WATER RESOURCES ENGINEERING
DEFINITION OF TERMS:
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Hydrology is the study of the occurrence, distribution, movement, and properties of waters of the
earth.
Engineering Hydrology involves understanding hydraulic processes, data collection, and analysis,
mathematical modeling, and hydraulic design.
Hydraulics – is the study of the mechanical behavior of water in physical systems and processes. It
is the practical application of the principles of fluid mechanics in water resources engineering.
Water resources systems engineering – defined as the formulation and evaluation of alternative
plans to determine that particular system configuration or set of actions that will best accomplish
public objectives within the constraints of governing natural laws, engineering principles, economics,
environmental protection objectives, social and political pressures, legal restrictions and institutional
and financial capabilities.
Hydrologic and hydraulic engineering are combined with other disciplines to support analysis and
decision-making processes involved in planning, designing, maintaining, and operating water
management systems.
Water is controlled and regulated to serve a variety of purposes. Flood mitigation, storm
drainage, sewerage, and highway culvert design are applications of water-resources engineering
to the control of water so that it will not cause excessive damage to property, inconvenience to the
public, or loss of life. Municipal water supply, irrigation, hydro-electric power development, and
navigation improvements are examples of the utilization of water for beneficial purposes.
Pollution threatens the utility of water for municipal and irrigation uses and seriously despoils the
aesthetic value of rivers- hence pollution control or water quality management has become an
important phase of water-resources engineering.
Water rights are legal concepts that define how water is distributed among various users within a
river basin, state or country.
The appropriation doctrine provides for acquiring rights for use of water by diverting it and putting
it to beneficial use in accord with procedures set forth in state laws or acknowledge by courts.
Appropriated water may be used on lands away from the stream as well as on lands adjoining the
stream. The earliest appropriator in point of time has the exclusive right to use of water to the extent
of his or her appropriation without diminution of quantity or deterioration of quality whenever the
water is naturally available.
Appropriations are for definite quantity of water and are valid only as long as the right is exercised.
Appropriations may be made only for beneficial and reasonable uses.
The riparian doctrine gives to the owner of land adjacent to a stream the right to use water from
that stream. This use is generally limited to riparian land but may be for any beneficial use.
Use of water for irrigation must be reasonable in relation to the reasonable requirements of the
owners of other lands riparian to the same water course.
No riparian user acquires priority over other riparian users by virtue of the time use began.
The riparian right is proportionate, not exclusive. It is not expressed in specific quantities of water
unless they have apportioned by a court decree. Such decree is based on conditions existing at the
time of the hearing and is subject to change by the court if the conditions change.
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A permit confers a right to use a specified quantity of water at a specific location and at specific
times. The issuing entity may include any reasonable conditions in the permit.
Permits are usually for a limited term, subject to renewal. Priority of issue does not control the
priority right, which all permittees usually have equal status and deficiencies must be shared on an
equitable basis.
Permit systems have some characteristics of riparian law (no priority) and some features of
appropriation law (use may be permitted on non-riparian land).
Rights to groundwater law are inherent in the overlying property, and the owner of this property is
free to remove and use the water as he or she wishes.
Roman civil law – specifies that owners of high land (dominant owner) are entitled to the
advantage that this elevation gives them and may discharge their drainage water onto lower land
through natural depression and channels without obstruction by lower, or servient, owners. A
dominant owner may accelerate the flow of surface by constructing ditches or by improving natural
channels on his or her property and may install drains.
Common-enemy rule – the basic principle is that the water is a common enemy of all, and
landowners may protect themselves from water flowing onto their land from a higher elevation. The
dominant owner cannot construct drainage works that result in damage to property of a servient
owner without securing an easement. The servient owner is allowed to construct dikes or other
works to prevent the flow of surface water onto his or her property.
Both doctrines of drainage law place the responsibility for damages on any person or organization
altering the natural stream pattern of an area or creating an obstacle that blocks the flow of natural
stream.
Water wells are installed to provide water supply, recharge, or observation of the aquifer.
A well is an excavated hole, usually a vertical shaft, in the earth allowing access to groundwater.
Precipitation is the main source of groundwater.
Zone of aeration or vadose zone is a zone or strata where some water are dispersed through the
soil and held by capillary forces in the smaller pores or by molecular attraction around the soil
particles.
Water in the upper layers of the zone of aeration is known as soil moisture.
If the retention capacity of the soil in the zone of aeration is satisfied, water moves downward into
regions where the pores of the soil or rock are completely filled with water. The water in this zone of
saturation is called the groundwater, and its replenishment by water moving downward is termed
as recharge.
Water table is the boundary between the vadose zone and the zone of saturation.
Aquifers are geologic formations that contain and transmit groundwater.
A confined, or artesian, aquifer is bounded above and below by relatively impermeable strata, so
that water pressure in the aquifer may be maintained above atmospheric pressure.
An unconfined aquifer is bounded above solely by the water table and overlying vadose zone.
Drawdown is the distance through which the water surface is lowered at the well
Specific capacity of the well is the discharge corresponding to a drawdown of 1 m.
Pipes are closed conduits through which fluids or gases flows. Conduits may flow full or partially
full. Fluid flow in pipes may be steady or unsteady. In steady flow, there are two types of flow that
exists; laminar flow and turbulent flow.
A pipe is equivalent to another one or to a piping system when, for a given head loss, the same
flow rate is produced in the equivalent pipe as occurred in the original.
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Pipes are in series if they are connected end to end so that a fluid flows in a continuous line without
any branching. The volume rate of flow through pipes in series is constant throughout.
Pipes are in parallel if they are connected in such a way that flow branches into two or more
separate pipes and then comes together again downstream.
THREE IMPORTANT PRINCIPLES IN THE APPLICATION OF PIPES IN PARALLEL:
1. The total flow entering each joint must equal the total flow leaving that joint.
2. The head loss between two joints is the same for each branch connecting these joints.
3. Within the range of velocities normally encountered, the percentage of total flow passing
through each branch will be constant, regardless of the head loss between the joints.
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Branching pipes consists of one or more pipes that separate into two or more pipes (or combine to
a single one) and do not come together again downstream. The general problem associated with
branching pipes is to find the flow rate in each pipe when other data (tank pressures and elevations,
pipe data, and fluid properties) are known. This type of problem can be solved by applying the
continuity equation. The flow rate in each pipe can be computed by one of the pipe flow formulas,
such as Darcy-Weisbach or Hazen-Williams, based on friction and minor losses and on elevation
differences. This type of problem generally requires a trial-and-error solution.
Pipe network is a pipe system consisting of numerous pipes connected in a complex manner with
many entry and withdrawal points. It is actually a complex set of pipes in parallel. The analysis
of a pipe network can be obtained using the Hardy-Cross Method.
Domestic use is that water used in private residences, apartment houses, etc., for dinking, bathing,
lawn sprinkling, and sanitary and other purposes.
Commercial and industrial use is that water used by commercial establishments and industries
such as factories, offices, stores, among others.
Public use includes the water required for use in parks, civic buildings, schools, hospitals, street
washing, fire protection, etc.
Loss and waste includes water which is “unaccounted for” in the sense that it is not assigned to a
specific user. Unaccounted-for water is attributable to errors in meter readings, unauthorized
connections, and leaks in the distribution system.
Factors affecting Water Use:
1. Size of the city
2. Industry and commerce
3. Characteristics of the population
4. Water rates and metering
5. Environmental concerns
6. Climate
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Water may be distributed by gravity, by pumps alone, or by pumps in conjunction with on-line
storage.
Gravity distribution is possible only when the source of supply is located substantially above the
level of a city, municipality, among others.
Pumping without storage is the least desirable method of distribution, since it provides no reserve
flow in the event of power failure and pressures will fluctuate substantially with variations in flow.
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Pumping with storage is the most common method of distribution. Water is pumped at a more or
less uniform rate, with flow in excess consumption being stored in elevated storage tanks distributed
throughout the system.
Water is stored to equalize pumping rates in the short term, to equalize supply and demand in long
term, and to furnish water during emergencies such as fires and loss of pumping capacity.
The network of pipes which makes up the distribution system may be subdivided into primary or
arterial lines, secondary lines and small distribution mains.
The primary or arterial mains form the basic structure of the system and carry flow from the
pumping station to and from elevated storage tanks and to the various districts of a city or
municipality, among others.
The secondary lines form smaller loops within the primary mains and run from one primary line to
another. They are located at spacings ideally of two to four blocks and thus serve to provide large
amounts of water for fire fighting without excessive pressure loss.
The smaller distribution mains form a grid over the entire service area – supplying water to every
user and to the fire hydrants. They are connected to primary, secondary, or other mains at both
ends and are valved so that the system can be shut down for repairs without depriving a large area
of water.
DISTRIBUTION SYSTEM MAINTENANCE
Maintenance of distribution systems includes the following:
1. Occasional cleaning
5. Disinfection of repaired sections
2. Servicing of valves and hydrants
6. Thawing of frozen lines
3. Leak surveys
4. Repairs
WATER CHARACTERISTICS AND QUALITY
Pure water is tasteless, colorless, and odorless liquid made up of hydrogen and oxygen with a
chemical formula of H2O. Because water is almost universal solvent, most natural as well as man-made
substances are soluble in it to some extent
Impurities of Water:
1. Ionic and dissolved
2. Nonionic and un-dissolved
3.
Gases
Physical Characteristics of Water:
1. Total, suspended and dissolved solids
4. Tastes and odors
2. Turbidity
5. Temperature
3. Color
 Total solids are determined by evaporating sample and weighing the dry residue.
 Suspended solids are found by filtering a sample of water.
 Dissolved solids are the difference between total solids and suspended solids.
 Turbidity decreases the clarity of water and results from finely divided impurities that may be
present in the water. It is usually caused by clay, silt, and soil particles and other colloidal
impurities. The degree of turbidity depends on the fineness of the particles and their concentration.
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Water sometimes contains considerable color resulting from certain types of dissolved and
colloidal organic matter leached from soil or decaying vegetation. True color is due to dissolved
impurities. Wastes from industrial activities are also often responsible for color in the water.
Tastes and odors in water are caused by the presence of decomposed organic material and
volatile chemicals and are measured by diluting the sample until the taste and odor are no longer
detectable by a human test.
The temperature of water is important in terms of its intended use, its treatment to remove
impurities, and its transport. The temperature depends on the source of the water.
Chemical Characteristics of Water
The chemical characteristics of water are quantified in terms of the inorganic and organic
constituents that may be present.
Inorganic Constituents
 The inorganic constituents found in the surface and groundwater are:
1. Natural sources
2. The commingling of contaminated waters and wastewaters
3. Dissolution of materials used for the storage and transport of water.
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The alkalinity of water is a measure of its capacity to neutralize acids. In natural waters, the
alkalinity is related to the bicarbonate, carbonate, and hydroxide concentration. Total alkalinity is
expressed in terms of equivalent calcium carbonate in milligrams per liter.
Acidity is expressed in terms of the amount of calcium carbonate required to neutralize the water.
The conductivity of a water sample is determined by measuring its electrical resistance between
two electrodes and comparing this resistance with the resistance of a standard solution.
Organic Constituents
 The organic constituents found in water are derived from the following:
1. The breakdown of naturally occurring organic materials
2. Domestic, commercial, industrial, and agricultural activities
3. Constituents that occur in both water wastewater treatment
 Naturally occurring organic materials include humus materials, microorganisms and their
metabolites, and aliphatic and aromatic carbons. Organic materials from man’s activities, often
identified as synthetic organic compounds (SOCs), includes constituents such as pesticides,
herbicides, among others.
Biological Characteristics of Water
Microorganisms are commonly present in surface waters, but they are usually absent from most
ground waters because of the filtering action of the aquifer.
 Common Microorganisms in Water:
1. Bacteria
5. Viruses
2. Algae
6. Pathogenic organisms
3. Fungi
4. Protozoa
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Sewerage refers to the collection, treatment, and disposal of liquid waste.
Sewerage works or sewage works include all the physical structures required for that collection,
treatment, and disposal.
Sewage is the liquid waste conveyed by a sewer and may include domestic and industrial
discharges as well as storm sewage, infiltration, and inflow.
Domestic or sanitary sewage is that which originates in the sanitary conveniences of dwellings,
commercial or industrial facilities, and institutions.
Industrial waste includes the liquid discharges from industrial processes such as manufacturing
and food processing.
Storm sewage is flow derived from rainfall events and deliberately introduced to sewers intended
for its conveyance.
Infiltration is water which enters the sewers from the ground through leaks.
Inflow is water which enters the sewers from the surface, during rainfall events, through flaws in the
system, or through connections to roof or basement drains.
Sewer is a pipe or a conduit, generally closed, but normally not flowing full, which carries sewage.
Common sewer serves all abutting properties.
Sanitary sewer carries sanitary sewage and is designed to exclude storm sewage, infiltration, and
inflow. Industrial waste may be carried in sanitary sewers, depending upon its characteristics.
Storm sewer carries storm sewage and other wastes which may be discharged into the streets or
onto the surface of the ground.
Combined sewer carries both domestic and storm sewage.
Combined system is a system composed of combined sewers.
Separate system is a system that segregates the storm water.
House sewer is a pipe conveying wastewater from an individual structure to a common sewer or
other point of disposal.
Lateral sewer is a common sewer with no tributary flow except from house sewers.
Sub-main sewer collects flow from one or more laterals as well as house sewers.
Main or trunk sewer collects flow from several sub-mains as well as laterals and house sewers.
Force mains are pressurized sewer lines which convey sewage from a pumping station to another
main or to a point of treatment or disposal.
Intercepting sewer intersects other sewers to separate the dry weather flow from storm-water flow
which they may carry.
Relief sewer is a sewer which has been built to carry a portion of the flow in a system with
otherwise inadequate capacity.
Outfall sewer is a sewer which carries the collected waste to a point of treatment or disposal.
Sewerage treatment includes any process which may be used to favorably modify the
characteristics of the wastewater.
Sewage disposal refers to the discharge of liquid wastes to the environment. Normally, but not
always, disposal implies some degree of treatment prior to discharge.
Combined and Separate Sewers
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Modern sewer systems are typically separate systems. Exceptions to this general rule are found
in some larger, older cities where combined sewers were constructed in the past and where new
additions follow the existing practice.
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As urban areas develop, the first need is for sanitary sewers. Storm water can be handled by street
and gutter flow to natural watercourses until development is fairly extensive. Since storm sewers
are larger and substantially more expensive than sanitary sewers, their construction is frequently
deferred. New sanitary sewers are designed specifically to exclude storm water, with strict
specification regarding allowable infiltration at joints and elimination of potential source of inflow.
Requiring treatment of urban storm water appears unreasonable. Although storm water may be
heavily polluted, particularly at the beginning of a run-off event, the flow is usually so great that it
cannot be economically contained and/ or treated.
IRRIGATION
 Irrigation is the application of water to soil to supplement deficient rainfall to provide moisture for
plant growth.
 Arable land is land that, when properly prepared for agriculture, will have a sufficient yield to justify
its development.
 Irrigable land is arable land for which a water supply is available.
 The total water requirement for an irrigation project, usually referred to as the diversion
requirement, consists of the water needed by the crop plus the losses associated with the
application and delivery of water.
 The crop – irrigation requirement is that portion of the consumptive use that must be supplied by
irrigation. It is the consumptive use less the effective precipitation.
Irrigation Methods:
1. Flooding
a. Wild flooding consists in turning the water onto natural slopes without much control or
prior preparation. It is usually wasteful of water, and unless the land is naturally smooth,
the resulting irrigation will be quite uneven.
Wild flooding is used mainly for pastures and fields of native hay on steep slopes where
abundant water is available and crop values do not warrant more expensive preparations.
b. Controlled flooding may be accomplished from field ditches or by use of borders, checks,
and basins.
c. Check flooding is accomplished by turning water into relatively level plots, or checks,
surrounded by levees. It is useful in very permeable soils where excessive percolation
might occur near a supply ditch. The basin-flooding method is check flooding adapted to
orchards.
2. Furrow irrigation is widely used for row crops, and small furrows called corrugations have
been used for forage crops.
3. Sprinkler irrigation requires a pressurized system in contrast with flooding and furrow
irrigation which depend on gravity flow.
4. Sub-irrigation system requires condition wherein there is a permeable soil in the root zone,
underlain by an impermeable horizon or a high water table.
5. Trickle (or drip) irrigation requires perforations designed to emit a trickle and spaced to
produce a wetted strip along the crop row or a wetted bulb at each plant.
Irrigation Systems and Structures
A typical irrigation system may include structures and devices such as dams, spillways,
diversion works, canals, ditches, wells, pumps, and pipelines.
SAMPLE PROBLEMS IN WATER RESOURCES ENGINEERING
1. A mechanical device which when installed in the pipe flow systems will add energy (output) to the
system is known as:
A. Pump
C. Turbine
B. Sluice gate
D. Orifice meter
2. It is defined as a hydrograph with a volume of 1 inch of run-off resulting from a rainstorm of
specified duration and a real pattern:
A. Stream flow hydrograph
C. Unit hydrograph
B. Flood hydrograph
D. Groundwater hydrograph
3. One of the rational methods of determining the reservoir-capacity yield analysis in dam design is
known as:
A. Hydrograph
C. Mass Curve
B. Flood routing
D. Isohyetal map
4. In a system of pipes in parallel, which of the following is true?
A. Velocity heads are equal
C. Discharge are equal
B. Pressures are equal
D. Head loss are equal
5. It is a term to denote the temperature which is the average of the monthly mean for the year:
A. Mean monthly temperature
C. Normal daily temperature
B. Daily range temperature
D. Mean annual temperature
6. Water that flows from the atmosphere to the earth’s surface in any variety of forms is known as:
A. Stream flow
C. Precipitation
B. Groundwater flow
D. Run-off water
7. A mechanical device which when installed in the pipe will extract (input) energy from the system:
A. Pump
C. Turbine
B. Sluice gate
D. Orifice meter
8. It is the term to denote the temperature range between the highest and lowest temperature
recorded for a particular day:
A. Mean monthly temperature
C. Normal daily temperature
B. Daily range temperature
D. Mean annual temperature
9. What is the rate of flow of water passing through a pipe with a diameter of 20 mm and speed of
0.50 m/s?
A. None of these
C. 6.28 x 10-4m3/s
-4
3
B. 1.57 x 10 m /s
D. 7.85 x 10-4m3/s
10. A graph that plots the measured the stream flow discharge versus water surface elevation:
A. Infiltration curve
C. Rating curve
B. All of these
D. Hydrograph
11. What is the term for capillary water in the smaller pore surface of the soil?
A. Interception
C. Depression storage
B. Soil moisture
D. Basin recharge
12. Which method of irrigation has the best control of water supplied?
A. Furrow
C. Flooding
B. Sub-irrigation
D. Trickle irrigation
13. What is the measurement of the amount of oxygen required to stabilize the waste completely?
A. Chemical oxygen demand
C. Theoretical oxygen demand
B. Biological oxygen demand
D. None of these
14. What are the principal impurities found in water?
A. Nonionic and Undissolved
C. All of these
B. Gasses
D. Ionic and Dissolved
15. Filtration of water is used to:
A. Filter fine impurities such as algae, silt, etc.
B. Filter residual solids that remain in water after settling
C. None of these
D. Remove particles such as silt, sand and flocculated suspensions.
16. What occurs whenever the absolute pressure of a liquid is close to the vapor pressure?
A. Upsurge
C. Cavitation
B. None of these
D. Scouring
17. Which is NOT a chemical characteristic of water?
A. Alkalinity
C. Total suspended and dissolved solids
B. pH level
D. Dissolved cations and dissolved anions
18. What are the methods for rainwater to reach a stream?
A. Surface run-off
C. Interflow
B. All of these
D. Percolation
19. What drainage structure is NOT considered as a cross drainage?
A. Bridges
C. NOTA
B. Culvert
D. Dips
20. Biological wastewater treatment:
A. Rotating biological disc
C. All of these
B. Activated sludge
D. Trickling filter
21. Three pipes are parallely connected. The pipe characteristics are as follows:
Pipe
D (cm)
L (m)
f
A
15
600
0.02
B
10
480
0.03
C
20
900
0.025
Find the rate flow in m3/s in pipe A if the difference in head at ends is 40.00 m.
A. 0.083
C. 0.055
B. 3.13
D. 0.18
22. The static head corresponding to a flow velocity of 3m/s is:
A. 0.46
C. 0.015
B. NOTA
D. 0.672
23. What is the simplest device for measuring river stage?
A. Weighing river gage
C. NOTA
B. Staff gages
D. Tipping bucket gage
24. Storm lasting 4 hours has 30 mm rainfall over an area of 800 hectares. Assuming zero base flow,
what fraction of precipitation appeared as run-off?
Time (hours)
Flow (m3/s)
0
2
1
4
A. 30%
B. 64%
25. A stream channel with perennial flow:
A. Influent stream
B. Effluent stream
2
5
3
4
C. 26%
D. 74%
C. None of this
D. Direct run-off
4
3
5
2
6
1
26. The unit work in N-m is called:
A. Joules
C. Watts
B. Horsepower
D. Erg
27. In sewerage, microscreening is used to:
A. Filter fine impurities such as algae
B. Remove particles such as silt, sand, and flocculated suspensions
C. Filter residual solids that remain in water after settling
D. NOTA
28. In hydrology, depression storage is:
A. Water retained as puddles.
B. Water that penetrates into the soil and flows laterally in the surface soil.
C. Rain water collected by the leaves and stems of vegetation or structures.
D. NOTA
29. What method of wastewater treatment involves removal of fine residual suspended solids
remaining after biological or chemical treatment?
A. Microscreening
C. Sedimentation
B. Flotation
D. Filtration
30. What method of wastewater treatment involves removal of settleable solids and thickening of
sludge?
A. Filtration
C. Microscreening
B. Sedimentation
D. Flotation
31. The water supply for a city is pumped to a distribution reservoir. The pumping rate is 600 m 3 per 4
hours. The estimated water requirements every 4 hours is shown below.
Hour
Demand (cum.)
Hour
Demand (cum.)
0400
200
1600
700
0800
800
2000
500
1200
1100
2400
300
What is the required reservoir capacity?
A. 3600 m3
C. 500 m3
3
B. 1100 m
D. 800 m3
32. Which type of dam may potentially have the smallest cross-section?
A. Arch dam
C. Earth dam
B. Buttress dam
D. Gravity dam
33. What spillway of a dam is suited where space is limited?
A. NOTA
C. Siphon spillway
B. Shaft spillway
D. Side channel spillway
34. What is the maximum quantity of water which can be guaranteed during a critical dry period?
A. Secondary yield
C. Reservoir yield
B. Safe yield
D. Specific yield
35. What wastewater treatment that involves the removal of course and settleable solids by
interception?
A. Flocculation
C. Flow equalization
B. Screening
D. Comminution
Answer Key:
1. A – Pump
2. C – Unit Hydrograph
3. A – Hydrograph
4. D – Head loss are equal
5. A - Mean Monthly Temperature
6. C – Precipitation
7. C – Turbine
8. C – Normal Daily Temperature
9. B - 1.57 x 10-4 m3/sec
Q = AV
10. C - Rating Curve
11. B – Soil Moisture
12. D – Trickle Irrigation
13. A - Chemical Oxygen Demand
14. C - All of the these
15. B – Filter residual solids that remain in water after settling
16. C – Cavitation
17. C – Total suspended and dissolved solids
18. B – All of these
19. C – NOTA
20. C – All of these
21. C – 0.055 m3/sec
Use Darcy-Weisbach Formula (HL-A = HL-B = HL-C = 40 m)
22. A – 0.46
H = v2/2g
23. B – Weighing Rain Gage
24. A – 30%
25. B – Effluent
26. A – Joules
27. A – Filter fine impurities such as algae
28. A – Water retained as puddles
29. D – Filtration
30. B – Sedimentation
31. D – 800 m3
32. A – Arch dam
33. C – Siphon spillway
34. B – Safe Yield
35. B – Screening
Hour
Pumping Rate (m3)
Demand (m3)
Inflow to Reservoir
Outflow to Reservoir
0400
0800
1200
1600
2000
2400
600
600
600
600
600
600
200
800
1100
700
500
300
400
0
0
0
100
300
0
200
500
100
0
0
800 m3
800 m3