Presentation on theme: "WORKSHOP ON DAM OPERATION By IR Chan Chiang Heng On 10th September 2014 At The Malaysian Water Association (Ground Floor)"— Presentation transcript:
1WORKSHOP ON DAM OPERATION By IR Chan Chiang Heng On 10th September 2014 At The Malaysian Water Association (Ground Floor)
2Table of contents SECTION DESCRIPTION 1 Raw Water Sources 2 Operation of Regulating Dam3Critical Volume Assessment4Formulation of Contingency Plan5Effect of Reservoir Storage on Water Quality6Limnological Survey of Impounded Water7Treatment Problems and Solutions
7c) Impounded Source (Dam) Classification by Function b) Underground SourceWellc) Impounded Source (Dam)Classification by FunctionClassificationExampleDam OwnerWater SupplyDirect AbstractionDam Release (Regulating Dam)Klang Gates DamSungai Tinggi DamWAb) IrrigationPedu DamMADAc) Flood MitigationSungai Batu DamJPSd)Flood Mitigation and Water SupplyWater Supply and Flood Mitigatione) Hydro ElectricTemenggong DamTNB
8NOTES:1) The Dam owner has control over:-Dam level (Volume)Point of Dam release (Water Quality)Quantity of Dam Release
112) All raw water sources do present some form of treatment problem 2) All raw water sources do present some form of treatment problem. The extent of treatment problem or pollution varies from source to source.3) Most water supply dam function as regulating dam i.e. Releases are made during draught to augment flow in river.
12OPERATION OF REGULATING DAM SECTION 2OPERATION OF REGULATING DAM
13Operation of regulating dam OPERATION PROTOCOLDEFINITION – Regulating dam: constructed to store water during wet spell and dam release during drought to augment low river flow.Flow to river at periodicalslow river flowControlled release(from impounded reservoir)Ensure adequate river levelAugment flow in the river at Intake
15B)ACQUISITION OF DATA & THEIR APPLICATION I) At Dama) Catchment AreaUpstream of damFor impounded reservoir volume estimation.b) Rainfall- In catchment of dam (daily).For estimation of possible increase in volume of impounded water.c) Characteristic of Impounded water- Frequent initially.- Thereafter bimonthly or monthly.For planning the treatment of water released at different levels of the impounded reservoir. Monitoring the water quality by conducting limnological survey.d) Dam Level (daily)For trending the decrease or increase in dam level and volume. Documenting the acquired data will indicate a cut back or increase in production.e) Record of quantity of release at varying times (when required).This information coupled with base flow in river will enable the likely water quantity at the abstraction point to be predicted.
16II) At Intake (a) Water level in river (i) Under normal flow condition (recording at 12 or 24 hourlywill suffice).ii) During drought recording oflevel at close interval isnecessary. 6 to 8 hours is likelythe frequency.For base flow volume and recessionconstant estimation.For river level monitoring, the installation of an automatic level recorder is ideal.(b) RainfallIn catchment of tributaries.For estimation of flow volume from tributaries into main riverIn relation to forecast of dam releases(c) Other users likely are the following:-- Compensation water.- Irrigation.- Water treatment plant upstream.To note water quantity requirement for estimation of required volume at intake in relation to available volume.
17c) APPLICATION OF RELEVANT DOCUMENTS FOR RESERVOIR OPERATION Rules forReservoir OperationElevation-Storage-Area CurveReservoir Control CurveEstimation of Time of TravelRecession ConstantRegulation of Discharge
18SG. TINGGI RESERVOIR Elevation-Storage-Area Curve 70605040302010Availability of surface area at different elevation.Storage / ElevationArea / ElevationElevation - metreStorage – cubic metre 1 x 106
19Reservoir Control Curves 2020 MLD MLD MLD MLD110100908070605040302010JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECAbstraction rates of 2020, 1900, 1700 and 1300 MLD were selected at intake for Sg Tinggi DamTotal Reservoir Storage (MCM)
20Estimation Time of Travel Based on the observation of the travel time of the wave generated when water was released from the dam to the intakeTime observed : hoursFactors to be considered:Ground Condition along the flow pathGround terrain along the flow path related to the rate of dam releasePossible abstraction of water by othersWeather at time of study of time travel
21Recession constant applicable to any river reach Value obtained from the equationReliable values of k can be derived when it is consistently dry across a river basin for many daysTotal River flow= Spill Over Weir + Abstraction + Dam releaseBase River Flow = Total River Flow – Dam ReleaseMin. Base Flow = Compensation Flow + Abstractionq=qo x ktFlow at any timeRecession constant applicable to any river reachFlow t days laterKt = of base flow
22Regulation of Discharge Reservoir (dam) release Factors to consider:- River level.- Base River Flow.- Impending Weather Condition.- Available Volume in Dam.- Affordable Quantity of release
24CRITICAL VOLUMEActive volume available in dam when the volume of dam release has to be regulated or controlled (restricted) to tie over an impending dry period.Water rationing may have to be implemented during controlled dam release period.
25Active volume Total Volume = Active Volume + Dead Volume Active volume = Total Volume – Dead VolumeDead volume is defined as the volume of water below the lowest outlet or drawoff level.
28SG. TINGGI DAM DRAWOFF TOWER – VALVE ARRANGEMENT Parallel Face Sluice ValveRegulating ValveGuard ValveAir Valve
29Advanced assessment of critical volume Every dam has its critical volumeThe specific critical volume of any specific dam varies with the weather condition in respect of time and quantity.To determine the relevant volume to choose from tabulate available active volume in advance based on the following percentages:75%60%50%40%
30AVAILABLE VOLUME BETWEEN DEPTHS Tabulations for Sungai Tinggi Dam Tabulation Of Data of Active VolumeAvailable volume between depths from top water level to first drawoff outlet and between subsequent drawoff outletAVAILABLE VOLUME BETWEEN DEPTHS Tabulations for Sungai Tinggi DamDam Level (M) Interval Volume Comments57.00 to M MG TWL is at 57.00M(70.01ML) 53.00 to M MG M is the 1st(57.51ML) Drawoff Level 49.00 to M MG(43.73ML) 45.00 to M 7.70MG M is the 2nd(35.00ML) Drawoff Level 41.00 to M 9.24MG(42.01ML) 36.00 to M 7.56MG M is the 3rd(34.37ML) Drawoff Level
31DAM VOLUME AT 0.01M INTERVAL (Sungai Tinggi Dam-Tabulation) Level M to 53.00MDepth Interval MTotal Depth Difference MVol. at this Depth Interval MGTot. Volume Difference MG56.8156.8056.7956.7856.7756.7656.7556.7456.7356.7256.7156.7056.6956.6856.6756.6656.6556.6456.6356.6256.6156.60Level (M)Volume (MG)56.9956.9856.9756.9656.9556.9456.9356.9256.9156.9056.8956.8856.8756.8656.8556.8456.8356.82
32Between Critical Depth Definition: Elevation or level of water in reservoir coinciding with the selected critical volume.
33FORMULATION OF CONTIGENCY PLAN SECTION 4FORMULATION OF CONTIGENCY PLAN
34FORMULATION OF CONTIGENCY PLAN Contingency plan can be formulated in advance for any active volume in dam and dam level.Criteria involved in a plan formulation are as follows:Volume of dam releaseA range of volume – Values based on past record related to river flow quantity and current based condition.Sustaining period selected– related to weather condition and active volume available.In contingency plan formulation rainfall is not taken into consideration. Any rainfall occurs during the planned period is considered a bonus.
35Example of Formation of Contingency Plan a) Status of available vol. in dam as on 5/7/2002:-Dam level = 53.32MTot. Active Vol. = 74,140 ML or 75.26% of Tot. active vol of98,503MLPlanning Strategy:-Consider – Critical level, Critical volume & sustaining periodCritical VolumeDamLevel(m)Active VolumeAt SpecificLevel (ML)VolumeBetweenSpecific (ML)PercentageTo Total53.3274,14075.2626.64049.0047,50048.228,75047.0038,75039.34Critical level1st critical level of 49.00M2nd critical level of 47.00M
36b) Sustaining period Available Volume (ML) Rate of Dam Release (MLD) 800700600500400300Sustaining Period In Days1st Critical Level(53.32M to 49.00M)26,6402nd Critical Level(49.00M to 47.00M)8,750331138134715531867228929Total44515971118
37Effect of reservoir storage on water quality SECTION 5Effect of reservoir storage on water quality
38WATER QUALITY IN DEEP RESERVOIRS IntroductionSeasonal density or thermal stratification varies for shallow (less than 6M) and deep (greater than 6M) lakes and reservoirs.In shallow reservoirs, water temperatures and oxygen concentrations will depend on the amount of wind induced mixing.At surface, water temperatures rise in relation to bottom waters, stratified density layers will form in the water column.An oxygen defiency will result at the sediment – water interface, creating anaerobic conditions that will solubilize nutrients and metals from bottom sediments.Deep water bodies experience thermal stratification and form three distinct layers of water below the surface.Top layer is called epilimnion.Bottom layer is called hypolimnion.The layer between is called metalimnion (thermocline).
39WATER QUALITY IN DEEP RESERVOIRS Thermocline:Intermediate/boundary layer that has sharp change in both temperature and densityEpilimnion: Upper layer of well-mixed warm waterEpliminion (warm, aerobic, well-mixed)30oC28.5oCThermal StratificationThermocline (sharp change in both temperature & water density)Hypolimnion (cool, anaerobic, poorly mixed)LakeHypolimnion: Lower layer, poorly mixed cool water. Low DO and anaerobic.
40CASE STUDIES 1)Demonstration by color intensity-Malut Dam Raw Water at Varying Depth
42LIMNOLOGICAL SURVEY OF IMPOUNDED WATER SECTION 6LIMNOLOGICAL SURVEY OF IMPOUNDED WATER
43OBJECTIVETo determine the raw water quality at varying depth in the impoundment or damFor a dam, the survey is conducted at varying depth in the Epilimnion, the Thermocline at the Hypolimnion.Knowing the water quality will facilitate treatment of the impounded water.
44PARAMETERS TO RECORD SAMPLING POINT At surface and at each drawoff point for a dam provided with a variable drawoff tower.PARAMETERS TO RECORDpHColourTurbidityIron (Soluble and Insoluble Form)Manganese (Soluble and Insoluble Form)Dissolved oxygenAlkalinityHydrogen Sulphide
45SAMPLING FREQUENCY Weekly initially, thereafter bimonthly and monthly. The frequency is dictated by water level or volume of water in the impoundment.
46TREATMENT PROBLEMSoluble manganese and iron are the common treatment problem encounters.Aeration of the dam normally overcames this problem.
47quality OF IMPOUNDED WATER Influent QualitySiting of the reservoirDepth of reservoir- depth of reservoir< 6.0M shallow- depth of reservoir> 6.0M deep stratify thermallyINFLUENTIALFACTORSDetrimental effects:-a) Thermal and chemical stratificationb) Algae problemsc) Insufficient or minimal mixing ofinflowing raw water with storedwater
48WATER QUALITY - Sungai Tinggi Dam Parameter EpilimnionHypolimnion1.0 Physical Changesa) pHb) Colour (HU)c) Turbidity (NTU) 6.5 to 7.2Higher value due to algae action (photosynthesis)35 to 1503 to 28Sedimentation6.0 to 6.5Lower value due to Stratification.375 to 625Decay of vegetation and leaching of organic matter from the soil.6 to 66Result of suspended matter.d) Temperature C30 to 32Subject to sunlight andwind action.28 to 29Shielded by the thermocline.
49Parameter Epilimnion Hypolimnion 2.0 Chemical Changesa) Dissolved Oxygenmg/lb) Iron mg/lc) Manganese (mg/l)d) Ammonia as N(mg/l)e) Alkalinity as CaCO35 to 7Exposed to atmosphere and wind action.0.40 to 1.50High dissolved oxygen content (aerobic condition resulting in precipitation).0.03 to 0.07High dissolved Oxygen content.0.10 to 0.13Nitrification can bring about a reduction inammonical Nitrogen in the aerated surface waters.4.4 to 6.9Algae remove calcium carbonate and CO2 by photosynthesis. The result is an increase in pH and decrease in calcium carbonate.2 to 5Shielded from atmosphere and wind action.7 to 20Low dissolved oxygen Content (anaerobic condition, Metal remain in soluble state).0.07 to 0.30Low dissolved oxygen content.0.54 to 1.73Increase in the cold anaerobic stagnantzone. 8.9 to 17.2
50Treatment problems and solutions SECTION 7Treatment problems and solutions
51TREATMENT CHANGING FORM OF METAL Aeration Use of Chemicals Source – Dam (Jetting, Mechanical pumping, Injection)Treatment Plant – Aerator (Cascading/Trickling Aerator)Oxidants: Potassium permanganate, chlorine, ozone, chlorine dioxide.Most favored!
52THEORY Metals (general) SourceNatural (a)Found in most natural waters- dissolution of rocks and minerals.(b)The hypolimnion of dam- the dark, cold and anaerobic.Man-madeIndustrial discharge.TypeIron (Fe), Manganese (Mn).FormSoluble and insoluble (particulate)Total (Fe) or (Mn) = Soluble + Insoluble FormAnalyticalAnalysisTotal Metal (Fe or Mn) Acidify Sample and BoilSoluble Metal (Fe or Mn) - Filter sample through a 0.45 Ωm filterpaper.
53THEORY Metals (general) RemovalInsoluble Formby coagulation and flocculation and filtrationSoluble FormBy first converting from soluble to insoluble followed by coagulation and flocculation and filtrationThus, it is easier to remove in the insoluble form than in the soluble form.In general, both iron and manganese invariably occur in both the insoluble and soluble form.
54TREATMENT Conversion of Form Oxidation Process (1) Aeration (Physical Means)(2) Use of Chemical(Chemical Means)
55TREATMENT (1) Aeration (Physical Means) The function of aeration To introduce oxygen to the water.To remove carbon dioxide (resulting in increase ofpH).Removal of iron and manganese is pH dependent,more so with manganese.Nature’s Way
64Stainless Steel pipe (grade 304) SIDE VIEW OF DIFFUSERDETAILED C120mmStopper Cap20MM X 5 MMReinforced rubber nosePerforated stainlessSteel pipeStainless Steel pipe(grade 304)Cross Connector0.75MC1Concrete Sinker0.5M0.5MConcrete SinkerPLAN VIEW OF DIFFUSER6MRenforced Rubber HoseThreaded EndsPerforated stainlessSteel pipeConcrete Sinker6MCross ConnectorCross ConnectorStainless Steel pipeC2Cross ConnectorStainless Steel pipe (grade 304)Source from UTMDETAILED C2
65Variation of DO vs Depth After Aeration at Location 2 Aeration Hrs: 0.00Aeration Hrs:Aeration Hrs:6.005.505.004.504.003.503.002.502.001.501.000.500.00Dissolved Oxygen (mg/L)12345678910111213141516171819188.8.131.52.44.34.24.03.184.108.40.206.03.02.72.52.220.127.116.11.18.104.22.168.04.94.13.83.22.214.171.124.21.11/9/0215/9/0229/9/02
66Variation of DO at Different Drawoff Level DO ( ) DO ( ) DO ( )6.506.005.505.004.504.003.503.002.502.001.501.000.500.00Dissolved Oxygen (mg/L)1st DrawoffLevel = 73.00m2nd DrawoffLevel = 66.60m3rd DrawoffLevel = 60.20m4th DrawoffLevel = 53.80mDrawoff Level
67TREATMENT (2) Use of Chemicals (Chemical Means) Chlorine Chlorine DioxideOzonePotassium Permanganate (KMnO4)
68USE OF CHEMICALS (CHEMICAL MEANS) (a) Use of Potassium PermanganateAdvantageBesides effective in removal of iron and manganese, it also helps in the reduction of TOC (Total Organic Carbon).Analytical AnalysisThe optimum dosage and time of reaction has first to be determined.Adverse Effect of Over DosageColour, add manganese to water.
69(a) Use of Potassium Permanganate JAR TEST ON USE OF POTASSIUM PERMANGANATE (KMn04)To determine KMnO4 Dosage and Reaction TimeTable 1 : Raw Water QualityDate06/10/03pH6.21Turbidity (NTU)97.1Apparent Colour (Pt.Co)521Manganese total (mg/L)0.224Manganese soluble (mg/L)0.128Iron (mg/L)0.132Aluminium (mg/L)0.038TOC3.90
70Table 2 : Jar Test DataDate of Test24/09/03Beaker No123456Pre-lime (mg/L)Potassium Permanganate (mg/L)0.000.100.200.300.400.50Liquid Alum Dosage (as mg/L product)24Flocculant AN910 (mg/L)Floc Sized3Settled water qualitySW pH126.96.36.199.106.086.11SW Turbidity (NTU)3.763.823.583.553.683.65SW Colour (Pt-Co)242122SW Fe (mg/L)0.12-0.110.13SW Al (mg/L)0.0980.0730.0610.054SW Mn (mg/L)0.0960.0910.0820.0660.0780.085SW TOC (mg/L)188.8.131.52
71Table 3 : Jar Test DataDate of Test24/09/03Beaker No123456Pre-lime (mg/L)Potassium Permanganate (mg/L)0.30Retention time for KMnO4 Dosing (mm)1197Liquid Alum Dosage (as mg/L product)24Flocculant AN910 (mg/L)0.10Floc Sized3
72Table 4 : Jar Test DataSettled water qualityBeaker No.123456SW pH6.106.096.116.086.056.07SW Turbidity (NTU)3.082.852.722.752.732.71SW Colour (Pt-Co)201918SW Fe (mg/L)-0.110.12SW Al (mg/L)0.0560.0550.057SW Mn (mg/L)0.0160.0170.0200.0320.046SW TOC (mg/L)1.92.02.1Filtered water qualityFW Turbidity (NTU)0.3410.3480.3350.3290.3890.350FW Colour (Pt-Co)65FW Fe (mg/L)-0.01FW Al (mg/L)0.080.07FW Mn (mg/L)0.0090.0100.0120.0140.0230.028FW TOC (mg/L)184.108.40.206