Mathematical Model of Reservoir Routing for Wadi Horan Dam Spillway

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 02, February 2019, pp. 341–354, Article ID: IJCIET_10_02_037
Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=2
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
©IAEME Publication Scopus Indexed
MATHEMATICAL MODEL OF RESERVOIR
ROUTING FOR SPILLWAY OF WADI HORAN
DAM
Alaa H. Alshami
Civil Engineering department, AL-FARABI University Coll. Eng., Baghdad Iraq
ABSTRACT
This research is to analyses hydraulic parameters of the spillway design for WADI
HORAN Dam. The spillway design of type Ogee overflow and the design based on
Water Experiment Station (W.E.S) of the U.S. Corp of Engineers. The inflow are
routed in order to decrease the maximum discharge passing on the spillway. The
maximum discharge passing are 1400 m3
/sec with maximum head over the crest equal
to 3.4 m and 50 m3
/sec Attenuation and 2 hrs Reservoir Lag. Froude number is
determined in order to select the type of stilling basin, the Froude number equal to 5
that can choose type II stilling Basin. The method used for routing is Inflow- Storage
Discharge ( I.S.D.) The profile of the downstream and upstream are calculated.
Key words: Spillway, Froude number, Reservoir Routing, Wadi Horan.
Cite this Article: Alaa H. Alshami, Mathematical Model of Reservoir Routing for
Spillway of Wadi Horan Dam, International Journal of Civil Engineering and
Technology (IJCIET) 10(2), 2019, pp. 341–354.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=2
1. INTRODUCTION
Hydrology is a branch of Earth Science. The important of hydrology in the assessment
development, utilization and management of water resources, of any region is being
increasingly realized at all levels. It was in view of this that the United Nation proclaimed the
period of 1965-1974 as the International Hydrology decade during which, intensive efforts in
hydrologic education research, development of analytical techniques and collection of
hydrological information on a global basis, were promoted in University, Research Institution,
and Government Organizations (Raghunath, 2006).
Hydraulics is a technology and applied science using engineering, chemistry, and other
sciences involving the mechanical properties and use of liquids. In fluid power, hydraulics is
used for the generation, control, and transmission of power by these of pressurized liquids.
Hydraulic topics range through most science and engineering disciplines, and cover concepts
such as pipe flow, dam design, fluidics and fluid control circuitry, pumps, turbines,
hydropower, computational fluid dynamics, flow measurement, river channel behavior and
erosion (Raghunath, 2006).

Mathematical Model of Reservoir Routing for Spillway of Wadi Horan Dam
Hydraulic structures are structures submerged or partially submerged in any body of
water, which disrupts the natural flow of water. They can be used to divert, disrupt or
completely stop the flow. A hydraulic structure can be built in rivers, a sea, or any body of
water where there is a need for a change in the natural flow of water. An example of a
hydraulic structure would be a dam, which slows the normal flow rate of the river in order to
power turbines. Hydraulic design involves the application of flow theory to the design of
various water containment and control structures. The designer should ensure that the
structure and the systems will function effectively and economically under all foreseeable
service conditions. Hydraulic structures must be capable of withstanding flow conditions and
forces caused by both static and flowing water loading. They must resistant deterioration,
aging, and extemporaneous forces due to weather extremes and earthquakes (Icold, 2018)
spillways are important in dams and study site, Water normally flows over a spillway only
during flood periods when the reservoir cannot hold the excess of water entering the reservoir
over the amount used so Spillways insure that the water does not overflow and damage or
destroy the dam Usually, spillways are provided with gates, which provide a better control on
the discharges passing through If the spillway is gated, then the discharging water (Q) is
controlled by the gate opening and hence the relation of Q to reservoir water level would be
different from that of an ungated spillway (Kargpur, 2008). The capacity of a spillway is
usually worked out on the basis of a flood routing study, is seen to depend upon the following
major factors: The inflow floods, The volume of storage provided by the reservoir, Crest
height of the spillway, Gated or ungated. The aim of this study is to analysis hydrological data
of inflow discharge at Horan dam area at Iraq and find the maximum flow by reservoir
routing analysis. In addition determine the best hydraulic section of dam spillway.
2. DESCRIPTION OF THE STUDY AREA
Figure 1 Study area (Sayl et al., 2017)

Alaa H. Alshami
Wadi Horan is the longest Wadi in Iraq. Located in Al Anbar Governorate west of Iraq, at
Latitude 33.0333°, Longitude 40.2500° Wadi Horan is roughly midway between Damascus
and Baghdad near the town of Rutba, it stretches for 350 kilometres (220 mi) from the Iraq-
Saudi border to the Euphrates river near Haditha.
Wadi Horan dam is located in the middle course of the (Khatsuria, 2004) Wadi Horan
channel serving the area of Block 7 area covered with Wadi Horan catchment on that profile
is 12,180 sq.km. The mean annual runoff is estimated at 19.3×106
cu.m Figures (1) .The dam
location is selected having regard of wadi channel width and of ground topography far
positioning of spillway. The dam height at this location is limited by low-lying and rather thin
saddles, present on the right bank. The saddles are reducing the pool level to about 15 m. The
profile of the valley at the said elevation is about 350 m wide. At the elevation of 6 m above
the channel bottom the width is almost the same.
3. RESERVOIR CAPACITY
As said above the saddles on the right bank are practically limiting the normal pool level in
the reservoir on this profile and reduce it to 15 m. Higher normal pool level would impose
considerably greater scope of the works, both on the dam and in securing safety of its
abutments against detrimental effect of percolation. The reservoir capacity to be formed at
this pool level would amount to 25×106
cu.m with this capacity, the uncontrolled part of
Wadi Horan runoff due to spilling over would reach 42% of runoff, for the controlled release
of water of 3.0cm/sec. The average evaporation rate of the reservoir is estimated at 1.7x106
cu.m/year. In this way, the average net annual yield of the reservoir might be estimated at
9.5x106
Cu.m, or 49% of the average Wadi Horan runoff, under the assumption that other
reservoirs are not constructed upstream of that dam site.
4. DAM DESIGN
The dam will be 21.5 m high above the river bed. Its width at crest will be 7 m and the length
504 m. At an elevation of 13 m on the upstream side, a 4m wide berm will be built. Total
volume of the dam is estimated at 360,000 cu.m. The impervious part of the dam will have e
volume of 70,000 cu.m and the pervious fill and pitching 290,000 cu.m. At the abutments the
dam will be founded in dolomite and lime stones. The impervious zone of the dam will cut 2
m deep into the bed rock. In river bed and on terraces, the dam will be founded on alluvial
deposits and on bedrock. Pervious Zones of the dam will be founded on sediments, except in
the sections which first have to be cleared of the materials of poor bearing capacity or
geological-engineering characteristics. The watertight core will be founded on bedrock cutting
2 m deep into it. After this section is excavated and cleared of alluvium through the
foundation width. The terrace and recent sediments, in which the foundation trench is to be
excavated for the core, are expected to be 5-8 m deep. Alluvium will be investigated in the
dam site by means of excavating wells, drilling of holes and examination in situ of density
and permeability of the Alluvium. The dam will be filled with local materials from borrow
pits near the site. The watertight core will be built of clay available on nearby Plateaus 0.5 to
3 km far from the dam site. Pervious zones of the dam will be filled with gravel and send of
terrace and recent alluvium from borrow pits near the dam Site. These materials are estimated
to be available in adequate quantities and to be of good quality. While excavating terrace
material blasting might be required. Fitter zones will be filled with processed material,
because no suitable material has been found in the prospected terrain which could be used
enslaved. Rock for upstream pitching and dry stones drain and rock spalls for dam crest and
base to rock fill will be supplied from the excavations for water discharge structures of the

dam and from nearby quarry.The contact of watertight core and the bed rock will be protected
by a grout blanket 5 m deep through the dam length.
5. SPILLWAY
The spillway position is predisposed by the saddle present on the right dam abutment. The
Spillway is dimensioned at flood flow of 0.1 frequency, with Confidence interval of 50%
amounting to 3,960 cu.m/sec. The spillway consists of ungated concrete weir and chute
channel. The weir is to suit overflowing head of 4.5 m. The weir is proposed to be buried into
Sound limestone down to depth of 2 m. The chute shall be constructed as 200 m wide open
unlined channel. Such a solution is caused both by the distance from the dam and by the
expected geological condition of rock making up spillway and chute foundations. The type of
spillway to be chosen shall depend on:
Inflow flood, Availability of tail channel, its capacity and flow hydraulics, Power, house,
tail race and other structures downstream.
6. OVERFLOW (OGEE) SPILLWAY
The overflow type spillway is most commonly used as the integral overflow section of a
concrete or masonry dam Figure 2. It is most commonly used with gravity dams. However, it
is also used with earth and rock fill dams with a separate gravity structure; the ogee crest can
be used as control in almost all types of spillways; and it has got the advantage over other
spillways for its high discharging efficiency (Kargpur, 2008).
Figure 2 Ogee spillway
7. MATHEMATICAL MODEL
7.1. Area Elevation Capacity Curve
Curve measures the volume (capacity) of the reservoir below a certain elevation the area
capacity curve are necessary for defining the storage capacity of reservoir (Hussein, 2010).
An area – capacity curve is obtained by plan- metering enclosed within each contour line in
the reservoir area. The graphical plotting of area and capacity curve relates the surface area
and the storage capacity of the reservoir to the elevation of the water surface.

Alaa H. Alshami
7.2. Topographical Survey at proposed site at WADI HORAN
The result of the topographical survey at WADI HORAN site , the following reading of the
elevation ground level versus the area in Hectar, the Table (1) represent the data of area
versus Elevation.
Table 1 Area, Elevation data
Area (Hectare)Elevation(m)Area(Hectare)Elevation (m)
172.95263.8519
233.85274.2520
329.15285.6521
330.652917.6522
381.703542.5523
431.203565.3524
108.6525
7.3. Establishing Storage – Discharge Relationship
The area at reservoir site are surveyed in detail and contour map is prepared with contour
interval one meter (1.0 meter) . From the map the area enclosed by various contours are plan
metered and curve of elevation versus area is prepared. Hence, the incremental volume of
water stored between any two successive contours can be determined using one of the
following equations:-
1- Trapezoidal Formula
= h/2 (A1 + A2)
2- Cone Formula
= h/3 (A1 + A2√
3- prismoidal formula
Where A1, A2 are area corresponding to two successive contour values and (h) is the
difference between them ,Am is the area enclosed by contour line midway between the two
adjacent a contours .If these incremental volumes are accumulated up to any contour value,
then that sum represent the storage volume of reservoir up to elevation of that contour. This
information is used to prepare a curve of elevation versus storage.
7.4. Out flow from the reservoir
The out flow from reservoir corresponding to any elevation can be determined by using the
discharge equation, one for ogee spillway and the sluices way opening
1- Ogee (Overflow) spillway
For Ogee spillway
Qsp = C L ( H–Hsp)3/2
Where Qsp = the discharge from the spill way
C = Coefficient of discharge of the spillway = 2.25
L = effective length of spillway, assumed as in HORAN DAM equal to 100meters
2- Sluicegate water way
Qsl = n Cd A √
Where

Qsl = discharge from sluice gate
n= the number of sluice ( 2 circular sluice pipes with one meter diameter and are placed at
elevation 520 m
A = area of each sluice opening
Hsl = sill level of the sluice opening (520 m)
Cd = Coefficient of discharge of sluice = 0.8
Trash racks for the opening of the sluices 2
Trash rack is a structure, whichis provided at the entrance to the intakes and sluiceways to
prevent entrance to debris. These are made in the form of semi – polygonal grid of iron or
steel bars as shown in the Figure 3.
Figure 3. Trash Rack
7.5. Elevation – Storage Curve
The calculation to obtain the storage versus elevation curve is given in the Table 2. The
contour interval is uniform and equal to 1 meter; Trapezoidal formula has been used to
compute incremental volumes. The storage in Hectar-meter is converted in to m3
/sec will be
usually convenient in the routing problems (A.Hussein and Alshami, 2018). The Elevation-
area curve and elevation – storage curve are prepared from the Table 2 as shown in the Figure
4 and Figure 5.
Figure 4. Elevation – area curve
518
520
522
524
526
528
530
532
0 50 100 150 200 250 300 350 400 450 500
Elevation
Area(hectar)

Alaa H. Alshami
Figure 5. Elevation – Storage curve
Table 2. Calculation Elevation area and storage curve
Storage
Cumecs-day
Cumulated
storage H-m
= h(A1+A2)/2A1 +A2
Area
(Hectar)
Elevation (m)
654321
003.8519
0.4634444.2520
1.0308.94.94.95.6521
1.9116.511.611.617.6522
4.8241.6530.0530.0542.5523
9.7283.9553.953.965.3524
16.30140.8586.9586.95108.6525
26.35227.70140.75140.75172.9526
42.88368.55203.35203.35233.8527
56.11484.80281.45281.45329.1538
70.76611.35329.90329.90330.7529
79.41686.10356.20356.20381.7530
88.27762.65406,45406.45431.2531
8. CALCULATIONS AND RESULTS
8.1. Out flow Discharge
The discharge from the pipe sluices is given by
Qsl = n Cd A √ )
The data used are as follows
Number of pipe used are 2 with a diameter equal to one meter, Coefficient of discharge = 0.8
Area of the pipe = 2 (1)2
𝜋 /4 = 1.571 m2
Qsl = 2 0.8 1.571 √ √
Qsl= 11.13√ .. (1)
The discharge from Ogee (over flow) spillway
Qsp = C L ( H –Hsp)3/2
Qsp = Discharge from the spillway
C =coefficient of discharge = 2.25
L = effective length of the spillway = 100m
518
520
522
524
526
528
530
532
0 10 20 30 40 50 60 70 80 90 100
Elevation
Storge (cumecs day)

Hsp = Sill level of the spillway = 527m
Qsp = 2.25 100 ( H – 527)3/2
Qsp = 225 ( H–527)3/2
(2)
Total discharge = Discharge of sluice gate + discharge of Ogee spillway
Q = Qsl + Qsp
The discharge obtained from reservoir at different levels are calculated using the above
equation (1) and (2) and result are tabulated in Table 3 and elevation discharge curve is
presented in Figure 6.
Figure 6. Elevation – Discharge
Table 3. Calculation for Elevation – Discharge curve
Q = Qsl+QspQsp(H-Hsp)Qsl(H-Hsl)Elevation m
654321
00000519
00000520
11.130011.131521
15.740015.742522
19.280019.283523
22.260022.264524
24.890024.895525
27.260027.266526
29.450029.457527
256.48225531.488528
669.78636.39233.399529
1204.331169.13335.2010530
1836.911800.0436.9111531
The final result of the Elevation - Storage in Cumecs-day and discharge in m3
/sec is
represented in the following Table 4.
Table 4. Elevation - storage - discharge
Discharge m3
/sStorage cumecs dayElevation
00519
00.463520
11.131.030521
15.741.91522
19.284.82523
22.269.72524
518
520
522
524
526
528
530
532
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Elevation
Discharge m^3/sec

Alaa H. Alshami
24.8916.30525
27.2626.35526
29.4542.88527
256.4856.11528
669.7870.76529
1204.3379.41530
1836.9188.27531
8.2. Inflow-Storage-Discharge Method (I.S.D. Method)
The inflow- storage-discharge method was developed by L.G. Puls of U.S.Army corps of
engineers. According to the method, the equation is arranged as follows:-
I – Q = ds/dt (3)
where:
I = inflow
Q = Out flow from the reservoir, and S = Storage in the reservoir. The suffixes 1 and 2 are
used to denote a given quantity at the beginning and the end of the time interval and if the
inflow and outflow have straight-line variable within time interval then equation (1) can be
written
(i1 + i2)/2) -(Q1+ Q2 /2) t = S2 – S1 (4)
Or
(I1 + I2)/2 + S1 –(Q1/2 =S2 +(Q2/2
In the above equation all the quantity on the left hand side are known and hence the
quantity (S2 + Q2/2
From the quantity, the value of Q2 can be find out from the storage discharge relationship
as explained below-
From the available storage discharge curve the curve of (S–Q/2 ) verus Q and (S+ Q /2
versus Q are developed such curve may called the ROUTING CURVE
From the known value of Q1 the value of (S1–Q1/2 t)is read from Q Vis ( S – Q/2 )
curve . This value is then added to(I1+ I2/2) t is given ( S2 + Q2/2 t) . Entering the graph
with the value of (S2 + Q2/2 t), the value of Q2 is read and from Q Vis (S + Q/2 t)curve the
value of Q2thus determined , becomes Q1 from next time interval.
The procedure is repeated for all the subsequent routing, period until the complete out
flow hydrograph is obtained.In preparing the routing curve, care should be taken to see that(S
+ Q/2 t) and ( S – Q/2 ) will have consistent unit for example if Q is in m3
/s and tis in
day , S should be in cumecs- day. Actually the routing can be performed with only one
routing curve that is Q is( S+Q/2 t). This because (S-Q/2 t) for any Q can be obtained by
first reading (S+Q/2 t) from Q vis (S+ Q/2 t)curve and then subtracting Q from this curve.
If the inflow and out flow hydrograph are plotted on the same time scale it will be observed
that the peak flow of out flow hydrograph is less than the peak flow of the inflow hydrograph.
In other words the peak flow is reduced similarly the time to peak in the out flow hydrograph
is more than the time to peak in the inflow hydrograph. These are effect of reservoir storage
on the movement of flood wave through reservoir. The reduction in peak is known as the
ATTENUATION of the difference in time to peak is known as the reservoir LAG
8.3. Routing Curve by I.S.D. Method
The inflow data for Wadi Horan Reservoir at period of one hour shown in the table 5 and
Table 6 shows the calculation the Routing curve by using the I.S.D method. Figure 7
represent a curve between Discharge Q m3
/s and (S+Q/2 t) and (S–Q/2 t).

Table 5 Inflow of Wadi Horan
Discharge m3
/sTime (hr)Discharge m3
/sTime(hr)
11601105
102412701
800132502
560148903
4001512504
3201614005
2561714506
1601813907
961913008
02013009
128510
Table 6. Routing calculation by I.S.D. method
S – Q/2 t
Cumecs -day
S + Q/2 t
Cumecs -day
Q/2 t
cumecs- day
Discharge Q m3
/s
Storagecumecs -
day
00000
0.4630.463000,463
0.7971.2630.23311.131.030
1.5802.2400.33015.741.91
4.4155.2250.40519,284.82
9.25310.1870.46722.269.72
15.77716.8230.52324.8916.30
25.77826.9220.57227.2626.35
42.26243.490.61829.4542.88
50.72461.4965.386256.4856.11
56.69584.82514.065669.7870.76
54.12104.70025.2901204.3379.41
49.695126.84538.5751836.9188,27
Figure 7. Curve between Discharge Q m3
/s and (S + Q/2 t) and (S – Q/2 t).
8.4. Routing Through Reservoir By I.S.D. Method
The following Table 7 shows the routing through the reservoir. The Procedure for finding the
out flow can be represent, Column (1) and (2) of the given inflow hydrograph, Column (3)
=(I1+I2/ 2 ) t =( 0 + 70 /2 )1/24= 1.47, Column (4) = (S – Q1/2 t)obtained from Q vs ( S –Q/2
t)curve fig.(5-3) against the value in column (6) first one assumed equal to 150 m3
/s then
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 20 40 60 80 100 120 140
Dischargem^3/sec
(S+Qt/t),(S-Qt/2) cumecs - day
S+Qt/2
S-Qt/2

Alaa H. Alshami
Column (5) = ( S2 + Q2/2 t) = Col. 3 + col.4. Column (6) = Q obtained from Q Vs ( S + Q/2
t)curve in Fig( 3-5) against the value of (S2+Q2/2 t) in col.(5) and Column (7)=Elevation of
water surface in the reservoir is obtained from elevation discharge curve in Fig (3-4) against
the value of Q in col(6)
Table 7. Routing through the reservoir
Elevation H
(m)
7
Out flow Q
6 m3
/s
S2+ Q2/2 t
5
S1-Q1/2 t
4
I1+I2/2
3
Inflow m3
/s
2
Time hr
1
527.615000
527.410049.47481.47701
537.612052.70466.722502
528.442072.04824.08903
529.6109099.05445.012504
529.81160110.55555.714005
530.31350113.55459.5514506
530.41400111.05259.613907
530.41400110.55357.5413508
530.11320109.05455.6513009
530.21300108.05454.30128510
530.01200104.05351.34116011
529.81120101.05645.80102412
529.690094.05638.3080013
529.268084.05628.3050014
528.855077.05720.1640015
528.438071.05615.2032016
528.230064.05212.1025617
528.028062.7548.716018
527.818055.4505.49619
527.48048.0462.0020
The inflow and out flow hydrograph and also the graph ofdischarge and storage are shown in
the Figure 8 and Figure 9 from which the above result are obtained from the calculation in the
Table 7, The Attenuation= 50 m3
/sec and the reservoir Lag equal to 2hr
Figure 8. Inflow and out flow hydrograph
0
200
400
600
800
1000
1200
1400
1600
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Discharge
Time
Inflow
outflow

Figure 9. Discharge and storage
8.4. Ogee (Overflow) Profile Spillway and Stilling Basin
Preface the Ogee profile to be acceptable should provide possible hydraulic efficiency,
structural stability and economy and avoid the formation of object able sub- atmospheric
pressure. Different types of up-stream face of spillway, which are crest profile for vertical up-
stream face and crest profile for inclined up stream face . Figure 10 shows the different profile
of the upstream face shape
Figure 10. W.E.S Standard Spillway crest
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800 1000 1200 1400 1600 1800 2000
StorgeHectar.m
Discharge m^3/sec

Alaa H. Alshami
In this study, type (a) is selected which called crest profile for vertical up-stream profile as
suggested by Water Way Experiment Station(W.E.S.), based on extensive experiment
conducted by U.S.B.R. Army Corps of Engineers.
The details of the downstream Crest profile for vertical upstream face by using the
following equation
X1.85
= 2 (Hd )0.85
y
Where x and y are co-ordinates of the crest profile measured from the apex of the crest
and Hd is design head excluding head due to velocity of approach. According to the latest
analytical studies of the U.S. Army the upstream curve of the Ogee shape has the following
equation
Y = 0.724 (x+0.27Hd)1.85
/Hd)0.85
+ 0.126Hd –0.4315(Hd)0.375
(x+ 0.27Hd)0.625
It should be noted here that the upstream curve at the crest should neither be made too
sharp no too broad. To determination downstream profile thee equations used is:
X1.85
= 2(Hd )0.85
y and
Q = C L(Hd)3/2
Where:
Hd = Head of water above the Crest, we can find from spillway equation
Q= discharge as maximum when routed = 1400 m3
/s
C = 2.25
L = 100m
1400= 2.24 100 (Hd)3/2
Hd = 3.4 m which is equal to the maximum depth of water above the crest after routed
From equation above
Y = X1.85
/ 2( Hd)0.85
= X1.85
/ 2 ( 3.4)0.85
= X1.85
/ 5.66
Y = 0.1767 X1,85
……. (1)
Let us now determine the tangent point (T.P.) for the downstream slope of0.75(H) :1 (V)
Hence dy/dx = 1/0.75…..(2)
Differentiating equation (1)
Y = 0.1767 X1.85
dy/dx = 1.85 0.1767 ( X )0.85
dy/dx = 0.327X0.85
1/0.75 = 0.327 X 0.85
……(3)
1 = 0.75 0.327X0.85
X =( 4.077 )1.176
= 5.11
Y = 0.1767(5.11)1.85.
Y = 3.612 and X = 5.11
For vertical upstream face the upstream profile is given by the following equation
Y = 0.724(x + 0.27 Hd) 1.85
/Hd
0.85
+ 0.126 Hd – 0.4316Hd
0.375
( x + 0.27 Hd)0.625
The upstream curve extend up to
X = - 0.27 Hd= 0.27 3.4 = 0.918m
Y = 0.724(x+0.27Hd)1.85
/Hd
0.85
+ 0.126Hd – 0.4316Hd
0.375
(x + 0.27Hd)0.625
Y= 0.724(( x+ 0.27(3.4))1.85
/(3.4)0.85
+ 0.126 3.4 – 0.4316 (3.4)0.375
(x+ 0.27 3.4)0.625

Y = 0.256(x+0.918)1.85
+ o.428– 0.683(x +0.918)0.625
X = 0.96
Y = 0.526(0.96+ 0.918)1.85
+ 0.428 – 0.683 (0.96+ 0.918)0.625
Y = 1.103
The value of the coordinate X = 0.96, y = 1.103m
Stilling basin are used to dissipate the energy of water exiting spillway of a dam. The
purpose is to prevent scouring that occurs when high velocity water enters the downstream
reach of the dam. This scouring can damage the foundation of the dam, leading to overtopping
and also cause severe erosion downstream. The primary method of dissipating energy is to
generate a hydraulic jump to transition flow from supercritical to subcritical. The design are
selected based off of the FROUD NUMBER of the flow and the velocity. The velocity
approach = 12.68 m/s and the Froude Number (F)= V2
/ √ =5 . The stilling basin type
which used in this case is Type II.
9. CONCLUSIONS
A spillway is the overflow portion of the dam over which surplus discharge flows from the
reservoir to the downstream. The most common type of spillway is the Ogee spillway or
Overflow spillway, which guided smoothly over the crest and the profile of the spillway so
that the overflow does not break contact with spillway surface. If this is not assured, a vacuum
may form at the point of separation and cavitations may occur. Inflow discharge from the
reservoir is routed through the spillway and two pipes sluices gated of one-meter diameter
placed at elevation of 520 m and find the maximum discharge is 140 0m3
/sec with
Attenuation of 50 m3
/sec and Reservoir Lag equal to 2 hrs. The method used for routing is
Inflow- Storage – Discharge ( I.S.D.)
The profile of the downstream and upstream are calculated depending on Water
Experiment Station (W.E.S.) belong to the U,S. Army corps of Engineers.
REFERENCES
[1] a.Hussein, H. & Alshami, A. H. 2018. Evaluation Of The Hydrological Behavior In The
Greater Zab River Basin. International Journal of Civil Engineering and Technology,
Volume 9, 240–258.
[2] HUSSEIN, H. A. 2010. Dependable discharges of the upper and middle diyala basins.
Journal of Engineering, 16, 4960-4969.
[3] ICOLD, C. 2018. Flood Evaluation and Dam Safety, Taylor & Francis Group.
[4] KARGPUR, I. 2008. Water Resources Engineering, IIT Karagpur, 2008: Water
Resources Engineering.
[5] KHATSURIA, R. M. 2004. Hydraulics of Spillways and Energy Dissipators, CRC Press.
[6] RAGHUNATH, H. M. 2006. Hydrology : Principles, Analysis And Design, New Age
International (P) Limited.
[7] Sayl, K. N., Afan, H. A., Muhammad, N. S. & Elshafie, A. 2017. Development of a
Spatial Hydrologic Soil Map Using Spectral Reflectance Band Recognition and a
Multiple-Output Artificial Neural Network Model. Hydrol. Earth Syst. Sci. Discuss.,
2017, 1-16.

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