RESERVOIR SEDIMENTATION ASSESSMENT GUIDELINE - Aneel

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Reservoir Sedimentation Assessment GuidelineFigure 7.11 –US-BM-54 sampler for bed material for deeper water and highervelocitiesNote – The North-American series equipment identified by US, for United States, fordirect bed load measurement are indicated as BL, for bed load, while the simplecollection for indirect measurement, are indicated by BM, for bed material, and may behand-operated whenever labeled as H, for hand; the number corresponds to the projectyear.7.4.1 Sediment samplingThere are several kinds of sediment load sampling, which may be punctual or byvertical integration. Table 7.4 presents the usual sampling methods.Table 7.4 – Methods for sediment samplingSampling Positions Average concentrationIn pre-established position when using anautomatic equipment (pumping) ormeasurer (turbidimeter, nuclear or other)PunctualA surface site with sampler or directlywith the semi-sunk bottle, in everyvertical sectionAverage concentration in the sectiondetermined through calibration andbased on the correlation with thehydrometrist's measurementsAverage concentration on the verticalsectionC mv = 1,2 C supPunctualA point at the vertical at 0,5 or 0,6 indepthTwo points at the vertical at 0,2 and 0,8in depthAverage concentration on the verticalsectionC mv = C 0,5 or = C 0,6Average concentration on the verticalsection3 5C mv= C0,8+ C8 80,2ANEEL – Brazilian Electricity Regulatory Agency / SIH – Hydrologic Studies and Information Department24
Reservoir Sedimentation Assessment GuidelineVerticalintegrationThree points at the vertical at 0,2, 0,5 and0,8 in depthSeveral points on the vertical section, at0,1, 0,3, 0,5, 0,7 and 0,9 (if concentrationvalues vary too much, the average shouldbe computed by weighing it with depthsamong the measured points)Using different transit rates for thesampler at each vertical section.Method of Equal Increment of Width,(IIL), using the same transit rate for allverticals and the same bill along theentire cross-sectionMethod of Equal Increment of Discharge(IID), performing the sampling at themiddle point of equivalent dischargeincrements along the whole crosssection,where the bill may be changedand one may use different transit rates foreach vertical, however sampling equalvolumes of the mixture water-sedimentAverage concentration on the verticalsectionC,2+ C0,5+C mv=3or,0C0,8C,2+ . C0,5+C mv=402 C0,8Average concentration on the verticalsection∑CiCmv=nConcentration is the average at thevertical section.The suspended sediment dischargeshould be determined by multiplyingsegments for the partial discharge,where the total suspended discharge isequivalent to the sum of partial valuesand the average concentration for thesection is equivalent to the totalsuspended discharge, divided by thetotal net discharge.All vertical sub-samplings are gathered(from 10 to 20) and a single analysis isperformed, thus providing the averageconcentration and, if required, a singleaverage granulometric curve for thesectionAll vertical sub-sampling are gathered(from 5 to 15) and a single analysis isperformed, thus providing the averageconcentration and, if required, a singleaverage granulometric curve for thesectionFor those sampling methods, the bottle should never be totally full; it isrecommended to collect no more than 400ml for bottles with total capacity of 500ml.The samplers using that kind of bottle cannot collect samplings in very deep waters,being the DH-48 for depths up to 2,0m, and the DH-59 and D-49 for depths up to4,50m.For the vertical integration process, the sampler is submerged and moved in asteady velocity, from surface to the bottom, then returning to surface. Each up or downmovement happens in a constant velocity, but not necessarily in equal velocities. Thesampler transit rate shall not be higher than a given value v t which must be computeddue to the constant of the bill used and the average velocity at the vertical (equations 7.1ANEEL – Brazilian Electricity Regulatory Agency / SIH – Hydrologic Studies and Information Department25
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RESERVOIR SEDIMENTATION ASSESSMENT GUIDELINE - Aneel

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