IS 6477 ( Part 2 ) : 198'+
~ qr;rcp
REAFFIRMED
\if~TWll1
CflT
efqcrT
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.
JUL200~
1fT1T 2 atst~ \i11~"
( ~.m ~'fU&fUT
)
Indian Standard FIXING THE CAPACITIES OF RESERVOIRS METHODS
PART 2 DEAD STORAGE
( First Revision)
UDC 6278156
e
MANAK BRAVAN,
SIS 1994
BUREAU OF. INDIAN STANDARDS
9 BAHADUR SHAH ZAPAR MARO, NEW DBLHI 110002
Price Group S
D,cember 1994
Reservoirs Sectional Committee, R VD 4
FOREWORD This Indian Standard ( First Revision) was adopted by the Bureau of Indian Standards, after the draft finalized by the Reservoirs Sectional Committee had been approved by the River Valley Division Council.
By providing extra storage volume in the reservoir for sediment accumulation. in addition to the live storage, it is ensured that the Jive storage, although it contains sediment, will function at full efficiency
for an assigned number of years. This volume of storage (in the fixation of which the minimum draw down level is also a major criterion in case of power projects) is referred to as the dead storage and is equivalent to the volume of sediment expected to be deposited in the reservoir during the designed life of the structure. The distribution pattern of sediments in the entire depth of a reservoir depends on many factors, such as slope of the valley, length of reservoir, constriction in the reservoir, particle size of the suspended sediment and capacity inflow ratio; but the reservoir operation has an important control over other factors. However, a knowledge of this pattern is essential. especially, in developing areas, in order to have an idea about the formation of delta and the recreational spots and the consequent increase in back water levels after the reservoir comes into operation. This standard ( Part 2 ) was first publisbed in 1969. The present revision has been prepared to incorporate the latest knowledge in this field in this revision an additional figure for determining the type of reservoir has been incorporated in addition to modifying Fig. 1 and 2 and some tables. This standard consists of four parts, Part 1 covers general requirements, Part 3 covers live storage and Part 4 covers flood storage.
For the purpose of deciding whether a particular requirement of this standard is complied with. the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2: 1960 Rules for rounding off numerical values (revised )'. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.
IS 5477 ( Part 2) : 1994
Indian Standard FIXING THE CAPACITIES OF RESERVOIRS  METHODS
PART 2 DEAD STORAGE
I (
First Revision)
record covered by the survey will then be equal to the total weigbt of tbe sediment deposited in the reservoir plus that which bas passed out of the reservoir based on the trap efficiency. In this way, reliable records may be readily and economically obtained on longterm basis,
1
S(~OPE
This standard (part 2) covers the methods for computing the sediment yield and for predicting the probable sediment distribution in tbe reservoir below normal (full) reservoir level (F.R.L.).
2
REFEREN(~ES
4.%.2 The density of deposited sediment varies with the
composition of the deposits, location of the deposit within the reservoir, tbe flocculation characteristics of clay content and water, tbe age of deposit, ell". For coarse material (0.0625 mm and above) variation of density with location and age may be unimportant. Nonnallya time and space average density ofdeposited materials applicable for tbe period under study is required for finding tbe overall volume of deposits. For this purpose the trapped sediment for the period under study would have to he classified in different fractions, Most of the sediment escape from getting deposited into the reservoir should be from tbe silt and clay fractions. In some special cases local estimates of densities at points in the reservoir may be required instead of average density over the whole reservoir.
The following Indian Standards are necessary adjuncts to this standard:
IS No.
4410 (Part 6) : 1~83
Title
Glossary of tenus rela ting to river valley projects : Part 6 Reservoirs (first revision) Methods of measurement of suspended sediment ill open channels Guidelines for determination of effects of sedimentation in planning and performance of reservoirs
4890: 1968
121M2: 1987
3 TERMIN()IJ()(;Y
For the purpose of tbis standard, tbe definitious given in IS 4410 ( Part 6 ) : 1983 sball apply.
4.Z.3 The trap efficiency mainly depends upon the
capacityinDow ratio but may vary with location of outlets and reservoir operating procedure. Computation of reservoir trap efficiency may be made using trap efficiency curves, sucb as tbose developed by Brune and by Churchill (see IS 12182 : 1987).
4 MEASlJREMENT OF SEDIMENT YIELDS
4.1 The sediment yield in a reservoir may be estimated by anyone of the following two methods:
a) Sedimentation surveys of reservoirs with similar catchment characteristics, or b) Sediment load measurements of the stream,
4.1.4 The sedimentation rates observed in adjacent
reservoirs also serve as guide while designing dead storage capacity for a new reservoir, the rate of sedimentation observed in similar reservoirs and/or adjacent basin should be suitably modified keeping in view the density of deposited material, trap efficiency and sediment yield from the catchment,
4.1 Reservoir Sedimentation Survey
4.%.1 The sediment yield from the catchment is determined by measuring the accumulated sediment in a reservoir for a known period, by means of echo sounders and other electronic devices since the normal sounding operations give erroneous results in large depths. The vol ume ofsediment accumulated in a reservoir is computed as the difference between the present reservoir l'apal'ity and the original capacity after the completion of the dam, The unit weight of deposit is determined in tbe laboratory trom the representative undisturbed samples or by field determination using a calibrated density probe developed for tbis purpose. The total sediment volume is then converted to dryweight of sediment Oil the basis of average unit weight of deposits. The total sediment yield for the period of
4.3 Sediment Load Measurements
Periodic samples from the stream should be taken at various discharges along with tbe stream gauging observations and tbe suspended sediment concentralion should be measured as detailed in IS 4890 : 1968. A sediment rating curve which is a plot of sedimeut concentration against the discharge is then prepared and is used ill conjunction with stage duration curve (or now duntion) based on uniformly spaced daily or shorter time units 1ata in case of smaller river basins to assess sediment load. For convenience, the correlation between sediment concentration against discharge OIlY
t
IS S477 (Part Z) : 1994
be altered to the relation of sediment load against runoff for calculating sediment yield. Where observed stage/Dow data is available for only shorter periods, these have to be. suitably extended with the help of longer data on rainfall. The sediment discharge rating curves may also be prepared from hydraulic considerations using sediment load formula, that is, modified Einstein's procedure. 4.3.1 The bed load measurement is preferable. However, where it is 110t possible, it may be estimated using analytical methods based 011 sampled data or as a percentage of suspended load (generally ranging from 10 to 20 percent). This should be added to the suspended load to get the total sediment load. b) The minimum drawdown level is fixed a little above the new zeroelevation computed in (a) above. When other considerations like command area elevation, providing extra head for power generation, etc, prevail, this elevation is fixed higher than one of these. S.z Several methods are ill use for predicting sediment distribution in reservoirs for design purposes. Either the empirical area reduction method or the area increment method may be used. S.1.1 Empirical Area ReductionMethod This method is based on tbe analysis of data ofsediment distribution. In this method, reservoirs are classified into four types, namely, (8) gorge, (b) hill, (c) Oood plainfoot bill, and (d) lake, based on the ratio of tbe reservoir capacity to the reservoir depth plotted on a loglog scale (see Fig. 1). Figures 2 and 3 give the sediment distributionarea design curves for each type of these reservoirs. The equation for the design curve used is: ......(1) where Ap · C, m and a nondimensional relative area at relative dis..nee 'p' above the stream bed, and
5 PREDICTIN(; SEDIMENT DISTRIBUTION
5.1 The sediment entering into a storage reservoir gets deposited progressively with the passage of time and thereby reduces the dead as well as live storage capacity of the reservoir, This causes the bed level near the dam to rise and the raised bed level is termed as new zero elevation. It is, tberefore, necessary to assess the revised areas and capacities at various reservoir elevations that would be available ill future and could be used ill simulation studies to test the reservoir performance and also tbe new zeroelevation. The following procedure may be adopted for fixing the dead storage level and sill levels of the outlets: a) The distribution of the estimated sediment load for the feasible service time of the reservoir should be carried out and new zeroelevations sbould be determined, and
n fixed depending on the type of reservoir. 5.1.1.1 These curves are used to work out the probable
sediment deposition in the reservoir at different depths. This method is more reliable than the area increment method. An example of the usage of this method is given in Annex A.
=nondimensional constants which have been
NoI.:
m= x
y
S
!
~
r....J
I~
l/l
........ 
I.'
V
~
V
I
x
:~
~
.r,
7
~
m io ro1.5.oT fFlE:1 v(GOA::
II
~
L~
~~
V
L......
m· 1.5to2.51YPE III (Hlll)
....... ~
'~
I
". I ~m.
L....o
II
~
II"""
II
/"
~..
......
~
~
2 5to3.5 TVFtEIi (flO D[ I ~N FOOT HILL ,.., m. 3.5to4.5 TYPE I (lAKE)
IIIII~
I
~
1
~
_I""
I .....
~1~
t.
III
~
!/lI' ~~ ~
~~~
~
~~ "..I'~
l..oIII'"
I~~ 1..00~
~~
~
~
....
CAPACln(C)
FIG. 1 C~IFICA11ON OF REsERVOJR pFYTH VERSUSCAPACTY RaAnONSHIP
2
IS !477 (Part %) : 1994
!.2.2 Area Increment Method
2.8 2.8 2.4 ttt......IV
Ap;: 1.486P 0.25
( 1 _ p) 1.34_
III Ap. 16.967p 1.15 (1p) 2.32 2.2 t  .......4~ II Ap = 2.487 P 0.57 (1 _ p) 0.41
2.0
I Ap = 5.074 P 1.85 (1 _ p) 0.36
!
L5 ex:
1.8 1.6
1.4
~
IX
c
The basic assumption in this method is that tbe sediment deposition in tbe reservoir may be approximated by reducing the reservoir area at each reservoir elevation by a fixed amount. Successive approximations are made. Average end area (or prismoidal formula) is used to compute the reservoir capacities on the basis of reduced surface areas until tbe total reservoir capacity below the full reservoir level is the same as the predetermined capacity obtained by subtracting the sediment accumulation with time from tbe original capacity. The basic equation in this method is: VI · A o (H  ho) + Vo ········ (2) where
1.2
1.0
VI 0.8
0.6 0.4
the sediment volume to be distributed in the reservoir in hectare metres, tbe area correction factor in hectares which is original reservoir area at the new zero elevation of the reservoir, tbe reservoir depth below full reservoir level (F.R.L.) in metres, tbe depth in metres to which the reservoir is completely filled with sediment, and
Ao 
,
H·
ho ·
0.0 ....'..I""'.....&.........................._~~~ o 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
RELATIve DEPTH ~ ,(MEASURED FROM BOTTOM)
FlO. 2 SED~ DISTRIBUTION  AREA DESIGN CURVES
(BT
ON REsERVOIR STORAGE CuRVES )
the sediment volume below new zero elevation in hectare metres, 5.1.2.1 In other words, the equation mathematically expresses that the total sediment volume Vs consists of two parts, namely, (a) tbe protion which is uniformly distributed vertically over the height H  110 with an
Vo ·
'00
TYPE 1""\
TYPE 11;\ ~
/
/
/"
r\ V
V
~
V
~
/"
~
r'
/
~~
J
j
VI
~
·
120
,L
o
FIG.
II
/
I
/ I
~/
/ v:
/
~
~
Y \V
/
/ V
~
,
/
/
/
./
~
K' \
V
t
LTYPE III
~
TYPE I'
~
20
40
60
80
100
PERCENT SEDIMENT DEPOSITED
3
TYPE CuRVES OF PERCENTSmlMen' DEPOSITED V,.ASUS PER(~ENT REsERVOIR DEPlH BASFD ON Acrue, Oa:uRRENCES
·
3
IS 5477 ( Part 1 ) : 1994
area equal to Ao and (b) the portion Vo below the new
zero elevation of the reservoir.
S.1.1.1 An exampleof the usageof this method isgiven in Annex B.
NOTE lbe applicability of this metbod decreases with . . . sediment deposit . . . If the the I nerease I n the rano of reservoi r capacity hundred years sediment, accumulation exceeds 15 percent of the original capacity, a more exact method should
be applied.
S· V (pH)·
H.
A (pH) ·
for a particular reservoirand itsanticipated sediment storage, total sediment in thereservoir in beda~ metres, reservoir capacity at a given elevation in hectare metres, the total depth ofreservoir for nonnal water surface in metres, and
S.l.J Moody:~ Metlwd to Find New Zero Elevation This method is used to determine the newzero elevation 0, directly without trial and error process. Two parametersf (p) and f' (P) as explained below are made use of:
1(P). 1  V(p~ a (P)
....(3) ....(4)
f' (P). S where f (P) ·
V (pH) HA(pH)
a function of the relative depth of reservoir for one of tbe four types of theoretical design curves, V (p). relative volume at a given elevation, relative area at a given elevation, a function of tbe relative depth of reservoir
(, (P).
f' V}) 
reservoir area at a given eleva tion itt hectares. S.1.3.1 Table 1 gives the values of the functionj' (p) for tbe four types ofreservoirs (see 5.2.1) and Fig. 4 sbows the plotting of !Cp) against relative reservoir depth, P, for the four types of reservoirs of tbe empirical area method (see 5.1.1) and also for the area increment method (see 5.1.1). S.1.J.l To determine the new zero eleva tion, f (P) should equal!' (p). This is done graphically by plotting the values of I' (P) and superposing this over the relevant ICp) curve. The intersection gives the relative deptb of (Po) reservoir at new zero elevation after sedimentation. New zeroelevation may be computed by adding the product Po H to tbe original stream bed elevation. After arriving at the new zero elevation, either empirical area method (see S.1.1) or the area increment method (see S.%.1) is used. 5.1.3.3 An example to lind out the new zero eleva lion is given in Annex C.
1 0000
..
I I
5000
\ rl'VPE I
100·0
500
,
\
'" ~
,
....
100
~
"
,
~~
~Tl PEII
" "
,a
~ ,~
/
'
~
~
....
I~ 10......
I
~ :rVPE
I
0·1
~05
IV
'" J
I
....... 1
1 .........
11oo.::
r
.........
.
~
1
~
V

""'lIIIIIiiII ~ ..........
,.. .;::: ~ """ ~~
'0..
~~
'
. VPE III
, ARE A INC ~EME~T
I
..
. ..
"'
~"

~
001
I
0'
02
~
10
.""v
&3
RELATIVE 'DEPTH (p)
~4
()&
06
07
08
0'
FIG.
4 CURVES TO DETERMlW THE DEPTH OF SFDIMENT IN mE
4
REsERVOIR
IS 5477 ( Part Z ) : J9,..
llIble 1 Values of the FUDdioD/ (P) Cor the Four 1)'pes o( Reservoirs
(Clause 5.2.3.1)
p
1)pe
II
III
(4)
IV
(5)
(1)
(2)
(3)
0 0.01 0.02 0.05 0.1 0.15 0.2 0.25. 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 iJ.9 0.95 0.98 0.99
1.0 996.7
10.568 3.758 2.233 1.495 1.169 0.9706 0.8299 0.7212 0.6323 0.5565 0.4900 0.4303 0.376 R 0.3253 0.2780 0.2333 0.1907 0.1500
O.IIO?
12.03
0.2023
277.5 51.49 14.53 6.971 4.145 2.766 1.900
1.495 1.109
5.544 2.057 1.013 0.682 1 0.5180 0.4178 0.348 6 0.296 8 0.2333 0.221 2 0.1917 0.168 7 0.1422 0.120 7
0.100 8
O.23Q 0 0.2796 0.2911 0.2932 0.2878 0.278 1 0.2556 0.251 8
0.236 5
0.9076 0.726 7 0.5860 0.4732 0.3805 0.3026 0.2359 0.1777 0.1202 0.080 11 0.05830 0.01494 0.007411 0.00
O.21Q7
0.2010 0.1826
0.1637 0.1443 0.1245 0.1044 0.083 Q7 0.06330
0.04239
0.08204 0.064 28 0.04731 0.031 OJ 0.01527 0.006057 0.003020 0.00
0.07276 0.02698 0.01425
0.007 109
0.021 23 0.008 534 0.002470
O.(X}
0.00
5
IS 5477 (Part 2) : 1994
ANNEXA (Clause 5.2.1.1 )
EMPIRICAL AREA REDUCTION MEmOD
AI DA1:4
AI.I The data given are as follows:
a) Origiual capacity curve, b) Annual sediment inOow 37.00bectare metres, c) Period of sedimentation 100 years (total sediment for the period 3 700 hectare metres), d) Bed elevation 1 265.00 Ill, e) Normal water surface elevation 1 302.50 m,
=
=
=
tions on a loglog paper. A line is drawn through tbe plotted points. Reciprocal of the slope of the line will give the value of m by which reservoir type is selected (see Fig. 1). in Ibis case, it is Type II (see Fig. 5). The plot may sometimes indicate a curve baving different slopes in different parts. III sucb cases, tbe reservoir may be classified into the type ill whicb major portion of the sediment would deposit. AZ.z Ap in col 5 is obtained from the relevant curve of Fig. 2. Zero elevation is assumed wbich in this case is 1 277.00 0). Surface area corresponding to this elevation is 121.40 bectares. Ap at this elevation is 1.10 (see Fig. 2). Find out K, tbe ra tio of o~iginal area a t assumed new zero elevation ( col 2 ) to the corresponding A p value ( col 5 ).
and
f) Spillway crest
=
= 1 3025001.
A2 PR()CEDlrRE
AZ.l Referring to Table 2, the data given itl coli, 2 and 3 are from original area capacity curves. The relative depth ratio lor different levels to the total depth from spillwa y crest (or FRL) to tbe stream bed is entered ill ("01 4. Reservoir depth is plotted as ordinate against reservoir capacity as abscissa It different eleva
K.
1~.li:  110.36
......(5)
AZ.l.l Column 6 is K multiplied A p values at each succeeding increment, which is sediment area.
100.0 80.0 70.0
60.0
~.
', 
I
.JI
''
,_. '   f   
_.
w
en
30.0
20.0
,
_.
~
~~
w :i
~
~
~.
~~
f
._~~
..
',

~,
I~
(J)
,IE
10.0

8.0 6.0 4.0 3.0 2.0
~
w w a:
~
cr:
~~
.»:

~
~v
~
~~
~lI"'"
I
. .....
Y=3,5
~
I
y =3.5
,~
x =10.5
.......
L
~
~
~t/
~ ,.,
V""""
~~
x = 10,5
/'


~
~
m=15
10.5
:; 3.0
t
0
RESERVOIR CAPACITY IN HECTARE METRES
FIG.
S
CURVE 10 DETBMINE
VALUE OF 'm'
6
IS 5477 ( Pal11 ) : 1994
Table Z Sedlmeat Deposition Computation by Empirical Area Reduction Method (Clause A2.1 )
Elevation m
Original
Relative Depth
Ap
(lype III)
Sediment
AcculDu
Area
Hectare
Capacity
Area
\blume
lated Sediment Volume
Hectare
Reylsed Area
Revised
C.apaclty
Hectare Metres
(3)
19330.00 16460.00 11 960.00 8480.00 S 889.00 4039.00 2713.0()' 1 758.00 1079.00 616.70 3OJ.30 123.30 30.83 0 (4) 1.00 0.96 0.88 0.80 0.72 (5) 0.000 0.65 0.97 1.13 1.22 1.26 1.28 1.25 1.19
Hectare
(6) 0.00 71.73 107.05 124.70 134.64 139.05 141.26 137.95 131.33 121.40 80.93 40.47 20.23 0 0
Hectare Metres
(7) 0.0 53.8 268.17 347.63 389.01 410.54 420.47 418.82 403.92 379.10 308.4 185.0 92.47 30.83 3708.16
Hectares
(9) 1 882.00 1 587.27 1 187.95 866.8 573.46 36'.75 222.94 125.05 50.67
Hectare
Metres
(8) 3708.16 3654.36 3386.19 3036.54 2649.55 2239.01 1 818.54 1 399.72 995.8 616.7 308.3 123.3 30.83 0
Metres
(10)
15621.84
(1) 1 302.5 1 301.0 1 298.0 1 295.0 1292.0 1289.0 1 286.0 1283.0
(2) 1882.00 165Q.OO 1 295.00 991.50 700.10 505.80 364.20 263.00 182.10 121.40 80.93 40.47 20.23 0
12805.64 8 173.81 5441.44 3239.45 17Q9.9Q 894.46 358.28 83.20 0 0 0 0 0
0.64
0.56 0.48 0.40 0.32 0.24 0.16 0.08 0
1280.0
1 277.0 1274.0 1 271.0 1 268.0 1 265.0
0
0 0 0 0
A·2.1.1 CoIunm 7 is the inaement of sediment volume computed by the average end area (onnula, that is equal to:
A·Z.2.3 Sum of col 7 gives the sediment volume of 3 708.16 which is nearly equal to the computed sediment volume of 3 700.00 hectare metres. Hence, the zero elevation assumed is correct If the values do not tally, further trials have to be made till tbe sediment values differ by not more than one percent. Column 8 gives the sediment accumulation volume in hectare metres. Revised areas in 001 9 are obtained by subtracting values in col 6 from col 2. Revised capacity in col 10 is obtained by subtncting values in 0018 from col 3.
2(Al +A2)· V
where
h
...... (6)
hAllndA2 ·
the height of the segment, the areas at the end of the segment, and the volume of the segment
v.
7
IS 5477 ( Part 2 ) : 1994
ANNEXB ( Clause 5.2.2.2)
AREAINCREMENTMETHOD
B1 DATA
81.1 Data given are the same as in AI.I.
B1 PROCEDURE
8%.1 Table 3.gives typical calculations of an example for working out the revised capacity. The procedure is IS given below: Step 1  Assume lao and corresponding to this ho read Ao IDd Vo from the original area capacity curve. Substitute the values in the basic equation V s  Ao (H  ha) + Vo · In this case Ito  12.0 metres, A o  121.40 hectares, Vo  616.70 hectare metres and Vs · 3 712.4 hectare metres which is nearly equal to the 3 700.00 hectare metres of the total sediment load within one percent, Step 2  Compute tbe cumulative volume of sedi
ment (col 5) by applying the area correction factorwhich is in col 4 ofTlble 2 andget the volume by average end area formula. Computed volume should then be within one percent of the predetermined sediment value. Step 3  Revised areas in col 6 are obtained by reducing the original area at each increment in col 2 by the Irea correction factor in col 4. Step 4  The revised capacity is determined by reducing the original capacity at each increment by the sediment accumulation (col 7 = col 3  col 5). BZ.Z The result obtained should be compared with actual resurvey curve. After verifying, the probable sediment deposition in the reservoir at different depths may be worked out for the sediment volume to be distnbuted in the period equal to the life of the reservoir.
18ble 3 Area Increment Method (Clause 82.1)
Elevation
lit
Original Area
Original Capacity
S~~lment
Revised
,a,
Vo,ume
Area
Capacity
Hectares
( 1) 1 302.5 (2) 1882.00
Hectare
Hectares
(4)
121.40 121.40 121.40 121.40 121.40 121.40 121.40 121.40 121.40 121.40 SO.Q3 40.47
~ectare
Hectares
Hectare
Metres (7) 1 5617.60 1292Q.70 87Q3.Q{) 5678.1 3451.3 1 <)85.5
Metres
(3)
Metres
(5) 3712.40 3530.3 3 166.10 2801.90 2437.7 2073.5 17CR.30 (6) 176.60
19330.00 16460.00
11 960.00
1 301.0
1 298.0
1659.00
1 295.00
1 537.60
1 173.60 870.10 586.70 384.40
1 295.0
991.50
708.10
8480.00 5889.00 4039.00
1 292.0 1 289.0
1286.0
505.80
364.20 263.00
182.10 121.40
2 713.00
1 758.00
1 079.00
242.80
141.40 60.70
1 003.7
412.QO <)8.10
J 283.0
1 280.0
1 277.0
1 345.10
980.90
616.70
~.30
616.70
0
o
0 0
1 274.0
1 271.0 1 268.0
80.93
40.47 20.23
308.30 123.30
30.83
0 0
0
123.30
30.83
20.23
0
0
1 265.0
0
0
o
8
0
0
IS 5477 (Part Z ) : 1994
ANNEXC ( Clause 5.2.3.3 )
MOODY'S METHOD TO FIND NEW ZERO ELEVATION
ci
DATA
Reservoir Bottom elevation Total depth (H) Total sediment in reservoir (5) Type II,
el.l The data given are as follows:
a) b) c) d)
= 1 265.00 m, = 37.5 m, and = 3 700 hectare
metres,
division of each depth corresponding to the elevations given in col 1 by the total depth (H). Col U11111 5 is worked out from the known original area versus depth curve and it is the product of the area at a specified elevation and the total depth. Column 4 is obtained by subtracting col 3 from '5'. Column 6 is obtained from Fig. 4, and column 7 is worked out by equation (4).
el.% Referring to Table 4, the data given in col 1 and 3 are taken from tbe known original capacity versus deptb curve. COIUID11 2 is worked out as the result of
Cl.2.1 In Fig. 6, f(P) and I' (P) curves are drawn against relative reservoir depth (P) and their interseclion corresponds to Po of 0.32. Therefore, PcII 12.00 m and the new zero elevation is 1 265oCx) + 12.00 1 277.00 Ill.
:I:
Table 4 Moody's Method for Determination of New Zero Elevation ( Clause Cl.2 )
Elevation m
p
V (pm
S  VCpH)
HA (PH)
l(p) from Fig. 4
I'
(p) from
Eq4
Hectare Metres
(1) (2) 0.08 0.16 0.24 0.32 0.40 0.48 0.56
(3) 30.83
Hectare
Metres
(4) 3669
Hectare Metres
(5) 759
1 518
(6) 1.80
1.22
(7)
1 268.00
1 271.00
1 274.00
1 277.00
4.83
2.36
123.30
308.30 616.70 1 079.00 1 758.00 2 713.00
3577
3392 3083 2621 1942 987
3035 4553 6829 9863
0.85 0.68
O~56
1.12
0.68 0.38
1280.00
1 283.00
0.46 0.39
0.20 0.07
1 286.00
13650
9
IS 5477 ( Part Z ) : 1994
2.0
1.0
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~
,,
f' (p).
SV(pH)
HA(pH)
I
~
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0.5
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PoS! 0.32
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=:
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0.2
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0.32 X
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=:
12.00M
I ·1 ElEVAllON OF SEDIMENT DEPOSITED AT DAM =1277.00M
0.1
o
0.1
0.2
0.3
0.4
0.5
0.6
0.7
RElATIVE DEPTH (p)
FIG.
6 EXAMPLE FOR DIRECT DETERMINATION
OF
NEW
ZERO ELEVATION
10
BlII'eaa of 1....&. Standards
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Reyiew'of Indian Standards
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This Indian Standard has been developed from Doc No. RVD 4 (136)
AmeDdmeDts IUBed SiDce Publlc.do.
Amend No.
Date of Issue
Text AU,., . c,\i
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