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P. Khatri, S.S Khadka, U.Bhattarai & R. Prajapati: Standardization and Development of Civil Design Framework for Small…
Rentech Symposium Compendium, Volume 4, September 2014 66
Standardization and Development of Civil Design
Framework for Small Hydropower Project in Nepal Pawan Khatri*, Shyam Sundar Khadka, Utsav Bhattarai and Rashmila Prajapati
Department of Civil and Geomatics Engineering,SoE, KU and Cross Momentum Engineers Pvt. Ltd.,
Abstract - The presence of perennial rivers originating from the
Himalayas and a steep topography providesan ideal condition for the
generation of hydroelectricity in Nepal. However, due to many socio-
political, technical and financial reasons, hydropower development in
Nepal has been very slow. Design of civil structures is the most
important phase of hydropower development as they are expensive and
the entire project depends their proper functioning throughout the
project life.
In Nepal, there are many guidelines and standards for the design
of civil works of micro/mini/small hydro power projects. These
guidelines are prepared by different organizations and the design
methods, parameters and procedures explained in them vary; as a result
conflicts arise between designers. Hence, a research was carried out
with the main objective of developing a framework for the design
procedures of civil works of mini/micro/small hydropower projects and
standardization of the design procedure. This paper is part of the major
outcome of that research.
All national and international guidelines/codes of
practice/manuals/detail design reports used in Nepal have been
reviewed and analyzed extensively. Based on these documents, the
design framework has been developed and the procedures
standardized. The proposed design procedures have been validated and
verified by case studies.
Index Terms-Small hydropower project, civil work components,
design framework, standardization
I. INTRODUCTION
The first hydropower plant (HPP) constructed and
operated in Nepal was at Pharping with an installed capacity of
500KW in 1911, 29 years after the establishment of the world's
first hydel station in Wisconsin, USA and one year before the
Chinese [2]. Nepal has a technical hydropower potential of
40,000MW [15]. With such early start in hydropower
development, now more than a century later, Nepal has a total
installed capacity of 708MW while the demand reported in
2012 was 1094MW [2]. Despite having a century long history
of electricity generation, half of the Nepalese population is
deprived of electricity and the other half is facing long hours of
power cuts.
Depending upon the installed capacity, HPPs are classified
into pico, micro, mini, small, large and mega projects. The large
to mega scale HPPs are mainly storage type and grid connected
which supply energy to a large population of consumers. The
micro and small HPPs are mainly run-off-river type (grid
connected or isolated) and supply electricity to meet the local
energy demands. The micro, mini and small HPPs have proven
to be very effective and worthy because of their simple design,
* Corresponding author: [email protected]
low cost and short construction period. These could be the
reasons that in fiscal year 2012/13 nine HPPs were
commissioned in Nepal and all of them had installed capacities
below 10 MW [2].
Hydropower projects that have an installed capacity less
than 10MW are called small HPPs. A small HPP contains basic
components: intake structure, diversion weir, diversion canal or
pipe, gravel trap, settling basin, forebay, tunnel, penstock,
powerhouse and tailrace. In general, intake structures are built
to divert the required design discharge while diversion work
ensures it by maintaining the full supply level of water upstream
of intake. Canals, pipes and tunnels are water conveyance
structures diverting the water from intake to
forebay/powerhouse. Gravel trap and settling basin settles and
removes sediment and flushesit back to the river. Forebay
ensures the submergence and retention of water for the pressure
flow at penstock. At the powerhouse, electricity is generated by
interaction of turbine and generator before flowing into the river
downstream through the tailrace.
Figure 1: General civil works components of small hydropower
project.
Proper design of each hydropower component is very important
at all stages of its life starting from its construction to operation
and maintenance. The most important design parameter of civil
components of any HPP is design discharge. Other parameters
that play vital roles in design process are velocity, sediment
properties, slope and temperature, among others. In Nepal, there
are a number of design guidelines and codes in use, however,
lack of consistency among them is largely felt. Therefore, this
research was carried out with an objective of developing a very
clear and pragmatic design framework for civil works in HPPs.
The standardization of the civil components is done as the
P. Khatri, S.S Khadka, U.Bhattarai & R. Prajapati: Standardization and Development of Civil Design Framework for Small…
Rentech Symposium Compendium, Volume 4, September 2014 67
function of the different design typical ready to use design
charts.
Figure 2: Standardization of civil work components of small
hydro power project.
II. METHODS
Although the bigger scope of this research had two parts
– the first one for micro and mini HPP (upto 1 MW) and the
second for small HPP (from 1 to 10 MW), this paper is
intended only for small HPPs. The methodology includes
literature review, case studies, field verification and analysis
of primary and secondary data.
A. Literature review and documentation
Available national and international level guidelines,
design aids, manuals, codes of practice, published design
reports, academic theses, and journal articles in use in Nepal
were compiled. They were thoroughly analyzed and the
design procedures were checked using different principles of
hydraulics. Any gaps and flaws prevalent in them were also
noted. These documents formed the foundation for
development of design framework based upon which the
design procedures were standardized.
B. Field visit, data collection and analysis
The existing design procedures and their implications in
theHPPs were assessed by a series of field visits from which
primary and secondary data were collected and analyzed. The
field visits were made to already constructedHPP sites below
10MW. The main aim of the field visitswas to check whether
the current design procedures and construction methodswere
successful in producing the hydro energy with high efficiency.
In order to achieve that, hydrological analysis, field study of
hydraulic structures and questionnaire survey were conducted.
The data collected for the civil structures were analyzed and
compared with the design requirements.
C. Problem identification and analysis
One of the objectives of this research was to compile all
available information in Nepal on design of civil structures for
HPPs and develop a database including all these information.
Analysis of the documents for civil works in hydropower
development in Nepal led to the identification of the existing
gaps in design procedures. These gaps were then addressed
using advanced methods and modifications were suggested on
the existing methods. Finally a comprehensive design
framework was developed choosing the most suitable and
applicable design procedures. Regular consultation with
experts was a very important activity during the research.
III. RESULTS AND DISCUSSION
Standardization of the HPP civil components was done
on the basis of the design framework.
A. Design framework
The design framework developed as a major outcome of
this research includes all the steps for the design of the HPPs
civil structures. The civil structures focused are of run-off-
river type small HPPs. The developed design framework has
clearly explained the design requirements, data required,
design parameters, design principles and equations. Five
sample flowcharts from the design framework for the design
of headworks, canal, gravel trap, settling basin and forebay
have been respectively presented in Figures 3 to 6.
Design
discharge
Continuity equation
Design
velocity
Flow area
Design coarse
trashrack
Calculation of
headloss at intake
and trashrack
Determination of
weir height
(if required)
Analysis of
discharge through
orifice:
-at normal flow
-at flood flow
Design of intake
canal
Figure 3: Flow chart for the design of headwork
P. Khatri, S.S Khadka, U.Bhattarai & R. Prajapati: Standardization and Development of Civil Design Framework for Small…
Rentech Symposium Compendium, Volume 4, September 2014 68
Figure 4: Flow chart for the design of canal
Figure 5: Flow chart for the design of gravel trap/settling
basin
Design
discharge
Fix design
parameter
-Retention time, T
-Penstock Diameter
-Sill height
-Freeboard
Calculate
-Volume
required
Calculate
Submergence
required
Calculate:
-Surface area
Calculate depth
required
Check for
submergence
Dimension:
-Trial Width
-Calculate Length
Design
-spillway
-Fine trashrack
Figure 6: Flow chart for the design of forebay
Note: In case of gravel trap, generally the sediment storage criteria
is not considered since it is generally continuous flushing type.
Hence “Design of sediment storage step is generally excluded in
figure 5 for gravel trap.
B. Standardization chart
Standardization of the civil design procedures for HPPs
has been done by developing standard charts considering
different combination of the discharge and design parameters.
For small HPPs, the discharge variation is done upto 5 m3/s. It
is assumed that this limit of the discharge shall cover all types
of run-off-river type small HPPs in Nepal. These charts are
believed to be extremely helpful as a ready reference material
that directly provides the dimensions of the civil structures.
The basic principles, equations and constants used in
generating these charts have been selected as per the
developed design framework. Some typical sample charts
with their brief description are presented below.
Side Intake: Side intake is standardized as the function of
discharge and different combinations of design velocity,
number of orifice and width to depth ratio of orifice. The
design velocity is taken so as to minimize the headloss at
intake. The design velocity is varied from 0.8m/s to 1.5 m/s
while the width to depth ratio is kept constant 2 so as to obtain
P. Khatri, S.S Khadka, U.Bhattarai & R. Prajapati
Rentech Symposium Compendium, Volume 4, September 2014
maximum efficiency. Figure 7 & 8below show some of such
possible combinations.
Figure 7: Standardization chart of side intake with design
from orifice 1m/s, number of orifice is 1 and width to
2.
Figure 8: Standardization chart of side intake with design velocity
from orifice 1.2 m/s, number of orifice is 3 and width to
is 2.
Diversion canal: The diversion canal is standardized as the
function of discharge and different combinations of
longitudinal slope. The longitudinal slope is varied from 1 in
500 to 1in 1500. The ratio of width to depth is fixed at 2 so as
to obtain maximum efficiency (Figures 9 and 10).
Figure 9: Standardization chart on diversion canal with longitudinal
slope of 1/500; lining of cement mortar 1:3 and of rectangular shape
P. Khatri, S.S Khadka, U.Bhattarai & R. Prajapati: Standardization and Development of Civil Design Framework for S
Rentech Symposium Compendium, Volume 4, September 2014
maximum efficiency. Figure 7 & 8below show some of such
Standardization chart of side intake with design velocity
from orifice 1m/s, number of orifice is 1 and width to depth ratio is
Standardization chart of side intake with design velocity
from orifice 1.2 m/s, number of orifice is 3 and width to depth ratio
The diversion canal is standardized as the
function of discharge and different combinations of
longitudinal slope. The longitudinal slope is varied from 1 in
500 to 1in 1500. The ratio of width to depth is fixed at 2 so as
m efficiency (Figures 9 and 10).
Standardization chart on diversion canal with longitudinal
slope of 1/500; lining of cement mortar 1:3 and of rectangular shape
Figure 10: Standardization chart on diversion canal with
longitudinal slope of 1/1000; lining of cement mortar 1:3 and of
rectangular shape
Gravel trap and Settling basin
basin are standardized as the function of the design discharge
and the combination of design particle size, water temperature
and width of the basin. The design particle size for the gravel
traps taken are 1mm, 2mm, 3mm and 4mm while that for
settling basin is 0.1mm, 0.2mm, 0.3mm and 0.4mm. The
water temperature is fixed at 15
fall velocity. The basin width is varies from 1m to 4m for
gravel trap while that for settling basin is from 1m to 12m.
Figures 11, 12, 13 and 14 show some of the standardization
chart for the gravel trap and settli
that Figure 13 is suitable for the settling basin with higher
discharge and Figure 14 for lower value of discharge.
Figure 11: Standardization chart on gravel trap with
size of 2mm, water temperature 15
Standardization and Development of Civil Design Framework for Small…
69
Standardization chart on diversion canal with
longitudinal slope of 1/1000; lining of cement mortar 1:3 and of
rectangular shape
Gravel trap and Settling basin: The gravel trap and settling
basin are standardized as the function of the design discharge
and the combination of design particle size, water temperature
and width of the basin. The design particle size for the gravel
traps taken are 1mm, 2mm, 3mm and 4mm while that for
settling basin is 0.1mm, 0.2mm, 0.3mm and 0.4mm. The
xed at 150C for the calculation of the
fall velocity. The basin width is varies from 1m to 4m for
gravel trap while that for settling basin is from 1m to 12m.
Figures 11, 12, 13 and 14 show some of the standardization
chart for the gravel trap and settling basin. It is to be noted
that Figure 13 is suitable for the settling basin with higher
discharge and Figure 14 for lower value of discharge.
Standardization chart on gravel trap with-design particle
ater temperature 150C and width of 3m.
P. Khatri, S.S Khadka, U.Bhattarai & R. Prajapati
Rentech Symposium Compendium, Volume 4, September 2014
Figure 12: Standardization chart on gravel trap with
size of 3mm, water temperature 150C and width of
Figure 13: Standardization chart on settling basin with
particle size of 0.2mm, water temperature 15
Figure 14: Standardization chart on settling basin with
particle size of 0.2mm, water temperature 15
Forebay: The forebay is also standardized as the
the design discharge and the combinations
time and width of the basin. The retention time
1minutes to 4 minutes while the width of the basin is
from 1m to 12m. Figure 15, 16 and 1
standardization chart for forebay.
P. Khatri, S.S Khadka, U.Bhattarai & R. Prajapati: Standardization and Development of Civil Design Framework for S
Rentech Symposium Compendium, Volume 4, September 2014
gravel trap with-design particle
C and width of 3m.
Standardization chart on settling basin with-design
particle size of 0.2mm, water temperature 150C and width of 15m.
Standardization chart on settling basin with-design
particle size of 0.2mm, water temperature 150C and width of 3m.
: The forebay is also standardized as the function of
n discharge and the combinations of the retention
time and width of the basin. The retention time is varied from
1minutes to 4 minutes while the width of the basin is varied
and 17 show the typical
Figure 15: Standardization chart on forebay given surface area as
output with-retention time 4 minutes.
Figure 16: Standardization chart on forebay given
asoutput with-retention time 4 minutes and basin width fixed to 3m.
Figure 17: Standardization chart on forebay given depth &
output with-retention time 4 minutes and basin width fixed to 12m.
Note: The tunnel, surge tank and penstock design are
specific and inter-related. The design parameters like tunnel length,
penstock length, net-head,
widely from site to site. Hence, the standardization chart has not
developed for these civil structures.
been developed for all these civil structures.
Standardization and Development of Civil Design Framework for Small…
70
Standardization chart on forebay given surface area as
retention time 4 minutes.
Standardization chart on forebay given depth & length
retention time 4 minutes and basin width fixed to 3m.
Standardization chart on forebay given depth & length as
retention time 4 minutes and basin width fixed to 12m.
rge tank and penstock design are very site
related. The design parameters like tunnel length,
mean monthly discharge, etc. varies
widely from site to site. Hence, the standardization chart has not
developed for these civil structures. But the design framework has
been developed for all these civil structures.
P. Khatri, S.S Khadka, U.Bhattarai & R. Prajapati: Standardization and Development of Civil Design Framework for Small…
Rentech Symposium Compendium, Volume 4, September 2014 71
IV. CONCLUSION
In Nepal very few guidelines and design documents are
available for the design of hydropower infrastructure and the
ones available are inconsistent and conflicting at times.
Therefore, the need of effective and complete design
framework and standardization of the design is of immense
importance. This research has been successful in the
development of correct, non-ambiguous, clear and effective
design procedures and their standardization for the civil works
of small HPPs. The developed framework and standardization
documents are believed to be extremely useful to practicing
engineers as well as other relevant stakeholders related to the
hydropower sector of Nepal.
ACKNOWLEDGEMENT
The authors would like to duly acknowledge Prof. Dr.
Ramesh K. Maskey and Mr. Kiran S. Yogacharya for their
valuable expert advice on the research. The authors are also
extremely thankful to Renewable Nepal Program and
NORAD in particular for funding the project. Authors' deep
gratitude goes to Kathmandu University, especially
Department of Civil and Geomatics Engineering and all the
staff of Cross Momentum Engineers Pvt. Ltd. for providing
the platform to conduct this research. The authors would also
like to thank REMREC, District Development Committee
(Dhulikhel), and all other who directly and indirectly
supported this research.
REFERENCE
[1] D. Adhikari, "Hydropower Development in Nepal,"
Economic Review, vol. 18.
[2] Nepal Electriciy Authority, "Annual Report 2012/13,"
NEA, Kathmandu, Nepal, 2013.
[3] Nepal Electricity Authority, "Annual Report 2010/11,"
NEA, Kathmandu, Nepal, 2011.
[4] ITDG, Kathmandu, Civil work guidelines for Micro
Hydropower in Nepal.
[5] JICA, Manual and Guidlines for development of Micro
Hydropower in Developing countries, Phillipines, 2009.
[6] Alternate Hydro Energy Center, Civil Works guidlines
for Hydraulic Design of SHP project, India, 2008.
[7] DOED, "Design guidelines for Water Conveyance
System of Hydropower project," Kathmandu, 2006.
[8] P. Novak, Hydraulic Structures.
[9] E. Mosonyi, Water Power Development, Volume A & B.
[10] E. Mosonyi, Low Head Hydro power, Volume-1.
[11] DOED, "Design Guidelines for Headworks of
Hydropower Project," Kathmandu, 2006.
[12] DOED, "Design guidelines for Water Conveyance
System of Hydropower Project," Kathmandu, 2006.
[13] A. Harvey, Micro Hydro Design Manaul, 1993.
[14] A. R. Inversin, Micro Hydro Power Source Book, A
Practical Guide to Design and Implementation in
Developing Countries.
[15] IPPAN, Independent Power Producer Associations'
Nepal, [Online]. Available:
http://www.ippan.org.np/HPinNepal.html.
[16] M. Andaroodi, "Standardization of civil engineering
works of small high-head hydro-power and development
of an optimization tool," LCH, Lausanne, 2006.
BIOGRAPHIES
Shyam Sundar Khadkahas obtained his
Master’s degree in Structural engineering from
Pulchowk Campus, Tribhuvan University. He is a
Ph.D. candidate and Assistant Professor at
Department of Civil and Geomatics Engineering
at Kathmandu University. He was the project
leader for the Renewable Nepal fundedproject.
Utsav Bhattarai obtained his Master's degree in
Water Resources Engineering from Pulchowk
Campus, Tribhuvan University. He is the
Executive Chairman of Cross Momentum
Engineers Pvt. Ltd. He was the activity leader for
this project.
Pawan Khatri obtained his Bachelo’sr degree in
Civil Engineering (with specialization in
hydropower) from School of Engineering,
Kathmandu University. Currently, he is working
as the research assistant at Kathmandu University
for Renewable Nepal funded project.
Rashmila Prajapatiobtained her Bachelor’s
degree in Civil Engineering from Khowpa
Engineering College, Tribhuvan University.
Currently, she is working as the research assistant
at Cross MomentumEngineers Pvt. Ltd for
Renewable Nepal funded project.