Scientific Bulletin of Politehnica University of Timișoara [616189]

Scientific Bulletin of Politehnica University of Timișoara

Transactions on HYDROTECHNICS

Volume 64(78), Issue 1, 2019

1 Politehnica University Timisoara, Faculty of Civil Engineering, Department of Hydrotechnical Engineering, Spiru Haret
Street No. 1/A, 300022, Timisoara, Romania, [anonimizat] ; [anonimizat]
Selection between different locations for dam construction
considering reservoir capacity

Gîrbaciu Cristian -Adrian1 Gî rbaciu Irina Alina1

Abstract: Choosing the right location for a dam
construction is one of the most important factors for a
complex water management arrangement. In order to
make a good choose for the location it’s imperative to
take into consideration water demands for the present
and for the future. Runoff flow, direct rainfall,
catchment characteristics, c limatic data, site geology
topography, tectonic outlines , evaporation are olso
important factors.
Keywords: Reservoir, dam, location .

1. INTRODUCTION

In the last hydrological years many parts of the
word was subjected to a drastic drought condition,
which caused several problems for the region
population, as the available water resources are not
satisfying water demands for humans and livestock
consumption, agriculture, etc.
Therefore, the water resources management
became one of the most important targets of the
World’s Government s and in order to satisfy water
management of the area, investigations and studies
started for water harvesting through the construction
of different sizes of reservoirs everywh ere possible,
that aims in collection of excess rainfall water and in
conservation of the eroded soil, in addition to ground
water recharge.
Considering that, the main purpose of the dam
construction in that area is to collect the biggest
amount of water, it is recommended to choose the
location where result the biggest designed reservoir
volume .
In order to make a good selection is
recommended to compare the locations considering
all important factors :
– Integrated complex water management factors
(development of the area for the next 25 year) – Purpose of the water management scheme
(irrigation, water supply, agreement, etc.)
– Satisfying water demands for the present and for the
future.

2. STUDY CASE

Figure 1: Catchment Areas on Google Image[ 2]

Table 1: Proposed Dam’s Locations
Name Catchment Area
(km2) Longest Path
(km)
Location 1 188.91 25.78
Location 2 179.44 23.38
Location 3 162.59 20.76
Location 4 159.06 19.54

Catchment characteristics
The flow delineation at the catchment area is
related to topographic maps of the largest available
scale up to the proposed hydraulic structure, as shown
in Figure 1. [3]

Figure 2: Catchment Area Flow Delineation [2]

Runoff Estimation
The runoff discharge is used to optimize the
reservoir volume, and for yield management
There isn't runoff discharge data available at the
dam site. A monthly rainfall runoff discharge
estimation for the proposed dam would be calculated
based on SCS (Soil Conservation Service); this
method depends on the average daily rainfalls, soil
used, and soil cover complex and land slope for the
catchments area has been used to generate the
monthly and then the annual runoff volume.
The runoff curve number CN is a function of land
use, antecedent soil moisture, and other factors
affecting runoff and retention in a watershed and its
values are presented in Table 1 below.
Table 2: Runoff Curve Numbers
Land Use Description Hydrology Soil Group
Cultivated land :
Without conservation treatment
With conservation treatment A B C D

72
62
81
71
88
78
91
81
Pasture or range land:
Poor Cover
Good Cover
68
39
79
61
86
74
89
80
Meadow:
Good Condition
30
58
71
78
Woods or forest land:
Thin stand, poor cover, non-much
Good Cover
45
25
66
55
77
70
83
77
Farmsteads 59 74 82 86
Roads 74 84 90 92 The curve number is a dimensionless number
defined such that 0 ≤ CN ≤ 100. For impervious and
water surface CN=100, for natural surface CN ≤ 100
Figure 2 presents the land use description for
catchment area and Table 2 presents the estimated
area and CN according to the plants .

Figure 3: Land Use Description [2]

Table 3: Calculated CN and Ia for Catchment Area
Land use Area
(Km2) % CN
Woods – vegetations cover
combination (orchard of tree
farm) / Good / Soil Type B 48.16 25.5% 58
Pasture, vegetations, or range –
continuous forage for grazing/
Fair / Soil Type B 103.52 54.8% 69
Brush – weed – grass mixture with
brush the major element / Poor /
Soil Type B 23.67 12.5% 67
Cultivated agricultural lands
/Row crops – Straight row/ Poor/
Soil Type B 13.44 7.1% 81
Urban areas / Open spaces (
lawns, parks, golf courses,
cemeteries) / Fair condition/ Soil
Type B 0.12 0.1% 69

Reservoir Management and Potential Yield
The purpose of reservoir management is to
control operations to obtain the maximum possible
economic benefit from reservoir based on available
information about rainfall, runoff, and region needs.
Reservoir management is a method to optimize
the water storage by producing a proper quantity of
water released from reservoir.
Table 4, Table 5, Table 6, Table 7 shows a summary
of potential yield for different dam capacities. The
best Capacity -Yield option for the dams, in
percen tage of yield over the capacity as indicated in
Figure 4, Figure 5, Figure 6, Figure 7.

Table 4: Potential Yield for location (1).
Capacity
(m3) Yield
(m3/Year) Yield/Capacity
(%)
35,000,000 15,656,250 44.73
33,000,000 15,406,250 46.69
30,000,000 15,062,500 50.21
27,000,000 14,375,000 53.24
25,000,000 13,875,000 55.50
23,000,000 13,468,750 58.56
20,000,000 12,656,250 63.28
17,000,000 11,925,000 70.15
15,000,000 11,281,250 75.21
13,000,000 10,542,500 81.10
10,000,000 8,823,375 88.23
9,000,000 8,096,875 89.97
8,000,000 7,276,875 90.96
7,000,000 6,295,000 89.93
6,000,000 5,310,000 88.50
5,000,000 4,321,875 86.44
3,000,000 2,290,625 76.35
2,000,000 1,303,125 65.16
1,000,000 386,875 38.69

Table 5: Potential Yield for location (2)
Capacity
(m3) Yield
(m3/Year) Yield/Capacity
(%)
20,000,000 12,537,500 62.69
17,000,000 11,850,000 69.71
15,000,000 11,175,000 74.50
13,000,000 10,406,250 80.05
11,000,000 9,556,250 86.88
10,000,000 8,893,750 88.94
9,000,000 8,156,250 90.63
8,000,000 7,437,500 92.97
7,000,000 6,487,500 92.68
5,000,000 4,450,000 89.00
3,000,000 2,381,250 79.38
1,000,000 428,125 42.81

Table 6: Potential Yield for location ( 3)
Capacity
(m3) Yield
(m3/Year) Yield/Capacity
(%)
12,000,000 9,081,250 75.68%
11,000,000 8,587,500 78.07%
10,000,000 8,068,750 80.69%
9,000,000 7,456,250 82.85%
8,000,000 6,746,125 84.33%
7,000,000 6,005,313 85.79%
6,500,000 5,590,625 86.01%
6,000,000 5,171,388 86.19%
5,000,000 4,250,000 85.00%
3,000,000 2,400,000 80.00%
1,000,000 461,875 46.19%
Table 7: Potential Yield for location ( 4)
Capacity
(m3) Yield
(m3/Year) Yield/Capacity
(%)
12,000,000 8,893,750 74.11%
11,000,000 8,396,875 76.34%
10,000,000 7,918,750 79.19%
9,000,000 7,264,688 80.72%
8,000,000 6,625,000 82.81%
7,000,000 5,898,813 84.27%
6,500,000 5,535,625 85.16%
6,000,000 5,128,969 85.48%
5,500,000 4,712,469 85.68%
5,000,000 4,294,594 85.89%
4,000,000 3,418,750 85.47%
3,000,000 2,429,500 80.98%
1,000,000 473,125 47.31%

Figure 4: Reservoir Capacity vs. Yield for location (1)

Figure 5: Reservoir Capacity vs. Yield for location ( 2) Reservoir Capacity vs. Yield
0%10%20%30%40%50%60%70%80%90%100%
0 5 10 15 20 25 30 35 40
Reservoir Capacity MCMYield %8.0 MCM 90.96%
Reservoir Capacity vs. Yield
0%10%20%30%40%50%60%70%80%90%100%
0 5 10 15 20
Reservoir Capacity MCMYield %8.0 MCM 92.97%

Figure 6: Reservoir Capacity vs. Yield for location ( 3)

Figure 7: Reservoir Capacity vs. Yield for location ( 4)

3. RESULTS AND CONCLUSIONS

Four options are studied in order to select the
proper location of dam considering reservoir volume,
yield, dam height, dam length, .
The inflow runoff is predicted for all options and
2-yr runoff volume varies from 10- 13 MCM for all
proposed dam locations. The flood peak flow is
predicted for different return periods for each dam
location and the difference between predicted values
is about 14m3/sec for 200 -yr return period and
13.9m3/sec for 1000- yr return period.
Reservoir management plan mainly depends on
the dam s ite properties area- capacity relationship.
Reservoir volumes for dams' loca tion are presented as
follows;
-for locations 1 and 2 the volume is 8.0 MCM,
-for locations 3 it is 6.5 MCM,
-for location 4 it is 6.0MCM.

The area capacity curves for each location is
drawn and the spillway height is derived as well. The
approximate dam axis length for each location is
listed as follows:
Earthfill dam with impervious clay core:
Location (1) → 223.5m at 25.92m Spillway Crest
Height
Location (2) → 640.5m at 21.33m Spillway Crest
Height
Location (3) → 637.7m at 20.87m Spillway Crest
Height
Location (4) → 737.7m at 19.18m Spillway Crest
Height
Comparisons between dams' locations and
options are performed in order to find the proper
location based on reserv oir capacity and average
annual yield volume as presented in Figure 8 .

Figure 8: Comparison between Proposed Dams Locations
versus Reservoir Volume & Average Annual Yield.

As shown in Figure 8 , dam location (1) and dam
location (2) have the largest dam's capacities respect
to other proposed locations and location (2) gives
slightly higher yield than location (1).

5. RECOMMENDATIONS

In order to select a proper location for the dam
between the first two locations , the cost benefit
analyses or discounted net income is one of the most
important factors. The cost benefit analyses shooed
take in consideration all the important factors for the
entire water management scheme from the dam to the
final user.

REFERENCES

[1] Applied Hydrology, Ven Te Chow, McGraw -Hill Book Co.,
International Edition, 1988.
[2] Preliminary Study Report – Kany Sard Dam
[3] http://age -web.age.uiuc.edu/classes/abe455/CN Table from
EFH (2 -3).pdf
Reservoir Capacity vs. Yield
40%45%50%55%60%65%70%75%80%85%90%
0 2 4 6 8 10 12 14
Reservoir Capacity MCMYield %6.5 MCM 86.01%
Reservoir Capacity vs. Yield
40%45%50%55%60%65%70%75%80%85%90%
0 2 4 6 8 10 12 14
Reservoir Capacity MCMYield % 6.0 MCM 85.48% Reservoir Volume VS Locations &
Average Annual Yield Volume VS Locations
0123456789Volume (MCM)Reservoir Volume (MCM)
Average Annual Yield Volume (MCM/Year)
Location (1) Location (2) Location (3) Location (4)