Alternative Barrages to Polavaram Dam
T. Hanumantha Rao, Former Engineer-in-Chief and
United Nations (OPS) Consultant, Tel. 040-23402048 Date : 13-08-2010
Construction of Polavaram multipurpose project is in progress since 2005. Expenditure incurred on this project is about Rs. 3,400 crores. Most of this is in construction of canals and land acquisition, and virtually there is no progress in the construction of the proposed dam for various reasons. Instead of the dam as head works for Polavaram project, 3 low barrages are suggested in the alternative design. In essence, it amounts to storing the required 75 TMC (live storage) at three places instead of at one place at the dam site. A low barrage at Polavaram at a suitable site on the downstream of the proposed Polavaram dam, a second low barrage on the downstream of Bhadrachalam across Godavari at a selected suitable location, and a third barrage across Sabari river at a suitable location in between Koonavaram and Andhra Pradesh border are proposed. These proposals are commended by some people and adversely criticized by some others. The purpose of this paper is to clarify various issues and objections raised on the alternative design. On a perusal from the details given below, it would be clear that the alternative proposals are technically feasible and gives more benefits than the earlier proposal. There was an earlier understanding about 5 years back that the upper two riparian states have agreed for the submersion in their states and that the agreement was clear on this. These states are now objecting to the construction of the dam, on the ground that earlier conditions got altered.
Technical Alternative (T.A) for the Polavaram Head works (PH), suggested by me are presently being discussed at the state and the central levels. The State Government has a responsibility to work out such an alternative for the headworks, in the interest of the state, in order to make the much needed project possible. The earlier design of a high dam for the headworks, which was found feasible and desirable about 6 years back, is now proving to be risky and extremely undesirable due to certain unprecedented later developments. Though the project was then found possible to execute at that time, it has now come to a stage where it cannot proceed further. These details are explained below. When an innovative concept was presented to solve the problems, it has to be either improved, wherever needed or a better alternative worked out in order to solve the problems now faced. Otherwise the project would get stalled or delayed extraordinarily, even though the State Government is keen to complete it early. This alternative given has to be treated as a helping hand in the direction of quickly completing the project. There is a feeling in some quarters that the alternative design is against the construction of the project. This is totally wrong and any such impression will get corrected, if the following details are perused. The following two main issues will have to be addressed and solved, first, before undertaking any discussions on technical alternative suggested. Any such technical discussion would only be futile, since the alternative is suggested only to solve the problems faced and not as an end in itself. Again this alternative should be considered as a solution to the existing problems and not a problem by itself.
2. Issue 1 : Peak flood flows and stability of earthen dam :
An earth-cum-rock-fill dam (commonly called as earthen dam) is proposed to be built at Polavaram, which is located almost at the end of the river, where the peak discharge of the river occurs. The maximum ever observed discharge at this place in Godavari is 24% more than the corresponding one of river Ganga, though Godavari catchment area is about one third and annual yield is about one fifth of that of Ganga. (vide CWC journal Bhagirath January – March 2001). Other major rivers in the world which have lesser peak flood discharges than Godavari are Yangtze (biggest river in China), Mekong (biggest in South East Asia), Mississipi (biggest in US), Volga (Russia), do not have earthen dams at locations where such high flood flow conditions occur. Nile, the longest river in the world, has an earthen dam, at almost at the end of the river, but the peak flood of this river at this place is less than one sixth of that of the Godavari. Though the proposed earthen dam at Polavaram, may be the first of its kind in the world, viewed according to peak flood flow parameters, it does not mean that we should not construct an earthen dam at this place. We can still do it, because we have a proven technology for the same. But this confidence was shattered due to the occurrence of two major events since 2005. Firstly, two earthen dams of about the height of Polavaram dam, which were started and completed as a part of the State Government’s “Jalayagnam” have breached (Gundlavagu dam once and Palem vagu twice), well before the receipt of the maximum flood, even though they were designed properly and quality control measures were followed during construction. This has shaken the confidence on earth dams, under Jalayagnam Programme. Secondly, another shock of an extraordinary flood which occurred in the river Krishna (an adjacent catchment) during October 2009. This flood was estimated as 2.7 times more than the ever occurred flood, during the past 100 years. If a similar flood in river Godavari occurs, at any time in the future, it would be of the magnitude of about 90 lakh cusecs. The possibility of this cannot be ruled out as we had practically witnessed such an event only a few months ago in a contiguous catchment. In this connection, it would be relevant to study the effects of global warming on the future rainfall patterns. Several International Organizations, such as the United Nations, Intergovernmental Panel on Climate Change (IPCC), Princeton University, Global Water Policy Project (GWPP) etc., have done research on “Climate Models” and concluded among several other things, that the Krishna and Godavari Basins in India would witness an increase in rainfall upto 50% more from 2000 to 2050 (National Geographic. April 2009). Climatologists feel that the recent phenomenal increase in Krishna floods is perhaps an indication of this.
Possible Dam collapse due to Extreme Floods:
The Possible Maximum Flood (PMF) was revised by the Central Water Commission and determined as 50 lakh cusecs, a few years back. Even though the dam spillway is designed for this huge discharge, it still falls short of the above extraordinary flood of 90 lakh cusecs. In such an event the breach (dam break) of the earthen dam is very much real and not hypothetical. The free board of about 7.5 m above the F.R.L. intended in the design of earth dam is just sufficient for the wave height and run up. When an inflow above 50 lakh cusecs occurs, water levels would rise to facilitate discharge over the spillway and at 90 lakh cusecs, the wave will flow well above the top of dam, resulting in erosion and would eventually breach the dam. If past occurrence of breachings of earthen dams in Andhra Pradesh and the world is any guide, the breach can occur suddenly without any warning even without receiving the P.M.F. Breaches in earth dams have occurred previously all over the world within a few hours of appearance (e.g. Teton Earthen Dam, USA). With regard to experience in the case of masonry/concrete dams, they are relatively free from such risk, since even when water over flowed over then, structures did not breach. In the case of Polavaram dam, it is not possible to build a masonry/concrete dam due to lack of rocky strata at any reasonable depth in the foundations. As such the proposed dam can only be earth-cum-rock fill dam (commonly called as earth dam).
Risk Analysis due to Dam Burst making 46 lakh people vulnerable to drowning:
Studies revealed that in the event of a dam break of Polavaram dam occurring in a night at about 10 P.M, 46 lakh people living in the delta, would have a watery grave before they get up in the morning. It is this real threat that frightens anybody and the need for seeking an alternative technical proposal (that would give the same benefits as the dam) would then arise. This is all the more necessary, since the proposed dam is located very close to a huge habitat area, where the density of population is the highest in the state. The technical alternative is a step in this direction and the technical details will have to be formulated/improved, so as to make it possible, or else another alternative solution will have to be worked out to solve the issues. Since the progress on the headworks is almost nil during the past 5 years, this alternative is possible. To proceed on the construction of the dam on the basis that there is no risk, would amount to gambling with the lives of 46 lakh people, and the planners would be well advised to consider whether it is worth taking such a risk when there is a scope for exploring alternative solutions.
When there is no dam and a flood of about 90 lakh cusecs occurs, it would be gradual and increases over a few days. In such a situation, people would have time to vacate their habitats as per the advance flood warnings, and move to the assigned safe places. Whereas in the case of a dam break, when it occurs without any early warnings, like Teton Dam, a Tsunami like flood wave would occur suddenly giving no scope for the people to vacate. This is the main difference between a natural calamity and a man made one. All the above details as known to the author are being furnished as a part of professional responsibility and not to create fear or panic in the minds of the public. If the government and public want the earthen dam, it would be according to their wisdom and choice, and there is no compulsion to choose any alternative design. In this connection it would be apt to recollect the words of caution of ICOLD (International Conference on Large Dams), Director of dams, Pensylvania and others that the worst large scale human destruction can be caused by man made activities, firstly through atomic plants and secondly through the major dams. It would also be relevant to note the Marphy’s Law (followed by NASA, USA), namely that “if there is a possibility for a failure to occur, it would certainly occur sometime or the other”. Thus, if there is an alternative to a major earthen dam, it can be preferred if so desired by the public and the government.
2nd Issue : Submersions in Orissa and Chattisgarh States :
The Polavaram dam would submerge 23 villages in Chattisgarh and Orissa States (13 + 10) as stated by Andhra Pradesh and more than 35 villages as contended by the two upstream states. These two upstream State Governments were objecting during the past six years, to the various clearances given by the Government of India, and being unsuccessful, they had taken up the issues with the High Court of Orissa and the Supreme Court. Among their several other objections, their main contention is that the conditions prevailing at the time of issue of the Bachawat award in 1980, have since changed now, and due to this, the award is not valid, and hence will have to be reopened and that the award itself made a provision for such reopening of the issues whenever the conditions changed. According to these states, the condition of 36 lakh cusecs flood (on which the award is based) is changed to 50 lakh cusecs flood and that due to this, more than 35 villages (as against 23 earlier) would get submerged and that they are not agreeable to the Polavaram dam on account of this. These issues are now pending with the Supreme Court and these states have requested for a stay on the construction of Polavaram dam.
Orissa obstructed since 20 years projects over Vamsadhara and Janjhavati rivers:
In this connection, it would be of interest to note how the Orissa government had stalled the construction of Vamsadhara Stage – II project and Jhanjhavathi project of Andhra Pradesh on the plea of submission of a few villages, in that state. The expenditure incurred by Andhra Pradesh Government about 20 years back, is lying as waste all these years as the full benefits of these projects could not be realized. In the case of the Jhanjhavathi Project, no storage at dam site could be made in the absence of dam in the river portion. The maximum that was possible was to construct a temporary collapsible rubber dam and divert the river flows and irrigate a few thousand acres. The sad thing about all this, is that nobody knows when these two irrigation projects can be completed, if at all they can be done. If this experience is any guide, the Andhra Pradesh Government would be well advised not to proceed with the construction of the Polavaram dam without obtaining the consent of Chhattisgarh and Orissa states. 20 years back the wastage was in tens and hundred Crores of rupees, and if Polavaram dam is stalled, the wastage would then run into thousands of crores of rupees, as already over Rs. 3,000 Crores, was spent on this project. Unless the long incomplete Vamsadhara Stage II and Jhanjhavathi projects are restarted now and completed, one would not be able to appreciate how difficult it would be to complete the Polavaram dam. Planners will have to note this as huge amounts of tax payers money is involved in such capital expenditures. The technical alternative proposed is exactly intended to address these serious problems and solve it them. In this proposal, there will not be any submersion of even a single village in Chhasttisgarh and Orissa states. There will also be additional benefits of this alternative proposal as stated in the subsequent paras. All the benefits of the earlier proposal will be fully realized without any reduction in any aspect.
To Make Polavaram Project Implementable Barrages Project is Considered Practicable:
From the above discussion, it can be seen that the technical alternative proposed is only intended to solve the above two main issues arising now, and also to ensure that the full benefits of the earlier proposal are achieved and the progress on the project speeded up so as to derive the benefits early and simultaneously ensure the safety of lives of 46 lakh people living in Godavari Delta. In fact the State Government will have to work out such solutions on their own, in the interest of common good, and therefore will have to treat this alternative proposal as a helping hand in this direction.
3. Alternative Barrages Design Proposals :
In the alternative design of the head works, all the benefits of the earlier proposal are fully retained without any reduction. They relate to diversion of 80 TMC water to Krishna Basin, irrigation facilities to Polavaram Ayacut (7.2 lakh acres). Godavari and Krishna Deltas, Industrial & Drinking Water Supply to Visakhapatnam area, Hydro Power Generation, etc.
The required live storage of 75 TMC, instead of being stored at one place at Polavaram High Dam, would be stored at three places (Down stream of Bhadrachalam across Godavari, Sabari, and at Polavaram) through low barrages, similar to the one existing at Dowleshwaram, with water levels kept at much lower than the High Flood Levels. Due to this, more than 200 tribal villages (about 2 lakh population) will be saved from submersion which would be resulting in the earlier proposal. Also there would be no submersion of any villages in Chattisgarh and Orissa States, and hence their earlier objection to the project would get automatically cleared. Since there will be no inter state objections, the alternative low barrages can be constructed without any delays. The pending Supreme Court cases would all get solved as there would then be no disputes with the upstream states.
Since the bottom level of barrage gates would be at average deep river bed level, all the gates would function as scour vents and hence there would be no siltation on the upstream side of the barrages.
About 1 lakh acres belonging to Girijan farmers, which would be submerged under the old proposals, can be given irrigation facilities, (without affecting the interests of Polavaram Project), through gravity flow canals taking off from the two upstream barrages of the alternative proposal.
In the alternative proposal, there is a facility for sea going vessels to navigate from Bay of Bengal to Sriramsagar Dam (700 Km), which would in turn lead to commercial and industrial development, giving employment to the rural poor, all the year round, similar to St. Lawrence Sea Way (America) constructed in the mid 20th century. There is no such facility in the earlier proposal, as the navigation canal will have to go through a tunnel about 1 km long.
The alternative proposal can be constructed at a lower cost (about Rs. 6,500 Crores cheaper) than the high dam, and can be completed in a lesser time than the Dam.
The most important issue is, even though the earlier proposal of the high earth – cum – rock filled dam is constructed, to withstand the possible Maximum Flood (PMF) of 50 Lakh Cusecs, there is every possibility for this to breach, called “Dam Break” as explained in the earlier paras. Earthen dams are breaching all over the world and also in India (Morvi Dam). It is therefore not a rare feature. In Andhra Pradesh there were several cases of breaches of earthen dams. For example the Kadem earthen dam (Adilabad District) had breached, whereas the adjacent cement based dam was intact. It has to be therefore considered as a catastrophe in waiting. In the alternative design, there is no dam, and the issue of dam break, does not arise. The low barrage will be with a vent way slightly more than the river cross section area. As such the regime of the river is not affected. This means that the river flows down the barrage, without any obstruction irrespective of the extent of the flood and there will be no afflux (i.e. level difference between upstream and downstream of the barrage).
Five more important approvals are required for constructing the high dam. They are related to (1) EFC (Expenditure and Finance Committee) of the Union Ministry of Finance, (2) Central Electric Authority and supportive data on Hydrology from CWC, (3) Stage II clearance on Environment from the Union Ministry of Forests and Environment, (4) Scheduled Tribes and other Forest Dwellers (Recognition of forest rights) Act, 2006, and (5) Report of the Wild Life Institute of India. The upstream two states are objecting for the construction of 43 kms. length of dykes within their state boundaries. Environmental Impact Studies (EIA), approval of Gram Sabhas, clearance of pollution control boards in their states and other formalities for the construction of these dykes are yet to be complied with. There is no hope of completing these tasks and obtain environmental Stage II clearances, unless these states agree to this. In this context, it is relevant to note that the National Appellate Authority (NEAA) in December 2007 had struck down the Environmental clearance (stage 1) given by the DOEF (Department of Environment and Forests). Also emergency Action Plan as per the guidelines issued in 2006, disaster management plans, inundation maps (dam break) are not yet prepared or got cleared. By the time these approvals are received, all the approvals for the alternative design can be obtained.
The State Government had worked out details and estimates without a proper understanding of the concept of the alternative design, and this resulted in erroneous and absurd figures. The manner, how these figures were wrong and the details of the correct figures which give rise to the above said major advantages are explained, below :
4. Comparison of Barrages with the old proposals of Dam at Polavaram :
The following picture would emerge if the concept of the alternative proposal is properly understood :
· Cost of the alternative proposal works out to Rs. 7,143 Crores and this is cheaper than the old proposal by Rs. 6,000 Crores, if realistic costs are considered for the old proposal. This old proposal would cost more due to cost of construction of dykes 43 Km. long in each of the two states, installing gates and pumpsets within the dykes, cost of NVP of forests, connectivity works, realistic R & R costs for greater submersion of villages, revised. I.B.M. value for works etc. The State Government initially estimated the cost of alternative proposal as Rs. 19,108.53 Crores and later modified it to 12,106.71 Crores and during the meeting of some MPs with the Chief Minister on 24-06-2010, it was mentioned (as reported in the press) that both the proposals cost the same. Thus it can be seen that as the concept is being understood gradually, the correct picture of the alternative proposal is emerging out. This is also reflected in the other details noted below.
· The alternative concept contemplates a live storage of 79 TMC i.e. not less than 75 TMC live storage, provided in the old proposal. All the benefits of the project contemplated originally using 75 TMC live storage are possible through the alternative proposals also. These relate to irrigating 7,20,000 acres ayacut and not 2.5 Lakh acres as stated by State Government, supply to Godavari delta, diversion of 80 TMC to Krishna delta, supply of 23 TMC water for drinking and industrial purposes. All these benefits are possible because the total live storages being provided at three places in the alternative proposal is not less than the 75 TMC of the old proposal. Though 2.5 Lakh acres was mentioned in the alternative proposal as the remaining area to be irrigated, actually the entire area of 7.2 Lakhs acres can be irrigated if it is so desired, since there is no reduction in the useful storage. The State Government has initially stated that the live storage under the three barrages would be very low and later during the meeting of some MPs with the Chief Minister of Andhra Pradesh on 24-06-2010, it was stated that this storage would be 59.017 TMC. As the understanding of the concept is getting improved, a better picture of the alternative was emerging out. Actually field surveys will have to be done, and investigated, such that optimum locations for the barrages and their water levels determined, so as to reduce village submergence and at the same time get the required storage. It is then likely to get the required 75 TMC live storage, as against the 59.017 TMC worked out by the State Government. In such a case, all the benefits of the old proposal can be achieved through the alternative barrages, without any reduction whatsoever.
· Reduction of Submersion of Villages : The report of the State Government on the Alternative proposal indicated initially that 345 villages would be submerged. This was later modified and drastically reduced to 130 villages, as informed to the MPs in the Chief Minister’s meeting on 24-06-2010. This was possible with a better understanding of the concept of the alternative proposal. It would further get reduced to 70 villages when properly investigated as mentioned above.
· Hydro-Power Generation unchanged: During the MPs meeting with the Chief Minister on 24-06-2010, it was mentioned by the State Government that the hydro power generation for the alternative proposal would be hardly 172 MW. When an upstream barrage on Godavari at Dummagudem (presently under construction) can produce 340 MW of hydro power. The proposed three barrages would be able to produce not less than 960 MW of power, if operated optimally as indicated in para 8 of part 3 of the Author’s 55 P on the alternative proposals and as per the calculations attached to it.
· Andhra Pradesh Government had agreed to spend Rs.600 Crores for constructing dykes to prevent submersion. Due to this, it was felt that the objections from the two upstream states were cleared. This is not correct, as explained in Para 3 above.
· Since the alternative proposal is costing less than the old proposal and the benefits are the same as the earlier proposal, the benefit cost analysis would work out favourably for the alternative proposal. Actually the benefits of alternative proposal are many more than the old proposal as explained in Para 3 above.
· There will be no difficulty in adopting the alternative design for the headworks of the project, since there is hardly any progress on the construction of the dam. The canals already under construction can be utilized, with a lift of about 11 m. from the proposed Polavaram low barrage pond and using about 54 MW of hydropower out of 1038 MW power generated. Details of this are given in the author’s 55 P. report. For a comparison, this lift of 11m. is insignificant when compared to the lift of about 300 m, in the case of the Godavari, Devadula major project (located on the upstream of Bhadrachalam), intended to irrigate nearly the same extent as that of Polavaram.
· Other very important issues are related to the two major lift irrigation projects (Pushkarini & Thatipudi) and another major gravity flow irrigation project Yeleru, ayacut which are all contemplated to be tagged on to the Polavaram Project as per the old proposal. These are discussed in great detail under Para 6 below. It was conclusively proved that there is no need to abandon these two major lift irrigation projects recently completed, and tag on their ayacut of 3,75,166 acres to the Polavaram Project command, as it would involve in wastage of hundreds of Crores of Rupees of tax payers money recently spent on civil works of the Lift Irrigation projects (such as intake, suction wells, approaches, pump houses, pumping mains including structures on them, other immovable structures, cisterns, etc.). It would be necessary to reexamine this proposal of the State Government, since the same ayacut served by recently completed major projects, should not be proposed to be served by another major project yet to be started. Also since this would involve a wastage of tax payer’s money, there would be a need for the Ministry of Finance and the Planning Commission to have a second look and review the situation. However, for purposes of comparison of the alternative proposal, storage as well as ayacut of 7.2 Lakh acres as envisaged in the old proposal were considered without any reduction.
5. Additional Irrigational facilities in Tribal Areas: In this alternative proposal about 75% of the submergible agricultural area (nearly 1 lakh acres) of the old dam proposal will not only be saved from submersion, but also can be provided with irrigation through the proposed two barrages on the upstream side of Polavaram. This is a great advantage to the backward tribal area farmers, who faced a threat of submersion as per the earlier high dam proposal. Water from these two barrages can be taken by gravity flow canals to irrigate the agricultural lands lying between the contours 46.00 m and 30.48 m. Kharif seasion crops can be irrigated in this area using the flood flows of river Godavari going to the sea in the rainy season. This will not adversely affect the supply of the required water to Polavaram project. Exact area to be irrigated, will have to be worked out after ground surveys during the DPR stage. Thus the alternative proposal would also benefit most of the submersion area of the old Polavaram proposal, while giving benefit to the coastal area.
6. Polavaram Ayacut will be reduced :- 75 TMC storage is essential for the purpose of irrigating 7.20 Lakh acres under Polavaram Project and 10.20 Lakh Acres under Godavari delta (Kharif and Rabi seasons) etc. In the alternative proposals also, provision for this 75 TMC is made and there is no deduction in this. Hence this full ayacut of 7.20 lakh acres and 10.20 lakh acres can be served fully under the alternative design also. However for cost of pumping equipment and pumping charges, realistic ayacut (2.5 lakh acres) under Polavaram Project and all other demands (e.g., Krishna, Industrial, Godavari Delta etc.,) are retained without any reduction. The manner how the real new ayacut under Polavaram would be only 2.5 lakh acres and not 7.2 lakh acres, will be evident from the following discussion.
There is no need to delink Yeleru ayacut of 67,600 Acres from Yeleru project and supply water to this area, from Polavaram canals, in order to utilize this extent of water for the future new ayacut of Yeleru project lying above the Polavaram geographical command. The existing system of Yeleru ayacut in Polavaram geographical command (67,600 Acres) can continue under Yeleru project, and water can be supplied to Yeleru ayacut above Polavaram Command by pumping water from Polavaram canals and the scheme can be designed accordingly. Polavaram left canal has adequate capacity for supplying the required additional discharge.
An ayacut of 2,77,234 Acres is shown as distributed in Visakhapatnam district (1,48,202 Acres), Krishna District (61,901 Acres) and West Godavari District (67,131 Acres). This will have to be analyzed with regard to what extent of area is already under irrigation through public lift irrigation schemes, tanks etc., where government funds were already spent. A Study has indicated that the area without any irrigation facility and where crops are raised under rainfed conditions would be less than 1.8 Lakh acres and that this much area only would need irrigation under Polavaram project. Considering that private lift irrigation systems (e.g. tube well, dug well etc., ) will have to be supplied water from Polavaram project and that M.I. tanks ayacut in the command has to be deleted, this ayacut would get reduced from 2,77,234 acres to about 2.5 lakh acres. It may be noted that ayacut under M.I. Tanks was deleted from the project Commands in the cases of Nagarjuna Sagar and SRSP. The Same procedure can be followed for Polavaram Project also.
With regard to the existing lift irrigation projects covering an ayacut of 3,75,166 Acres, it is mentioned that the “life of some of the existing L.I. Schemes is already over and the life of other schemes will be over by the time Polavaram Project is completed”. It is also stated that “since they will have to be anyway abandoned, there is a need to supply this ayacut of 3,75,166 Acres under Polavaram project.” Pushkara, Chagalnadu and Tadipudi L-1 Schemes comprising of 3,23,126 acres do not come under this category to be abandoned since they were also taken up for construction along with the Polavaram project at almost the same time or slightly earlier. In fact these schemes are still under construction, partly completed and about to be completed. With regard to the other four L.I. Schemes comprising of 52,040 Acres, there is no need to abandon them for the reason that their life is over and then supply water from Polavaram Project. Their life time can be extended by repairs and renewals where ever needed. Many of the present major lift irrigation projects under Jalayagnam are lift schemes and they cannot be abandoned after a life time of the pumping equipment of say 10 or 15 Years. By appropriate renewals, whenever needed their life times can be extended and brought on par with other major gravity flow projects. The cost of renewals will have to be included in the maintenance cost and would not form part of capital cost.
From the above discussion, it can be inferred that the Polavaram Project will have to Supply water to an ayacut not exceeding 2.5 Lakh Acres. With regard to Uttarandhra Sujala Sravanthi, Rudramkota irrigation and other lift irrigation projects from Polavaram Canals, the cost of pumping equipment and pumping charges for lifting Godavari water will have to be borne under the respective schemes, as they cannot be a charge on the Polavaram Project. They are not existing schemes and they would take shape only after Polavaram Project is constructed. They have to be designed on the basis of the available conditions in Polavaram project. Also this lift from Godavari river would be relatively minor when compared to the big lifts required to pump Polavaram water to much higher areas under these schemes. Hence these costs of new lift irrigation projects will have to be deleted for purposes of comparison. There is no need to abandon the existing L.I. Projects as discussed above. Such an action would result in wastage of public funds, since the Civil works (such as Pump houses, structures along pumping mains, immovable structures, cisterns etc…) executed at a high cost would all go to waste.
The alternate proposal gives an added advantage to the existing Krishna and Godavari deltas since the saved water from Polavaram Rabi demands (due to reduction in ayacut), can be diverted to these deltas during the Rabi season. However for comparison purposes, it is once again reiterated that the alternative design can provide irrigation for 7.2 lakh acres as envisaged in the original proposal since there is no reduction in the live storage of 75 TMC.
Conclusion : The above technical alternative design for the Head works of the Polavaram Project are mainly intended for quickly completing the project without objections from the upstream states of Orissa and Chhattisgarh on account of submersion of villages in their states. This alternative design is technically feasible and the concept given when fully understood would lead to preparing a Detailed Project Report (DPR), after a detailed field survey and investigation. As the understanding of the concept improved, the cost of alternative proposal got reduced to less than half than that thought of earlier by the Government. Also the number of villages that would submerge as per the alternative proposal got reduced to 1/3rd, with a better understanding of the concept by the State Government. Similarly, the innovations made with regard to providing the spill way gates for the entire length of the barrage as scour vents, when grasped fully would lead to understanding that there would be no siltation due to the barrage. Since the regime of the river is not affected and full cross section of the area of the PMF (Possible Maximum Flood) is provided as went way, the river continues to flow as if there is no obstruction, whatever may be the flood magnitude. During the non-peak flood flow days (for example : one or two lakh cusecs flow) barrage gates would be opened partially to allow this flow downstream, while maintaining the water level in the pond, at near FRL of 100 feet. This is to facilitate maintaining a hydraulic head (difference of water levels on upstream and downstream) for generation of hydro power. In addition to saving about 200 tribal villages from submersion, the alternative proposal envisages about irrigating 1 lakh acres of land belonging to the tribals. This land was originally contemplated for submersion according to the earlier proposal. Apart from saving these lands from submersion, the same can be provided with irrigation facilities for one Kharif season crop through gravity flow canals from the upper two proposed barrages. The existing Polavaram canals, now under construction, where more than Rs. 3,000 crores expenditure was incurred can be fully made use of, by pumping water from the proposed Polavaram low barrage with a pumping head of about 11 metres (54 megawatts power required). All the benefits of the earlier proposal namely irrigating 7.2 lakh acres of land under Polavaram, irrigating Godavari and Krishna deltas, diversion of 80 TMC to Krishna basin, supply of 23 TMC for drinking and industrial purposes. Hydro power of 1038 Megawatts can be generated. Water supply to North Coastal Andhra, contemplated in the future, water supply to Khammam district areas by lift irrigation etc. can all be achieved through this alternative design also. Since the peak river flood passes through the low barrage, without any obstruction (river regime not being disturbed), dam break and risk to the lives of 46 lakh people living immediately downstream of the project, do not arise. This is another major advantage of the alternative proposal.
ABOUT THE AUTHOR :
In addition to experience in field investigation, planning, design, research and water management in irrigation projects, the author had field experience in the construction of Rallapadu Project, Hirakud Dam (Orissa), Nagarjuna Sagar Dam, Mid Pennar Dam, Tungabhadra High Level Canal – Uravakonda Deep Cut, Kalyani Dam, Srirama Sagar Dam, Telugu Ganga Project (noted in the order of his service from 1950 to 1989). His later field experience in irrigation projects till 2006 was in the African countries, during his assignments with the World Bank and in the Asian Countries during his assignments with the United Nations (O.P.S).
Annexure 1 - POLAVARAM DAM V/S BARRAGES
(Replies given by Sri.T.Hanumantha Rao to the doubts raised by Govt. Experts)
Doubts expressed by Experts on
Remarks of the Author
1) Storage at the alternate low barrage site at Polavaram would be 22.8 TMC with FRL 100 ft and out of this only 5 TMC can be used
|1.As per the area capacity tables, storage at 100’ level is 36 TMC and out of this 35 TMC can be utilized for pumping into canals, during the non flood season. There will be a slight reduction in this due to locations of U/s barrages. It is possible to utilize 33 TMC. There is no need to provide any dead storage, since water up to sill level i.e., bed level can be used.|
|2) Due to siltation, utilization of water and useful storages in barrages will be reduced.||2. The proposed barrages are not like others, where sill levels of weirs are raised (like Prakasam and Cotton Barrages) and intended to facilitate supply of water to canals. In Such cases siltation will occur. The alternate barrages will have sill levels at bed levels similar to scour sluices and the regime of the river U/s and D/S is not disturbed. The vent way would be equal to the river cross section and the flows would be as per the open-channel flow hydraulics and not as per the weir flow hydraulics. (Ref: Ven Te Chou) The water profile levels will be same as with or without a barrage. |
Thus the river section will be the same (i.e. with same bed levels) with or without a barrage. In other words, there will be no bed load sedimentation due to the barrage. The Colloidal Clay settlement in the pond due to long storage will be washed down as turbid water during the next floods.
|3) Total storage in 4 barrages will be 53 TMC and only 33.5 TMC out of this can be utilized.||3. As explained in item 2, the full storages in the U/s barrages up to the bed level namely 35 TMC can be utilized without any limitations of Minimum Draw Down Level (M.D.D.L).with skillful selection of sites, approximate F.R.L.s & Limiting Submersions it is possible to get maximum storage at a place in between Bhadrachalam and Kunavaram and another on Sabari. |
Thus the total useful storage of 79 TMC can be obtained only in 3 barrages. (35+25+19) (e.g. Storage at Kanthalapally = 22.5 TMC)
|4) Cost of barrages would be Rs. 9,000 Crores||4. On the basis of cost of Kanthalapally Barrage prepared in details in 2008-09 as Rs 880 Crores, the cost of three barrages can be estimated at 3500 Crores. |
As a comparison the cost of Polavaram spillway and rock fill dam (2004 – 05 rates) was Rs.1627 Crores including the surplus course. Selection of locations of barrages will have to be done to get economic designs. For example, cost of alternate barrage at Polavaram was estimated as Rs. 3000 Crores. This is almost double the cost of Dam & Spill Way. Whereas it should be only a fraction of this.
|5) As against 277 villages submersion in Polavaram dam, 128 villages will get submerged under the barrages||5. According to the submersion area tables of Polvaram Dam, 30 Villages will get submerged with FLR @ 100ft. This includes a portion of the submerged areas under the upstream barrages also. Another 30 additional villages may get submerged under the two upstream barrages. The exact details will have to be worked out based on submergence area 1 m interval contour map and the F.R.L.s selected for the upstream barrages. The upstream barrages should have dykes in continuation of barrages such that the upstream floods may not submerge the Down Stream Areas.|
|6) Power Production in the 4 Barrages will be 271 MW||6. Power production contemplated at the Dummagudem barrage is 310 MW. On the basis of this it is possible to produce about 1038 MW at the three barrages. However details will have to be worked out by GENCO.|
|7) There will be 7.1 Lakh acres under Polavaram Dam and not 2.5 Lakh acres.||7. WWF Officials have made a realistic study of existing irrigated areas, Mandal wise in the Command area and came to a conclusion that only 85,330 Ha (2.1 Lakh acres) are available. for Irrigation. (Vide book on Perspectives of Polavaram) This is said to be due to a part irrigation under Tatipudi and Pushkaram L.I. Projects, Yeleru Project, Minor Irrigation, G.W.(Public, Private) etc., there is no need to give irrigation to areas already under irrigation through G.W.Minor Irrigation tanks and L.I.Projects. There is a need to reconcile the figures of the Govt. and W.W.F. Officials. A much lesser storage than 75 TMC (As per the dam proposal) would be able to meet the requirements of the new Ayacut. G.W. & L.I. projects would need power and under this plea, it would not be prudent to abandon the existing infrastructure & supply water to these areas with gravity flow canals from Polavaram Dam.|
|8) Orissa Government will oppose the alternative design||8. In fact they would welcome this, since there is no back water curve effect (due to storage or obstruction of flow). During the floods the whole length of river, flows to sea without any obstruction or storage anywhere. Also no villages in Orissa areas will get submerged.|
|9) There is no navigation facilities for sea going vessels d/s of Dowleshwaram and hence the same need not be provided on the u/s of Polavaram Dam||9. Two or three barrages will have to be constructed Down Stream of Dowleshwaram up to the sea to facilitate the navigation of sea going vessels. This will be similar to what has already been done in St.Lawrence River (USA) where 7 navigation barrages were constructed from the starting of river (Lake Ontario) to the sea. The cost of these barrages will go to the Navigation Budget and not the Irrigation Budget.|
POLAVARAM PROJECT --- SALIENT FEATURES
(AS PER AP STATE GOVERNMENT REPORTS)
Polavaram project is a major multi-purpose irrigation project proposed across Godavari River at Ramaiahpet village in Polavaram Mandal of West Godavari district. The project location is about 42 kms. upstream of existing Sir Arthur Cotton Barrage at Dowleswaram and about 34 Kms. upstream of Rajahmundry.
Brief Details of the Project :
Full Reservoir Level (FRL) + 150 Ft.
Top of Bund Level (TBL) + 175 Ft.
Length of earth-cum-rock fill dam 2.31 Kms.
Capacity of Powerhouse (on the left flank) 960 MW
Length of left main canal 181.5 kms.
Length of right main canal 174 Kms.
Major benefits of the project :
· Irrigation water to 4.00 lakh acres in East Godavari and Visakhapatnam districts through left main canal and 3.2 lakh acres in Krishna and West Godavari districts through right main canal.
· Generation of 960 MW of hydel electricity
· Transfer of 80 TMC water to Krishna basin at Prakasam Barrage, Vijayawada.
· 23 TMC of water for domestic and industrial needs of Visakhapatnam
· Drinking Water supply to all villages enroute the left and right main canals.
Details of submergence :
Number of submergence villages 276 villages in 7 Mandals of
Khammam, 1 mandal each in
East and West Godavari districts
Project affected people 1,17,034 people as per 2001 census
Total area of submergence 94,357 acres
Forest area under submergence 7,964 acres
Total land to be acquired due to
submergence and canal construction 1,17,323 acres
Estimated cost of the Project Rs. 8,198 crores as per 2003-2004
(Rs. 18,000 crores approx. 2010)
Benefit Cost Ratio 2.4 : 1