Foundation raft concrete for the piers, will have to be designed so as obtain sufficient anchorage required for these gates. The bottom of gates will have to be kept at the average bed level, in order to facilitate drawal of water upto the bed level (for Godavari delta Rabi crop). In other words when gates are opened the river would be flowing down naturally as earlier, as if there is no obstruction. This stored water from top of gates upto bed level can also be pumped for the requirements of the Polavaram canals, during the non flood periods. There is no need to provide dead storage by keeping MDDL at 28.956, as provided in page 21 DR The assumption that water stored above this MDDL only (4.204 TMC) is available for pumping is not correct. For calculation of pumping during the flood period, the water levels are considered as varying from 28.956 and 30.48 in the DR. During this flood flow period of over 4 months the water levels will have to be maintained at near FRL of 30.48 by suitably regulating the barrage gates and allowing the excess flows down the barrage. Thus it may be seen that there is no need to pump stored water, as long as there are flood flows in the river and the entire 169.61 TMC demand of Polavaram (Page 37 of final report June 2007) during Khariff season can be pumped when the river is in floods and water is then available at near FRLs.
In the Polavaram Original proposals, the Rabi season demands of Godavari delta and Polavaram canals were contemplated to be met through the yields (flows in the river) and 75 TMC stored water. In the Alternative proposals also, a similar method will have to be followed. Stored water will have to be pumped from a level of 30.48 extending up to almost the bed level and to facilitate, this the suction foot valve will have to be kept at a level corresponding to the bed level in a depressed sump so as to avoid vortex problems. The static head of pumping will than be increasing as the water levels fall from 30.48M to about 11.00 M in the pond. The quantity of water to be lifted from lower levels will be a fraction of the quantity of water to be lifted from higher levels and the actual power requirements to pump during January-May will have to be calculated on a weekly or fortnightly basis. The installed pumping capacities (HP) to pump large quantities of water for Khariff Season requirements (from higher water levels) would be more than the required capacity to pump relatively a fraction quantity of water during the Rabi season (from the lower levels in the pond).
The cost of alternative Polavaram barrage is estimated in page21 Dr as Rs.3415 crores almost the same as the original Polavaram dam proposals which comprise of a high earth cum rock fill dam, separate spillway, bridge, lengthy surplus course over 3km long etc. (Rs.3630 crores) With proper selection of site for the alternative proposals, the earth dam in the river will get replaced by a gated structure and there will be no necessity for a separate spillway (similar to Kantalapalli and Dummagudem which are now under construction). In such a case, the cost of barrage as per AP will get reduced to about ½ to 1/3rd of the original Polavaram dam proposals (e.g. cost of Kantalapalli barrage is Rs.880 crores). The main cost will be due to gates of Size 18M x 20M, Rs.650 crores (based on figures given in page 26 of DR) 4 rows of 12m depth piles for 1km length of barrage (1000 x 4 x 12 x Rs.5900) Rs.28 crores, Spillway bridge 1km long Rs.8 crores (page 27 of DR) piers Rs77 crores (Page 27 Dr) and adding for all other items like aprons concrete, steel etc. (On the basis of Kantalapalli barrage) Rs.637 crores, the total cost of the alternate barrage would then workout to Rs.1400 crores, as against Rs.3415 crores provided in page21 DR. The topographical problem of aligning off take canals on either side will no more be an issue in the case of the down steam site for the low barrages of AP water can be drawn and pumped directly into the cisterns and the gravity canals can start immediately from the cisterns. There is no need to provide pumping mains on either side due to the advantage of plain terrain conditions being available on both the sides of the structure. The canals can take off directly from the barrage structure without any need for separate pumping mains.
A gross storage capacity of 21.944 TMC is indicated in the design of DR (page 21) As pr the reservoir capacity tables (page 39, June 2007 report) the storage capacity at the proposed FRL 30.48(100ft) is 36.082 TMC. Since the Kunavaram barrage proposal is not there in the AP design, the interception of storage due to Bhadrachalam & Sabari barrages as designed in the AP would be very low, sine the river bed levels at these places will be close to the FRL of 30.48. If these interceptions in storage are considered as 1.082 TMC (to be actually calculated based on submersion area contour map) the storage available for usage would then be 35TMC and not 4.204 TMC as provided in page 21 Dr. The reasons for this (as already discussed above) are that water stored and available up to bed level can either be drawn to the down stream side or pumped into canals and that there is no need to maintain an MDL of 28.956. Gross and live storage capacities in the cases of Bhadrachalam and Sabari (Chatte Kunta) barrages were rightly shown as the same (vie page 21 of DR) and the same concept will have to be followed for this Polavaram barrage also. Villages that would be submerged under this barrage at FRL 30.48 are noted as 66 nos in the DR (page21) out of this 32 villages are stated to be below FRL 30.48 M level and balance 34 villages above 30.48M level and extending upto 42.50 M (page 34 and 35 of DR) villages situated upto 12 M above FRL are shows under the list of submergible villages for the adduced reason that the ayacutdars lose approach to their fields due to water stored in the barrage. The villagers can be provided with detoured cart tracks to approach their fields, and for this reason, they need not be asked to vacate their villages situated far above the FRL. As such, the number of villages that will get submerged upto FRL 30.48 can be considered as 30 (vide page 129 of June 2007 report) and not 66 no’s as indicated in page 21 DR
In the comparison of costs (Page 18 of DR) the cost of original Polavaram project was indicated as Rs.8713.09 crores and that of the AP as Rs.19,108.53crores. The details of alternative proposals will have to be corrected as indicated below, incorporating the changes indicated in the above paras. Item I will get reduced from Rs.12,895 crores to Rs.3,500 crores. Item2 can be the same as per original Polavaram proposals (Rs.940 crores and Rs.1800 crores), since the same amount of hydro power under alternative proposals would be generated. Thus there would not be any decrease in costs(as explained in the power calculations). Item3 & 4 fro R&R, LA & Forests (Rs.2343.09 crores) provided under original Polavaram proposals will get reduced to about 1/4th i.e Rs.600 crores in view of the submersion areas in AP getting reduced about 1/4th of the original dam proposal. The item5 regarding pumping mains etc. Rs.1543 crores (page 58 DR) provided in AP will have to be reduced to Rs.303 crores as there will be no pumping mains as explained under para 3 above.
As against 182 MW power required for pumping provided in the DR, only 54 MW power is needed (as per calculations in AP due to reduction in ayacut). For these reasons item 1 of the statement (page 58 DR) will get reduced to Rs.60 crores and items3 & 4 reduced to 243 crores and thus a provision of Rs.303 crores will be adequate for this. The total cost of Alternative proposals including Hydro power component would then work out to Rs.7143 crores (Rs.3500+940+1800+600+303=7143) as against Rs.19,108.53 crores provided in DR. When compared to the original Polavaram project cost of Rs.8713.09 crores, the cost of AP would be cheaper by Rs.1570.09 crores. Since the realistic submergence cost is expected to be about Rs.6000 crores, much higher than Rs.2343.09 crores provided in the original proposal, the actual cost of alternative proposal would be cheaper by more than Rs.4000 crores when compared to the original dam proposal.
To assume that it is not possible to generate power in a barrage during the flood period because there would be no afflux is therefore not correct, for the reasons explained above. Additional hydro-power units can be added on either side of the three barrages, and more power generated at a later date.
There is no need to delink Yeleru ayacut of 67,600 acres from Yeleru project and supply water to this area from Polavaram canals, so as to utilize this extent of water for the proposed new ayacut of Yeleru project lying above the Polavaram command. The existing system of Yeleru aycut 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.
The total ayacut of 2,77,234 acres (page 51 DR) is shown as 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 rain fed conditions, would be less than 1.8 lakh acres and that this much area only would need irrigation under Polavaram project. Considered that private lift irrigation systems (e.g. tube wells, dug wells 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 regards to the existing lift irrigation projects covering an ayacut of 3,75,166 acres (Page 51DR) it is mentioned that the “life of some of the existing L.I scheme 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 abandoned, there is a need to supply this ayacut of 3,75,166 acres under Polavaram project”. Pushkara, Chagalnadu and Tadipudi L.I 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 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 project under Jalayagnam are lift schemes and they cannot be abandoned after a life time of the pumping equipment of say 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 repard to Uttarandhra Sujala Sravanthi, Rudramkota irrigation and other lift irrigation projects from Polavaram canals (Page 59 DR) 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. Hence these costs 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.
Such economic development of Godavari basin through navigation of sea-going vessels will one for all get deprived, if Polavaram dam is executed as originally proposed, resulting in great loss to the nation.
(T.HANUMANTHA RAO)
Encl: Design details : 2 pages
L.S. Sketch : 1 page
Extracts of DR 24 pages
Extracts of June 2007, Report 3 pages
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 = 3333 cusecs
75
(b) Krishna Diversion in 120 days = 80 TMC
Q in 1 day = 80/120 = 2/3
@ 1 TMC/day discharge = 11,574 c/s
2/3 TMC/day discharge = 11,574 x 2/3 = 7,716 cusecs
(c) Domestic & Industrial water
365 days = 24 TMC
1 day = 24/365 TMC Q = 24/365 x 11574 =761 Cusecs
Therefore Total Discharge in both the canals = a+b+c= 11,810 cusecs
or 11810/35.316 = 334.5 Cumecs
(Note: during the non Kharif season there will be pumping mainly for (c) requirement)
2. HP of pump sets required for both left & Right canals:-
FSL Left Canal =40.54 m
Water level in barrage (Allowing 1m lower level during 4 month flood season) = 29.48m
Therefore Static head = 11.06
Adding Friction losses @ 10% = 1.10, total Head = 12.16m
HP = 334.5 x 1000 x 12.16 /75 x 100/76 (eff. of motor 95% x eff ump 80% = 76% )
= 71,360HP or 71360 x 0.746 = 53235 kw or 54MW
3. POWER CONSUMPTION FOR PUMPING FROM RIVER TO CANALS:-
Data
a) Total max discharge in canals = 11810 cusecs or 334.5 cumecs
b) Total head=12.16m; HP=71.360; KW= 53235 (54 MW)
c) Maximum pumping would be in 4 months (120 days or 2840 hrs)
d) In the other days of the year, pumping for Krishna delta and drinking water will be less and power consumed during this period can be considered as 30% of the peak power consumed in 120 days.
CALCULATION OF POWER CONSUMED:
KW hrs consumed in 120 days or 2880 hrs = 54,000 x 2880 = 15,552 x10(power 4)
KW hrs consumed during the other days in the year (say about 30% of above)
=4,448 x 10 (power 4) or = 20,000 x 10 (power 4 ) or 2 x 10 (power 8)
Cost at Rs.1.50 per unit = 2 x 10 (power 8) x 1.5=3 x 10 (power 8) or Rs.30 crores
Thus the annual notional power consumption cost=Rs.30 crores. This would be a notional profit to the irrigation Department, as hydro-power is produced with capital and maintenance cost borne by the irrigation Department.
4. POLAVARAM LOW BARRAGES –HYDRO-POWER GENERATION
1.Barrage D/s of Bhadrachalam:
Q= 1,00,000c/s or 2832 cumecs on an average for peak power
H=20m (water level differences between U/s and D/s 50.75-30.48 = 20.27 or 20m) M.W.=cum x Head/75 x eff x 0.746 = 2832 x20/75 x 0.75x0.746=423 MW
Very large discharge axial flow turbines will have to be used.
2. Barrage across Sabari: Q = 65000 c/s or 1841 cum and H = 14m;
44.72-30.48:14.24 or 14m MW = 1841 x 14/75 x 0.75 x 0.746 = 192 MW
3. Low barrage at Polavaram; Q = 1 lakh c/s or 2832 cum & H = 30.48-10.48 = 20m
MW= 2832 x20/75 x 0.75 x 0.746 = 423 MW
4. Total Hydro power = 423 + 192+423 = 1038 MW