RESERVOIR SEDIMENTATION ASSESSMENT GUIDELINE - Aneel

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Reservoir Sedimentation Assessment GuidelineBed loadentrainment dischargeDirectIndirectDirectUse of satellite pictures and comparisonwith simultaneous field measures forcalibration in large rivers.Samplers or portable measurers of threemain kinds (the sampling is collected inseveral points of the cross-section,determining its dry weight, thegranulometry and calculating theentrainment discharge); the measurer isfixed on the bed from 2 minutes to 2hours, in such a way as to receive in itsreceiver from 30 to 50% of its capacityCrevasse or water well structures – thebed crevasses are opened for a fewminutes and the sediment is collectedBed load collection, granulometricanalysis, slope gauge, temperaturehydraulic parameters and computationon entrainment discharge and bed loadthrough formulas (Ackers and White,Colby, Einstein, Engelund and Hansen,Kalinske, Laursen, Meyer-Peter andMuller, Rottner, Schoklitsch, Toffaleti,Yang and others)Dunes displacement – by measuring thevolume of the displacing dune, usinghigh-resolution echobathymeter1) Radioactive trackers2) Dilution trackers, being bothmethods by setting the tracker on thesediment and monitoring it by using thesuitable equipment (the tracker shall bechosen in such a way as to avoidpolluting environment)Lithologic properties – use ofsediments’ mineralogical featuresAcoustic method – used for stonesstriking against the measurementSampling photograph method – usedfor stones. A scale is settled and alsophotographedUse of block-type structures, on thebed, to cause turbulence and allsediments become suspendedEquations are established in orderto correlate the values of pictureobservation and measuredconcentrations1) Crate or case - Muhlhofer,Ehrenberger, SwitzerlandAuthority and other measurers2) Tray or tank – measurersLosiebsky, Polyakov, SRIH andothers3) Pressure difference –Helley-Smith, Arnhem, Sphinx, USCE,Károlyi, PRI, Yangtze, Yangtze-78 VUV measurers and othersMulhofer measurer (USA)Kinds of equipment:1) horizontal penetration, likedredge and shell bucket2) vertical penetration, likevertical tube, scraper bucket,excavation bucket and gravelexcavation3) piston-core, which holds thesampling though partial vacuum1) successive bathymetric surveysalong the cross-section2) successive bathymetric surveysalong longitudinal sectionsMethods:1) by settling the tracker directlyon the bed sediment2) by collecting sediment, settlingthe tracker on the sediment andreturning it to the bed.Collection of tributaries and mainbed sediment, determination ofsediments’ mineralogical featuresand comparison by using suitableequations based on the quantityof components existing in thesampling(Unsatisfactory)1) Photos of underwater stones2) Photos of dry beds stonesSediment sampling is performedand computed as suspendeddischargeANEEL – Brazilian Electricity Regulatory Agency / SIH – Hydrologic Studies and Information Department18
Reservoir Sedimentation Assessment GuidelineSedimentdischargetotalIndirectTopo-bathymetric survey for thereservoir, determination of depositsvolume and trap efficiency in the lakeCollection of suspended and bedmaterial, concentration analysis,granulometric analysis, temperaturemeasurement, hydraulic parameters andcomputation of total discharge –Einstein’s method modified andColby’s method simplified1) For small reservoirs, it allowsfor the computation of bedsediment2) For large reservoirs, it allowsfor the computation of totalsedimentSeveral kinds of equipment –pumping, equipment using bottlesand bags, being instantaneouspoint, points by integration andvertical integrators (in Brazil ismainly used the North-Americanseries U-59, DH-48, DH-59, D-49, P-61 and bag sampler)Several measurement or suspended sampling equipment may be classified indifferent kinds, such as:• Instantaneous or integrators, where the instantaneous quickly gets the sampling orread them, while integrators admit sampling in a few seconds through a beak or abill, storing it in a recipient;• Portable or fixed, where portable ones are manually operated, by pole or shrill, oreven fixed to a boat, while the fixed ones are installed in a adequate structure, eitheron a bridge or at the bed;• Beak or with bill, where the beak are of pumping or other, and those using bills arethe portable ones furnished with bottles, plastic recipient or plastic bag;• Punctual instantaneous, punctual by integration and by vertical integration, wherepunctual instantaneous are cylinder-like with a device for capturing the samplingsending a messenger/weight that closes the valves. The punctual by integrationcollects sampling in a few seconds at a vertical point. The vertical integrators or indeep waters collect sampling by moving the equipment along vertical in a steadymovement that may be in a single way or back and forward from surface to bottom.• Horizontal tube sampler, of bottle, collapsible bag, pumping, integration,photoelectrical, nuclear, optical ultrasonic flowmeter, dispersion ultrasonic,Doppler Ultrasonic Flowmeter– the horizontal sampler is a punctual instantaneousone. The bottle sampler is hydrodinamically built and has a cavity for inserting acollection bottle; the sampling is performed through a bill that may report severaldiameters (1/4”, 3/16” e 1/8”) while the air is expelled through a tube. Thecollapsible bag sampler is also hydrodinamically built and has an aluminum-maderecipient for holding the plastic bag, which is compressed in order to expel the air;its capacity is greater than the bottle’s capacity and it also uses exchangeable bills.The pumping device may be settled on a boat or installed at the bed; normally, it isused a hose furnished with a beak or a bill adjusted for allowing in the sampling;the pumping is monitored according to the stream velocity, and there are severalkinds of such equipment. The equipment working through integration is bottle orbag collapsible . The photoelectrical and the nuclear ones operate through light andrays, respectively, through a constant intensity source. The optical and thedispersion ultrasonic work with sources that produce ultrasonic rays that arereceived by adequate equipment. The Doppler Ultrasonic Flowmeter uses Doppler19ANEEL – Brazilian Electricity Regulatory Agency / SIH – Hydrologic Studies and Information Department
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RESERVOIR SEDIMENTATION ASSESSMENT GUIDELINE - Aneel

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