43.23 143.05 286.68 316.80 199.25 87.57 46.97 31.59

22 25.87 23.26 24.25 29.89 42.29 136.77 294.92 304.57 187.99 84.94 45.88 31.10

23 25.69 23.24 24.89 31.84 45.48 146.27 304.51 315.09 187.63 82.76 45.23 30.72

24 25.46 23.06 24.42 30.06 44.46 160.01 309.96 304.96 183.99 81.09 44.29 30.88

25 25.40 23.18 23.78 31.58 43.31 165.48 331.63 309.68 181.31 78.36 43.72 30.67

26 25.39 23.17 23.98 29.11 48.87 169.25 309.76 324.81 178.68 76.60 43.51 31.51

46

27 25.47 23.07 24.08 29.50 53.47 174.18 325.26 293.94 172.15 74.36 42.83 30.80

28 25.03 23.07 23.85 30.93 49.95 189.05 324.28 280.15 167.49 72.93 41.98 30.08

29 25.02 24.17 31.50 48.69 214.30 349.24 290.17 175.50 71.94 41.41 29.47

30 24.82 25.20 31.81 48.07 223.36 333.02 273.54 160.84 71.07 39.78 29.16

31 24.53 24.48 46.99 335.69 264.13 67.79 28.27

Avg 27.02 23.67 23.94 27.40 40.82 113.31 286.76 323.23 226.52 112.39 51.24 34.23

Source: NEA, 2001

5.4.5 The power plant parameters

In HEC-ResSim, the power plant module is used in order to define the electric power

generated by the turbines. The total installed capacity of the Upper Seti Plant is 127 MW

at the maximum discharge of 127.4 cumecs. The tail water elevation is set at 289.00 m.

The efficiency of the power plant is taken as 90%.The simulation performed in this study

is set to a daily time interval

5.4.6 Definition of Operational parameters

In HEC-ResSim, the dam operation is defined by three typical operation modes, also

called “zones”, which are respectively called: Flood control, Conservation and Inactive.

These “zones” of operation are based on specific reservoir elevations and contain a set of

rules that describe the goals and constraints that should be followed when the reservoir's pool

elevation is within a particular zone.

Operation zones are provided for each month. For each mode of operation (zone), the rules

are ordered by priority. The HEC- ResSim ad-Hoc algorithm attempts to fulfill the

requirements of the highest priority rule, if these are successfully reached, the program

switches to the next rule and will proceed in the same fashion.

5.4.7 The flow requirements for environmental constraints

As my study is primarily aimed at studying the possible benefits of the

Upper Seti project in terms of maximum power production, particular focus has been put

on the flow requirements necessary to meet this goal the environmental obligation as well.

Regarding the state of the environment, it has been assumed that 10 % of original river

flow will be set as minimum downstream release.

5.4.8 Operational Strategy

Identifying the optimum operating strategy is one of the major tasks of water resource

planning. The approach is always based on how to manage or run the reservoir during

47

each time-step. The reservoir must be operated in accordance with a predefined strategy.

The strategy alternatives are:

• Automatic reservoir balancing

• Reservoir release specification

• Reservoir guide curve

One of these strategies must be used for reservoir defined.

Development of Reservoir guide curve is one of the objectives to be provided for the

operation of reservoir. The reservoir guide curve tells us how the reservoir should be

operated most economically.

VI. RESULTS AND DISCUSSION

The study was conducted for the optimum operation of the reservoir of USHEP

using HEC Reservoir Simulation model. Since the only priority of the project is the

power production, simulation was carried out for maximum of power generation.

As an environmental mandatory release minimum of monthly inflow was allocated

as downstream release. For this purpose, two different scenarios were analyzed.

6.1 Scenario 1: When reservoir sediment flushing operation is carried out.

Sedimentation in reservoir is a serious problem wherein the live storage capacity is

decreased effecting the operation of the reservoir. In this case, the sediment

flushing facilities were proposed at the lowest possible elevation, thus the sill level

of the facilities was decided at Elevation 320 .00m as recommended by JICA study

in 2007.

The reservoir water level is lowered less than MOL during the sediment flushing

operation which is carried out during rainy season, so power generation is at

minimum during this operation. It is estimated that suspension of power generation

of the Project in the rainy season does not affect electricity supply in national grid

48

because other ROR type plants can supply sufficient electricity during this period.

The sediment flushing operation is carried out in former half of the rainy season

because flood forecast network is not prepared in Nepal, the sediment flushing

operation may not be completed within the rainy season if the operation is planned

in the period of season in which inflow of river water decreases.

According the daily river discharge record, the average monthly discharge gets to

the maximum in August ,so it is not desirable that the sediment flushing operation

is carried out in August so that river flows through sediment flushing facilities. It is

desirable that the sediment flushing operation is carried out in June so that

secondary electricity generation decreases due to flushing operation as little as

possible.

The results obtained shows that maximum power can be generated during August

and September and gradually decreases as the inflow is decreased with the

reservoir level is maintained at FSL. During January, the power produced increases

as the drawdown begins. Simulated results are shown in Table 5.1.

Table 6.1: Scenario 1 Results

Simulated Jan Feb Mar Apr May JunParameters Inflow (cm) 27.02 23.67 23.94 27.40 40.82 113.31Reservoir Storage(Mcm) 340.70 270.04 204.56 155.36 92.74 16.20Reservoir Elevation(m) 420.85 411.35 401.34 391.53 376.81 335.79Power generated(MW) 62.10 51.97 43.22 38.94 51.62 4.88Total Energy(GWh) 46.20 34.92 32.16 28.04 38.41 3.39Plant Factor 0.49 0.41 0.34 0.31 0.41 0.04Release for Power(m^3) 53.31 48.54 43.65 42.75 65.35 12.69Target Elevation (m) 419.50 408.50 397.50 386.50 375.50 345.00

Table 6.1: Scenario 1 Results (contd...)

Simulated Jul Aug Sep Oct Nov DecParameters Inflow (cm) 286.76 323.23 226.52 112.39 51.24 34.23Reservoir Storage(Mcm) 24.58 209.08 374.59 374.55 374.57 374.42Reservoir Elevation(m) 344.66 399.69 425.00 425.00 425.00 424.98

49

Power generated(MW) 56.81 127.00 127.00 107.48 54.61 36.72Total Energy(GWh) 42.27 94.49 94.49 79.97 39.32 27.32Plant Factor 0.44 1.00 1.00 0.85 0.43 0.30Release for Power(m^3) 111.69 134.30 107.08 90.63 46.04 30.96Target Elevation (m) 346.25 398.75 425.00 425.00 425.00 425.00

The guide curve developed suggested that the following ideal criteria for operational

purpose:

1. The reservoir is operated for 6 hours daily during dry period.

2. The power station is operated 24 hours in wet period.

3. The drawdown in the reservoir, if required, starts on January 1.

4. The reservoir is at MOL on June1, if possible.

5. The reservoir flushing operation starts on June 1 and is expected to

take 20 days to lower the reservoir level to sill level of the sediment flushing gates.

6. The reservoir sediment flushing gates are closed on July 31.

7. Filling of the reservoir starts on August 1, if not earlier.

8. The reservoir is full on September 1, if not earlier.

9. Inflow of the river and plant discharge is equal for the month of October and the

reservoir is full, if possible.

10. Minimum downstream discharge (10%) shall be spilled during

October to June, if possible.

11. If more water is available in the month of July, August and September than utilized by

the optimum plant capacity, it will be spilled.

12. Dry season energy is the available from the month of November to

May.

13. Wet season energy is available energy for the months June to

October.

The reservoir operation curve developed is as shown in figure below.

50

Figure 6.1: Rule curve for scenario 1

51

6.2 Scenario 2: When no sediment flushing operation carried out and inflow is

reduced by 20 %.

In this case, the inflow is reduced by 20 % of the input provided in scenario 1.Other

physical parameters of the reservoir are similar to those of the scenario 1.Daily

Simulation is carried out for every month .Results show that the power production

decreases uniformly as the inflow decreases. The water level drops to MOL (370.00 m)

during the month of June wherein the storage drops to an average of 83.54 MCM. The

power generated is to maximum capacity during July, August and September. (127

MW).Due to increased inflow the water level increases and attains FSL (425.00 m)

during September. The water level is maintained at FSL up to the month of December

before the drawdown starts from the month of January.




Simulated Jul Aug Sep Oct Nov DecParameters Inflow (cm) 229.41 258.58 181.22 89.91 40.99 27.38Reservoir Storage(Mcm) 95.48 303.17 374.57 374.57 374.57 374.57Reservoir Elevation(m) 377.52 415.34 425.00 425.00 425.00 424.98Power generated(MW) 127.00 127.00 127.00 99.31 47.03 30.96Total Energy(GWh) 3048.00 3048.00 2961.20 1228.10 805.80 0.00Plant Factor 1.00 1.00 0.97 0.40 0.26 0.00Release for Power(m^3) 120.01 107.05 103.44 42.48 27.89 0.00Target Elevation (m) 383.75 411.25 425.00 425.00 425.00 425.00

The guide curve developed suggested that the following ideal criteria for operational

52

purpose:

1. The reservoir is operated for 6 hours daily during dry period.

2. The power station is operated 24 hours in wet period.

3. The drawdown in the reservoir, if required, starts on January 1.

4. The reservoir is at MOL on June1, if possible.

5. The reservoir water level is maintained at MOL up to July 1 to make room for

expected flood.

6. Filling of the reservoir starts on August 1, if not earlier.

7. The reservoir is full on September 1, if not earlier.

8. Minimum downstream discharge (1 cumecs) shall be spilled during October to

June, if possible.

9. If more water is available in the month of July, August and September than

utilized by the optimum plant capacity, it will be spilled.

10. Dry season energy is the available from the month of November to May.

11. Wet season energy is available energy for the months June to October.

Summary of the results obtained from scenario 2 are tabulated below.

The reservoir operation curve developed is as shown in fig 5.8:

53

54

Figure 6.2: Rule curve for scenario 2

55

6.3 Scenario 3: When no sediment flushing operation carried out.

In this case, the inflow provided is similar as in scenario 1.Other physical parameters of

the reservoir are similar as well. Daily Simulation is carried out for every month .Results

show that the power production decreases uniformly as the inflow decreases. The water

level drops to MOL (370.00 m) during the month of June wherein the storage drops to an

average of 82.24 MCM. The power generated is to maximum capacity during July,

August and September. (127 MW).Due to increased inflow the water level increases and

attains FSL (425.00 m) during September. The water level is maintained at FSL up to the

month of December before the drawdown starts from the month of January. The guide

curve developed is similar to that of scenario 2.




Simulated Jul Aug Sep Oct Nov DecParameters Inflow (cm) 0.00 0.00 0.00 0.00 0.00 0.00Reservoir Storage(Mcm) 218.36 374.57 374.57 374.57 374.57 0.00Reservoir Elevation(m) 403.40 425.00 425.00 425.00 425.00 425.00Power generated(MW) 127.00 127.00 127.00 60.47 49.82 0.00Total Energy(GWh) 3048.00 3048.00 3048.00 1451.20 1195.70 0.00Plant Factor 1.00 1.00 1.00 0.48 0.39 0.00Release for Power(m^3) 122.88 107.07 106.84 50.96 42.18 0.00Target Elevation (m) 383.75 411.25 425.00 425.00 425.00 425.00

Figures 6.3 to 6.9 shows the comparative graphs of all the scenarios mentioned above.

56

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Months

Infl

ow

(Cu

mec

s)Scenario 1 and 3

Scenario 2

Figures 6.3: Inflow Curve

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

400.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Months

Res

ervo

ir S

tora

ge(

MC

M) Scenario 1

Scenario 2

Scenario 3

Figures 6.4: Reservoir Storage Curve

57

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Months

Infl

ow

an

d R

ele

as

e(C

um

ec

s)

Inflow 1 and 3

Q-Power 1

Inflow 2

Q-Power 2

Q-Power 3

Figures 6.5: Inflow and Release Curve

300.00

320.00

340.00

360.00

380.00

400.00

420.00

440.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Months

Re

se

rvo

ir E

lev

ati

on

(m)

Scenario 1Scenario 2Scenario 3Target 1Target 2 and 3

Figures 6.6: Reservoir Elevation Curve

58

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Months

Po

wer

(M

W)

Scenario 1

Scenario 2

Scenario 3

Figures 6.7: Power Production Curve

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Months

To

tal

En

erg

y(G

Wh

)

Scenario 1

Scenario 2

Scenario 3

Figures 6.8: Annual Energy Generation Curve

59

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00

Months

Pla

nt

Fac

tor

Scenario 1

Scenario 2

Scenario 3

Figures 6.9: Plant Factor Curve

6.4 Validation of results

In order to gain confidence that the HEC-ResSim model developed for the Upper

Seti Hydroelectric Project is acceptable for modeling and simulating the operating

plants, comparison is done with other study results conducted by NEA and

JICA. The models used by NEA and JICA were "Reservoir Simulation

Version 1.0" and EPDC/KCC FLOW 500 MODEL respectively. The

comparision charts are shown below:

Table 6.4: Comparision chart-1 (With Sediment Flushing)

S.NAverage Head

Optimum Plant

Plant Capacity Wet season Dry season

Annual Energy

(m) Capacity(MW) Energy(GWh) Energy(GWh) (GWh)

JICA 116.2 126 0.52 344 230.1 574.1

Current Study 109.5 127 0.505 314.6 246.35 560.95

Table 6.5: Comparision chart-2 (Without Sediment Flushing)

60

S.NAverage Head

Optimum Plant

Plant Capacity Wet season Dry season

Annual Energy

(m) Capacity(MW) Energy(GWh) Energy(GWh) (GWh)

NEA 111.04 122.2 0.555 422.43 171.93 594.36

Current Study 114 127 0607 425.11 253.43 678.54

These validation results show that the HEC-ResSim model developed for the

current study shows good reflection with the results obtained from the NEA and

JICA model simulations and can be used to assess the relative impacts of the

various operating plans on the Reservoir system of Upper Seti Project. It can be

concluded that the HEC Reservoir Simulation model has proved to be flexible

enough to adequately simulate the operating plans for reservoir.

VII. CONCLUSIONS AND RECOMMENDATIONS

61

7.1. Conclusion

The conclusions that can be drawn from this study are as follows:

1. The application of simulation models is one of the most efficient ways of analyzing

water resources systems, which is based on physical relations accompanied by a series

of operational rules attempting to simulate a phenomena as close as possible to reality

and the system behavior under a specified policy. HEC-ResSim is one of the

simulation models that possess of multi reservoir simulators and can simulate water

resources systems. In this research, performance of Upper Seti storage dam and its

water supply was evaluated. Model verification results of Upper Seti reservoir indicate

that, this model is able to simulate the behavior of the system very well.

2. The results obtained from the simulation suggest that it is in close agreement with the

results of the feasibility study prepared by JICA in 2007.The rule curve suggested by

the present study shows the reservoir is filled by September 1.The study suggests that

reservoir be filled maximum in the first day of September instead of December. Water

level should be allowed to go below the FSL before the start of dry season so that

peak demand can be fulfilled.

3. Results obtained from scenario 1 suggest that sediment flushing operation can be

carried out before the start of rainy season. Inflow considered was 45 % probability

of exceedence and this inflow is enough to recover the water level to FSL before the

end of wet season.

4. Results obtained from scenario 2 suggest that production of energy is not affected

even by decreasing the inflow by 20 % .Inflow considered was 70 % probability of

exceedence and this inflow is also enough to recover the water level to FSL before

the end of wet season.

5. Results obtained from scenario 3 suggest that higher plant factor is achieved than

previous scenarios and annual energy generation is increased by 17.32% and 8.68%

than scenario 1 and scenario 2 respectively.

6. Total annual generation of energy with and without sediment flushing facilities is

560.95 GWh and 678. GWh respectively, whereas, 619.63 GWh energy is generated

when sediment flushing facilities are not carried out and inflow decreased by 20% of

previous scenarios. This shows that higher plant factor is obtained if sediment

flushing is not carried out but it would decrease the live storage of the reservoir in

62

future.

7.2. Recommendations

Based on the present study, following recommendations are made for further work:

1. The present study is done with generated daily stream flow data. Simulation is

done for a typical year taking average of the generated data. It is recommended that

simulation to be done for every year i.e from 1964 to present.

2. Due to time and study limitations, the study focused on the power generation only. It

is recommended that other aspects of the simulation like downstream routing,

provision of multiple reservoirs could be taken into account.

3. The present study has performed with simple operation rules. HEC Res Sim is

equipped with advanced operating system which also includes scripted operation

rules. This allows the project to be studied with more elaborate operation rules.

4. It is recommended to perform the simulation taking in consideration of reservoir

sedimentation.

5. Reliability, resiliency and vulnerability indices were not used for system evaluation.

These model verification results indicate would further help in establishing it as a

powerful tool in reservoir simulation.

REFERENCES

63

1. Beard L.R., 1975. Models for optimizing the multipurpose operation of

a reservoir system. Proceedings of Application of Mathematical Models in

Hydrology and Water Resources Systems, Bratislava 1975, pp. 13-21.

2. Djordjevic B., Jovanovic S., Opricovic S., Simonovic S., 1975. Simulation

models of the Velika Morava basin for the design of a

multipurpose reservoir system. Proceedings of Application of

Mathematical Models in Hydrology and Water Resources Systems, Bratislava

1975, pp. 85-94.

3. Feasibility Study, Upper Seti Storage Hydroelectric Project, Hydrology and

Sediment study, Vol II-Appendix B, Nepal Electricity Authority, 2001.

4. Hall W.A. and Dracup J.A.(1970), Water Resources system Engineering, McGraw

Hill Book Co., New York.

5. Hanbali, F. (2004). HEC-ResSim Reservoir Model for Tigris and Euphrates River

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6. Harboe et al. (1970), Optimal policy for reservoir operation, Journal of Hydraulic

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7. Harboe R. (1970),Optimal policy for reservoir operation, Journal of Hydraulic

Division ,ASCE vol. 96 HY 11

8. Hartzell H., 1936. Continuous measurement of water-flow through

turbines and dam gates. Association Internationale d’hydrologie

scientifique, Edimbourg 1936, pp. 397-412.

9. Jacoby, H.D. and Loucks, D.P.(1972), Combined Use of Optimization and

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aux essais des grandes centrales hydroélectriques. Association

Internationale d’hydrologie scientifique, Edimbourg 1936, pp. 357-382.

11. Lien, N.D. (1976), Effect of sample size of stream flow record and output of Water

resources system, M.Engg Thesis (1976), Asian Institute of Technology, Bangkok,

Thailand.

12. Loucks D.P (1976) , Stochastic method for analyzing river basin system, Cornell

64

University, New York

13. Ph.d Thesis, Charalampos Shoulikaris, Mathematical modeling applied to the

sustainable management of water resources projects at a river basin scale The case of

Mesta Nestos, 2008

14. Reddy, W.W.(1962), Conventional methods of analysis in design of water

resources system, Harvard University Press, Cambridge.

15. Siminovic, S.P.(2002), World Water Dynamic: Global Modeling of Water

Resource. Journal of Environmental Management, 66:24,367.

16. Upgrading Feasibility Study on the Upper Seti Storage Hydroelectric Project in

Nepal, JICA, 2007

17. USACE-HEC (2007), HEC-ResSim 3.0 Reservoir System Simulation, User

manual. US Army Corps of Engineers, Hydrologic Engineers Center. Sep07, PP:

426.

18. Yeh W.W-G, (1985), Reservoir Management and Operation Model: A State of the

Art Review, Water Resource Research, 1797-1817.

19. Performance evaluation of Jhiroft storage dam operation simulation using HEC-res

sim 2.0,Hossein Babazadeh,Hossein Sedghi,Feriydon Kaveh and Habib Mousavi

Jahromi,P.hd candidate,Islamic Azad University,2007.

20. Hari Shankar Shrestha, 2009, Assessment of energy production from major hydro

power projects in Nepal.

65

Annex A: Monthly Operation curves

A1: Operation for January

66

A2: Operation for February

Fig A3: Operation for March

A4: Operation for April

67

A5: Operation for May

A6: Operation for June

Fig A7: Operation for July

68

Fig A8: Operation for August

Fig A9: Operation for September

Fig A10: Operation for October

69

Fig A11: Operation for November

Fig A12: Operation for December

70

Annex B: Monthly Power Production curves

71

B1: Power for January

B2: Power for February

B3: Power for March

72

B4: Power for April

B5: Power for May

B6: Power for June

73

B7: Power for July

B8: Power for August

B9: Power for September

74

B10: Power for October

B11: Power for November

B12: Power for December

75

Annex C: Tables

76

C1 - Table:Probability of Exceedance of flow at Dam Site

SN ExceedenceDischarge Equalled or Exceeded(Cumecs)

Janaury Feb March April May June July Aug Sep Oct Nov Dec

1 0% 39.85 36.60 36.11 40.78 68.91 255.88 445.10 460.52 319.36 326.56 85.89 53.81

2 5% 37.09 33.68 33.54 39.22 63.95 188.31 425.60 448.37 313.19 175.77 75.75 48.96

3 10% 35.44 32.78 31.74 36.78 59.12 169.23 390.80 429.28 292.85 144.43 68.69 44.32

4 15% 33.72 30.70 30.14 34.07 54.47 152.67 380.67 410.96 273.87 137.29 60.31 41.07

5 20% 33.02 29.58 29.80 32.62 51.25 150.99 343.35 389.00 264.03 129.86 57.50 39.24

6 25% 31.90 28.33 29.72 31.19 48.70 147.29 334.08 374.10 252.78 125.15 56.09 39.00

7 30% 30.64 27.63 27.87 30.34 46.58 129.74 320.26 365.49 250.88 119.80 55.87 37.73

8 35% 29.90 26.33 27.17 29.80 40.75 114.94 309.58 347.78 247.12 113.54 54.62 36.32

9 40% 28.12 24.00 26.47 29.13 40.07 111.73 291.21 328.44 242.69 111.56 54.23 35.63

10 45% 27.35 23.17 25.46 28.86 39.05 107.04 288.18 320.68 238.99 107.83 53.24 34.18

11 50% 25.49 21.90 24.70 28.61 38.46 102.18 280.50 320.09 219.37 106.64 51.86 33.80

12 55% 25.06 21.16 21.59 26.38 37.43 96.65 270.09 313.90 215.54 105.17 50.01 33.43

13 60% 24.71 20.61 21.10 25.27 36.80 92.91 264.43 300.57 212.78 102.64 49.27 33.31

14 65% 24.32 20.44 20.78 24.87 35.66 91.84 258.44 287.91 203.97 96.29 45.59 31.92

15 70% 23.62 20.38 19.70 24.33 34.94 88.07 247.84 279.18 199.78 87.81 44.12 30.98

16 75% 23.08 19.94 18.83 23.46 34.42 83.81 230.90 267.82 193.15 85.04 43.59 30.47

17 80% 22.32 18.66 18.00 22.82 31.00 77.94 228.35 259.65 185.77 79.47 43.27 27.33

18 85% 20.78 17.82 16.76 20.34 28.84 73.35 220.57 243.71 177.83 69.85 40.72 26.13

19 90% 20.09 17.41 15.93 19.00 26.02 70.70 198.38 235.62 166.98 65.14 37.11 25.77

20 95% 18.32 14.78 14.99 14.90 23.50 62.04 171.68 209.30 152.36 62.39 32.06 21.68

21 100% 10.52 9.93 11.28 11.93 16.63 34.36 127.99 193.91 141.59 37.74 17.67 12.93

0

50

100

150

200

250

300

350

400

450

500

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Probability of Exceedance (%)

Dis

char

ge

(m3/

s)

Jan

Feb

Mar

Apr

May

Jun

July

Aug

Sep

Oct

Nov

Dec

77

C - 2: Mean monthly flows at the dam site

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1964 31.80 30.40 30.10 31.90 68.90 78.00 134.30 460.50 313.10 112.40 82.00 53.80

1965 34.00 29.50 29.70 32.70 36.30 151.00 293.50 368.50 190.30 62.60 46.90 31.30

1966 24.60 22.20 21.00 19.40 22.20 63.50 228.40 259.60 159.80 66.00 48.60 25.50

1967 20.60 20.70 20.10 22.80 24.50 57.80 231.30 213.20 185.80 77.20 43.50 33.80

1968 24.90 20.50 24.70 25.30 34.90 141.90 336.10 287.00 222.70 326.60 42.10 23.70

1969 18.30 14.60 15.20 15.00 16.60 34.40 128.00 315.00 264.00 79.50 40.30 26.10

1970 20.20 17.30 16.30 24.60 35.30 91.20 380.80 412.00 202.10 106.10 56.80 33.40

1971 23.70 18.70 18.80 29.10 39.60 187.70 291.20 300.60 212.80 145.70 67.70 40.00

1972 25.70 20.30 19.40 20.50 52.90 106.60 325.60 362.50 251.60 108.60 51.40 33.40

1973 25.10 17.60 18.00 25.80 39.20 176.30 244.00 389.00 265.30 259.40 74.40 39.20

1974 36.80 33.70 32.60 40.80 39.00 91.70 343.30 411.60 254.40 131.70 43.80 34.10

1975 33.00 32.10 30.20 22.80 24.00 84.90 427.00 328.40 305.50 139.20 54.10 30.40

1976 22.30 23.10 19.80 24.90 40.90 190.20 380.30 342.30 216.00 88.40 43.60 33.80

1977 22.70 20.40 20.70 30.20 46.80 92.40 288.50 409.00 428.30 111.80 74.80 43.30

1978 32.30 29.60 27.20 29.40 68.70 162.10 381.00 349.60 215.60 106.00 64.30 47.70

1979 37.70 33.70 29.80 37.70 51.90 84.70 315.00 447.00 239.40 107.20 57.50 34.60

1980 25.20 22.90 25.30 26.60 37.10 107.90 425.10 446.50 313.70 82.50 43.80 26.20

1981 18.20 14.90 15.60 28.70 40.10 95.50 400.60 376.50 242.70 97.00 50.20 36.90

1982 33.30 30.80 36.10 40.10 48.90 96.90 257.70 271.30 155.50 85.90 54.50 45.30

1983 39.80 36.60 35.30 34.50 46.70 72.80 210.40 270.50 276.70 143.20 54.70 35.60

1984 28.00 21.20 21.70 24.00 62.80 151.90 445.10 287.30 243.50 96.10 58.60 41.30

1985 36.90 33.50 33.00 39.10 61.10 114.90 333.40 197.50 202.90 126.20 56.50 36.00

1986 24.70 19.80 21.40 28.50 27.90 117.60 260.70 259.80 280.20 147.90 59.20 30.70

1987 23.50 20.40 21.40 23.60 31.20 72.20 280.00 279.50 183.60 87.30 54.20 39.20

1988 30.20 26.80 27.00 28.80 40.70 111.70 264.40 320.50 238.90 102.60 52.90 38.60

1989 33.90 27.80 27.80 30.50 59.40 146.60 251.70 310.70 240.20 113.90 53.80 36.40

1990 28.10 24.80 26.00 35.90 55.20 152.90 271.90 237.30 194.10 102.80 44.50 27.30

1991 20.00 17.60 16.80 20.30 33.40 114.90 281.00 320.40 250.20 117.20 56.30 39.00

1992 31.10 27.90 26.50 25.20 35.70 82.00 188.90 289.80 197.40 124.80 50.30 30.50

1993 23.20 20.60 14.50 14.70 30.00 97.80 218.40 321.30 215.40 122.40 56.80 33.30

1994 29.30 27.50 29.80 30.10 37.00 106.80 184.20 233.90 142.80 37.70 17.70 12.90

1995 10.50 9.90 11.30 11.90 28.30 255.90 314.90 193.90 175.90 129.90 85.90 52.70

1996 30.10 21.60 30.90 31.00 37.60 69.20 227.00 319.80 252.20 107.60 45.80 31.50

1997 27.20 24.00 28.40 32.60 38.40 74.90 229.60 258.90 141.60 61.80 35.00 33.10

1998 24.20 21.50 24.90 29.10 48.70 149.30 288.10 452.60 207.30 64.20 35.60 26.00

1999 21.30 17.90 17.00 18.80 34.80 93.10 264.80 238.70 174.20 67.40 23.10 15.30

max 39.80 36.60 36.10 40.80 68.90 255.90 445.10 460.50 428.30 326.60 85.90 53.80

mean 27.01 23.68 24.01 27.41 41.02 113.31 286.84 320.63 229.33 112.41 52.26 34.22

min 10.50 9.90 11.30 11.90 16.60 34.40 128.00 193.90 141.60 37.70 17.70 12.90

972.40 852.40 864.30 986.90 1476.70 4079.20 10326.20 11542.50 8255.70 4046.80 1881.20 1231.90

78

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Mean Montly Flow

Flo

w (

m3

/s)

C – 3: Probability of Exceedance of flow at Dam SiteSN Exceedence Discharge Equalled or

79

Exceeded (cumecs)1 0% 460.502 5% 338.893 10% 288.024 15% 254.935 20% 215.566 25% 165.137 30% 120.968 35% 96.229 40% 72.56

10 45% 56.5211 50% 46.7512 55% 39.2013 60% 35.7814 65% 33.3915 70% 30.5016 75% 28.4817 80% 25.7218 85% 23.6719 90% 20.7020 95% 17.9621 100% 9.90

0

50

100

150

200

250

300

350

400

450

500

0% 20% 40% 60% 80% 100%Probability of Exceedance (%)

Dis

char

ge

(m3/

s)

C – 4: Probability of Exceedance of flow at Dam Site

SN ExceedenceDischarge Equalled or

Exceeded (cumecs)

80

1 0% 460.502 1% 439.893 2% 411.754 3% 381.565 4% 367.066 5% 338.897 6% 325.748 7% 318.989 8% 313.41

9.1 9% 294.9910 10% 288.0211 11% 280.1212 12% 271.4713 13% 264.3914 14% 259.5315 15% 254.9316 16% 250.2617 17% 239.9818 18% 235.3319 19% 227.1520 20% 215.5621 21% 208.8222 22% 197.4223 23% 190.0324 24% 183.9425 25% 165.1326 26% 151.8527 27% 146.2728 28% 141.7029 29% 129.9230 30% 120.9631 31% 114.2932 32% 108.8533 33% 106.7534 34% 102.6935 35% 96.2236 36% 91.6237 37% 85.9038 38% 82.1139 39% 76.9940 40% 72.5641 41% 67.9942 42% 64.1943 43% 61.5744 44% 58.0945 45% 56.5246 46% 54.4247 47% 53.2948 48% 51.4649 49% 48.6850 50% 46.75

81

51 51% 43.9352 52% 43.1653 53% 40.7654 54% 40.0355 55% 39.2056 56% 38.8657 57% 37.7058 58% 36.9059 59% 36.3760 60% 35.7861 61% 35.3062 62% 34.5863 63% 33.9564 64% 33.7065 65% 33.3966 66% 33.0067 67% 32.3768 68% 31.4869 69% 30.9670 70% 30.5071 71% 30.2072 72% 30.0773 73% 29.6474 74% 29.1175 75% 28.4876 76% 27.9477 77% 27.5478 78% 26.9679 79% 26.1580 80% 25.7281 81% 25.2082 82% 24.9083 83% 24.6384 84% 24.0085 85% 23.6786 86% 23.1087 87% 22.7088 88% 21.6789 89% 21.3490 90% 20.7091 91% 20.4892 92% 20.2593 93% 19.8094 94% 18.7995 95% 17.9696 96% 17.3797 97% 16.2598 98% 14.9699 99% 13.40

100 100% 9.90

82

Flow Duration Curve

0

50

100

150

200

250

300

350

400

450

500

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Probability of Exceedence (%)

Dis

char

ge

(m3/

s)

83

Final Report

Documents

higher plant

weighted average

load shedding

velika morava

identified

probable maximum

average annual

minimum operating