R NAVIGATION OF SEA GOING VESSELS
(Proposals first appeared in Eenadu 5-1-2008)
Former Engineer-in-Chief, Government of Andhra Pradesh and
United Nations (OPS) consultant
- Introduction: The recent peak flood, that occurred during the first week of October 2009, in the river Krishna has given a clear indication of what the maximum peak discharges in the Indian rivers would be in the future. Though the effects of global warming are not clearly established in physical terms, scientists (after analyzing the existing data) had concluded that the peak flood discharges in the Indian Peninsular rivers, Krishna and Godavari would be increasing in the future. The peak flood flow in Krishna river on 3-10-2009, is reported to be 25.5 lakh cusecs and this is nearly 2.5 times than the peak flood of 10.6 lakh cusecs ever occurred in the past 100 years. If the same phenomenon is predicted to the Godavari river at Polavaram Dam, certain startling issues would emerge. The maximum flood discharge ever occurred in Godavari river during the past 100 years, was 33 lakh cusecs and the Polavaram Dam was designed for 36 lakh cusecs. The Central Water Commission had determined the Possible Maximum Flood (PMF) as 50 lakh cusecs and the dam spillway was redesigned accordingly. The recent floods in the Krishna river had created a scare in the minds of engineers and policy makers as to what would happen to Polavaram earthen (rockfill) Dam if such a 2.5 times increase in flood flow, namely 83 lakh cusecs occurs in the Godavari river. The dam break analysis done by the National Institute of Hydrology (NIH) from Polavaram to Rajahmundry and by other scientists from Rajahmundry to the sea, indicated that when a peak flood of 50 lakh cusecs occurs in the river and the dam breaks, Rajahmundry area would be under 40 feet of water. This would lead to the death of 46.15 lakh people (2001 census) in the Godavari Delta. http://shivajirao32.googlepages.com/polavaramdam-Such a global tragedy in waiting, should be avoided at all costs. The 2.5 times increase in Krishna floods at Srisailam, has resulted only in a few hundred deaths, whereas the same increase in Godavari floods at Polavaram would result in a major catastrophe of a gigantic scale Now a question arises – is it not possible to avoid all these risks and yet realize the same benefits of the Polavaram Dam through suitable technical alternatives, which do not result in huge submersions of villages, agriculture lands, forests etc. Fortunately the answer is yes, in the case of Polavaram Dam. A study of latest thinking in the world on this subject would be relevant.
- Big storage: The consensus of opinion evolved during the past decade of various international for a (including the World Water Forum), where engineers, environmentalists, social scientists and economists meet, favoured the entire river length to be developed as a continuous series of stepped reservoirs, limiting the water submersion tos the peak flood flow section of the river. Big storage reservoirs will have to be considred, only in special cases, such as flood storage (to prevent serious damages) carry over storages to meet drinking water requirements during drought years, and special hydro electric locations where adverse environmental impacts would be a maximum Live storage in Polavaram Dam is 75 TMC, but it submerges 293 villages, over 1 lakh acres land 3731 hectares of forest land all resulting in displacing about 1.6 lakh people. All these can be avoided if a barrage is constructed in place of the dam. Let us examine how the barrage proposal an give all the benefits envisaged in the dam proposal. It has to be understood that this alternative is suggested only for the dam and not the project as such. In fact this barrage proposal aims at increasing the benefits of the project without causing submersion of villages. There is no doubt that Polavaram Project is very much needed for the development of all the regions in Andhra Pradesh.
- Details of barrage: The barrage suggested in place of Polavaram Dam would be similar to the one existing at Dowlaiswaram across the Godavari river. It would be designed in such a manner that the upstream water level at the barrage will be the same, as the water level on downstream of the barrage, irrespective of the flood discharge – whether it is 20 lakh cusecs or 33 lakh cusecs or 50 lakh cusecs. The vent way of gates of barrage will be increased to correspond to the river flow cross section area during the maximum flood, by extending its length into the flanks and providing smooth approaches and the whole process will be determined by hydraulic model studies. In other words the ‘afflux’ would be limited to near zero, for all river discharges, eliminating the need for flood banks on the upstream side of barrage. It is reported that a water level o 100ft above MSL was recorded at Polavaram, during 1986 when the recorded maximum flood at Dowlaiswaram was 33 lakh cusecs; This water level will not get increased to a higher level even though the barrage is constructed. Whatever natural submersion that will occur for a river discharge of either 33 lakh cusecs flow or 50 lakh cusecs flow will continue to occur and will not get increased even after the barrage is constructed. In other words, there will be no additional submersion due to the barrage, and the entire flow will be limited to the high flood zone section of the river. Some tribals have occupied certain places in the high flood zone area and are now residing there. During high floods, they would vacate their houses and move to the higher areas, and again get back within a few hours or days when once the floods recede. But when the barrage is constructed, the high flood zone will be filled with water for a few months and hence they will have to be rehabilitated. The cost of this relief and rehabilitation will be negligibly small. In this proposal, there is no question of submersion of the 293 villages, forest areas, lands etc as in the dam proposal, and hence the construction of protective dyke walls in Orissa and Chattisgarh does not arise. Salient features of the barrage are briefly explained.
- Salient Features:
- Upstream and downstream water levels with 33 lakhs cusecs = 100ft (30.48m) above MSL.
- Sill level of spillway gates = 40ft (14m) i.e. bed level of river.
- Height of spillway gates +54ft (16.5m)
- Top level of gates = 100 ft (30.48m)
- Top level of bridge on spillway = 3m free board from water level when 50 lakh cusecs flood flows through the gates.
- Maximum Observed Flood in 100 years = 33 lakh cusecs
- Possible Maximum Flood (PMF) = 50 lakhcusecs. Provision is made in the design of gates for PMF exceeding 50 lakh cusecs also.
- Storage in barrage upto top level of gates = 30 TMC
- Ayacut: 2,50,000 acres. Originally 7,20,000 acres ayacut was contemplated. But, this got reduced to 2,50,000 acres due to the actual availability at site. As per the studies conducted by scientists of an International Organization (WWF), it was revealed that more than 4,70,000 acres within the ayacut area of the project, is already under irrigation through a) several major lift irrigation projects about to be completed, (e.g. Tatipudi, Pushkaram, Chagalnadu), b) Minor irrigation tanks completed (c ) private ground water tube/dug wells d) public tube well projects built by the State Irrigation Department Corporation, etc. To think that the ayacut under Polavaram project would still be 7,20,000 acres is a myth and it would therefore be wrong to proceed on this basis.
- Canals: Gravity flow canals with FSL at 95ft an be planned on either side of the barrage. But this would involve in excavation of new canals. New gravity canals would need additional land acquisitions and capital costs over and above the amount of about Rs.2000 crores already spent on the two canals. Though it is technically possible to divert 80 TMC from Godavari to Krishna river at point just upstream of Prakasam Barrage (as against Budameru through the left canal under construction) it may ultimately be economical to use the canals now under construction, rather then excavating new gravity canals. In such a case water will have to be lifted from 95ft level in the river to 133ft level of the annals. For a discharge of 12,00 cusecs (required for 2.5lakh acres, diversion of 80 TMC water to river Krishna etc.) and a static head of 38ft. (11.6 m) it would require 54MW and this can be met out of the 350MW hydro power that would be generated in the barrage.
- Hydropower: The Central Electricity Authority was holding a view that it would be possible to generate about 720MW hydropower in Polavaram dam as against 960MW proposed by the State Government. On account of constructing a barrage (instead of the dam), the hydro power component, would get reduced to 360 MW. However, this can be improved to 1260 MW by constructing three barrages on the upstream side – one near Bhadrachalam, second near Kunavaram on the Godavari river and the Third across the Sabari river. All these barrages will have submersions within the high flood zone of the river and no village/forest/lands will get submerged. Thus, 540 MW more hydro power can be generated through these 4 barrages proposed, as alternative to the Polavaram dam.
- Water Requirements: Polavaram dam envisages a live storage of 75 TMC and for the sake of this, a huge submersion problem is being faced. Incidentally, this live storage gets filled up in 8.5 hrs when the flood is 25 lakh cusecs. Since the ayacut area got reduced from 7.2 lakh acres to 2.5 lakh acres, there is no need to have any storage for the Polavaram project. Just as the run of the river system at Dowlaiswaram is able to supply water for more than 10 lakh acres, the alternative barrage at Polavaram can easily irrigate 2.5 lakh acres as a run of the river system. This is possible because, the cropping pattern is only for one crop and that too in the Kharif rainy season when there will be adequate flows in the river. All other benefits that are envisaged in the Polavaram dam proposal can still be achieved through this barrage proposal. For example the inter basin transfer of Godavari water to river Krishna to an extent of 80 TMC can be drawn during the rainy period of four months when there will be adequate flows in Godavari. Drinking water and industrial water requirements throughout the year (24 TMC) can be met with, through the 30 TMC storage available in the barrage. If for any reason at a later date, storage of water is needed for the project an utilizable storage of 80 TMC would still be available in these four barrages as against the urilizable live storage of 75 TMC in the Polavaram Dam. The only main difference in the barrage proposal is that water has to be lifted from the barrage to canals over a static head of 11.6M The same canals can also be utilized for carrying additional discharges (during the rainy season) to meet the requirements of further lift irrigation projects (Uttara Kosta Sujala Sravathi) on the left and right main canals. In such a case additional pumping units will have to be installed in future, at the barrage site, to pump this additional water for a static head of 11.6m.
- Costs: The latest estimated cost of Polavaram Dam (without canals) is stated to be as 16,500 crores, out of which Rs.10,000 crores would be for spillway, rock fill dam and Hydropower civil works plus Rs.6,500 crores for Relief & Rehabilitation (R&R) of displaced persons. On the basis of the recent estimate for the barrage at Kantalapalli on Godavari river (Rs.880 crores) the cost of the above mentioned four barrages can be estimated as Rs.6000 including the capital cost of pumping at Polavaram barrage. Thus the alternative proposal would lead to a saving of about Rs.10,500 crores apart from having the facility of quick execution and completion of the project much earlier than the Dam proposal. Added to this there will be no interstate or submersion problems. More importantly there is no risk of “dam break” of the earthen (rock fill ) dam threatening the lives of 46,15,000 people, which cannot be ruled out as a figment of imagination in the light of recent floods in Krishna river (when 2.5 times the maximum flood occurred). When all the benefits of Polavaram Dam project could be achieved through the barrages at less than one third of the cost and without submersions it requires a revised thinking on this project, especially in the revised context of the magnitude of the peak floods.
- Interstate problems: The barrages proposal will have no interstate problems with Orissa and Chattisgarh states, as there will be no submersion in those states when the alternative barrage proposal is implemented. If the past experience with the Orissa state regarding Vamsadhara stage II and Janjhavati dam is any guide (stalling the projects for over 2 decades), it will not be prudent to assume that they will allow construction of Polavaram dam since it involves submersion of about 20 villages in their states.
- Inland water navigation for seagoing vessels: The entire length of Godavari river will have to be converted into a series of continuous stepped reservoirs, one below the other by constructing a number of barrages, all along the rive. The author termed this as “Step Ladder Technology” about a decade back. Sufficient draft (depth of water) will be maintained all along the river, even in summer, to facilitate sea going vessels (ships upto 3000T capacity) to ply in the river. This would be similar to St.Laurence river seaway (7 barrages), Tennessee (9 barrages) river Illinois (9 barrages), Missouri (10 barrages) and Mississippi river (27 barrages) in USA. The entire Godavari river will be a storage reservoir with submersions limited to the high flood zone of the river. A ship load of coal from Singareni can go to any Indian seaport like Tuticorin, Haldia, Mumbai etc and also directly to any other foreign country. This is also called as Green Technology. Similarly ships from other countries can ply in the Godavari river and reach any place all along the river. Villages and towns along the river will get international connectivity as happened in the cases of US, Europe(Rhine-Danube linkage) and China (from the Pacific sea to Chungking through the 3 Gorges dam). This will facilitate development of major and minor industries duly utilizing the mineral and human resources in the area. Employment throughout the year is possible through navigation, Industries including mass mineral based units (e.g. coal, cement). Water required for these units as well as hydropower can be made available to these units. Any raw materials imported can be done at a cheap transport cost. Likewise goods (including manufactured goods) can be transported to other places (including international) at a cheap transport cost. Ultimately Andhra Pradesh can develop economically like parts of China, withstanding international competition by producing goods at competitive rates. More important is the employment generation to the youth in this navigation and allied sectors and the disposable incomes generated, boosting the economy of the area, (through several chain reactions of development). The economic development of US and Europe in the mid Twentieth Century can be attributed to this navigation associated sectors, where nearly 70% of the workforce is employed, whereas only 15% of work force was employed in the agriculture and irrigation sectors. Through Irrigation is important for food security, many people still think that eradication of poverty can be done by irrigating every acre of arable land. All the irrigation projects in Andhra Pradesh are being executed for raising one assured irrigated crop during the rainy season. This will give employment to the landless labour for about 90 days in a year. They will have to go out to seek employment for the balance 9 months in a year. This is the reason why poverty still continues among the landless labour (who constitute 50% of rural population) in the Krishna and Godavari deltas inspite of every acre in that area being irrigated.
In the case of Godavari river, inland water navigation for sea going vessels can be made possible through construction of 11 barrages as shown in the map in the vicinities of 1. Pedda Bellala, 2. Yellampalli, 3. Chinnur, 4 Suraram, 5. Kantalapalli, 6. Edira, 7. Dummagudem, 8. Bhadrachalam, 9. Koonavaram, 10. Sabari and 11. Polavaram. Out of this the items 2, 5 and 7 are now under construction. Items 8, 9, 10 and 11 will form part of Polavaram Dam alternative plan as described above, under the para 5 ‘Costs’. Thus there will be a need to construct additionally four barrages (items 1,3,4 and 6). There may also be a need for a few more barrages for navigation and this can be determined after a detailed investigation. The cost of the above 4 additional barrages, locks and hydropower (about Rs.6,000 crores) can be met out of the savings of Rs.10,500 crores (as mentioned above in para 5 ‘Costs’). Grants available in the Inland Water Navigation sector in Government of India, can also be utilized for this navigation requirement as well as other works such as developing inland water ports, rail and road connectivity to such ports, construction of wharfs, godowns, warehouses, purchase of loading and unloading equipment (cranes) extensionof power lines etc. Also there is a possibility by considering all the above development project as a “National Project”. This is the stage when Andhra Pradesh will have to plan for total economic development all along the Godavari basin, revolving round the water sector, rather than limiting all the development only to one irrigation sector.
POLAVARAM BARRAGE (ALTERNATIVE TO DAM)
1. Discharges in canals (left & right) in Kharif season:-
(a) Ayacut (Total) = 2.5 lakh acres @ a duty of 75 ac/cusec
Discharge = 2,50,000/75 = 3333 cusecs
(b) Krishna diversion in 120 days = 80 TMC
Q in 1 day = 80/120 = 2/3 TMC
@ 1 TMC / day discharge = 11,574 c/s
2/3 /day discharge = 11,574 x 2/3 = 7,716 cusecs
(c ) Domestic & Industrial water
365 days = 24 TMC
1 day = 24/365 Q = 24/365 x 11574 = 761 cusecs
Therefore Total discharges in both the canals = a+b+c = 11810 cusecs
Or 11810/35.316 = 334.5 cumecs
(Note : During non Kharif season, there will be pumping only for item (c ) requirement)
2. HP of pump sets required for both left andright canals: FSL Left canal =40.54 m
Water level in barrage (allowing 1.0 m lower level) = 29.48;
Therefore Static head = 11.06m
Adding frictional losses @ 10% = 1.10, Total head = 12.16m
HP = 334.5 x 1000 x 12.16 x 100 ( eff. Of motor 95% x ef. pump
75 76 80% = 76%
= 71,360 HP or 71360 x 0.746 = 53235 KW or 54 MW
3.Four additional balancing reservoirs can be constructed infuture, on each, on Pampa, Thandavar, Varaha and Sarada rivers to store about 24 TMC for future domestic and industrial uses. These reservoirs can be fed through the left canal by pumping additional discharges (as part of a future project).
POLAVARAM DAM VERSUS MULTIPLE BARRAGE
(Contentions raised by AP State Government experts on the article on Polavaram project without submersion by Sri.T.Hanumantha Rao and the clarifications thereon)
Question No.1: It is contended that Storage at the alternate low barrage site at Polavaram would be 22.8 TMC with FLR 100ft and out of this only 5 TMC can be used.
Answer: 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
Question No.2: It is contended that due to siltation, utilization of water and useful storages in barrages will be reduced.
Answer: The proposed barrages are not like others, where sill levels of weirs are raised (like Prakasam and Cotton Barrages) to facilitate supply of water to canals. In such cases siltation will occur. The alternate barrages will have sill levels at bed levels and the regime of the river U/S and D/s is not disturned. The vent way would be equal 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.
Question No.3: It is contended that the Total storage in 4 barrages will be 53 TMC and only 33.5 TMC out of this can be utilized.
Answer: As explained in item2, the full storages in the U/s barrages upto the bed level namely 35 TMC can be utilized without any limitations of Minimum Draw Down Level (MDDL) with skillful selection of sites, approximate FRLs and Limiting submersions it is possible to get maximum storage at a place in between Bhadrachalam and Kunavaram and another on Shabari. Thus the total useful storage of 75TMC can be obtained only in 3 barrages. (33+23+19) (e.g. Storage at Kanthalapally=22.5TMC)
Question No.4: It is contended that cost of barrages would be Rs.9,000 crores.
Answer: 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 4000 crores. Asa comparison the cost of Polavaram spillway and rock filled dam (2004-05 rates) was only 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.
Question No.5: It is contended that as against 277 villages submersion in Polavaram dam, 128villages will get submerged under the barrages
Answer: According to the submersion area tables ofPolavaram Dam 30 villages will get submerged with FRL @ 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 1m interval contour map and the FRL 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.
Question No.6: It is contended that power production in the 4 barrages will be 271 MW
Answer: Power production contemplated at the Dummagudem barrage is 310MW. On the basis of this of this it is possible to produce about 960MW at the three barrages. However details have been worked out by GENCO. If there is any reduction, this will be only a disadvantage of the alternative proposals, and this has to be viewed against all other major advantages mentioned in my paper (especially eliminating dam break costing 46.15 lakh lives, limiting submergence of villages to 1/4th reduction of cost, early completion, navigation of sea going vessels etc.
Question No.7: It is contended that there will be 7.1 lakh acres under Polavaram dam and not 2.5 lakh acres.
Answer: 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 apart irrigation under Tatipudi and Pushkaram L.I. Projects , Yelur project, Minor irrigation, GW (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 Government and WWF Officials. A much lesser storage than 75 TMC (As per the dam proposal) would be able to meet the requirements of the Ayacut. GW &LI 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.
Question No.8: It is contended that Orissa Government will oppose the alternative design.
Answer: 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.
Question No.9: It is contended that there is no navigation facilities for sea going vessels down stream of Dowlaiswaram and hence the same need not be provided on the upstream of Polavaram dam.
Answers: Two or three barrages will have to be constructed downstream of Dowlaiswaram upto the sea to facilitate the navigation of sea going vesseles. 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 DAM ALTERNATIVES : DOUBTS AND APPREHENSIONS
Question No.1 on Polavaram Ayacut : While AP state Government experts assert that Polavaram project irrigates an ayacut of 7.2 lakh acres independent engineering experts challenge the claim by stating that the project command area is already getting irrigated by other projects and hence Polavaram project provides irrigation to less than 2.5 lakh acres only. What is the correct position?
Answer: Andhra Pradesh Government proposals envisages an ayacut of 7.2 lakhs acres to be fed by the left and right main canals by gravity. Dr.Bhiksham gujja, Scientist, WWF and others, after a detailed study f the ayacut mandal-wise, determined that not more than 2.5 lakhs acres ayacut is available (for gravity flow), since more than 4.7 lakhs acres are already covered under various other irrigation sources (vide, chapter9 “Perspectives on Polavaram”) These irrigation sources are:
- Pushkaram and Tadipudi Lift Irrigation (LI) projects which are having 2 lakhs acres under the gravity command of Polavaram canals (and 1.92 lakh acres outside the command).
- Yeleru project ayacut (Gravity flow) = 0.67 lakh acres
- Minor irrigation tanks, public (IDC) tube wells, private tube wells, flowing wells (artesian) dug wells and others having more than 2.1 lakh acres in command.
Their report concludes that after deleting the above ayacuts, the remaining area to be irrigated under Polavaram canals by gravity will not be more than 2.5 lakhs acres. This is a very strong point for re-examining the whole Polavaram project proposals. The state Government will have to reconcile these figures in the interest of the state, instead of sticking on to the figure of 7.2 lakh acres. The avowed reasons for considering the ayacuts as 7.2 lakhs acres and how they are not valid are discussed below.
The AP State Engineers are arguing on the various aspects of project as follows:
- “Pumpsets for lifting water from Godavari river to Pushkaram and Tadipudi main canals will be disbanded and their ayacut of 2 lakhs acres will be fed from Polavaram main canals, thus avoiding the pumping costs from Godavari. These pump sets will be used elsewhere and the main canals of the LI projects will serve as part of the distribution system”.
- “Minor irrigation tanks do not have assured water supplies and for this reason, it is preferable to supply to this ayacut also from Polavaram Canals”.
- Yeleru gravity flow ayacut of 67,000 acres will be tagged on to Polavaram gravity canals, as this ayacut lies within command of Polavaram Left Canal”.
- “For pumping ground water through tube wells, dug wells etc., it requires electric power and to avoid this, it is preferable to supply water to this ayacut also from Polavaram canals”.
A brief study is needed to examine the technical, financial and administrative aspects of the above issues. How far the above contentions are tenable and valid are discussed:
A) Pushkaram and Thatipudi LI Projects:
o The average static head of pumping from Godavari river is 18m and with frictional losses, the total head would work out to about 20m, when compared to the Devadula LI project (on the same river Godavari, now under construction), the static head is 275m (from Gangavaram river site to station Ghanapur) and with frictional losses along the long pumping mains, the total head would then work out to about 400m. The pumping head for Pushkaram and Tadipudi LI projects will be about 5% of that of Devadula LI projects and therefore, the power consumption for these two LI project would be rather insignificant, when compared to the other major lift irrigation projects on the same Godavari river. To scrap both these LI projects, on the plea of power consumption would not be prudent for the following financial reasons:
o Elsewhere in the state, lift irrigation schemes are not scrapped when gravity flow is found possible through another project taken up later on. These two LI projects are of major category (not Minor or Medium) and also huge amounts are even now being spent on them to lift water and irrigate.
o The two lift irrigation projects Pushkaram and Tatipudi cannot be considered as temporary works till Polavaram project takes shape, since all the component works are permanent and form durable assets. These are unlike temporary structures like Coffer dams (dismantled later on) dewatering pumpsets (removed after construction is over)Assuming that the pumpsets of the LI projects would be dismantled and used elsewhere, the civil works constructed such as intake well, approach channel, pump house, mains etc. would all go waste.
o The contention that the main canals of these two LI projects would be used as a part of the distribution system is not technically sound. The main canals of the two LI projects are contour canals, running parallel and very close to the Polavaram main canals. They need not be operated when once the Polavaram main canals function and hence, they would become redundant. A distribution system comprises of branch canals, taking off from main canals at an angle (or perpendicular) to the main canal, and runs along ridge lines. Similarly majors/minors take off from Branch canals and distributaries take off from minors, forming the entire distribution system. In this scenario, the main canals of the two LI projects would have no role in the distribution system, when once the Polavaram canals take this role. Thus the amount spent on these main canals including the cross masonry works, structures etc would all go waste.
o Lift for the two LI projects cannot be entirely avoided, even if their ayacut is tagged on to Polavaram canals. 1.92 lakhs acres of ayacut, will have to be served by lifting only, as the same cannot be commanded by gravity by the Polavaram canals. The extra lift if these LI projects are continued, is only at Godavari river, which is relatively minor as discussed above. On the plea of avoiding this lift, it is not financially advisable to allow all the huge expenditures incurred on civil works (canals, structures etc.) to go waste. Also, it would not be administratively acceptable, since large private lands were already acquired to build these engineering works.
Yeleru: Ayacutdars of 67,000 acres are not willing to tag on to Polavaram ayacut, since they get water for only one crop from Polavaram canals, whereas, they are now getting water for two crops under Yeleru project. Thus there is no need to supply water to this ayacut of 67,000 acres from Polavaram canals.
Minor Irigation (MI) Tanks: The ayacuts under minor irrigation (MI) tanks is included under Polavaram canals while calculating its ayacut as 7.2 lakh acres. This seems to have been done on the plea that this ayacut is not having assured water supply, there is no precedent for such a procedure in AP while localizing the ayacut under Sri Rama Sagar Project (SRSP) the ayacut under minor irrigation tanks was excluded. The same was the case with Nagarjuna Sagar and other projects. Polavaram project ayacut area is having much better rainfall than the SRSP ayacut, and hence the water resources for the tanks in this area, are more assured than the other projects. On the Principle that no area should be served simultaneously by two separate and independent sources, the ayacut under MI tanks will have to be deleted from the Polavaram project. The procedures followed in the other major irrigation projects in the state, will have to be followed in this project also.
Tube Wells, dug wells etc.,: Ayacuts irrigated under these sources are also included under Polavaram project. This is said to be for the reason of avoiding pumping costs and electricity consumption. Ground water can be utilized only by pumping and this can therefore never be avoided. In fact the Polavaram project report contemplates and encourages the usage of ground water, as a measure of utilization of total water resources in that area. Such usage of ground water is also contemplated in the National water policy, relating to conjunctive utilization of ground water with surface water. It would therefore be a retrograde step to scrap these ground water extraction devises and provide water to these areas from Polavaram canals. It is thus necessary to delete the areas served by ground water, from the Polavaram project Ayacut, and also encourage further usage of ground water in the ayacut (as proposed in the project report). When all the areas ( mentioned above) are deleted, the Ayacut under Polavaram project gets reduced to less than 2.5 lakh acres as mentioned in the article of Dr.Bhiksham Gujja et.al. The project proposals including the extent of storage of water needed at Head works, discharge capacity of main canals and distribution system, will all get reduced significantly, as the ayacut is reduced to one third i.e. from 7.2 lakh acres to 2.5 lakh acres.
This means redesigning the project as per the existing realities. The reservoir working tables will also have to be revised and correct and realistic storage required will have to be worked out.
Question No.2 on impacts on Godavari delta: If the proposed Polavaram dam is replaced by multiple barrages Godavari delta irrigation system will suffer due to water scarcity in Godavari river. Is it true?
A) No Water Scarcity due to alternate proposal: There are apprehensions (as seen in the print media reports) that Godavari Delta will not get adequate water if the alternative proposals are implemented. It is in fact the other way round. Since the ayacut of Polavaram project is getting reduced from 7.2 lakh acres to 2.5 lakh acres, (in the alternative proposals), the Godavari Delta will get more water than what is contemplated under the Polavaram dam proposal (now about to be constructed). This is more so when the same extent of live storage of 75 TMC would be made available in the proposed three barrages.
B) Possible dam collapse kills lakhs of people in the delta: The risk of dam break is not imaginary and when this occurs, the lives of 46.15 lakh people living in the Godavari delta and surroundings would be endangered. All the while there was a thinking that when the dam is constructed strongly, it will never break, and hence this risk is imaginary. In this context, it would be relevant to study the huge flood that occurred in river Krishna (an immediate neighbouring catchment of Godavari river) recently in October 2009. As against the maximum ever occurred flood of 9.5 lakh cusecs (in the past 100 years) at Srisailam (and corresponding maximum discharge of 10.6 lakh cusecs at Vijayawada Barrage), a flood of 25.5 lakh cusecs had occurred at Srisailam during this year in October 2009. This is 2.7 times more than the ever observed maximum flood. If a similar flood occurs in river Godavari which is quite likely in the future, the discharge in the river would be 89 lakh cusecs (i.e.2.7 x 33 lakh observed maximum flood in Godavari river). Such a possibility is very much real and not a figment of imagination, as it already occurred similarly in the Krishna river recently. Climatologists who are watching “global warming” say that peak floods in Godavari river would increase in the future. Meteorologists and hydrologists have similar views and hence caution is needed. Though the Polavaram dam and spillway are designed for a Possible Maximum Flood (PMF) of 50 lakh cases, when a flood much larger than this occurs, water levels in the reservoir would rise above the Full Reservoir Level (FRL) of 45.72m, and may overflow over the dam causing erosion and ultimate breach of the earth cum rock fill dam. Also any increase in water level above the FRL of 45.72would encroach on the free board and the same is not permissible in the case of earth-cum-rock fill dams. This is because the wave action and the wave run up on the slopes of earth dam would cause spilling and erosion leading to a breach. The stability of the earth dam will get endangered when water levels rise above FRL.
It is good to start construction of Polavaram earthen dam with a firm conviction that it would be built very strongly and would never break due to any quality reasons. If the recent experiences on the earthen dam constructed in the state are any guide one cannot be so sure of this conviction. Infact, all the earth dams will be constructed only with such convictions. But we see different results all over the world.
C) Actual cases of Dam collapses: The Earthen dams of two medium irrigation projects (namely Gundlavagu project and Palemvagu project) constructed during the past four years in the state, have breached even without the designed maximum flood occurring. There are innumerable similar examples of dam breaks throughout the world. The recent one in India was the Morvi Earth dam (Gujarat) breach, which killed about 15,000 people. Earthen dams can also break due to reasons other than quality. That is why the recent international recommendation is to avoid as far as possible, construction of earthen dams in the close vicinity of thickly populated areas. Polavaram earthen dam sits just upstream of an extremely thick populated area.
D) Water storage in the dam provides incremental floods: There is an argument that when a flood of 89 lakh cusecs occurs in the river, the areas on either side of the Godavari river will any way get flooded (with or without the dam), and the population will get effected since the protective flood banks are designed only for a maximum discharge of 36 lakh cusecs But there is a difference between a dam break and a natural flood increase. In the case of a Polavaram dam break, the stored water of 194 TMC along with the huge flood of 89 lakh cusecs will flow down below as a gigantic wave, similar to the Tsunami wave. People will have no time to leave their habitats. If such a break occurs during the nights, 46.15 lakh people will have a watery grave within some hours of occurring of the dam break. With regard to natural occurrence of 89 lakh cusecs, this would occurs gradually over a number of days and people will have time to observe the same, vacate their habitations and move to the designated higher grounds. It has happened similarly in Krishna Delta during the extraordinary floods that occurred in Krishna river in October 2009. In other words the increase in water levels does not happened suddenly in a few hours (unlike the dam burst wave)
E) Alternate Proposals ensures safety for people and their lands: This alternative proposal is suggested primarily in the interest of population residing in the Godavari delta, especially in the light of the recent occurrence f Krishna huge flood of 2.7 times the ever observed maximum flood. As a matter of fact, this alternative proposal will have to be strongly favoured by the Godavari delta people instead of opposing it, since this gives all the benefits of the earlier “Dam proposal” without any risk to their lives in future. This apprehension may be due to information gap about the alternative proposal. In the case of the alternative barrage proposal the huge incoming flood of 89 lakh cusecs will pass down the structure, as it is without any obstruction, and hence there is no need to do any “dam break analysis” (as there is no dam).
Question No.3 on Navigation facilities: If the Polavaram dam is replaced by a barrage navigation will be adversely effected. Is it true?
Answer: The present Polavaram dam design provides for a small navigation canal, going in a tunnel and is suitable only for small boats and launches. It is not suitable for sea going ships, which is possible only in the case of the low barrage alternative proposal.
Question No.4 on National Project status: If the proposed Polavaram dam project is modified Union Government will not