The document discusses methods for selecting locations for hydropower projects, focusing on the importance of water availability and various techniques for measuring water debit, including gauged and ungauged stream flows. It details different flow measurement methods, such as conductivity meters, current meters, and float methods, along with concerning factors affecting hydrological data collection essential for hydropower planning. Additionally, the document covers rainfall measurement techniques and the significance of watersheds in managing water resources.

1. Location Selection for Hydropower

2. Contents
Hydropower Location Selection
Section.1
• Scientific Methods
• Method of measuring water debit.
• Rain Probability Method.
Section.2
• Watersheds.
Section.3
• Mainstay Debit.
2

3. Scientific Methods
• Scientific method is the step taken to
obtain scientific results by carrying
out basic steps i.e. Hypothesis,
Qualitative or Quantitative Analysis,
Prediction and Verification. The
scientific methods for measuring
water debit are as follows:
3

4. Water Debit
• Available flow is of utmost importance for site selection.
• The study of any potential hydroelectric scheme must first
of all address the availability of an adequate water supply.
• The amount of water and its annual distribution affects
hydropower project viability.
• The hydropower project energy output depends on annual
flow distribution, hence hydropower project without a
reservoir can produce energy only from available water
and cannot compensate during dry periods.
• Hydropower project with a reservoir can compensate
during dry periods by using water stored during wet
periods and is able to produce energy during peak
demand.
• When selecting a site and estimating energy generation, it
is crucial to consider hydrological flow and other factors
that may reduce flow available for energy generation,
including minimum flow leakage, and evaporation.
(Malovic, Engelmann Pilger et al. 2015)
4

5. Water Debit
• Therefore to estimate the water potential one
needs to know the variation of the discharge
throughout the year.
• In the best circumstances the hydrologic
authorities would have installed a gauging
station, in the stretch of stream under
consideration, and streamflow time series
data would have been gathered regularly over
several years.
• For an ungauged watercourse, where
observations of discharge over a long period
are not available involves the science of
hydrology and will suffice to make use of one
of the several approaches, explained later, to
estimate the long term average annual flow
and the flow duration Curve.(Penche 1998)
5

6. Measuring Water Debit for Gauged Stations
• Hydrological or Hydrometeorological Services or related
agencies have been established in countries for
systematic water resources data collection, archiving
and dissemination.
• Their primary role is to provide information to decision
makers on the status of water resources and trends in
water resources.
• Conventional water resources information comprises
the statistics of a variety of meteorological and
hydrological elements. The elements include the
following:(WMO 2008)
• Precipitation
• River levels and flows
• Lake and reservoir levels
• Groundwater levels
• Evapotranspiration
• Sediment concentrations and loads in rivers
• Water quality of surface water and groundwater 6

7. Measuring Water Debit for Un-Gauged Stations
7
• Often small streams suitable for micro hydropower
projects are not gauged.
• Therefore, river flow data are not usually available.
• So, direct spot measurement of the river flows
become essential to estimate what the low flows are
and how the river flows vary throughout the year.
• In the absence of flow records, a minimum of one flow
measurement per month for at least one year should
be performed close to the proposed intake area so
that the installed capacity can be finalized and the
energy generation can be reliably estimated.
• Various flow measurement methods pertinent to
micro hydropower projects are described herein.
(Pandey and Karki 2016)

8. Conductivity Meter
• A conductivity meter measures the amount of electrical current or
conductance in a solution.
• The meter is equipped with a probe, usually handheld, for field or
on-site measurements.
• After the probe is placed in the liquid to be measured, the meter
applies voltage between two electrodes inside the probe.
• Electrical resistance from the solution causes a drop in voltage,
which is read by the meter. The meter converts this reading to milli
or micro-Siemens (mS or μS) per centimeter.
• This value indicates the total dissolved solids.
• Flow measurement using conductivity meter is also known as the
salt dilution method.
• This method involves pouring a salt solution some distance
upstream and measuring the change in conductivity as the salt
wave approaches the gauging location (where the probe is placed).
• The salt solution changes the conductivity of the river (as the salt
wave travels downstream), and this change in conductivity can be
related to the river flow if baseline conductivity of the river, the
type and amount of salt added, and the water temperature are
known. (Pandey and Karki 2016) 8

9. Conductivity Meter
• As the salt wave passes the measurement location, the conductivity of the river
returns to its original level (i.e., baseline conductivity).
• Conductivity meters can be used in small, highly turbulent streams with rough,
irregular channels and for flow measurements of a river.
• Table salt (sodium chloride, NaCl) is the most commonly used salt because it is
inexpensive and widely available.
• Stream flow is determined by using the following formula
• Q = M · k/A
• Area can be calculated from the following formula:
• A = (ΣC(t) − N · C0) · T
• where ΣC(t) = sum of conductivity values (μS), N = number of observations, C0 =
base conductivity (μS), and T = time interval (seconds).
• Salt constant K is found by using following equation:
• K = k/(1 + αΔT)
• where K = salt constant at temperature T, k = salt constant at temperature t, α =
temperature compensation slope for salt and ΔT = Temperature Change
• The advantages of this method are that it is simple and fairly accurate.
• It is also reliable for a wide range of flows and measurements can generally be
taken within 30 minutes. This method can be used in fast-flowing rivers ranging
from 25 l/s to about 2.5 m3/s.(Pandey and Karki 2016) 9

10. Current Meter
• A current meter is the most commonly used instrument to
measure the velocity at a point in the flow cross-section.
• A current meter is a mechanical device with revolving cups or a
propeller attached to a shaft.
• These cups or propellers revolve when the instrument is
immersed in flowing water because of flow velocity.
• The revolving frequency is dependent on flow velocity i.e. the
higher the flow velocity, the faster the revolution.
• With the correlation between the revolutions of the cups or
propeller, the flow velocity can be determined.
• During flow measurement using a current meter, the river
section is divided into a number of strips (trapezoidal and
triangular), and velocity corresponding to each strip is
determined by using a current meter.
• Area of the segment can be found by multiplying segment width
w, and segment depth d. (Pandey and Karki 2016)
10

11. Current Meter
• Then the flow through the hatched
segment is:
Q = w * d * v
• Thus, calculating the flow of each
segment and adding all flows will
result in total river. flow at the time of
measurement.
• At least three sets of measurements
should be taken during flow
measurement to avoid error.
• The current meter is a suitable
method of flow measurement for
rivers with relatively higher flows.
• The current meter is most suitable
for flow measurement in the
velocity range between 0.2 m/s and
5 m/s where the accuracy can be as
high as 98%. (Pandey and Karki
2016) 11

12. Float Method
• Float measurement is a simple method to measure
flows in small rivers.
• In this method, any object that floats in water is
released at the surface of the river, and its velocity is
estimated by recording the time required for it to
travel a certain distance.
• Thus, the surface flow velocity can be obtained by
dividing the length of the river stretch that the
floating object has traveled by the time taken.
• This value should be multiplied by following the
correction factor to obtain the mean flow velocity of
the river at the measurement location.
• And the discharge can be calculated by using the
following equation:
• Q = A*k*V
• where Q = discharge of the river in m3/s, A = cross-
section area of the stretch (m2; computation of
cross-section was discussed earlier), V = float
velocity or velocity of the floating object (m/s), and
k = coefficient to correct the surface velocity .
(Pandey and Karki 2016)
12

13. Representation of Discharge Data
• So, the table of stream
discharges over a period of
years at a particular site ,
which to be of any use has
to be organised into a
usable form.
• This can be done mainly by
using two following
methods:(Penche 1998)
• Hydrograph
• Flow Duration Curve
13

14. Precipitation
• The precipitation is mainly in the form of
rainfall.
• Though there is appreciable snowfall at
high altitudes in the mountain range and
most of the water comes through the
snow-melt in summer.
• The total rainfall received in a given period
at a location is highly variable from one
year to another. The variability depends on
the type of climate and the length of the
considered period.
• Because of the strong variability of rainfall
in time, the design and management of
irrigation water supply and flood control
systems are not based on the long-term
average of rainfall records.(Raghunath
2006)
14

15. Measurement of Precipitation
• Rainfall may be measured by a network of rain gauges
which may either be of non-recording or recording type.
• The non-recording rain gauge mostly used is the
Symon’s rain gauge .
• It consists of a funnel with a circular rim and a glass
bottle as a receiver.
• The cylindrical metal casing is fixed vertically to the
masonry foundation with the level rim.
• The rain falling into the funnel is collected in the
receiver and is measured in a special measuring glass
graduated in mm of rainfall.
• The rainfall is measured once in a day while during
heavy rains, it must be measured three or four times in
the day.
• The non-recording or the Symon’s rain gauge gives only
the total depth of rainfall for the previous 24 hours (i.e.,
daily rainfall) and does not give the intensity and
duration of rainfall during different time intervals of the
day. (Raghunath 2006)
15

16. Self/Automatic Recording Rain Gauge
• This type of rain gauge has an automatic mechanical arrangement
consisting of a clockwork, a drum with a graph paper fixed around it
and a pencil point, which draws the mass curve of rainfall.
• From this mass curve, the depth of rainfall in a given time, the rate or
intensity of rainfall at any instant can be determined.
• The self-recording rain gauge is generally used in conjunction with an
ordinary rain gauge exposed close by, for use as standard, by means
of which the readings of the recording rain gauge can be checked
and if necessary adjusted. (Raghunath 2006)
• There are three types of recording rain gauges as described
below:
• Tipping bucket gauge
• Weighing gauge
• Float gauge
16

17. Tipping Bucket Rain Gauge
• This consists of a cylindrical receiver
with a funnel inside.
• Just below the funnel a pair of tipping
buckets is pivoted such that when one
of the bucket receives a rainfall of 0.25
mm it tips and empties into a tank
below, while the other bucket takes its
position and the process is repeated.
• The tipping of the bucket actuates on
electric circuit which causes a pen to
move on a chart wrapped round a
drum which revolves by a clock
mechanism.
• This type cannot record snow.
(Raghunath 2006)
17

18. Weighing Rain Gauge
• In this type of rain-gauge, when
a certain weight of rainfall is
collected in a tank, which rests
on a spring lever balance, it
makes a pen to move on a chart
wrapped round a clock driven
drum.
• The rotation of the drum sets
the time scale while the vertical
motion of the pen records the
cumulative precipitation.
(Raghunath 2006)
18

19. Float Rain Gauge
• In this type, as the rain is collected in
a float chamber, the float moves up
which makes a pen to move on a
chart wrapped round a clock driven
drum.
• When the float chamber fills up, the
water syphons out automatically
through a syphon tube kept in an
interconnected syphon chamber.
• The clockwork revolves the drum
once in 24 hours.
• This type of gauge is mainly used by
Meteorological department.
(Raghunath 2006)
19

20. Representation of the Rainfall data
• So, the rainfall data over a period of
time at a particular site , which to be
of any use has to be organised into a
usable form.
• This can be done mainly by using two
following methods:(Penche 1998)
• Hyetograph
• Mass-Curve
20

21. Watersheds
• It’s a land area that channels rainfall and
snowmelt to creeks, streams, and rivers,
and eventually to outflow points such as
reservoirs, bays, and the ocean.
• Watershed is an area of land where water
naturally drains to a one point
• Rainfall, snowmelt and other precipitation
flows into Lakes, rivers , ocean and pond
etc.
• Watershed boundaries are natural and
have constructive features that directly
flows water.
• It is normal for watersheds to cross state,
boundaries and countries.
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22. Importance of Watersheds
• It is important for watersheds to clean because this water is used for many purpose like drinking water.
• Wild Life also depends on watersheds for food ,water and shelter.
• Aquatic animal also depends on watersheds.
22

23. Factors harming Watersheds
• Non Point source Pollution is the largest cause of water pollution and biggest threat to the health of
watersheds.
• Non Point source Pollution start with rainfall or Snowmelt moving over and through the ground.
• As water moves it kills natural and human made Pollutants from different places like road, parks and
construction sites.
• Eventually water follows into lakes and rivers carrying these pollutant harming underground water
also.
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24. Objectives of Watershed Management
• To manage and utilize the runoff water for useful purpose.
• To Protect , conserve and improve the land of watershed for more efficient and sustained
production.
• To check soil erosion and to reduce the effect of sediment yield on the watershed.
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25. Mainstay Debit
• Hydrological planning is always associated with the characteristics of the watershed. Rainfall and
watershed characteristics greatly affect the flow conditions.
• The fact of getting river flow data in many watershed areas is often incomplete. The availability of
long-term river flow data at the site of the taking building is necessary for planning purposes of MHP.
• This is because the water building function depends heavily on water requirements throughout the
season, so to get continuity of water supply according to the calculation planning required for
reliable debit.
• The expected release of the mainstay debit is always available throughout the year with the risk of
failure being calculated as small as possible. Mainstay debit data is generally required for hydro-
power plant development planning, namely to determine the calculation of water supply in building
intake (intake).
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26. References
1. Malovic, D., et al. (2015). Hydroelectric power: a guide for developers and investors, The World
Bank.
2. Penche, C. (1998). Layman's guidebook on how to develop a small hydro site, DG XVII, European
Commission.
3. WMO (2008). Guide to Hydrological Practices. Volume I. Hydrology–From Measurement to
Hydrological Information, World Meteorological Organization (WMO) Geneva.
4. Pandey, B. and A. Karki (2016). Hydroelectric Energy: Renewable Energy and the Environment,
CRC Press.
5. Raghunath, H. M. (2006). Hydrology: principles, analysis and design, New Age International.
6. US Geological Survey, Water Resources of Pennsylvania SRBC Streamflow Information.
7. Kunwor, A., Technical Specifications of Micro Hydropower System Design and its Implementation.
2012.
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