Prof.T.Shivaji Rao,
Director, Centre for Environmental Studies, GITAM, Visakhapatnam
Browse all the 7(0 to 6) websites on Polavaram dam
profshivajirao.googlepages.com/seemakugodavarijalalesaranyam (Telugu Article)
(See other chapters 1 to 8 of the above website)
http://www.sakti.in/godavaribasin/indira-ICad.htm [Details of Polavaram Project]
http://cgwb.gov.in/watershed/GODAVARI.jpg (detailed sub-basin maps)
http://cgwb.gov.in/watershed/cdgodavari.html (detailed sub-basin areas)
http://en.wikipedia.org/wiki/Image:India_annual_rainfall_map_en.svg [Rainfall map,India]
For more details on Dam safety,see:
includes standards followed by China,asian coutries and ICOLD
[ Public Hearing]http://www.hinduonnet.com/thehindu/thscrip/print.pl?file=2005101113940300.htm&date=2005/10/11/&prd=th&
PART-01
First see web site : http://www.sandrp.in/drp/feb-Mar2006.pdf
HUNDREDS OF DAM FAILURES EVEN IN USA AND CHINA DUE TO MANY FAULTS
According to the American Dam safety officers, out of 75,000 dams in USA, several hundreds of them are disasters waiting in the wings. Far too many dams are facing the risks of failure, threatening lakhs of human lives and billions of dollars worth of properties. Out of many old dams about 50-year old ones account for 85% of the dams by 2020 and most of these dams were built without adequate spillway capacities to release flood waters during torrential rains, causing extreme floods that overtop the dams ,resulting in their collapse. Even in China the Water resources Minister, Zing Ping recently stated that about 68 dams collapse every year. During the last 50 years about 3500 out of about 85,000 dams collapsed, placing dam collapse rate at 4%.In Guangdong province 50% of the dams amounting to 3685 are classified as Dangerous Reservoirs.Many cities are under threats of dam collapses and among them are 25.4% of cities with 179 dangerous reservoirs, and16.7% of county towns with 285 reservoirs. In addition to 146 million people, about 9 million Hectares of cultivated fields also face serious threat. In fact in 1975,the collapse of Banquiao Dam caused death of 1,00,000 people due to drowning and 1,40,000 people due to the repercussions of the floods like epidemics and food shortage.
In western countries where scientific opinion is highly respected,knowledge is treated as power to promote the welfare of the people.But in poor countries like India since considerations other than merit are given utmost importance in decision-making,it is the power that is treated as knowledge .Hence the business lobby influences the senior administrative officials who in turn influence the decisions to be taken by the politicians and hence the scientific and engineering considerations even in the planning,design and execution of major Irrigation projects get very low weightage.Even Epert committees are constituted by choosing mostly YES men and sometimes people whose fields of specialization fall out side the subjects under consideration.The Constitution of Boards and Technical committees of the pollution control Boards and Ministries of Environment at both the state and central levels are glaring examples of how the officials virtually make the functioning of the Environmental laws most ineffective in public interest and more useful to the vested interests whose business thrives by making maximum profits by avoiding installation of pollution control measures that help in keeping under check the levels of poisoning of man and nature.
In the case of Polavaram Dam project of Andhra Pradesh,I have been appointed as an Expert committee Member for Environmental Appraisal of the project during 1980’s and I have been studying the problem in depth for over 25 years .During these long years,I had discussions with eminent Engineering experts and most of them have expressed misgivings about the improper design of the spillway and the safety of the Dam and the environment. Since my studies clearly show that it is a prescription for Disaster, I felt it my duty to create awareness among the Environmentalists and the concerned people who can advise the Government to consider the need to convert the Polavaram Dam into a Barrage to serve water needs for drinking and irrigation and to use alternate methods for generating the power as contemplated by the project and thereby provide safety to the dam and to lakhs of people living downstream of the dam.
EXTREME FLOODS IN GODAVARI RIVER (In chronological order)
S.No.
|
Date of peak flood
|
Peak flood discharge
|
Synoptic system
| |
Thousand cumecs
|
Lakh cusecs
| |||
1.
|
16-8-1953
|
81.00
|
28
|
D (Depression)
|
2.
|
16-8-1962
|
37.1
|
13
|
L (Low pressure )
|
3.
|
22-9-1962
|
49.8
|
17.8
|
D
|
4.
|
26.9.1964
|
25.3
|
9.0
|
D
|
5.
|
8-9-1966
|
62.6
|
22.0
|
L
|
6.
|
29-7-1967
|
26.9
|
9.5
|
L
|
7.
|
11-9-1969
|
25.2
|
8.5
|
D
|
8.
|
23-9-1969
|
35.7
|
12.5
|
D
|
9.
|
23-8-1970
|
56.7
|
20.0
|
D
|
10.
|
8-7-1972
|
21.9
|
7.7
|
D
|
11.
|
12-7-1973
|
19.9
|
7.0
|
D
|
12.
|
17-7-1975
|
27.0
|
9.5
|
L
|
13.
|
23-7-1976
|
54.4
|
20.0
|
L
|
14.
|
26-8-1977
|
23.3
|
8.0
|
D
|
15.
|
18-8-1978
|
40.5
|
14.0
|
D
|
16.
|
7-8-1979
|
30.6
|
11.0
|
L
|
17.
|
13-8-1981
|
42.2
|
15.0
|
D
|
18.
|
16-8-1983
|
57.9
|
20.0
|
L
|
19.
|
16-8-1986
|
99.3
|
36.0
|
D
|
20.
|
4-10-1988
|
36.7
|
13.0
|
D
|
21.
|
27.7.1989
|
43.1
|
15.0
|
D
|
22.
|
4-9-1989
|
27.9
|
10.0
|
L
|
23.
|
2-9-1990
|
61.0
|
22.0
|
L
|
24.
|
20-9-2005
|
62.0
|
22.0
|
D
|
25 7-8-2006 81.5 28.5 L
NOTE: The data in the above table on extreme historical flood events in River Godavari must be considered to determine the magnitude of return flood flows as per the International norms followed as indicated in the other websites on this subject.
ENGINEERS ERRORS
The govt was well aware that the highest level that Godavari had ever touched was in 1986 when the water discharge was as high as 35 lakh cusecs. In August this year, when the discharge was 28 lakh cusecs, even without the Polavaram project in place, 322 villages were flooded. On the other hand, the govt has all along been planning for the rehabilitation of people on the premise that only 276 villages would get inundated. Is there some serious flaw in the computation of the levels and the area of submergence?
MODEL EXAMPLE ON DAM BREAK ANALYSIS, RISK ASSESSMENT AND ENVIRONMENTAL IMPACTS IN CASE OF HORSETOOTH RESERVOIR, USA
(to be followed by the Indian engineers concerned with Polavaram and other dams)
FLOODING PROBLEM:
The dams that form Horsetooth Reservoir were modified in 1988-1989 by raising the crests approximately 3 feet to accommodate storage of the Probable Maximum Flood. Therefore, no significant flood issues exist presently at the Horsetooth Reservoir Dams. The ability of the reservoir to handle flood inflows was demonstrated by events during the July 28, 1997, flash flood that occurred in the Spring Creek drainage in the southwestern corner of Fort Collins. A localized storm produced as much as 10 inches of rain in less than 5 hours. Unfortunately, a majority of the rain and resulting flood runoff occurred below the reservoir. The flash flooding in Fort Collins resulted in 5 deaths, numerous injuries, and many millions of dollars in damages. However, Horsetooth Reservoir captured and stored about 4,000 acre-feet of flood runoff during this event, which resulted rise in an elevation of the reservoir water surface of approximately 2 feet. The ability of the reservoir to store a portion of the flood flows helped reduce the death and destruction caused by the flood.
Consequences of Dam Failure
Horsetooth Reservoir Dams have a high-hazard classification, based on the population at risk. If one of the dams experienced sudden catastrophic failure, the resulting flood would jeopardize the lives of tens of thousands of people living downstream. The flooding would destroy or extensively damage homes, businesses, property, utilities, and the environment through minor drainages immediately below Horsetooth Reservoir and for an approximately 30 mile section of the Cache La Poudre River between Fort Collins and Greeley, Colorado. Near Greeley the flood waters would enter the South Platte River where the flooding would be somewhat attenuated. The flood plain between Horsetooth Reservoir and the South Platte River contains several communities that would experience complete or partial inundation from a sudden catastrophic failure. These are listed in Table 3-1.
The information presented here assumes a probable maximum flood, which would be an extremely rare event. The U.S. Department of the Interior, Bureau of Reclamation issued an Emergency Preparedness Plan Brief regarding Horsetooth Dams and Reservoir in October, 1983. That document states that a dam failure during a probable maximum flood would inundate or cause severe damage to the following areas:
1) Fort Collins 2) Timnath 3) Laporte
4) Interstate 25 5) Windsor 6) Kodak Plant
7) Portions of Greeley 8) Hardin 9) Masters
10) Orchard 11)Goodrich 12) Weldona
13 )Low lying areas of Fort Morgan
Table 3-1 Population at Risk below Horsetooth Reservoir
Dam
|
City
|
Population at Risk
|
Travel Time for Flood Wave Peak (hours)
|
Horsetooth
|
Bellvue
|
356
|
0.25
|
Horsetooth
|
Laporte
|
2,707
|
0.7
|
Horsetooth
|
Ft. Collins
|
13,981
|
1.55
|
Soldier Canyon
|
West Ft. Collins
|
15,763
|
0.6
|
Soldier Canyon
|
East Ft. Collins
|
17,130
|
1.5
|
Dixon Canyon
|
West Ft. Collins
|
30,180
|
0.6
|
Dixon Canyon
|
East Ft. Collins
|
37,139
|
1.5
|
Spring Canyon
|
West Ft. Collins
|
26,407
|
0.6
|
Spring Canyon
|
East Ft. Collins
|
34,510
|
1.5
|
All Dams
|
Timnath
|
678
|
2-3
|
All Dams
|
Windsor - Greeley
|
23,383
|
4
|
A Loss of Life Study and a Risk Analysis were conducted to estimate the consequences of a dam failure at Horsetooth Reservoir. Loss of life estimates vary by dam, failure mode, estimated time for breach to develop, etc. The range of the best estimate of loss of life is summarized in Table 3-2. It should be noted that the majority of the population at risk resides in or near Fort Collins, and dam failures can occur suddenly, with little or no advance warning. A sudden failure of this nature, compounded by the minimal travel time for a flood wave to reach the highly populated area of Fort Collins, would not allow for a sufficient warning to be issued to those living closest to the reservoir. The higher loss of life values in Table 3-2 reflect this scenario.
Table 3.2 Estimated Loss of Life
Dam
|
Estimated Range of Loss of Life
|
Horsetooth Dam
|
170 - 5,000
|
Soldier Canyon Dam
|
300 - 9,600
|
Dixon Canyon Dam
|
680 - 19,700
|
Spring Canyon Dam
|
600 - 17,700
|
An estimate was made of potential downstream damages and lost project benefits that would result from failure of Horsetooth Dam. Failure of any of the other 3 dams which retain Horsetooth Reservoir would result in even greater damage because their floodplains would encompass a greater portion of Fort Collins. Thus, in terms of potential maximum damage that would result from failure of any of the dams, the damage estimate is conservative. According to inundation data, failure of Horsetooth Dam would result in damage for about 87 miles downstream and would impact residential, commercial and public property, including infrastructure, throughout the area. All or parts of the communities of Fort Collins, Timnath, Windsor, Greeley, Kersey, Hardin, Masters, Orchard, Goodwin, and Weldona, along with other towns in Larimer and Weld Counties, would be severely damaged or destroyed.
Enumeration of individual properties within the various categories was provided by a computerized remote sensing geographic information system (GIS). The property damage estimates probably overestimate potential losses since they assume total destruction of property within the flood plain. The actual damages would vary with varying water depths and velocities of the flood waters. However, the estimates include only direct damages to structures and contents. No attempt was made to include measures of lost income for business and industry or expenditures that would be required for alternative interim residential shelter and facilities for government, schools, hospitals, etc. Also, as noted, the Horsetooth floodplain is the smallest of the four dams retaining the reservoir. Therefore any overestimation of these direct damages is at least partially counterbalanced by unquantified costs.
In addition to direct damages, dam failure would involve lost project benefits, including irrigation, municipal and industrial water, power, recreation, and flood control, which total about $696 million on a capitalized present worth basis. Thus, dam failure would result in total damages and lost benefits of about $6.4 billion, categorized as follows:
Flood Inundation Damages
| |
Residential Property
|
$1,971,000,000
|
Commercial Property
|
$3,143,000,000
|
Public Property
|
$ 427,000,000
|
Infrastructure
|
$ 183,000,000
|
Total Estimated Flood Inundation Damages
|
$5,724,000,000
|
Capitalized Project Benefits
|
$ 696,000,000
|
Total Damages/Lost Benefits Due to Dam Failure
|
$ 6.4 billion
|
EXPLANATORY NOTES FOR THE FIGURES AND GRAPHS PRESENTED UNDER POLAVARAMDAMIMAGES-4 WEBSITE
Fig -1 represents the Log-Log graphical presentation indicating the relationships between the return period of the floods used for determining the size of the dam for providing adequate storage for flood control and the peak floods that can be safely discharge through adequate size of the spillways. Thus the probable maximum flood has to be scientifically estimated for optimizing the sizes of the dams and spillways to ensure the based upon the hazard potential due to a hypothetical dam failure. The tables below the graph also indicate proportional factors and the extreme flood discharges for different return period.
Fig-2 is a colourful artists view of the Machchu dam before and after its collapse due to erroneous design flood assumed by the engineers for design of the dam and its spillway. This is one glaring example of several hundreds of dams that collapsed in all the countries including India mostly due to the improper planning execution and maintenance of dams by the irrigation engineers.
Fig-3 is an important illustration on incremental increase of floods produced by the transformation of the enormous man-made reservoir storage behind the dam which gets added to the natural extreme floods caused by torrential rainfall and sometimes by the collapse of man-made damsin the upper states of river basin. This clearly indicates that while people have a chance to protect their lives from natural flood as had happened in Godavari in August 1953 and August 1986 they have no chance at all to save themselves from the sudden flash floods caused not only by the natural peak floods but also by the additive impact of man-made reservoir floods that will be 2 to 3 time far higher than the extreme natural floods.
Fig-4 is a graphical representation of the peak flood elevation due to a hypothetical dam failure at Polavaram for different storage capacities of 200 TMC, 110 TMC and 70 TMC which clearly shows that larger the height of the dam greater will be the risks to loss of life and properties and this clearly shows that Polavaram dam must be converted into a small sized barrage to satisfy all the agricultural needs of the state excluding hydro-power generation but provides for safety of the project and the people becomes more economical for the state.
Fig-5 is a map of the Polavaram dam area and the other areas of Godavari delta that will be submerged due to intense floods caused by a hypothetical dam failure due to a maximum credible accident.
The tables below this figure indicate the input data fed to the computer software, NWS dambreak model and the output data has been presented in the previous pages which shows the villages, towns and cities with a population of 45 lakhs of people who will be victimized due to a dam failure.
Fig-6 shows the Indian Earthquake highways and danger zones. This figure clearly shows that Godavari river is in a rift zone and they Bhadrachalam under the Polavaram project has already faced an earthquake of magnitude 5.7 on the Richter scale and due to reservoir induced seismicity the dam may face a seismic threat like its counter part at Koyna located in a similar seismic highway. The subsequent pages from the Environmental Impact reports from Polavaram dam clearly show that dam break analysis report is not only incomplete but also shows that with limited data presented. The experts warned that Rajahmundry and Kovvuru regions will be submerged under flood waters upto elevation of 25 to 30 meters, the report is presented extensive inundation zones by means of maps and tables which have not been presented to the concerned people during the public hearing as envisaged by the rules and regulations of the Environmental Protection Act. The state Government has not made any risk assessment and consequently the disaster management plans which are the basic foundations for obtaining environmental clearances from the Union Ministry of Environment and Forests. The disaster management report is based upon wrong assumptions because the previous historic flood of August 1986 which should have been normally taken as a 150 year return flood has been presumed to be a 500-year return flood and this flood is again mistakenly assumed to be the probable maximum flood as per the International standard norms already mentioned in the paper. In the absence of these crucial reports it was not possible for the state Government engineers to make any genuine attempts to consider several alternatives to the project to arrive at a proper cost benefit analysis of the project and to ensure safety of the dam and the lakhs of people who will be facing a watery grave due to a dam failure.
The Union Ministry of Water Resources who have conducted dam break analysis reports for a large number of dams in other states like Rajasthan, Madhya Pradesh, Orissa and Tamil Nadu by using the World Bank assistance have miserably failed to conduct similar dam break studies for Polavaram dam to ensure safety of the project and the lakhs of people in the downstream of the dam.
The last 3 graphical presentations are self explanatory and they are used to estimate the maximum peak floods resulting from the collapse of a dam based on storage capacity in one graph and both volume of storage and height of the dam in the subsequent figure. The last graph is more or less a reputation of the graph in Fig-1 including the table tables and the same explanation apply.
SPILLWAY DESIGN FLOOD (SDF) FOR DAMS IN VIRGINIA,USA
(http://legis.state.va.us/codecomm/register/vol18/iss14/f4v5020.doc)
Class of Dam
|
Hazard Potential if dam fails
|
Size Classification
|
Spillway Design Flood (sdf)
| |
Maximum capacity (Ac.ft
|
Height (ft)
| |||
I
|
Probable Loss of life, Excessive Economic Loss
|
Large > 50,000
Medium 1,000 to
50,000
Small 50 to 1,000
|
>100
40 to 100
25 to 40
|
PMF
PMF
0.5 PMF to PMF
|
II
|
Possible Loss of Life; Appreciable Economic Loss
|
Large > 50,000
Medium 1,000 to
50,000
Small 50 to 1,000
|
>100
40 to 100
25 to 40
|
PMF
0.5 PMF to PMF
100-YR to 0.5 PMF
|
III
|
No Loss of Life Expected; Minimal Economic Loss
|
Large > 50,000
Medium 1,000 to
50,000
Small 50 to 1,000
|
>100
40 to 100
25 to 40
|
0.5 PMF toPMF
100-YR to 0.5 PMF
50-YR to 100YR
|
IV
|
No Loss of Life Expected; No Economic Loss to Others
|
> 50 (non-agricultural)
> 100 (agricultural)
|
>25 (both)
|
50-YR to 100-YR
|
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