The Study On Countermeasures For Sedimentation Final

The Study on Countermeasures for Sedimentationin the Wonogiri Multipurpose Dam ReservoirFinal ReportSupporting Report Annex No.6In this stretch, two (2) water level gauging stations have been installed at the Jurug (51km downstream of the dam) and the Kajangan (131 km downstream of the dam). SSconcentration in the mainstream has been periodically observed by JICA Study Team atfour (4) locations, i) the bridge immediately downstream of the Wonogiri dam, ii) theColo weir, iii) Jurug bridge and iv) Tangen 000SURAGEN9180000917500010JURUGNGAWI09Tributaries of Upper Solo River9170000GS 508GS 49165000SURAKARTAGS 30791600000605915500004GS 20391500009145000GS 102019140000COLOBridge d/s of DAM9135000WONOGRI g 3167.3180.0: TSS Monitoring Station (JICA): WL/Discharge Monitoring Station (PBS): Boundary Condition: Ground Sill91300009120000460000Confluence ofMadiun RiverKAJANGAN520000530000540000550000560000Source: JICA Study TeamFigure 3.3.1 Location Map for Turbidity Analysis Model3.3.2Analysis ModelFor the turbidity analysis model the MIKE 11, which is in wide usage as commercialsoftware, was used because of its high versatility. The calculation method on the turbidityanalysis model used basically the same equations as the reservoir sedimentation model asdescribed in the Supporting Report II Annex No.4 “Reservoir Sedimentation Analysis”.In this model, basic hydraulic parameters could be calculated by the one-dimensionalunsteady flow calculation. Applying the results of the hydraulic parameters, the turbidity(suspended sediment concentration) in the river was calculated from the conservationequation and the advection-diffusion equation. For the downstream reaches,one-dimensional model was applied because the fluctuations of flow in the cross sectionaldirection become negligibly small.Generally turbidity in the river was dominant on not only advection and diffusion of thesteam but also settling and re-suspension between the bed materials and suspendedsediments. It is, however, convenient to assume the fixed bed conditions on this turbidityanalysis model because the sediment hydraulic conditions in the Upper Solo River has aNippon Koei Co.,Ltd.Yachiyo Engineering Co.,Ltd.6-30July 2007

The Study on Countermeasures for Sedimentationin the Wonogiri Multipurpose Dam ReservoirFinal ReportSupporting Report Annex No.6distinguish characteristics as below. Important issue to be considered in the analysis is theimpact to the downstream reaches by wash load not bed material road.--Fixed Bed Condition: The Colo weir and five groundsills have been placed from theColo to Jurug, and the hard bed rocks/soils without erosion widely appeared over theobjective stretch such as Lawu. They make stabilize the riverbed from degradation.By this effect, suspended loads supplying from the bed materials is relatively muchsmaller than those supplying from the dam outflow and from the tributaries.Washload: Washload would be main composition of the released sediments from theWonogiri dam and they tend not to be deposited with river flow velocity in the riverchannel. Important issue to be considered in the analysis is the impact to thedownstream reaches by wash load not river bed movement.Relative Grain SizeMode of TransportWash LoadSuspended LoadBed Material LoadBed LoadTotalLoadSource: Reservoir Sedimentation Hand BookFigure 3.3.2 Classification of Sediment Transport by Grain Size and by Mode of TranspoteThe outline of calculation method is presented in the Table 3.3.1 below.Table 3.3.1 Calculation Method of Turbidity Analysis ModelItemi) Riverbed MovementConditionFixed bed conditionii) Sediment rationRe-suspension and settling velocity ofnon-cohesive sedimentiii) Interaction between bedmaterials and suspendedloadRemarksSource: JICA Study Team3.3.3Conditions of Analysis(1)Cross Section, Structures and RiverbedThe basic condition such as river structures, cross sections, bed materials in the UpperSolo mainstream were already described in Chapter 1. Based on these data, initialconditions on the turbidity analysis model were produced as listed in the Table 3.2.2below.(2)Boundary ConditionBoundary conditions are set out at three locations as presented in Table 3.2.3 below. Inview of accuracy of the simulation, the boundary condition of sediment inflows andoutflow over the stretch are vitally important. However, as for the SS concentration dataof the Wonogiri dam outflow, no field measurement data had been available since itscompletion. In this model, SS concentration of the dam outflow were applied thesimulation results of the reservoir sedimentation analysis. For the inflow from tributaries,SS concentration was calculated applying a sediment rating curves which was createdNippon Koei Co.,Ltd.Yachiyo Engineering Co.,Ltd.6-31July 2007

The Study on Countermeasures for Sedimentationin the Wonogiri Multipurpose Dam ReservoirFinal ReportSupporting Report Annex No.6based on the past field data measured in tributaries by PBS in 1988 – 1995 as presented inFigure 3.3.2.Table 3.3.2 Applied Cross Section, Structure and Riverbed for Turbidity Analysis ModelItemData TypeSourcei) Cross SectionTotally 163 cross sections in Upper Solo Rivermainstream from Wonogiri dam to the Madiun Riverconfluence with the interval of 500 mii) ExistingStructuresRiveriii) Riverbed materialColo weir and Ground Sills no.1 to no.5 of fixed weir.Totally 17 samples taken with interval of 10 km andanalyzed it grain size distributionCross SectionSurvey from 2004JICA, 2004WECFR&CIPCross SectionSurvey from 2004WECFR&CIP2004 JICA,WECFR&CIPSource: JICA Study TeamTable 3.3.3ItemBoundary Conditions of Dam Outflow and Inflow from TributariesData TypeIntervalSourcei) Dam Outflowii) Colo Intakeiii) Inflow fromtributariesiv) SS Concentration ofdam outflowv) SS Concentrationof inflow fromtributariesAvailable records of hourly powerdischarge and spillout discharges releasedfrom the Wonogiri dam.Available discharge records of intakedischarge to west canal, east canal andoverflow discharge at Colo weir.Using the unit discharge per catchmentarea estimated from the observationdischarge at Jurug sta. and Kajangan sta.,inflows from major 16 tributariesbetween Wonogiri - Ngawi weredetermined.Reservoir sedimentation analysis resultsof SS concentration at both intake andspillwayComputed from sediment rating curve oftributaries based on the field data atmajor tributaries in 1988 to PJT-1Daily (1986-1999),3 times per day at 6:00,12:00, CAStudyTeamDaily (1986-1999),3 times per day at 6:00,12:00, 18:00(2000-2005)Source: JICA Study Team0.499y 90.665xConcentration 1.010.0100.01,000.010,000.0Q (m3/s)Source: JICA Study TeamFigure 3.3.33.3.4Sediment Rating Curve of Tributaries in Upper Solo River BasinOutput of the ModelAfter set-up of the above conditions, a dry run was conducted. The results showed thatthis model could be adaptable and sufficient for the analysis of the hydraulic parametersof water level, discharge, velocity, shear velocity and sediment parameters of SSNippon Koei Co.,Ltd.Yachiyo Engineering Co.,Ltd.6-32July 2007

The Study on Countermeasures for Sedimentationin the Wonogiri Multipurpose Dam ReservoirFinal ReportSupporting Report Annex No.6concentration, mass transportation and deposition of SS, etc. in the Upper Solo Rivermainstream below the Wonogiri dam.3.4Calibration of Analysis Model3.4.1Data for CalibrationThe turbidity analysis model was calibrated based on the field observation data on bothdischarge and SS concentration in the wet season in 2004/2005 as presented in Figures3.4.2 and 3.4.3. The data for calibration are listed in Table 3.4.1 below. At Jurug and atTangen, calibration data for SS concentration are applied the data which was created froma sediment rating curve at Jurug as shown in Figure 3.4.1.Table 3.4.1ItemDischargeSSLocationJurug(52 km )Tangen(97 km)Data List for CalibrationDate Sourcei) field monitoring dataD/S of the dam(0.7km)Colo weir (14km)Jurug (52km)Tangen (97km)Source: JICA Study Teami) calculated discharge databased on the unit dischargesper area at both Jurug andKajanagan station.i) field measurement data byStudy Teami) field measurement data byStudy Teami) calculated SS data based onthe sediment rating curves atJurugii) field measurement data byStudy TeamdittoIntervalthree times per day(6:00, 12:00, 18:00)ditto3 hours in flood andevery day in non-floodevery two weeksthree times per day(6:00, 12:00, 18:00)every two weeksditto0.6776y 21.469x100,000Concentration (mg/ltr)10,0001,0001001011.010.0100.0Q (m3/s)1,000.010,000.0Source: JICA Study TeamFigure 3.4.13.4.2Sediment Rating Curve at Jurugin Upper Solo River BasinCalibration Result(1)DischargeThe hydrographs at Jurug and Tangen from December 1, 2004 to May 31, 2005 arepresented in Figures 3.4.1 together with the observation data and simulation data. AsNippon Koei Co.,Ltd.Yachiyo Engineering Co.,Ltd.6-33July 2007

The Study on Countermeasures for Sedimentationin the Wonogiri Multipurpose Dam ReservoirFinal ReportSupporting Report Annex No.6shown in the figure, the simulated discharges were well reproduced the field observationdata at both stations.JURUG1400Discharge ANGEN3000Discharge urce: JICA Study TeamFigure 3.4.2 Simulation Result for Discharge at Jurug and Tangen in 2004/05 Wet Season(2)SS ConcentrationThe hourly SS hydrographs at four locations are presented in Figures 3.4.2. The results ofcalibration for SS concentration on the turbidity analysis model are summarized below:--The simulated hourly SS hydrographs at the immediately downstream of theWonogiri dam is well reproduced the field observation data. There are slightly delaysof peak values in the simulation results due to the boundary conditions of reservoirsedimentation analysis model as described in the Annex No.4.At the Colo weir, only weekly field observation data was available. In this sense, thesimulated SS hydrographs at Colo are well reproduced the weekly fluctuation.The simulated hourly SS hydrographs at Jurug and Tangen stations are wellreproduced both the short term fluctuation that was calculated from the sedimentrating curves and the weekly field observation data.Judging form the above calibration results, this model can be applied for a estimation forhourly basis fluctuation of SS concentration in the Upper Solo mainstream.Nippon Koei Co.,Ltd.Yachiyo Engineering Co.,Ltd.6-34July 2007

The Study on Countermeasures for Sedimentationin the Wonogiri Multipurpose Dam ReservoirFinal ReportSupporting Report Annex No.67.0D/S of DAM(0.7km)Observation6.0SimulationSS tionSS ationSediment Rating CurveSS lationSediment Rating CurveSS 3/105/3/3105/4/30note :1) "Observation" is the field measurement results of water samples.2) "Simulation" is the result obtained by turbidity analysis model.3) "Calculation" is the result obtained from the sediment rating curve at Jurug.Source: JICA Study TeamFigure 3.4.3 Simulation Result for SS Concentration in 2004/05 Wet Season3.5Case of Turbidity Analysis3.5.1Analysis Case for Current ConditionTo assess i) the current sediment hydraulic conditions “Without Measure”, ii) the impactsof the proposed urgent measure (a sediment storage reservoir with new gates) to theNippon Koei Co.,Ltd.Yachiyo Engineering Co.,Ltd.6-35July 2007