*WELCOME TO THE PRESENTATION ON CONCEPTUAL TWIN PROJECTSDe silting Vaigai Reservoir and ejecting silt into River.Eco restoration of Vaigai River by reclamation of bed using reservoir silt.Concept: Er.T.KRISHNASWAMY, B.E.(Hons), M.Sc.(Engg.), Dip H.E.(Delft), FIE, Formerly Chief Engineer, PWD, Government of Tamilnadu.

*Why the desilting Project?Augmentation of supply in vaigai basin is necessaryThere is additional water potential augmentation but could not accessed / hornesed Additional storage space is necessary for accessingTwo options : 1. New reservoir 2. Desilting the vaigai reservoir

*Comparison of the OptionsNew site for 800 Mcft : Below Vaigai Dam?Land AcquisitionCostEnvironment & R.R issues.Longer time required

* APPREHENSIONS OF DESILTINGWhether reservoir should be emptied of water ?Whether possible to desilt under water ?Whether water regulation is affected ?Where to dump the huge quantity of silt ?Whether economically viable ?Whether the process/ Technique will affect the safety of dam ?Whether a new compensating reservoir ? Will be Cheaper Alternative ?The Answers are in the twin projects ?

*Vaigai DamVAIGAI DAM

*Designed storage capacity 6800 Mcft.Loss of Storage - 800 Mcft.

*How the projects are framed?Basic factsThe processThe product quantificationThe pricing of the projects

*Facts on occurrence movement and sedimentationSilt is non floating solid matter.In Rivers, it moves along with flowing water.Classification: Moving silt, Rolling silt and resting silt.Silt is lifted and kept in suspension by vertical velocity component of eddies in moving or in standing water.Any river has its own potential silt carrying capacity.

*INFERENCES:Silt is in dynamic or static form. Dynamic form can be converted into static form and vice versa artificially or by natural phenomenon.Dynamic Form : 1. Gravity Flow 2. Pressure Flow

*Flow Pass in Vaigai Dam

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*MORNING GLORY SYPHON

*Mechaniqual Transportation

*Process :Principles and techniques

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*SLUICE FLOWRIVER SLUICESILT - CHURNERSILT DEPOSIT 800 MCFtFLOATING PANTOONFRL2052RIVER FLOWSYPHON PIPESUSPENDED SILT EJECTION GRAVITY FLOW123W.L.

*SLUICE FLOWDELIVERY PIPE FORSILT LADEN WATERRIVER SLUICECUTTER - ROTTERSILT PUMPSILT DEPOSIT 800 MCFtFLOATING PANTOONFRL2052RIVER FLOWFLOW PATH4W.L.MOTOR

*CAISSON

*Whether normal reservoir operation is interfered?Whether the present outlets and water releases can act as flow paths -- YESWhether additional flow paths are necessary -OPTIONAL

*OUTLETS AND NORMAL RESERVOIR OPERATIONSA. River sluiceIrrigation supply through PMC AND TMC 1500 cusecs- 125 mcft per day 250 days can be used as flow path with silt trap.Irrigation supply through river Vaigai forold ayacut - 1500 cuses - 125 mcft per day 20 days Suitable flow pathDrinking water through river 600 mcft / year Suitable for flow path.Chitra festival through river 300 mcft/ year Suitable for flow path._ Flood relese 12000 cusec -125mcft per day 7 days

*Contd..B. Spill wayFlood release through river 60,000 cusecs / 5000 Mcft per day Suitable for flow path.Assumed 12000 cusecs 125 Mcft per day 7 days.

C. Additional paths contemplatedSyphon pipes over the dam and through the sluices (gravity flow).Pumping mains through River sluices (Artificial energy).Lorry conveyance dry process._ Conveyor Belt (N.L.C.Model)

*Ejected silt ComputationObserved data on Silt Water ratioKrishna River = 1/68 (by volume)Cauvery in delta = 1/500 Assumed ratio for primary project 1.For gravity irrigation and flood flow 1/502. For gravity Syphon flow 1/303. For dreadging and pumped flow 1/5

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Discharge path Discharge rate CusecsDays of operationTotal volume of water McftSilt Volume McftA. Irrigation season for PMC and TMC Ayacut- June to January1.River Sluice1200250250005002.Pressure pipe of Dredger15025031256253.Gravity Syphon1501001250424.Spill wayNilB.Irrigation of old Ayacut October-December1.River Sluice1500202500502.pressure Pipe15020250503.Gravity Syphon1502025084.Spill wayNilC.Drinking Water March-June1.River Sluice4501245092.Pressure Pipe15012150303.SyphonNil4.SpillwayNil

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D.CHITRAI FESTIVAL -- MAY1.River Sluice450311322.Pressure Pipe15033883.SyphonNil4.Spill wayNilE.Flood Discharge- October-December1.River sluice12000770001402.pressure pipe150788183.SyphonNil4.Spillway120077000140TOTAL1509 + 140G.SILT REMOVAL BY LORRY CONVERYOR BELT etc March to June100 Grand Total1609 +140

*ABSTRACT ESTIMATE -PRIMARY PROJECT

Sl.No.DescriptionQuantityMcft.RateRsAmountRs1Under water survey below 50 feet contourL.S.4 x 10 62Surveying in Fringes dry zone above 50 feet contourL.S.1 x 10 63Artificial eddies dredging and ejecting.7001.0 per cft.700 x 10 64Excavation and transportation (dry, wet and or saturated silt by lorries. 1000.75 per cft.75 x 10 65Silt traps 3 Nos.-----L.S.20 x 10 6Total800 x 10 6

*BENEFITS OF PRIMARY PROJECTAugmentation of water 2400 Mcft.Augmentation of Sand for construction.Loamy silt is used for brick making.Fine silt is a manure.

*A: Reclamation of River Bed

*Why Reclamation of River bed?Flood absorbing capacity is lostSand Aquifer is lost : No rain harvesting No ground water recharge Mal functioning of infiltration wells Ecology and Environment is affected Flora and Founa is missing Beneficiary bacteria are missing

*A: Reclamation1231234

*Whether dumped silt can be transported to downstream along vaigai river -- YESSilt carrying power of rivers.Nile 1270 Mcft annuallyMissipi 6750 Mcft annuallyKrishna 4220 Mcft annually

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*How to induce sedimentation?

*FLOWGRADE WALLFLOOD CARRIER SLUICEERODED BEDINDUCED SILT DEPOSITFLOOOD BANKDESIGN CONCEPT BYEr.T.KRISHNASAMY B.E(Hons),M.SC(ENGG)CHIEF ENGINEER,(RTD)PWD,MADURAIRECLAIMED BED

*FLOWGRADE WALLFLOOD CARRIER SLUICEERODED BEDINDUCED SILT DEPOSITFLOOOD BANKDESIGN CONCEPT BYEr.T.KRISHNASAMY B.E(Hons),M.SC(ENGG)CHIEF ENGINEER,(RTD)PWD,MADURAIRECLAIMED BED

*B.Eco RestorationAuxillary worksMitigation of sewage in flux.Eviction of encroachmentDevelopment of flora and fauna

*ABSTRACT ESTIMATE SECONDARY PROJECT

Sl.No.DescriptionQuantityMcft.RateRsAmountRs1Part A : Reclamation.Bench mark survey by GPS GIS L.S.L.S.5 x 10 62Convert solid anicut to Regulator1L.S.20 x 10 63Grade walls1010 x 10 6100 x 10 64Post assessment survey GPS GIS. 5 x 10 6Total for A130 x 10 6

5Part B : Auxiliary works .Remove Encroachment L.S.L.S.10 x 10 66Mitigation of sewageL.S.L.S.200 x 10 67Promoting Flora and fouraL.S.L.S.10 x 10 6Total for B220 x 10 6Grand Total350 x 10 6

*BENEFITS SECONDARY PROJECT Rain harvesting 1575 Mcft.Ground water recharge 125 Mcft.Flood harvesting1000 Mcft.Comprehensive Eco restoration of RIVER.