Report No. 525-IN 2FLE Copy India ur Appraisal of the Godavari Barrage Project January 10, 1975 South Asia ProjectsDepartment IrrigationDivision Not for Public Use U Document of the International Bank for Reconstruction and Development International Development Association Thisreport was prepared for official useonly by the Bank Group. It maynot be published, quoted or cited without Bank Groupauthorization. TheBankGroupdoes not accept responsibility for the accuracy or completeness of the report. Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized
Document of the International Bank for Reconstruction and DevelopmentInternational Development Association
This report was prepared for official use only by the Bank Group. It may not be published,quoted or cited without Bank Group authorization. The Bank Group does not accept responsibilityfor the accuracy or completeness of the report.
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CURRENCY EQUIVALENTS
US$1.00 = Rupees (Rs) 8.00 /aRs 1.00 = US$0.125US$1 million Rs 8,000,000Rs 1 million = US$125,000
WEIGHTS AND MEASURES (NETRIC SYSTEM)
1 meter (m) = 3.28 feet (ft)1 kilometer (km) = 0.62 miles1 hectare (ha) = 2.47 acres (ac)1 million cubic meters (Mm ) = 810 acre-feet1 ton = 1,000 kilograms (kg)
CAD - Command Area DevelopmentGOAP - Government of Andhra PradeshGOI - Government of IndiaHYV - High Yielding Varieties (of rice)ICAR - Indian Council on Agricultural ResearchICB - International Competitive BiddingNSC - National Seed CorporationNVP - Net Value of Production0 & M - Operation and MaintenancePWD - Public Works Department (Andhra Pradesh)
FISCAL YEAR
GOI, GOAP and agencies - April 1 - March 31
/a The Indian Rupee is linked to the Pound Sterling and the exchangerate with the United States Dollar has varied between US$1.00 - Rs 7.60and Rs 8.40 in recent months.
INDIA
APPRAISAL OF THE GODAVARI BARRAGE PROJECT
Table of Contents
Page No.
SUMMARY AND CONCLUSIONS .................... *. .. i-i
I. INTRODUCTION ..... ................................... . 1
II. BACKGROUND ......... o .......................................... 1
The Economy *.................... 00 1Agriculture in India 2............................ 2Agriculture in Andhra Pradesh ...................... 2
III. THE GODAVARI DELTA .....00000000 00000000000000........ 3
Location ................................. 3Climate *.ooo*..... *.***********.*.o........*.........4Topography, Soils and Drainage *.*oooooooooooo*oo 4Fam Size and Land Tenure .......................... 4Hydrology .............. 00000000000000000000000 0000 5Agricultural Production .... oooooooooooo.ooooo.o@. 5Agricultural Supporting Services *.................. 6Transportation ..... *.0.0..... ....................** 7
IV. THE EXISTING WEIR AND IMPLICATIONS OF ITS FAILURE ..o. 7
VII. BENEFITS AND JUSTIFICATION *..* ... 00................. 15
VIII. AGREEMENTS REACHED AND RECOMMENDATIONS ............... 17
ANNEXES
1. Climatic Data and River Flow2. Current Production in the Command Area3. Existing Weir and Implications of Its Failure4. Project Works5. Contingency Plan for Failure of the Old Weir6. Cost Estimates7. Equipment Requirements8. Schedule of Expenditure, Allocation of the Proceeds of the Credit
and Disbursements9. Economic Analysis
CHARTS
8977 Organization Chart - Project Implementation8978 General Layout of the Barrage8979 Typical Plan of the Barrage8980 Typical crosssection of the Barrage9343 Critical Path Diagram for Civil Works Contract
MAP
11189 Location Map
INDIA
APPRAISAL OF THE GODAVARI BARRAGE PROJECT
SUMKARY AND CONCLUSIONS
i. The proposed project would consist of the construction of a barrageto replace an existing weir which is in danger of collapse. The existingweir at Dowlaiswaram was completed in 1852 and has deteriorated with thepassage of time. In 1965, a high-level committee established by the Govern-ment of India, reviewed the state of the weir and recommended the immediateconstruction of a new barrage. However, because of a shortage of funds,work was not started until 1971 and less than 5% of the construction has beencompleted to date.
ii. Three main canals take off from the weir to serve a command areaof 400,000 ha in the Godavari delta. Some 160,000 farm holdings with anaverage farm size of 2.5 ha are supplied with water from the weir. Over90% of the irrigated area is under rice in the wet season. Some 150,000 haare irrigated in the dry season. Cropping intensity is approximately 150%.Agricultural production in the command area is about 1.4 million tons ofpaddy and 2.2 million tons of sugarcane. The expected loss in net value ofproduction following a weir failure is estimated at Rs 800 million (US$100million).
iii. The barrage is to be located 24 m upstream of the old weir andwill use the existing weir as its downstream protective apron. The barragewill be 3,600 m long and will be divided into 175 bays, each equipped witha spillway gate. The gates, when closed, will raise the pond level one meterhigher than in the existing weir. Site exploration for the whole barrage,hydraulic model studies and detailed designs for part of the structure arecomplete and are sufficient for the tendering of the whole structure. Designstandards are satisfactory.
iv. Project costs, including the cost of preparing a second-phaseCommand Area Development project as well as funds for technical assistanceto GOI for preparing CAD projects in other parts of India, are estimated atUS$70.0 million, with a foreign exchange component of US$20.0 million or29. of the total. This foreign exchange estimate is based oin the assumptionthat all works would be carried out by local contractors. If the works arecontracted to foreign bidders following International Competitive bidding(ICB) Procedures, the foreign currency requirements are likely to be US$32million. Estimated costs are based on price levels prevailing in January1974 and include expected price increases. A 25% physical contingency hasbeen included for civil engineering works to allow for unusual contingencieswhich could arise in case of a partial failure of the existing weir duringthe four-year implementation period. A plan for emergency repairs to theexisting weir during the construction of the new barrage has been preparedand equipment and materials would be kept ready near the weir to enablerepair work to start immediately.
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v. The proposed credit of US$45 million would finance the foreignexchange component of the project and 34% of local costs if the works arecarried out by foreign contractors and 50% of local costs if the works arecarried out by local contractors or 64% of total project costs. The creditwould be made to GOI under usual IDA terms. Both the civil works contractand the gate manufacture and erection contract would be subject to internationalcompetitive bidding (ICB). Works carried out between February and June 1975on the barrage, dismantling of the crest of the existing weir and site prepara'tionworks would be by departmental force account. Building materials would beprocured by the PWD, locally or through ICB, and made available to contractorsat fixed prices. The 1974 price of these materials, delivered to theconstruction site, is estimated at US$8.0 million.
vi. In accordance with Bank policy regarding Preference to DomesticConstruction Industries (R 73-291 dated December 21, 1973) local contractorswould be entitled to a 7.5% preference on the civil works contract, estimatedat 1974 prices, net of price contingencies, at US$24 million. A 15% preferenceon the gate manufacture and erection contract would be given to local bidders;at 1974 prices this contract is estimated at US$12.0 million net of contin-gencies.
vii. Project implementation for all civil engineering works excludingthe road bridge would take three and a half years and would be completed byJune 1978. The manufacture of all 175 gates and the erection of at least130 gates would be completed by June 1978 with the balance of the gateserected by June 1979. To meet the construction schedule, the main civilengineering contract would be awarded by June 1975 and the gate manufactureand erection contract by September 1975. Responsibility for preparingconstruction drawings, specifications and tender documents would be withthe PWD under the Chief Engineer, Major Irrigation Works. Once the barrageis completed it would be maintained by the existing PWD organization inDowlaiswaram, as is the case with the existing weir and associated canalsystem. Preparation of the second-phase project would be carried out bythe Command Area Development Department of the Government of Andhra Pradesh.
viii. The economics of constructing a new structure to replace theexisting one, once the old structure has failed, are obvious; using con-servative estimates for production losses, the economic rate of return on theinvestment in the new barrage would be over 50%. Taking into account estimatedprobabilities of failure, the expected rate of return is estimated to beabout 44%. The probabilities of failure for the various sections of the weirhave also been used to examine various alternatives for construction phasing.In particular, three alternatives have been examined in detail:
(a) a four-year implementation period;
(b) a six-year implementation period; and
(c) a ten-year implementation period.
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ix. These alternatives have been compared on the basis of the presentvalue of the expected costs, where the costs include the construction costsand the expected losses in production. The present value of the expected costsfor the three alternatives is estimated to be Rs 1,020 million (US$127.5million), RS 1,090 million (US$136.3 million) million and Rs 1,350 million(US$168.8 million) respectively. The difference of Rs 70 million (US$8.8million) between alternative A and the next best alternative B is almostone-fifth of the present value of the total construction cost for theproposed barrage. A number of sensitivity tests indicate that the orderingof the three alternatives is preserved even after substantial changes inthe assumptions about the probabilities of failure, the expected lossesassociated with a failure, the construction costs and the opportunity costof capital.
x. The project is suitable for an IDA credit of US$45.0 million.The borrower would be the Government of India.
I, INTRODUCTION
1.01 The Government of India (GOI) has requested IDA assistance tofinance the Godavari Barrage Project in Andhra Pradesh State. The projectis to include construction of a new barrage to replace the existing weirwhich is in imminent danger of collapse. This would be the third IDAinvestment in agriculture in Andhra Pradesh, the two preceding ones beingthe Andhra Pradesh Agricultural Credit Project (Credit 226-IN, 1971) andthe Pochampad Irrigation Project (Credit 268-IN, 1971). The Bank Group hasalso assisted in over twenty agricultural projects in other parts of India.
1.02 Bank Group strategy for agriculture in India is to promote thefull use of existing irrigation potential through on-farm developments,spread of modern cultivation practices and provision of inputs such ascredit, seeds, fertilizers and pesticides. In areas where intensive culti-vation is already being practiced, Bank Group strategy is oriented towardsensuring the continuation of those practices through proper maintenanceand, where necessary, rehabilitation of the existing major works.
1.03 The existing Godavari weir was built over 120 years ago andhas deteriorated with the passage of time. A similar structure on theKrishna river, built about the same time, collapsed in 1952 and had to bereplaced with a new barrage. In 1965 a high-level committee, establishedby GOI to review the state of the Godavari weir, recommended immediateconstruction of a new barrage. However, due to a shortage of funds, workwas started only in 1971, and less than 5% of the construction has beencompleted to date. In April 1974, GOI asked IDA for assistance in completingthe project. In May 1974 a FAO/IBRD Cooperative Program (CP) mission visitedAndhra Pradesh to assist the Government in preparing the project for IDAconsideration. Their recommendations are given in a report (No. 18/74IND. 19) dated June 3, 1974. The present report is based on the findings ofan appraisal mission comprising Messrs. G. J. Tibor, P. C. Garg, U. Hpu(IDA) and F. Ritchey (Consultant) which visited India in June 1974.
II. BACKGROUND
The Economy
2.01 India covers some 3,270 million km of which 43% is arable andabout 9% is under some kind of irrigation. India's population is about580 million. Rapid population growth (2.2% p.a.) and a relatively poornatural resource base have imposed sharp limitations on India's economicgrowth. However, since the inception of economic development planning in1950, national income has grown at nearly 4% per year, compared with anaverage growth rate of less than 1% during the preceding 50 years. In 1970,per capita GNP was about US$110.
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2.02 The Government's development program for the next five yearsaims at an economic growth rate of 5.5%, but with greater emphasis thanin previous plans on alleviating poverty and creating employment. Thiswould be accomplished by promoting labor-intensive techniques, raisingthe productivity of subsistence farmers, a national program to supply theminimum needs of the poorest segments of the population, and tax measuresto curb consumption by the richer classes. However, these objectives arelikely to be difficult to attLin, given the severe balance of payments crisistriggered by recent increases in oil prices.
Agriculture in India
2.03 About 70% of India's population are engaged in agriculture andthe sector accounts for about 45% of GNP. Agriculture also provides the basefor most of India's exports, the most important commodities being jute, tea,leather, cotton goods and cashew nuts. Since 1965, India's developmentefforts have placed a major emphasis on agriculture and have been orientedto promote the spread of moderm technology by increasing the availability ofhigh-yielding seeds and fertilizer, expanding irrigation and developingmodern credit institutions. let, despite the impressive results of thegreen revolution in some areas since 1967, the overall annual growth rate inagricultural output in the ten-year period ending in 1972 was only 3%, whichwas little more than population growth and slightly lower than the growthrate in the previous decade. However, these figures conceal an importantstructural change; growth in production is now coming primarily from yieldincreases rather than from increases in cropped area as has traditionallybeen the case.
2.04 The green revolution has mainly affected wheat and its effectshave been concentrated in the northwestern states which are well endowedwith irrigation facilities. The spread of high-yielding rice varietieshas been disappointingly slow, because of inadequate water control and, inthe last two years, a severe shortage of fertilizer. Most other crops havehad stagnant or low growth rates.
2e05 Despite the progress made in food production, Indian agriculturestill depends heavily on the vagaries of the weather, as evidenced duringthe 1972/73 drought when reserve stocks were seriously reduced and largeamounts of grain had to be impcrted. A major factor in reducing India'sdependence on the weather will be the expansion of irrigation and the moreeffective use of existing irrigation potential.
Agriculture in Andhra Pradesh
2.06 Andhra Pradesh, with an area of 27.5 million ha, is one of thelargest States in India. It is predominantly agricultural, with a populationof about 43.3 million which is 82% rural. About 40% of the total area ofthe State is cultivated; rice, millet, pulses and groundnuts are the majorcrops. A quarter of the total cultivated area is under irrigation; the restdepends upon rainfall which ranlges from 500 mm annually in the southwest to1,100 mm in the northeast.
2.07 The main source of irrigation in the State are two major rivers,the Godavari and the Krishna, and their tributaries. Numerous irrigationcanals branch from these rivers. The upland areas use rainfed tanks andgroundwater for irrigation. Largely because of the intensively cultivateddeltas of the Godavari and the Krishna rivers, the state is one of the few"aurplus" states in India.
2.08 During the past 25 years, Andhra Pradesh State has invested heavilyin irrigation projects. However, the returns have been rather low, mainlybecause the available resources have been spread over too many projects,resulting in long construction and gestation periods and delayed benefits.Two major projects, the Nagarjunasagar and the Pochampad Irrigation Projects,are presently under construction, the latter with IDA assistance. Theprogress of these projects has been slower than expected and the land devel-opment works are lagging behind water availability. The Government of AndhraPradesh (GOAP) is aware of the inadequacy of the current land developmentoperations and is proposing to set up a well-coordinated technical andadministrative organization, backed up by suitable legal measures, to expeditethe development in the command areas of the two projects. When completedthe two projects will benefit some 1.0 million ha.
III. THE GODAVARI DELTA
Location
3.01 The proposed barrage is near the site of an existing weir atDowlaiswaram. At that point the Godavari river branches into two channels,the Gautami Godavari flowing to the east and the Vashista Godavari to thesouthwest. Three main canals take off from the weir to serve the East, Centraland Western areas of the Godavari Delta located along the Bay of Bengal in theeastern region of Andhra Pradesh (Map 11189). The respective net irrigatedareas are as follows:
Hectares
(a) Eastern Godavari 112,000(Lying east of Gautami)
(b) Central Godavari 82,000(The island between Gautami and Vashista)
(c) West Godavari 209,000(Lying west of Vashista)
Total 403,000
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Climate
3.02 The delta has a tropical and humid climate, and is influenced by thesouthwest monsoons from June to September and the northeast monsoons from -October to December. Mean annual rainfall is approximately 1,100 mm, of which65% occurs during the southwest monsoon period. The onset date of thesouthwest monsoon varies greatly, as does the amount of monthly and annualprecipitations of both monsoons. Mean maximum monthly temperatures rangefrom 28e to 370 C (Annex 1, Table 1).
Topography, Soils and Drainage
3.03 The Godavari deltaic plain is about 50 miles wide and extends forabout 100 miles along the sea. The land slopes gently toward the sea ata gradient of some 0.2 m per km. The soils of the Godavari delta vary fromcoastal sands bordering on the Bay of Bengal, through deltaic alluvium ofthe middle delta to heavier clay loam and some laterite soils at the headof the delta. The deltaic alluvium is composed of brown clay and sandy siltswith nodules of kankarlime and covers 70% of the area. The Godavari siltsare rich in lime, potash and phosphate and are very fertile.
3.04 Except for parts of the lower delta and some areas around Kollerulake (Map 11189) the drainage problems are relatively minor. Where theyoccur, they are caused by inadequate drainage channels, inundation of low-lying lands, and obstructions to drainage flows by railway and road embank-ments. Some of these problems are affecting crop yields and can be partiallyovercome by earlier sowing and transplanting of the kharif crop. TheGOAP is taking some measures to improve the drainage system. Also, specialemphasis would be given to these problems in the proposed second phase study(Annex 4).
Farm Size and Land Tenure
3.05 There is a lack of reliable data on the farm size and the landtenure situation in the command area. It is estimated that the area hasabout 160,000 farm holdings with an average farm size of 2.5 ha. Thefollowing table gives a rough indication of the distribution by farm size:
Farm Size Farm Holding Cultivated Area
2 ha or less 70 252-5 ha 15 25over 5 ha 15 50
About one-third of the farmers in the area are tenant farmers. Tenancyarrangements vary over the area, with tenants paying between one-third andone-half of the gross production to the landlords. Socio-economic surveysto be conducted for the proposed second phase study would provide morereliable information about farm sizes and the land tenure situation in thearea.
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Hydrology
3.06 The Godavari river, which drains an area of some 300,000 sq km, isthe third largest in India. Mean monthly flows and annual discharge atDowlaiswaram, for the period 1906-1961, are shown in Annex 1, Table 2. Thehighest recorded flood in the Godavari river at Dowlaiswaram was 85,000 m3 /secin 1953; the second highest was 79,000 m3 /sec in 1959. In the last fewyears flows have been affected by increased consumption in upstream irrigationprojects. The Godavari is an inter-state river and its utilization is subjectto the ruling of an inter-state tribunal. However, the water requirementsof the command area at current irrigation levels are assured.
3.07 In addition to diversions from the river, small tubewells, operatedby centrifugal pumps, are widely used in the middle delta, particularly forpaddy nurseries and garden crops. However, their yields are not generallyadequate for the needs of the main crops. In the middle and upper delta thequality of water is excellent. In the lower delta groundwater is saline dueto the proximity of the sea. The proposed second phase study would furtherexplore the groundwater resources of the area (Annex 4).
Agricultural Production
3.08 The command area of the veir has been under irrigation for over 120years and has a well-organized water distribution system. Host of the irri-gable land has been levelled and cropped for a very long time.
3.09 Rice is by far the most important crop. There are two crops ofirrigated rice, namely, (a) wet season or "kharif" which is usually sown inJune-July and harvested in November-December and (b) dry season or "rabi" whichis usually sown in December-January and harvested in April-May.
3.10 The kharif rice crop covers some 375,000 ha of the command area;the remaining 28,000 ha is mostly under sugarcane. The kharif rice crop isfollowed by a "rabi" rice crop on about 150,000 ha. Water availability isthe limiting factor for rabi rice. To give equal opportunity to all farmersin the area, a rotational system for growing rabi rice has been introducedand is strictly followed. Other rabi crops are grown on some 90,000 ha withresidual soil moisture following the kharif rice; these include pulses, edibleoilseed and chillies. On the whole the cropped area totals 615,000 ha, givinga cropping intensity of 154%.
3.11 A number of high-yielding varieties (HYV) of rice responsive tofertilizer applications and non-photosensitive, have been introduced for bothkharif and rabi crops since 1964-65. At present HYV cover about 46% of thekharif crop and 80% of the rabi crop. All the rabi HYV are dwarf varietieswith an average yield of 3,500 kg/ha. Because of the recurrent water shortagesin May and June which delay sowing and transplanting, a large part of thekharif crop is under tall varieties, reducing the average yield for the kharifpaddy to 2,600 kg/ha. In the low-lying areas the risk of flooding in September
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and early October dictates the use of tall varieties. Average paddy productionin the project area during the last five years was about 1.4 million tons,about two-thirds from the kharif crop and the rest from the rabi crop.
3.12 Sugarcane is planted from December to February and harvested fromNovember to April. The varieties planted are mainly improved, high-yielding,developed at the Coimbatore Sugarcane Research station in Southern India.Average yields are 90 tons/ha in the first year. The first ratoon yields80 tons/ha and the second ratoon 70 tons/ha. Annex 2 gives details of currentagricultural production in the command area.
Agricultural Supporting Services
3.13 Agricultural extension services in the command area, particularlyin the West Godavari district, are well organized and adequately staffed.The West Godavari district is one of the seven Indian districts in which theIntensive Agricultural Program was introduced in 1961 (with assistance fromthe Ford Foundation and USAID). Since 1970, all the expenditures for theprogram have been met by the GOAP.
3.14 In both the West and East Godavari districts there is a DeputyDirector of Agriculture. He is responsible for agricultural extension inthe district and is assisted by several subject matter specialists, about adozen in the West and four in the East. Village Development Officers areresponsible for agricultural extension at the village level; a number ofAssistant Agricultural Officers supervise their work.
3.15 Agricultural research on rice is conducted at the AgriculturalResearch Station at Maruteru, in the West Godavari district; variety andfertilizer trials are also conducted at the Samalkot farm in the EastGodavari district and on private farms. Seed multiplication, processingand distribution are the responsibilities of both the National Seed Corpora-tion (NSC) and the GOAP Department of Agriculture. There are two modern seedprocessing units in the project area.
3.16 Fertilizers and pesticides are procured and distributed by theDepartment of Agriculture, the Cooperatives Department and private traders.Fertilizer consumption per hectare in 1971-72 averaged 50 kg of nitrogen,16 kg of superphosphate and 10 kg of potash for paddy; and 150 kg of nitrogenfor sugarcane. Fertilizer use has since decreased somewhat because of supplyshortages.
3.17 Current agricultural practices in the command area are adequate,but yields could be further increased by improved water control, bettervarieties and improved cultivation practices. The proposed second phasestudy would assess the potential for such improvements (Annex 4).
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Transportation
3.18 Transport facilities in the command area are better than those inmost other agricultural areas of the country. The main centers in andaround the area are connected to each other by all-weather roads. The mainrailway line and road connecting Calcutta to Madras pass through the area,providing easy access to all major ports and cotmercial centers of the country.The Godavari river and the three main irrigation canals are navigable (locksare provided around the cross regulators in the canals) and facilitate thetransport of farm produce to the road network and the railheads.
IV. THE EXISTING WEIR AND IMPLICATIONS OF ITS FAILURE
General
4.01 The existing Godavari weir, built entirely of bricks and masonry,was constructed during the years 1847-1852. As irrigation demand in thecommand area increased, the weir crest was raised and steel shutters added,raising the pond level by 1.19 m over the original design level. As theweir is founded on sand and as flood flows are large, erosion immediatelydownstream from the structure has been a continuing problem and constantmaintenance has been necessary. In spite of such maintenance, however, thecondition of the structure has steadily deteriorated.
4.02 By 1965 deterioration of the Godavari weir had progressed to sucha degree that a high-level committee was set up by the Ministry of Irriga-tion and Power, GOI, to advise on immediate remedial measures and on thedesirability of reconstruction. The committee recommended immediate con-struction of a new barrage and provided outline designs and cost estimatesfor the work. However, due to a shortage of funds, work was started onlyin 1971 and less than 5% of the construction has been completed to date.
4.03 The primary cause of deterioration has been erosion on the down-stream side of the weir, due in part to flows across the weir but also insome areas to strong lateral flows along the toe of the weir. The secondarycause of deterioration has been piping 1/, aggravated by erosion of the down-stream apron. Severe piping of fill from beneath the weir has causedconcentration of load onto the cylindrical brick caissons which partiallysupport it. This in turn may cause structural failure of the foundations.
1/ Piping is the movement of soil particles by percolating water throughthe body of the dam, leading to the development of gradually wideningseepage channels.
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Engineering Implications
4.04 Failure would most likely occur in the form of a sudden settlementof a portion of the weir during a period of maximum hydraulic gradientfollowed by the formation of open shear cracks on either side of the settle-ment area. Flow concentration through the cracks and over the collapsedportion of the weir would cause rapid widening of the breach by lateralerosion and an undermining of the weir foundations. By the time repairscould be effected, at low flows, the break could be a major one, probablyseveral hundred meters wide and of considerable depth.
4.05 Assuming that a weir failure occurs early in the flood season(July), the recurring floods could wash away most of the affected sectionand deeply scour the riverbed in the breached area. The scouring wouldgradually move upstream into the reservoir. Such bed erosion would requirea design change in the new barrage which could result in a significantincrease in the cost of the affected section. There could also be a delayin the construction schedule because of the need for additional hydraulicmodel studies and the preparation of new designs (Annex 3).
4.06 There is some possibility that through emergency repairs, similarto those undertaken following the breach of the weir on the Krishna river,the breach could be plugged before it has a major effect either on theriverbed or on the irrigation water supply to the command area. The successof such repairs would depend upon the initial width of the breach and onthe stages of the river following the breach. To avail of the favorablecircumstances, if they occur, assurances have been obtained from GOAP thatmaterials needed for emergency repairs would be stockpiled and equipmentwould be kept ready at the weir site during the construction of the newbarrage (Annex 5).
Agricultural Implications
4.07 A breaching of the weir would lower the pond level at the canalinlet structures. During the wet season water levels in the river wouldbe only occasionally higher than the canal beds, restricting the availabilityof irrigation water to those occasions. This would result in the loss of amajor part of the kharif crop. During the dry season no diversion would bepossible and there would be no rabi rice crop as rice can only be grown withirrigation. Areas under rabi crops other than rice would also be considerablyreduced, because of the lack of soil moisture build-up during kharif irriga-tion. If water supplies remain interrupted for more than one year, farmerswould follow the pattern of rainfed agriculture, practiced in the surroundingnon-irrigated areas (Annex 3, Table 1). The expected loss in net value ofproduction following a weir failure is estimated at Rs 800 million (US$100million).
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V. THE PROJECT
5.01 The proposed project includes construction of a barrage acrossthree branches of the Godavari river (Dowlaiswaram, Maddur, and Vizzeswaramsections) and completion of construction of the fourth branch (Ralli section).Construction of that section was started in 1971 and the completed portionsequal about 5% of the total works. The project also includes funds for thepreparation ofia second-phase Command Area Development (CAD) project (moderni-zation of the irrigation and drainage system, groundwater development and on-farm works) in the Godavari delta as well as funds for technical assistanceto GOI for preparing CAD projects in other parts of India. The works to befinanced under the project are described briefly below and in more detail inAnnex 4.
Project Works
5.02 The new barrage is located some 24 m upstream of the old weir andwill use the existing structure as its downstream protective apron. Thebarrage will be in four independent sections across the four branches ofthe river and connected in between with embankments across the three islands(Chart 8978). The length of these sections are:
The barrage structure will comprise 175 reinforced concrete sills, eachabout 18 m wide, between reinforced concrete piers. The elevation of thesill will be at +10.57 m. Spillway leaf gates will raise the pond level to+13.64 m, one meter higher than in the existing weir. A two-lane roadwaywill be provided over the barrage.
Water Demand and Supply
5.03 The water conveyance system from the weir is designed for a grosswater duty of 1.0 lit/sec/ha and a yearly diversion of some 5,000 Mm3. Exceptfor the land preparation and transplanting period in May and June, the dutyis sufficient to meet irrigation demand in the kharif season. During thatperiod the required water duty is considerably higher. Owing to reduced riverflow during May and June, and the lack of canal conveyance capacities, theland preparation and transplanting season has to be staggered from May 15to August 15. Paddy transplanted later in the season produces lower yieldsand is more susceptible to flood damage. From May 15 to July 15 the flowin the Godavari is subject to rapid fluctuations. By properly operating
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the gates in the new barrage, some of the flows, which presently spill overthe weir, could be stored and utilized to increase the supply to the delta.(Some 50 Mm3 of additional storage would be available with the new barrage.)The increase in the diversion head, from + 12.64 m at present to + 13.64 mon the new barrage, would also increase conveyance capacity through the maincanal network by 25X, from 1.0 lit/sec/ha to 1.25 lit/sec/ha. To carry tneseincreased flows, the freeboard in some stretches of the main canals would haveto be reduced to 0.50 m. Such a reduction in freeboard, for short periodsof time, is acceptable if the canals are properly maintained and water dis-tribution is well controlled.
5.04 Supply to the rabi crop is limited by the availability of water inthe river, rather than by canal capacities. With a gross water requirementof approximately 1.0 lit/sec/ha, the dry season crop, on some 150,000 ha,can be supplied in three years out of four during January, February andearly March. A deficit of some 50 Mm3 occurs in tne second half of Marchand April which would be made up from the additional storage available inthe barrage.
Engineering Design
5.05 Site exploration for the whole barrage, hydraulic model studiesand detailed designs for the civil engineering works of the Ralli sectionare complete. As all four sections are similar in design, the Ralli sectiondesign can be used for tendering for the remaining civil works. Design workis carried out by the Central Water and Power Commission (CWPC). The designstandards are satisfactory. Responsibility for the preparation of workingdrawings, construction specifications, negotiations of contract and super-vision of construction, rests with the GOAP Public Works Department (PWD).Tne quality of construction work on thie completed parts of the Ralli sectionis satisfactory. The work is closely supervised and adequate testing facil-ities for construction materials are provided at the site. Constructionmethods are described in Annex 4.
Implementation Schedule
5.06 Project implementation for all civil engineering works, includingmost of the road bridge over the barrage would take three and a half yearsand would be completed by June 1978. The manufacture of all 175 gatesand hoists and the erection of at least 130 gates would be completed byJune 1978 with the balance of the gates erected by June 1979. To reducethe risk to the water supply in the delta, if a section of the weir isbreached during this period, each section of the new barrage will have itsgates installed as soon as the piers are completed. The first constructionseason, from February to June 1975, would be used for the construction ofsix bays of the Dowlaiswaram section. The construction seasons, fromNovember 1975 to June 1978, would be used to complete civil works constructionexcept for portions of the road bridge on the Dowlaiswaram and Vizzeswaramsections. During this period the power connection to operate the hoists
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would also be completed and 75% of the crest gates and hoists installed.
From November 1978 to June 1979 the road bridge would be completed and the
remaining gates and hoist arrangements installed (Chart 9343).
Cos t Es tifma4tes
5.07 The estimated tqtal cost of the project is US$70.0 million,
including US$20.0 million (29%) in foreign exchange. The foreign exchange
requirements are based on the assumption that all works would be carried out
by local coutractqrs. If the works are contracted to foreign contractors
the foreign exchange requirements are likely to be US$32 million. Estimated
costs are based on price levels prevailing in January 1974 and include
expected price tncreases, beginning at 17% in the first year and tapering
to 11% in tho fourth year. Overall price increases are estimated at 26%
of the total coot of the project. Physical contingencies of 15% for the
mechanical engineering works and 25% for the civil works have been included.
The relattvely large physical contingencies for fairly simple civil engineer-
ing construction works have been included to allow for risks arising from a
possible failure of one of the weir sections during the four-year implementa-
tion period (Annex 9). Such a failure may involve an increase in the cost
of the barrage in the affected section (Annex 3). A breakdown of project
costs is presented in Annex 6 and is summarized below.
Total Project Co0Ss 399.0 159.9 558.9 49.86 20.00 l 69.86
(or say) 70.00
/a If tne works are contracted to a foreign bidder the foreign exchange
requirements are likely to be US$32 mdllion.
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Financing
5.08 The proposed credit of US$45 million would finance the foreignexchange component of the project (US$2U.U million) and 34% of the localcosts, if the works are carried out by foreign contractors and 50% oflocal costs if the works are carried out by local contractors, or 64%of the total project cost. The credit would be made to GOI under usualIDA terms. Operation and maintenance of the barrage would be financedby GOAP from its regular budget-.
Procurement
5.09 Contracts for civil works (about US$24.0 million net of pricecontingencies) and for the manufacture and installation-of the gates (aboutUS$12.0 million net of price contingencies) would be awarded on the basisof international competitive bidding in accordance with Bank Group guidelines.Local contractors participating in the bidding for civil works would beentitled to a 7.5% preference in accordance with the Bank Group policyapproved by the Executive Directors on January 22, 1974 (R 73-291). Forgate manufacture and erection, the usual preference limited to 15% of thecif price of imported goods, or the prevailing customs duty if lower, wouldbe extended to local bidders during bid evaluation. Tender documents wouldclearly specifX these preferences and the manner of their application. Workscarried out between February and June 1975, before the civil works contractis awarded, and the dismantling of the crest of the old weir after completionof the new barrage would be done through PWD force account.
5.10 Equipment and vehicles, estimated at US$0.6'million (net of pricecontingencies) and required by PWD for project preparation and supervision ofworks, would not be suitable for international tendering and would be procureddirectly from local suppliers. (Annex 7 gives equipment requirements.) PWDwould ensure that building and construction materials for civil and mechanicalworks (cement, structural steel and sheet piling) would be made available tocontractors at fixed prices to be stated in the tender documents. PWD wouldobserve the general procurement provisions of the GOAP, which are acceptable.Assurances were obtained from GOI that cement required for the project shall beallocated as part of Andhra Pradesh's annual allocation and if necessary,such cement shall be earmarked to the project by GOI, and if other buildingand construction materials cannot be supplied in accordance with the detailedtime-schedule for their supply, they would be promptly imported.
Disbursements
5.11 Disbursements would be made at a rate of 100% against the cif costof directly imported equipment and building materials, or the ex-factoryprice for equipment procured locally. Disbursements for civil works carriedout by contract would be on a percentage basis. Disbursements for forceaccount work by PWD would be made against a certificate of expenditure. Theestimated schedule of expenditures on the project, the proposed allocation
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of the proceeds of the credit and a semi-annual disbursement schedule arepresented in Annex 8. Any savings in the credit account would be reallocatedby increasing the percentage disbursement for civil works. It is expectedthat disbursements would be completed by December 31, 1979, about six monthsafter completion of project construction.
Accounts and Audits
5.12 The PWD would be subject to normal Government control and auditingprocedures which are considered satisfactory. Assurances were obtainedfrom GOAP that the accounts and financial statements of the project wouldbe submitted to the Association within six months after the end of eachfiscal year.
Environmental Effects
5.13 The project would have no adverse effect on the environment in thearea commanded by the canal network. Raising the pond level behind the bar-rage by 1.0 m during the dry season would have no environmental effect as thepond is confined between the flood banks of the river.
VI. ORGANIZATION AND MANAGEMENT
Project Implementation and Maintenance
6.01 Responsibility for preparing construction drawings (civil andmechanical engineering works), specifications and tender documents wouldbe with the PWD of GOAP under the Chief Engineer, Major Irrigation Works.The Department is fully competent to carry out these tasks. During thelast two decades it has been responsible for major construction works in theTungabadhra, Nagarjunasagar and Pochampad projects.
6.02 The Chief Engineer, Major Irrigation Works, would nominate aProject Engineer with overall responsibility for the management of theproject during implementation. The Project Engineer would be in charge oftwo Superintending Engineers (civil and mechanical), located at the barragesite, with responsibility for contract management and supervision. TheSuperintending Engineer for civil works would have four executive engineers,one for each of the four sections of the barrage. Each executive engineerwould be assisted by about four assistant engineers and about twenty juniorengineers. The Superintending Engineer, mechanical works, would have twoexecutive engineers to supervise erection of the gates and hoists, and oneexecutive engineer in charge of transport, machinery and workshops (Chart8977). Fully qualified staff is available within PWD to fill these posts.
6.03 Responsibility for the adequacy of the barrage as constructedwould rest with the design agency (CWPC). To ensure the safety and properfunctioning of the barrage, all changes and additions to the original
- 14 -
designs would be drawn or approved by CWPC, whose staff would also maintainsurveillance over the construction standards. CWPC would assign competentstaff of appropriate seniority for continuous review of work, with partic-ular emphasis on quality control. At completion, CWPC would certify thatwork has been carried out in accordance with their designs and specifica-tions. From then onwards the barrage would be operated and maintained bythe existing PWD organization in Dowlaiswaram as is the case with theexisting weir and associated canal system.
6.04 Concerning technical assistance to GOI for preparing CAD projectsdiscussions would be held between GOI and the Association and a detailedplan of operation would be drawn up by April 1975.
Tendering Requirements
6.05 A construction schedule drawn up by the Chief Engineer, PWD (MajorIrrigation), GOAP sets the minimum time required for constructing all foursections except for portions of the road bridge and including the installa-tion of 75% of the gates, at three and one-half construction seasons, i.e.,by June 1978 the essential portions of the barrage to secure water suppliesto tle delta would be completed. To meet the above construction schedule,the following tendering schedule would have to be adhered to:
Civil Works Tender
Tender notification with briefdescription of works January 10, 1975
Review of tender documents by IDA January 25, 1975Issue of tender February 10, 1975Openings of bids April 15, 1975Award of tender after IDA review July 15, 1975
Manufacture and erection of 175 spillway gates
Call for Prequalification February 1, 1975Prequalification April 15, 1975Review of tender documents by IDA April 1975Issue of tender Mfay 1, 1975bid opening July 15, 1975'Award of tender after [DA review September 1975
Cost Recovery
6.06 With an estimated average annual family income of about Rs 7,500(US$940), the farmers in the command area are prosperous, relative to rwstother agricultural areas of India. If the existing weir were to fail, theaverage annual farm income would be reduced to about Rs 2,000 (US$250). Thus,the farmers in the area have a very considerable stake in the constructionof the barrage.
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6.07 In sanctioning the construction of the project in 1969 the GOAPimposed an advance betterment levy on the farmers at the rate of Rs 125/- perua (in addition to the regularly collected 0 & M charges) for a total amountof Rs 50 million. This represents about 10% of the estimated total costof the project. Up to July 1974, Rs 35 million in levy had already beencollected. During appraisal, GOAP pointed out that any additional costrecovery would be difficult to impose as the farmers do not perceive thisproject as adding substantially to their current income. While recognizingsome logic in this argument, it is considered, that, in view of the relativeprosperity of the area, the concentration of land ownership and the need forinvestments in many less prosperous areas of the State, it is imperativethat substantially all investment costs be recovered from the beneficiaries,preferably on a progressive basis.
6.08 Assurances were obtained from GOAP that it would undertake sucharrangements as would be necessary to levy and collect from beneficiariesof the barrage all investment costs, including interest of not less than5% per annum thereon, over a perio4 of not more than fifteen years.
VII. BENEFITS AND JUSTIFICATION
7.01 The project under consideration is somewhat different from theusual investment projects as the primary objective in this case is to ensurecontinuation of existing benefits rather than to generate additional benefits.The 120-year-old existing weir is the key structure in supplying irrigationwater to some 400,000 ha in the Godavari delta. Collapse of the weir wouldbe a major setback for the economy of a major rice-producing area of India.
7.02 Due in large part to the well-developed irrigation system, thecommand area is currently under intensive cultivation, producing annuallyabout 1.4 million tons of paddy and about 2.2 million tons of sugarcane.The annual net and gross values of production are estimated at Rs 900 million(US$112.5 million) and Rs 1,680 million (US$210 million) respectively.
7.03 Disruption of the irrigation water supply because of a breach inthe weir would result in a loss of at least the major part of one kharifcrop and a whole rabi crop, amounting to a loss of about Rs 800 million(US$100 million) in net value of production. Hopefully, during the dryseason following the failure of the weir it would be possible to plug thebreach and to restore temporarily the water supply for the next kharif crop.However, if these efforts were to be unsuccessful, there would be no alter-native for the farmers but to follow the cropping pattern prevailing in theadjacent non-irrigated areas; the estimated annual production from the areaunder rainfed conditions would be about 100,000 tons of paddy and about180,000 tons of other crops like millets, pulses, oilseeds and chillies etc.having a net value of production of about Rs 100 million (US$12.5 million).
- 16 -
7.04 The losses in terms of the net value of production, even thoughlarge, fail to reflect the full impact of the weir failure on the area'seconomy. The loss of agricultural production would mean unemploymentfor much of the agricultural labor force as well as a depression in theservice industries such as marketing, milling, transportation and process-ing, which are based upon the agricultural production in the project area.Finally, on the national scale, a reduction of over 800,000 tons in riceproduction would have serious implications for India's already difficultfoodgrain situation.
7.05 The existing weir has been in a precarious condition for the pastdecade or so. As far back as 1965 a high-level expert committee found itto be unreliable and recommended immediate construction of a new barrage.The weir has escaped a breach so far partly because it was not exposed toprolonged flow patterns of a type which cause destructive erosion (Annex 3,para 7) and partly because of the timely maintenance and repairs by thePWD, GOAP. However, deterioration of the weir as a result of erosion andpiping is a cumulative process which even with the best of maintenance willeventually cause failure. The assessment is that the existing weir is inserious danger of failure and that even if the construction of a new barragewere to be started right away and implemented as fast as physically possible(four years), there is a relatively high probability that one of the sectionsof the old weir would collapse before the new barrage was completed (Annex 9,para 6(b)). The chances that alL four sections of the weir would surviveanother 10 years are considered negligible.
7.06 The economies of constructing a new structure to replace theexisting one, once the old structure has failed, are obvious: using con-servative estimates for production losses, the economic rate of return onthe investment in the new structure would be over 50%. Even if the construc-tion costs were to be increased by 20%, the benefits further decreased by20% and the construction period extended from four to six years, the rateof return would still be over 35% (Annex 9).
7.07 The probabilities of failure for the various sections of the weirhave been assessed and using-them the various alternatives for the phasingof the construction have been examined. In particular, the following threealternatives have been examined in detail:
(a) Alternative A - A four-year implementation period,representing the minimum time necessary to completethe construction of all four sections of the barrage.
(b) Alternative B - In this alternative the implementationperiod is extended to six years.
(c) Alternative C - The construction is continued at thecurrent rate extending the implementation period toten years.
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7.08 The appropriate criterion for comparing various constructionalternatives is the minimization of the present value of the expected costs,where the costs include the construction costs and the expected losses inproduction. Using the probability assessments of failure for the varioussections given in Annex 9, and assuming that if there is a break in the weirit would be repaired before the onset of the next monsoon season, and using10% as the annual cost of capital in the Indian economy, the present valueof the expected costs for the three alternatives is estimated at Rs 1,020million (US$127.5 million), Rs 1,090 million (US$136.3 million) and Rs 1,350million (US$168.8 million) respectively (Annex 9, para 9). The differenceof Rs 70 million (US$8.8 million) between alternative A and the next bestalternative B is almost 20% of the present value of the total constructioncost for the proposed barrage. A number of sensitivity tests indicate thatthe ordering of the three alternatives is preserved even after substantialchanges in the assumptions about the probabilities of failure, the expectedlosses associated with a failure, the construction costs and the opportunitycost of capital. Thus, alternative A, corresponding to the fastest possibleconstruction schedule, is clearly superior to the other two.
7.09 Taking into account the estimated probabilities of failure andrelated production losses, the expected economic rate of return for alter-native A would be about 44%. Even if the construction costs were to be 20%higher, the production losses associated with a weir failure were 20% lowerand the probabilities of failure substantially lower, the expected rate ofreturn for alternative A would still be 20% (Annex 9, para 10).
VIII. AGREEMENTS REACHED AND RECOMMENDATIONS
8.01 Assurance was obtained fronm GOI that:
(a) cement required for the project would be allocated aspart of Andhra Pradesh's annual allocation and ifnecessary, such cement would be earmarked to theProject by GOI, and if other building and constructionmaterials could not be supplied in accordance with thedetailed time-schedule for their supply, they would bepromptly imported (para 5.10).
8.02 Assurances on the following points were obtained from GOAP:
(a) that materials required for emergency repairs would bestockpiled and equipment to carry out the repairs wouldbe kept ready at the weir site (para 4.06);
(b) that the accounts and financial statements of the projectwould be submitted to the Association within six monthsafter the end of each fiscal year (para 5.12); and
- 18 -
(c) that it would undertake such arrangements as shall benecessary to levy and collect from beneficiaries ofthe barrage all investment costs, including interestof not less than 5% per annum thereon, over a periodof not more than fif-teen years (para 6.08).
8.03 With the above assurances, the proposed project would be suitablefor an IDA credit of US$45.0 mLillion. The borrower would be the Govern-ment of India.
Table 1
INDIA
GODAVARI BARRAGE PROJECT
Climatological Data!/
Mean MeanAverage MonthlyMonthly 2/ Monthly Max. 3/ Monthly Min.3/ Relative
1/ Including labor costs (both family and hired) valued at thfŽ average market wage rate of Rs )¢ per day.2/ Irrigated.3/ Average of the main crop and two ratoon crops.
ANNEX 3Page 1
INDIA
GODAVARI BARRAGE PROJECT
The Existing Weir and Implications of Its Failure
General,
1. The existing weir across the Godavari at Dowlaiswaram was construct-ed between 1847 and 1852. It consists of four sections: Dowlaiswaram,Ralli, Maddur, 400 m3/sec and Vizzeswaram, separated by three small islands.The structure diverts 400 m3/sec into three canals, serving the Eastern,Central and Western Godavari Districts. The weir, founded on sand, consistsof two rows of wells constructed of clay bricks, 1.82 m apart. For theDowlaiswaram, Maddur, and Vizzeswaram sections the wells were taken downto elevation + 5.22 m and + 4.80 m respectively. In the Ralli section thewells were sunk to elevation + 6.70 m and founded on dumped rubble. Thebody of the weir is built of 1.50 m thick rubble masonry, finished with0.90 m thick outstone masonry. The downstream slope is made of 1.50 m thickrubble masonry and finished with 0.30 m diameter stones. The fall betweenthe end of the downstream slope and the riverbed is negotiated by a riprapslope, with rubble masonry training walls which extend some 100 m downstreamfrom the axis of the weir. The original crest elevation was at + 11.50 m.
2. As irrigation water demand in the Command Area increased, the weircrest was raised by 0.23 m, and 0.60 m high steel shutters were added,raising the pond level to 12.33 m. In 1936, new shutters were installed,bringing the pond level to elevation + 12.64, some 1.14 m higher than inthe original design. The raised crest and the installation of the shuttershave significantly increased the design head on the dam. The gradual decayof the 120-year-old structure and the extra strain of the higher pond levelhave seriously weakened the weir, especially in the Dowlaiswaram and Rallisections.
3. The primary cause of deterioration has been erosion on the down-stream side of the weir, due in part to flows across the weir but also insome areas to strong lateral flows along the toe of the weir. The secondarycause of deterioration has been piping under the weir. During the dryseason the ponded water behind the weir causes piping and the formation ofcavities under the rubble masonry structure. At maximum pond level, seepagegradients are too steep at 3.5 horizontal to 1.0 vertical. Numerous cavitiesare continuously located by using electrical resistivity tests and thenverified by breaking open the dam. After the heavy floods of 1963, gaps aswide as 0.45 m were observed between the downstream wells of the Dowlaiswaramsection, with all the supporting subsoil washed out. The load of the weir
ANNEX 3Page 2
was transmitted directly to these wells, causing buckling and the disintegration
of the clay bricks. The floods also caused extensive scouring in the apronof the Ralli section.
4. During the 1973 flood season, some 150 m of the Ralli sectionsettled by more than 0.30 m. The weir was again examined by electricalresistivity methods and by drilling holes through the outstone masonry.The settlement was again caused by piping and the formation of cavities.
5. Repairs have consisted of replacing and strengthening the apron(grouted-stone and dry-stone pitching), construction of cross-bunds orgroynes to control lateral flow, grouting to fill voids beneath the weir,and placing of a clay blanket with stone protection on the upstream side ofthe weir to reduce under-seepage and piping. The repairs have only beenpartially successful.
6. During the field examination the mission observed visible signsof deterioration on all four sections, although the Maddur and the Vizzes-waram sections appeared to be in a somewhat better shape than the other two.Conditions for failure by piping or erosion or both exist in all four sections,and any unusual flood pattern could cause failure in one of the sections.Quantitative assessments of the life expectancy of the various sections isgiven in Annex 9 para 6(b).
Description of Likely Failure
7. Failure would most likely occur as a sudden settlement of a portionof the weir during a period of maximum hydraulic gradient early in the mon-soon with formations of open shear cracks on either side of the area of settle-ment (model studies indicate that flows of the order of 2.0-2.5 m3/sec/meterover the weir are the most damaging as far as erosion of the apron is con-cerned). Concentrated flows through these cracks would cause a rapid widen-ing by lateral erosion (typically, the differential head through the crackwould be about 3.0 m). Velocities of about 6-7 m/sec would be experiencedas soon as an open breach was formed, causing rapid downward erosion intothe sand below the structure and undermining of the old brick caissons.Failure would progress laterally as long as the differential head across thebreach remained more than 1.0 m. Assuming that the failure occurred in lateJune, flows through the breach would continue without possibility of repairuntil October or November. By that time, the breach would be a major one,probably some 100-200 m wide and of considerable depth. Reconstruction wouldtake at least one low-flow season.
Agricultural Implications of Weir Failure
8. The agricultural consequences of the failure, assumed to occurafter transplanting of the kharif crop, would most likely be as follows:
ANNEX 3Page 3
(a) MNost of the kharif rice crop and sugarcane would failcompletely and the portions which survived would mostprobably give very much reduced yields. As for rabicrops, there would be no rice as it can be cultivatedonly with irrigation, and the area under the other rabicrops would also be greatly reduced due to lack ofresidual soil moisture.
(b) In the event the failure continues over the followingyear, farmers would have no alternative but to followthe prevailing cropping pattern of rain-fed agricul-ture in the adjacent non-irrigated areas where kharifcrops include about 15% upland rice, 35% jowar, 25% ptulsesand 25,c edible oilseeds and chillies, and there arelittle or no rabi crops. On this basis, the yearlyproduction from the command area would be only 65,000tons rice, 100,000 tons jowar, 35,000 tons pulses and35,000 tons of oilseeds and chillies (Table 1).
Engineering Implications of Weir Failure
9. Effect on Riverbed. Assuming that a failure occurs early in theflood season, the recurring floods could ultimately wash out a major portionof the affected sections and deeply scour the riverbed in the breached areaand gradually upstream into the reservoir.
10. Effect on Design of New Barrage. A major breach in a section ofthe old barrage before the new barrage is constructed would require a changein design of the barrage for the affected section as follows:
(a) The affected old section would have to be removedcompletely.
(b) The deeply scoured r iverbed would have to be back-filled with a compacted sandy or gravelly materialto provide a foundation for the new barrage. Also,there would be the possibility that the section wouldhave to be relocated.
(c) The reinforced concrete apron used to form the hydraulicjump downstream from the gates would have to be placedmuch lower and the lengths of the steel sheet pilingincreased to compensate for the lack of the backlwatereffect produced by the weir.
ANNEX 3Page 4
11. Alternatively, the present design could be used and a baffledreinforced concrete drop structure added to the end of the hydraulic jump-apron to take the fall in river water surface instead of lowering theapron as described above. The added steel sheet piling length would stillbe required.
12. Increase in Cost. Due to the additional work required, a majorfailure in the existing weir before the new barrage is completed would resultin a significant increase in the construction cost of the new barrage section.Also, there might be a delay in construction due to the need for additionalhydraulic model studies, new designs and added construction features.
MhDIA
GODAVARI BARRAGE PROJECT
Possible Cropping Pattern & Production From Project Area Without IrriUation
Grous Value Net Value Gross Net ValueFarm of Production of Area Value of of
Yield Gate Price Production Costa91 Production in Production ProductionCrop ton/ha Rs/ton Rs/ha Rs/ha Rs/ha 1,000 ha Rs Million Rs Million
1/ -c' uding -:.bor costs (both family & hired) valued at the average market wage rate ofR- a ner d
ANNEX 4Page 1
INDIA
GODAVARI BARRAGE PROJECT
A. Project Works
1. The project comprises the execution of all works necessary forthe completion of the Godavari Barrage, other than works now under contractin the Ralli section. The project also includes funds for the preparationof a second phase Command Area Development project and assistance to GOIfor preparing CAD projects in other parts of India. The general layout ofthe complete barrage is shown in Chart 8978. The proposed new barrage willconsist of four sections.
The Ralli section, typical of all four, is shown in Charts No. 8979, 8980.Total structural height, from top of gate-operating platform to bottom ofconcrete cut-off, is about 17.50 m. Steel sheet-piles or a concrete curtainwall extend down a further 5.00 m. The structure comprises essentially aheavily reinforced concrete slab, 1.37 m thick and 25.00 m long, formingthe sill, together with reinforced concrete gate piers 2.13 m thick, spacedto provide bays for steel leaf gates 12.27 m long and 3.60 m high. Steelsheet-piles or a concrete curtain wall are provided at the upstream anddownstream limits of the sill slab. For erosion protection, a mat of lneavyconcrete blocks 0.90 m thick is provided, both upstream and downstream ofthe slab, and on the upstream side a supplemental 1.50 m thick mat of heavystone. The sill slab is located some 24.00 m upstream from the existingweir crest, which will remain in place as an extension to the downstreamprotective apron of the barrage. The crest of the existing weir will belowered from the present E.L. + 11.73 m to E.L. + 10.67 m. Double piers,with integral contraction joints, divide the sill slab structurally intolengths of not more than ten spillway bays. The piers support a reinforcedconcrete road bridge 7.50 m wide, as well as the gate operating platform.The barrage is founded on sand (bedrock is at great depth) with some localhorizons of stiff, silty clay. In the Vizzeswaram section a thick continuousbed of silty clay occurs across the whole length of the structure at adepth of about 6.00 m below the bottom of the sill slab.
ANNEX 4Page 2
2. The increased pond level in the new barrage would permit diversionof flows at elevation + 13.64 meters instead of at the present elevationof + 12.64 meters. The resulting additional pondage and higher head inthe canals would enable the dry season irrigation of an additional 5,000 hain the Delta and a somewhat large and earlier start of the water supplies atthe beginning of the rainy season.
B. Review of Design
Foundations
3. The area beneath the barrage has been explored by drive-sampling,generally to a depth of 15 to 18 meters. The exploratory holes were in threerows parallel to the barrage axis and consisted of from two to three holesfor each of the 175 bays.
4. The foundation consists primarily of well-graded sand, about 90Zof the material being between 0.1 mm and 1.0 mm in size, with lenses ofsilty clay, clay and gravel, and clay interspersed in the foundation atvarying depths. The clay lenses are generally at least 7.0 m below thebottom of the reinforced concrete raft where the surchage load is very low.The clay layers are therefore not structurally significant except possiblyfor a small area at the right end of the Ralli section where the clay isnear the bottom of the slab and for a portion of the Vizzeswaram section.
5. The silty-clay in the Vizzeswaram section has a liquid limit inthe range of 40 to 70 with a plastic index in the range of 20 to 35 and canbe described as inorganic clay of medium plasticity. The silty clayselsewhere have slightly greater plasticity. The strength of the siltyclays in the Vizzeswaram section are generally of the order of 0.7 kg/sqcm (1.6 Kips/sq ft) as obtained in triaxial shear tests (consolidatedundrained at field moisture capacity). The friction angle is 100 to 150.Impact penetration tests (Raymond sampler) were generally in the rangeof eight to nine blows per foot of penetration. Impact penetration testsin the sand and silty sands generally ranged from 10 to 25 blows per footof penetration, indicating in general an adequate foundation.
6. Wherever clay lenses are found at shallow depths they are removedand backfilled with sand and compacted. In places where thick clay layersat deeper depths are encountered it is not economical or practical toremove these layers. They are preloaded in advance of construction with asufficient depth of sand to create the design load. Drains are installedin the layers to relieve pore pressure, and settlement is allowed to takeplace. In the Vizzeswaram section some modification of foundation designis necessary to reduce 9treSse~s.
ANNEX 4Page 3
7. In considering the foundation for the barrage it should be keptin mind that loading from the existing weir approximates the loading of thenew barrage. It appears that settlement from load has not been a problemfor the old weir. The settlements that have occurred were the result ofpiping with the masonry settling into the cavities. For additionalsecurity, the bearing area of the new barrage is confined by sheet piling.
Seepage
8. A primary consideration for the safety of the barrage is securityagainst underseepage (piping). The design makes adequate provisions for this.With the two rows of sheet piling, or concrete curtain walls upstream anddownstream a weighted creep path (Lane's method) of 8.5 is provided. A valueof 8.5 is considered safe for most materials. If the existing weir shouldbe breached and scour occur immediately downstream from the sheet piling,the weighted creep path would be reduced to 6.5 which is still a safe valuefor this type of foundation material. Check calculations for the expectedscour in the breach confirm this assumption.
Structural Design
9. A structural design review of the barrage indicates adequatethickness and reinforcement for the weir slab and piers. The barrage isconstructed in continuous units of 10 gate bays and piers, per unit. Doublepiers are provided at the junction between the units. An examination ofthe Ralli section, now under construction, showed no shrinkage cracks. Tyinga large number of bays together has the effect of increasing the safety ofthe dam, allowing for a generally strong foundation to compensate for localareas of less strength. Also, scour areas that might occur because offailure of the old weir would have to be longer and deeper to affect thefoundation of the barrage. The concrete used is of 2,500 psi strength forstructural work, and 1,500 psi for gravity blocks (28-day strengths).Working stresses have been taken as 750 psi for concrete in compression,75 psi in shear, and 18,000 psi for reinforcement. These values are con-sidered appropriate for the construction techniques used in India.
Hydraulic Design
10. Extensive hydraulic modeling of the barrage by three-dimensionalmodel at the Poona Laboratory and two-dimensional model at the HyderabadLaboratory has been made. These model tests were used to determine expectedwater surfaces upstream and downstream for each of the four sections ofthe barrage, distribution of flow among the sections, distribution of flowdownstream between the Gautami and Vasista branches, approach flow conditions,tailwater exit conditions and adequacy of the barrage stilling pool. Themission observed the flow in the two-dimensional hydraulic model at Hyderabadand recommended rounding of the upstream edge of the piers above 15.24 meterselevation.
ANNEX 4Page 4
Use of the Old Weir in the New Barrage
11. The design of the new barrage incorporates the existing weir asa downstream protective apron and for the dissipation of energy, by ahydraulic jump on the weir apron. By dismantling the shutters anddecapitating the weir, the seepage head will be reduced by some 2.0 m andthe safety of the old weir structure assured. The old weir will be coveredwith a 0.15 meter thick layer of concrete. Hydraulic model studies indicatethat the hyraulic jump on the downstream face of the old weir will becomesubmerged at a flow of some 8,900 m3/sec (flow concentration of 2.5 m3 /sec/m),reducing erosive action on the weir. Although maintenance of the old weir willhave to be continued, the costs will not be significant. In case tne existingweir is breached after the new barrage is completed, the new barrage willremain protected by the downstream sheet pile curtain. The barrage wouldcontinue to operate with no interruption in the delivery of water. Closingthe appropriate spillway gates would enable the repair of the breachedsection by backfilling with a suitable pervious material and providing a0.90 meter thick concrete block apron.
C. Construction Method
12. The construction season lasts from late November to the middle ofJune. As it is impractical to carry coffer-dams to above flood levels, thework would be divided into portions of such size that foundation excavation,sheet piling or construction of the curtain walls, placement of concrete andconstruction of piers to above high water level can be completed during oneworking season. The overall length of the barrage is some 4,000 m, dividedinto four sections by three fairly large islands. At present, the only meansof approach to the barrage sections is a single-lane road on top of theexisting weir. Provided approach roads are built from the left bank quarriesto the worksites, construction could be carried out simultaneously in allfour sections. At the start of each construction season, several suchapproach roads would be built through the riverbed, downstream of the existingweir. Aggregates would be centrally batched at one or two batching elantslocated on the river banks or the islands. Concrete (some 300,000 m3) wouldbe either centrally mixed and conveyed to the sites or mixed near each of thework sites. After dewatering of the construction area behind the coffer-dams,the two rows of sheet piles would be driven to the required depth or theconcrete curtain wall constructed. Excavation of foundations for theupstream and downstream aprons would follow. The portion covered by thereinforced concrete slab would then be excavated to the required shape andcompacted, taking care that all clay lenses are removed and filled withcompacted sand. Following the excavation of the pile caps to the requireddepth and their concreting, the concreting of the slab section would becompleted. During this operation the stainless steel crest gate guides andstop log grooves would be put into place. On completion of the slab, theraising of the piers and the construction of the gate lifting platform andbridge would be completed. As soon as a sufficient number of bays have
been completed, the vertical gates and hoist arrangements would be installed.
ANNEX 4Page 5
D. Second Phase Command Area Development Project in the Godavari Delta
13. Project preparation for a CAD project would include studies forthe:
(a) Socio-economic profile of the area with particular emphasison the existing farm size distribution and land tenuresituation;
(b) Rehabilitation and modernization of the water conveyancesystem;
(c) Drainage plan for the affected areas;
(d) Extension to the feeder road network;
(e) Groundwater study to investigate the feasibility of a large-scale groundwater development project to permit an increasein the rabi water supply;
(f) On-farm development works;
(g) Improvements to the agricultural support services;
(h) Economic and financial evaluation of the proposed developments,including an analysis of the likely effects on small farmersand landless laborers; and
(i) Recovery of investment costs.
The preparation report will follow the project preparation outlines for thePochampad/Nagarjunsagar Command Area Development Projects currently underpreparation by the Command Area Development Department of GOAP.
E. Assistance to the GOI in Project Preparation for Command AreaDevelopment Projects in Other Parts of India
14. The project also includes funds for the Water kanagement Divisionof the Ministry of Food and Agriculture of GOI to assist in project prep-aration of a number of Command Area Development Projects in other States ofIndia. Over the next five-year period, a large number of irrigation projects(each with a CAD element) would be prepared for Bank Group financing.Present arrangements for project preparation, with short term technicalassistance from the FAO/IBRD Cooperative Program, are totally inadequate.The Water Management Division of the Ministry of Agriculture needs to hcstrengthened by a suitably qualified irrigation and land development
ANNEX 4Page 6
engineer, an irrigation agronomist, and an extension specialist. The team
would be recruited by the Bank, on fixed term appointments, and seconded toGOI for a two-year period at a cost of approximately US$0.4 million. A
revolving fund of US$0.5 million would also be made available to GOI for
onlending to the States to cover project preparation costs in the field,particularly the cost of pilot on-farm development operations in the projects.
These pilot developments are essential for project preparation to try outconstruction techniques and organizational set ups and to monitor farmers'reaction to the proposed developments.
ANNEX 5
INDIA
GODAVARI BARRAGE PROJECT
Contingency Plan for Failure of the Old Weir
1. There is a high probability that one of the four sections of theexisting weir would be breached during the four-year construction period(Annex 9, para 6). If that happens, then to prevent the loss of agriculturalproduction and damage to the riverbed it would be essential that the breachbe plugged immediately.
2. Following the failure of a similar weir on the Krishna river inSeptember 1952, a system was developed to carry out emergency repairs. Thesuccess of the emergency repairs was a result of considerable ingenuity onthe part of the engineers involved but also very much due to the relativelysmall initial breach (about 40 m) as well as favorable stages of the riversubsequent to the breach.
3. The repairs consisted in loading old steel barges (weighing about30 tons) with stones and floating them down from a steamer anchored in theriverbed some 100 m upstream of the breach. When the barges reached a pointsufficiently near the breach, holes were cut on the side of the barges. Thebarges were then released from the steamer so that they sank exactly at thebreach site. In all, 42 barges were sunk. The intervening spaces betweenthe barges were filled with rough stones. Through these repairs the breachwas closed in a short period of 12 days, thus avoiding any significantdamages to either the crops or the riverbed.
4. It is unlikely that the circumstances accompanying a possiblefailure of the Godavari weir would be as favorable as they were in the caseof the Krishna weir. It is possible that the initial breach would be toolarge for emergency repairs or that the subsequent river flows would be toohigh to permit a successful plugging operation. Nevertheless, to avail ofthe favorable circumstances, if they occur, it was agreed during appraisalthat materials and equipment would be kept ready near the weir site forimediate repairs to the damaged section.
5. Some 50-60 barges, available for emergency service, are alreadyin stock at Dowlaiswaram. However, 30,000 m2 of stone blast costing aboutUS$300,000 would also have to be stored in advance. In case this stone isnot needed for emergency repairs during the construction, it could be usedfor completing the downstream protective apron of the barrage. The proposedemergency stockpile of stone would therefore not involve any significantaddition to the project cost.
INDIA
GODAVARI BARRAGE PROJECT
Cost Estimates
ForeignExchange
Local Foreign Total Local Foreign Total %- Rs Million ------- --------- US Million------------
1e Civil Works
a. Dowlaiswaram Section
Site Preparation and Oe-rvce Roads 6.9 0.8 7.7 o.86 0.10 0.96 10Construction of Weir 26.9 9.0 35.9 3.36 1.12 4.48 25Construction of Piers 10.8 3.6 1J4.4 1.35 o.45 1.80 25Stone Protection 5.2 1.8 7.0 0.65 0.22 0.87 15Dismantling of Old Weir 0.2 - 0.2 0.03 - 0.03 -Completion of Stone Protection 8.9 3.0 11.9 1.11 0.38 1.49 15Road Bridge 4.1 1.4 5.5 0.51 0.18 0.69 25Miscellaneous -9 0.3 0.2 0.36 0.04 0.40 10
Subtotal 65.9 19.9 85.8 8.23 2.h9 10.72
b. Ralli Section
Site Preparation and Service Roads 2.4 0.3 2.7 0.30 0.04 0.34 10Construction of Weir 2.8 1.0 3.8 0.35 0.12 o.47 25Construction of Piers 5.5 1.8 7.3 0.69 0.22 0.91 25Stone Protection 5.6 1.0 6.6 0.70 0.12 0.82 15Dismantling of Old Weir 0.2 - 0.2 0.03 - 0.03 -Completion of Stone Protection 11.5 2.0 13.5 1.44 0.25 1.69 15Road Bridge 2.5 0.8 3.3 0.31 0.10 0.41 25Miscellaneous 1.0 0.1 1.1 0.13 0.01 0.14 7 PI
Subtotal 31.5 7.0 38.5 3.95 0.86 4.81 HHo
i/ Exchange rate: Rs 8.00 = US$1.00,
INDIA
GODAVARI BARRAGE PROJECT
Cost Estimates
ForeignExchange
Local Foreign Total Local Foreign Total %------Rs Million---- -$US Million-----______
c. Maddur Section
Site Preparation and Service Roads 2.2 0.3 2.5 0.28 0.04 0.32 12Construction of Weir 9.6 3.2 12.8 1.20 0.40 1.60 25Construction of Piers 4,5 1.5 6.o o.56 0.19 0.75 25Stone Protection 2,0 0.3 2.3 0.25 0.04 0.29 14Dismantling of Old Weir 0.3 - 0.3 0.04 - 0.04 -
Engineering and Supervision 9.3 3.1 12.h 1.16 .39 lo55 25
Total 107.8 36.7 144.5 13.47 4.59 18.06
5. Assistance to GOI for PreparingCAD Projects 4.8 2.4 7.2 Mo60 0.30 0.90 30
6. Preparation of Second Phase Project 2.6 o.6 3.2 0.32 OoO8 0.40 20
Total Project Cost 399.o 159,9 558.9 49.86 20.00 69.86
2/ Due to rounding off, the above figures may not exactly agree. In additionthe Rupee portion has been used as the basis for conversion into Dollar equivalents.
ANNEX 7
INDIA
GODAVARI BARRAGE PROJECT
Equipment Requirements
1. Estimated equipment requirements for the PWD's design and super-vision activities and for transporting the building materials required forconstruction of the barrage from the railhead to the PWD stores atDowlaiswaram are listed in the following table. This list should be usedas a guide only and would be revised during project implementation.
2. Prices shown in the table include delivery to the project areaor to the PWD offices in Hyderabad in June 1974 currency. To obtain actualcosts for delivery in 1975, the prices have been escalated by 20%.
ANNEX 7Table 1
INDIA
GODAVARI BARRAGE PROJECT
Quantity Rs
a) Monitorinff Equipment to be Incorporated in the Barrage
Transmitters for soil pressure meters .oTransmitters for reinforcement meters 12Transmitters for tilt meters 2Receivers 2 ...Miscellaneous small items for installation
of the equipment
Subtotal 350
b) Equipment for PTD
Drafting machines o ...Automatic printing machines 2 ...Xerox copier 1Photostat copier 1Electronic digital computer 1Desk calculators 6Slide projector 1Cine projector 1Cine camera 1Miscellaneous office equipment
III. Engineering and Supervision 5.86 0.59Price Contingencies 1.55 0.39
Subtotal 7.41 0.98 .6 8%
IV. Second Phase Project Preparation 0.40 0.08 0.1 25%
V. Techical Assistance to GOI forPreparation of CAD Projects 0.90 0.30 0.3 33%
VI. UnallocatedPhysical Contingencies ofCategories I and II 8.09 2.37
Price Contingencies 2.98 0.82
Subtotal 11.07 3.19 2.1 19%
Total 69.86 20.00 45.00
/ As rounded off.
6NTE 8Table 3
INDIA
GODAVARI BARRAGE PROJECT
Estimated Schedule of Disbursements
Bank Fiscal Year Accumulated Disbursementsand Semester US$ Million Equivalent
19752nd 3.0
19761st 6.o2nd 16.0
19771st 23.02nd 32.0
1978lst 36.02nd 4Oo.o
19791st 43 02nd 1UL.0
19801st 45.0
ANNEX 9Pate 1
INDIA
GODAVARI BARRAGE PROJECT
Economic Analysis
1. The economic evaluation of the Godavari Barrage Project is somewhatcomplicated because of the difficulties involved in specifying the "without
project" situation. Unlike most other investment projects, the primary
objective of this project is to ensure the continuation of the existing
benefits rather than to generate additional benefits. The specification
of the "without project" situation requires the assessment of factors such
as:
(a) the life expectancies of the four sections of the
old weir;
(b) the timing, location and size of the likely breach;
(c) the prospects of successfully plugging the breach;
and
(d) the magnitude of the production losses likely to
accompany a breach in the weir.
Answers to aly of the above are essentlally a matter of speculatior -JJ
must necessarily be highly subjective.
2. For the sake of simplicity the economic amialysis is divided
into two parts:
(a) Assuming that the existing weir has collapsed,is the construction of a new barrage justifiedeconomically? The answer to this question dependsupon the estimated construction costs for theproposed new barrage and the loss in net value of
production which would be prevented by the newbarrage. An affirmative answer to this question -is
a necessary condition for any construction at all.
(b) If the answer to part (a) is yes, then how shouldthe construction of the new barrage be phased overtime? Ideally, the construction of the varioussections should be phased such that each sectiorof the new barrage is comlpleted just ahead of tLe
ANNEX 9Page 2
time at which the corresponding section of the oldweir were to collapse. In practice it is impossibleto predict accurately such timing and accordingly,the construction must be phased so as to strike abalance between the risks associated with delayedconstruction and the interest charges incurred througha "premature" construction.
Should a New Barrage be Constructed?
3. The following assumptions were made for analyzing the firstquestion:
(a) Construction Costs: All construction costs exceptprice contingencies (Rs 144 million), the cost of preparinga second phase project (Rs 3 mi llion) and the assistanceto GOI for preparing CAD projects (Rs 7.2 million) areincluded in the economic analysis.
(b) Cost of Materials: The estimated construction costs includeabout Rs 64 million for the procurement of materials suchas cement, reinforcing steel, steel plates and sheet piles.These materials are in short supply in India and would beprocured by the PWD, Andhra Pradesh, at controlled prices,which are roughly one-half of their free market prices.Accordingly, for economic analysis the constructionmaterials are shadow-priced at 200% of their controlledprices.
(c) Physical Contingencies: Even though the civil engineeringworks are relatively simple, physical contingencies atthe rate of 25% have been included in the cost estimatesto cover the complications which iight arise from a partialfailure of the existing weir during construction. Ideally,the margin for this contingency shoul1d depend upon theparticular construction sclhedule, being higher foralternatives with longer implementation period. For simplicity,however, in the following analysis it is assumed to be thesame for all construction alternatives.
(d) Project Benefits: Annex 2, Table 1 shows the current croppingpattern, yields, prices, gross returns, production costs andnet returns per ha for various crops, in the command area ofthe weir. Annex 3, Table 1 shows the same for the rainfedagriculture whicl would follow the collapse of the old weir.The higher pond level envisaged for the new barrage would makeit possible to irrigate additional 4-5,000 ha during the rabiseason. In addition, the average paddy yields would be
ANNEX 9Page 3
increased by the earlier trans planting in the lowerdelta (para 5.05). For simplicity, however, theseincremental benefits are not included in the analysisand it is assumed that the production with the newbarrage would be the same as the current production.
Since the current commodity prices are unusually highbecause of particularly bad crops during the recentyears, the prices used in the economic analysis are thefarm gate prices derived from the projected world marketprices in 1980. kLl farm labor has been priced at itsaverage market wage rate of Rs 4 per day.
On this basis the annual net value of production "with"and "without" the barrage is estimated to be Rs 900million (US$112.5 r.illion) and Rs 100 million (US$12.5million) repsectively, giving imputed annual projectbenefits of Rs 800 million (US$100 million). The fullproject benefits are assumed to start immediatelyafter the completion of the new barrage.
4. Assuming a 50-year life for the new barrage, the economic rate ofreturn is estimated to be over 50, (Table 1). Even if it is assumed thatthe construction costs increase by 20%, benefits decrease by 20% and theimplementation schedule increases by two years, the rate of return wouldstill exceed 35%. The unusually high rate of return merely confirms theintuitive judgement that in view of the crucial importance of the weir tothe project area, in the event of a failure, it should be replaced as fa.;as possible.
Phasing of Construction
5. In theory the number of combinations in which the construction Wthe four sections can be phased is very large. However, a number of practi,.ziconsiderations, e.g. the data quality and the computational complexity, makeit imperative that the analysis be restricted to a few "najor" altern.L!_In the following analysis three alternatives are considered:
Alternative A, corresponds Lo the four-year implementa-tion period prcmposed in this report. This period re-presents the minimun; tine necessary to complete all foursections of the barrage, assuming that there are noconstraints due to either the lack of funds or the un-availability of construction mlaterials. In this alLer--native, the Ralli and the Maddur sections are securedafter three years of construction.
ANNEX 9Page 4
Alternative B, has been tentatively proposed by the GOI.In this alternative the implementation period is extendedto six years and the Ralli, Dowlaiswaram, Maddur andVizzeswaram sections are secured after three, four,five and six years of construction respectively.
Alternative C, assumes that the annual budgetaryallocations to this project can not be increasedvery much beyond the levels of the past three yearsand that the implementation period would be extendedto 10 years. In this alternative the Ralli, Dowlaiswaram,Vizzeswaram and Maddur sections are secured after three,six, eight and ten years of construction respectively.
6. The following assumptions are made in addition to those madeearlier in para. 3:
(a) Description of the Likely Breach: It is assumedthat the breach, if it occurs, would occur during theearly monsoons (late June-early July) and would be-come 100-200 meters wide. It is further assumedthat the high river flows in the ensuing period wouldrule out the possibility of undertaking any repairwork until the end of monsoons (late October - earlyNovember); however, by the end of the dry season (nextJune) a solution would be found to plug the breachand to bring the structural soundness of the oldweir to the pre-breach standards. Thus, disruptionof the water supply would lead to a total loss ofone rabi crop and a large part of one kharifcrop (para 8, Annex 3). For simplicity, it isconservatively assumed that the loss in NVP would bethe same as the annual loss estimated in para. 4.
(b) Life Expectancy of the Old Weir: The followingassessment assumes that the principal factor governingthe collapse of the weir is the occurrence of floodsof a certain threshhold level. however, even otherfloods have a detrimental effect on the structuralcondition of the weir through gradual wear and tear.The occurrence of the destructive flood is a randomevent whose probability would increase with the passageof time because of the gradual deterioration of theweir.
It is estimated that the probabilities of failureduring the next year (year 1) for Ralli, Dowlaiswaram,Vizzeswaram and Maddur sections are 10%, 10%, 5/ and3% respectively. It is further estimated that the
ANNEX 9Page 5
conditional probabilities of failure in a subsequentyear, assuming that the respective sections arestill operative, i.e. either they have not failedor they have been repaired, would increase at an
annual rate of 1% for the Ralli and the Dowlaiswaramsections and at a rate of 1/2% for the Maddur and
the Vizzeswaram sections. Thus, for example, the
conditional probability that the Dowlaiswaramsection would fail in year 4, assuming that it has
not failed until the end of year 3, is estimated at
13%. For simplicity, it is assumed that the pro-
babilities of failure for the four sections are
independent of each other so that a failure in one
section would not affect the probabilities of failure
in the other sections. Notice that it is possible,
though unlikely, that the same sections can fail
more than once or two sections can fail in the sameyear.
The conditional probabilities estimated above can
be used to derive the probability of weir failureduring a given year for various construction alter-
natives. Thus, for example, the probability of weir
failure in year four under alternative A is merely
the probability that either the Dowlaiswaram or the
Vizzeswaram section would fail during the year whichis equal to 1- (1-0.13)(1--0.065) = 0.19.
Three main implications oE the above assessment are
worth emphasizing here: (i) the probability that
at least one of the four sections would be breached
during the next year is quite large; there is aone in four chance that this may happen; the pro-
bability that all four sections of the old weirwould survive four more years is only 30%, thus even
under alternative A there is a high probability ofweir failure before completion of the new barrage;and (iii) the probability that all four sections ofweir would last 10 years Js less than 1%, making italmost a certainty that within 10 years one of the
sections would be breachect.
7. The appropriate criterion for comparing the various construction
alternatives is the minimization of the present value of the expected costs,
where the costs include the construction costs and the expected losses in
production. It is assumed that in the Indian economy the opportunity cost
of capital is 10% per annum.
ANNEX 9Page 6
8. Under these assumptions the present value of the expected costs foraltermatives A, B and C is found to be Rs 1,020 million, Rs 1,090 millionand Rs 1,350 million respectively, indicating the superiority of alternativeA over the other two (Table 2). The difference of Rs 70 million betweenalternative A and the next best alternative B is 1996 of the present valueof (shadowed) construction costs of Rs 368 million.
9. Sensitivity Analysis. Tests were made to determine the sensiti-vity of the ranking of three alternatives to various assumptions. Some ofthe more important results are as follows:
Total Expected Cost Differences in Expected Costs.... (Rs Million) ... (Rs Million).
Assumption Alt. A Alt. B Alt. C Alt. B - Alt. A Alt. C - Alt. A
(h) Combination of (c),(d) and (e) 865 885 1,005 20 140
(i) Combination of (c),(d), (e) and (f) 680 685 760 5 80
/a The probabilities of failure during the next year (year 1) for Ralli,Dowslaiswaram, Vizzeswaram and Maddur sections are reduced to 5%, 5%,3% and 2% respectively. The annual rates of increase for the con-ditional probabilities in subsequent years are assumed to be the sameas earlier.
ANNEX 9Page 7
Thus, alternative A remains superior to the other two for wide variationsin the various parameters. Even in the highly unlikely situation wherethe cost of capital is 15%, expected production losses because of weirfailure are 20% lower, construction costs are 20% higher and the probabilitiesof failure for the various sections are substantially lower, alternative Ais still preferable to alternative B.
10. Assuming "no construction'" to be the "without project" situation andtaking into account the estimated probabilities of failure, the expected rateof return on alternative A is estimated to be 44%. Given below are theresults of some of the tests conducted to determine the sensitivity of therate of return to variation in various estimates.
Assumption Rate of Return
(a) Base Run 44%
(b) 20% increase in expected production losses 49%
(c) 20% decrease in expected production losses 37%
(d) 20% increase in construction costs 35%
(e) Lower probabilities of failure for thevarious sections (as irn 9(f)) 33%
(f) Combination of (c), (d) and (e) 20%
Thus even after allowing for substantial margins of error in the variousbase estimates, the project would still have a high rate of return.
ANNEX 9Table 1
INDIA
GODAVARI BARRAGE PROJECT
Economic Costs and Benefits
CostsYear Construction O&M Benefits
… (Rs million)-----------
1 40 - -
2 205 - -
3 145 - -
4 70 - -
5 10 35 800
6
h _
*~~~~~~~ S
50 - 35 800
Economic Rate of Return: 69Z
INDIA
GODAVARI BARRAGE PROJECT
Economic hAialysis of Construction Phasina
Alternative A Alternative B Alternative CExpected Present Expected Present Expected Present
Prob.of Loss in Const. Total Value of Prob.of Loss in Const. Total Value of Prob.of Loss in Const. Total Value ofYear Failure Production Cost Cost Total Cost Failure Production Cost Cost Total Cost Failure Production Cost Cost Total Cost
EXCTIVE ENINER EXECU rIVE ENGINEER EXECUTIVE ENGINEER EXECUTIVE ENGINEER EX ECUTIVE ENGINEER
BARR IDOV'LAISLIVARAM (MADDUR (VIZZESVVARAM ~~~~~~~~~TRANSPORT, EXECUTIVE ENGINEER EXECUTIVE ENGINEERURAL I BARG OWAFISRAREAO BARAGEU IVZARWRAGE PERSONAL ASSISTANT MACHINARY ERECTION OF GATES ERECCTION OF GATES PESNAL ASSISTANT
STRUJCTION) CONSTRUCTION) CONSTRUCTION) AND WORKSHOPS
4 ASSISTANT 4 ASSISTANT 4 ASSISTANT A ASTNT4 ASS ISTANT 4 ASSISTAN4T 4 ASSISTANTENGINEERS WITH ENGINEERS WVITH ENGINEERS WITH ENGINEERS WITH ENGINEERS WITH ENGINEERS WITH ENIER
