WORKSHOP ON DAM OPERATION By IR Chan Chiang Heng On 10th September 2014 At The Malaysian Water Association (Ground Floor)

Table of contents SECTION DESCRIPTION 1 Raw Water Sources 2 Operation of Regulating Dam 3 Critical Volume Assessment 4 Formulation of Contingency Plan 5 Effect of Reservoir Storage on Water Quality 6 Limnological Survey of Impounded Water 7 Treatment Problems and Solutions

SECTION 1 RAW WATER SOURCES

Raw water sources a) Surface Source River River with augmentation from dam release Irrigation Canal Off River storage River Bank Filtration System

Sg. Selangor Phase 1 (SSP1)- Intake

Sg. Sireh Intake

c) Impounded Source (Dam) Classification by Function b) Underground Source Well c) Impounded Source (Dam) Classification by Function Classification Example Dam Owner Water Supply Direct Abstraction Dam Release (Regulating Dam) Klang Gates Dam Sungai Tinggi Dam WA b) Irrigation Pedu Dam MADA c) Flood Mitigation Sungai Batu Dam JPS d) Flood Mitigation and Water Supply Water Supply and Flood Mitigation e) Hydro Electric Temenggong Dam TNB

NOTES: 1) The Dam owner has control over:- Dam level (Volume) Point of Dam release (Water Quality) Quantity of Dam Release

2) 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.

OPERATION OF REGULATING DAM SECTION 2 OPERATION OF REGULATING DAM

Operation of regulating dam OPERATION PROTOCOL DEFINITION – Regulating dam: constructed to store water during wet spell and dam release during drought to augment low river flow. Flow to river at periodicals low river flow Controlled release (from impounded reservoir) Ensure adequate river level Augment flow in the river at Intake

Overflow Dam Release Sg. Selangor Dam

B)ACQUISITION OF DATA & THEIR APPLICATION I) At Dam a) Catchment Area Upstream of dam For 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.

II) At Intake (a) Water level in river (i) Under normal flow condition (recording at 12 or 24 hourly will suffice). ii) During drought recording of level at close interval is necessary. 6 to 8 hours is likely the frequency. For base flow volume and recession constant estimation. For river level monitoring, the installation of an automatic level recorder is ideal. (b) Rainfall In catchment of tributaries. For estimation of flow volume from tributaries into main river In 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.

c) APPLICATION OF RELEVANT DOCUMENTS FOR RESERVOIR OPERATION Rules for Reservoir Operation Elevation-Storage-Area Curve Reservoir Control Curve Estimation of Time of Travel Recession Constant Regulation of Discharge

SG. TINGGI RESERVOIR Elevation-Storage-Area Curve 0 1 2 3 4 5 6 7 8 9 10 11 12 70 60 50 40 30 20 10 Availability of surface area at different elevation. Storage / Elevation Area / Elevation Elevation - metre 0 20 40 60 80 100 120 140 160 180 200 220 240 Storage – cubic metre 1 x 106

Reservoir Control Curves 2020 MLD 1900MLD 1700MLD 1300MLD 110 100 90 80 70 60 50 40 30 20 10 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Abstraction rates of 2020, 1900, 1700 and 1300 MLD were selected at intake for Sg Tinggi Dam Total Reservoir Storage (MCM)

Estimation Time of Travel Based on the observation of the travel time of the wave generated when water was released from the dam to the intake Time observed : 16-17 hours Factors to be considered: Ground Condition along the flow path Ground terrain along the flow path related to the rate of dam release Possible abstraction of water by others Weather at time of study of time travel

Recession constant applicable to any river reach Value obtained from the equation Reliable values of k can be derived when it is consistently dry across a river basin for many days Total River flow= Spill Over Weir + Abstraction + Dam release Base River Flow = Total River Flow – Dam Release Min. Base Flow = Compensation Flow + Abstraction q=qo x kt Flow at any time Recession constant applicable to any river reach Flow t days later Kt = 0.95 of base flow

Regulation of Discharge Reservoir (dam) release Factors to consider: - River level. - Base River Flow. - Impending Weather Condition. - Available Volume in Dam. - Affordable Quantity of release

CRITICAL VOLUME ASSESSMENT SECTION 3 CRITICAL VOLUME ASSESSMENT

CRITICAL VOLUME Active 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.

Active volume Total Volume = Active Volume + Dead Volume Active volume = Total Volume – Dead Volume Dead volume is defined as the volume of water below the lowest outlet or drawoff level.

EMPANGAN SG. TERIP DAM DRAWOFF TOWER Syphon No. 1 TWL 103.00M Syphon No. 1 Crown Level = 100.75M Spill Level = 99.65M Inlet Soffit Level = 95.70M Inlet Cill Level = 94.60M 100.75M 99.65M 95.70M 94.60M Syphon No. 2 Crown Level = 92.50M Spill Level = 91.50M Inlet Soffit Level = 87.70M Inlet Cill Level = 86.60M 92.50M 91.50M 87.70M 86.60M 84.60M Syphon No. 3 83.50M Crown Level = 84.60M Spill Level = 83.50M Inlet Soffit Level = 79.70M Inlet Cill Level = 78.60M 79.70M 78.60M

LOWEST

SG. TINGGI DAM DRAWOFF TOWER – VALVE ARRANGEMENT Parallel Face Sluice Valve Regulating Valve Guard Valve Air Valve

Advanced assessment of critical volume Every dam has its critical volume The 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%

AVAILABLE VOLUME BETWEEN DEPTHS Tabulations for Sungai Tinggi Dam Tabulation Of Data of Active Volume Available volume between depths from top water level to first drawoff outlet and between subsequent drawoff outlet AVAILABLE VOLUME BETWEEN DEPTHS Tabulations for Sungai Tinggi Dam Dam Level (M) Interval Volume Comments   57.00 to 53.00 0.01M 15.40MG TWL is at 57.00M (70.01ML)  53.00 to 49.00 0.01M 12.65MG 49.00M is the 1st (57.51ML) Drawoff Level  49.00 to 45.00 0.01M 9.62 MG (43.73ML)  45.00 to 41.00 0.01M 7.70MG 41.00M is the 2nd (35.00ML) Drawoff Level  41.00 to 36.00 0.02M 9.24MG (42.01ML)  36.00 to 32.00 0.025M 7.56MG 32.00M is the 3rd (34.37ML) Drawoff Level

DAM VOLUME AT 0.01M INTERVAL (Sungai Tinggi Dam-Tabulation) Level 57.00M to 53.00M Depth Interval 0.01M Total Depth Difference 4.00 M Vol. at this Depth Interval 15.40MG Tot. Volume Difference 6159.30MG 56.81 22364.71 56.80 22349.32 56.79 22333.92 56.78 22318.52 56.77 22303.12 56.76 22287.72 56.75 22272.32 56.74 22256.93 56.73 22241.53 56.72 22226.13 56.71 22210.73 56.70 22195.33 56.69 22179.93 56.68 22164.54 56.67 22149.14 56.66 22133.74 56.65 22118.34 56.64 22102.94 56.63 22087.54 56.62 22072.15 56.61 22056.75 56.60 22041.35 Level (M) Volume (MG) 56.99 22641.88 56.98 22626.48 56.97 22611.09 56.96 22259.69 56.95 22580.29 56.94 22564.89 56.93 22549.49 56.92 22534.09 56.91 22518.70 56.90 22503.30 56.89 22487.90 56.88 22472.50 56.87 22457.10 56.86 22441.70 56.85 22426.31 56.84 22410.91 56.83 22395.51 56.82 22380.11

Between Critical Depth Definition: Elevation or level of water in reservoir coinciding with the selected critical volume.

FORMULATION OF CONTIGENCY PLAN SECTION 4 FORMULATION OF CONTIGENCY PLAN

FORMULATION 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 release A 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.

Example of Formation of Contingency Plan a) Status of available vol. in dam as on 5/7/2002:- Dam level = 53.32M Tot. Active Vol. = 74,140 ML or 75.26% of Tot. active vol of 98,503ML Planning Strategy:- Consider – Critical level, Critical volume & sustaining period Critical Volume Dam Level (m) Active Volume At Specific Level (ML) Volume Between Specific (ML) Percentage To Total 53.32 74,140   75.26 26.640 49.00 47,500 48.22 8,750 47.00 38,750 39.34 Critical level 1st critical level of 49.00M 2nd critical level of 47.00M

b) Sustaining period Available Volume (ML) Rate of Dam Release (MLD) 800 700 600 500 400 300 Sustaining Period In Days 1st Critical Level (53.32M to 49.00M)   26,640 2nd Critical Level (49.00M to 47.00M) 8,750 33 11 38 13 47 15 53 18 67 22 89 29 Total 44 51 59 71 118

Effect of reservoir storage on water quality SECTION 5 Effect of reservoir storage on water quality

WATER QUALITY IN DEEP RESERVOIRS Introduction Seasonal 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).

WATER QUALITY IN DEEP RESERVOIRS Thermocline:Intermediate/boundary layer that has sharp change in both temperature and density Epilimnion: Upper layer of well-mixed warm water Epliminion (warm, aerobic, well-mixed) 30oC 28.5oC Thermal Stratification Thermocline (sharp change in both temperature & water density) Hypolimnion (cool, anaerobic, poorly mixed) Lake Hypolimnion: Lower layer, poorly mixed cool water. Low DO and anaerobic.

CASE STUDIES 1)Demonstration by color intensity-Malut Dam Raw Water at Varying Depth

Treated Water at Varying Depth

LIMNOLOGICAL SURVEY OF IMPOUNDED WATER SECTION 6 LIMNOLOGICAL SURVEY OF IMPOUNDED WATER

OBJECTIVE To determine the raw water quality at varying depth in the impoundment or dam For 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.

PARAMETERS TO RECORD SAMPLING POINT At surface and at each drawoff point for a dam provided with a variable drawoff tower. PARAMETERS TO RECORD pH Colour Turbidity Iron (Soluble and Insoluble Form) Manganese (Soluble and Insoluble Form) Dissolved oxygen Alkalinity Hydrogen Sulphide

SAMPLING FREQUENCY Weekly initially, thereafter bimonthly and monthly. The frequency is dictated by water level or volume of water in the impoundment.

TREATMENT PROBLEM Soluble manganese and iron are the common treatment problem encounters. Aeration of the dam normally overcames this problem.

quality OF IMPOUNDED WATER Influent Quality Siting of the reservoir Depth of reservoir - depth of reservoir< 6.0M  shallow - depth of reservoir> 6.0M  deep  stratify thermally INFLUENTIAL FACTORS Detrimental effects:- a) Thermal and chemical stratification b) Algae problems c) Insufficient or minimal mixing of inflowing raw water with stored water

WATER QUALITY - Sungai Tinggi Dam Parameter  Epilimnion Hypolimnion 1.0 Physical Changes   a) pH b) Colour (HU)    c) Turbidity (NTU)  6.5 to 7.2 Higher value due to algae action (photosynthesis) 35 to 150 3 to 28 Sedimentation 6.0 to 6.5 Lower value due to Stratification. 375 to 625 Decay of vegetation and leaching of organic matter from the soil. 6 to 66 Result of suspended matter. d) Temperature C 30 to 32 Subject to sunlight and wind action. 28 to 29 Shielded by the thermocline.

Parameter Epilimnion Hypolimnion 2.0 Chemical Changes   a) Dissolved Oxygen mg/l b) Iron mg/l c) Manganese (mg/l) d) Ammonia as N (mg/l) e) Alkalinity as CaCO3 5 to 7 Exposed to atmosphere and wind action. 0.40 to 1.50 High dissolved oxygen content (aerobic condition resulting in precipitation). 0.03 to 0.07 High dissolved Oxygen content. 0.10 to 0.13 Nitrification can bring about a reduction in ammonical Nitrogen in the aerated surface waters. 4.4 to 6.9 Algae remove calcium carbonate and CO2 by photosynthesis. The result is an increase in pH and decrease in calcium carbonate. 2 to 5 Shielded from atmosphere and wind action. 7 to 20 Low dissolved oxygen Content (anaerobic condition, Metal remain in soluble state). 0.07 to 0.30 Low dissolved oxygen content. 0.54 to 1.73 Increase in the cold anaerobic stagnant zone.  8.9 to 17.2

Treatment problems and solutions SECTION 7 Treatment problems and solutions

TREATMENT 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!

THEORY Metals (general) Source Natural (a) Found in most natural waters - dissolution of rocks and minerals. (b) The hypolimnion of dam - the dark, cold and anaerobic. Man-made Industrial discharge. Type Iron (Fe), Manganese (Mn). Form Soluble and insoluble (particulate) Total (Fe) or (Mn) = Soluble + Insoluble Form Analytical Analysis Total Metal (Fe or Mn) - Acidify Sample and Boil Soluble Metal (Fe or Mn) - Filter sample through a 0.45 Ωm filter paper.

THEORY Metals (general) Removal Insoluble Form by coagulation and flocculation and filtration Soluble Form By first converting from soluble to insoluble followed by coagulation and flocculation and filtration Thus, 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.

TREATMENT Conversion of Form Oxidation Process (1) Aeration (Physical Means) (2) Use of Chemical (Chemical Means)

TREATMENT (1) Aeration (Physical Means) The function of aeration To introduce oxygen to the water. To remove carbon dioxide (resulting in increase of pH). Removal of iron and manganese is pH dependent, more so with manganese. Nature’s Way

Oxidation Of Fe & Mn – Sg. Terip Dam

Oxidation Of Fe & Mn – Sg. Terip Dam

Oxidation Of Fe & Mn At Pedas Lama WTP from Beringin DAM, Negeri Sembilan

Oxidation Of Fe & Mn At Scour - Malut Dam

Oxidation Of Fe & Mn At Scour - Sg. Semenyih Dam

Quality Surveillance of Treatment of Impounded Water Contaminants, Iron and Manganese Weir Downstream of The Dam Intake 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Quality Surveillance of Sg. Semenyih Dam to Intake (Year 1994) 06 Jan 20 Jan 03 Feb 17 Feb 03 Mac 24 Mac 14 Apr 28 Apr 12 May 26 May 16 Jun 30 Jun 11 Aug 25 Aug 14 Jul 28 Jul 08 Sep 22 Sep 06 Oct 27 Oct 10 Nov 24 Nov 15 Dec 29 Dec \ IRON (ppm) Dates of Sampling

TREATMENT Man-Made Aeration at Source (a) Dam

View Of Air Diffuser – Sg. Terip Dam

Stainless Steel pipe (grade 304) SIDE VIEW OF DIFFUSER DETAILED C1 20mm Stopper Cap 20MM X 5 MM Reinforced rubber nose Perforated stainless Steel pipe Stainless Steel pipe (grade 304) Cross Connector 0.75M C1 Concrete Sinker 0.5M 0.5M Concrete Sinker PLAN VIEW OF DIFFUSER 6M Renforced Rubber Hose Threaded Ends Perforated stainless Steel pipe Concrete Sinker 6M Cross Connector Cross Connector Stainless Steel pipe C2 Cross Connector Stainless Steel pipe (grade 304) Source from UTM DETAILED C2

Variation of DO vs Depth After Aeration at Location 2 01-09-02 Aeration Hrs: 0.00 15-09-02 Aeration Hrs: 118.77 29-09-02 Aeration Hrs: 221.39 6.00 5.50 5.00 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 Dissolved Oxygen (mg/L) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 4.7 4.6 4.5 4.4 4.3 4.2 4.0 3.9 0.4 0.3 0.2 0.0 3.0 2.7 2.5 2.4 2.2 1.9 1.5 0.1 5.9 5.8 5.2 5.0 4.9 4.1 3.8 3.7 3.6 3.3 2.3 1.2 1.1 1/9/02 15/9/02 29/9/02

Variation of DO at Different Drawoff Level DO (01.09.02) DO (15.09.02) DO (29.9.02) 6.50 6.00 5.50 5.00 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 Dissolved Oxygen (mg/L) 1st Drawoff Level = 73.00m 2nd Drawoff Level = 66.60m 3rd Drawoff Level = 60.20m 4th Drawoff Level = 53.80m Drawoff Level

TREATMENT (2) Use of Chemicals (Chemical Means) Chlorine Chlorine Dioxide Ozone Potassium Permanganate (KMnO4)

USE OF CHEMICALS (CHEMICAL MEANS) (a) Use of Potassium Permanganate Advantage Besides effective in removal of iron and manganese, it also helps in the reduction of TOC (Total Organic Carbon). Analytical Analysis The optimum dosage and time of reaction has first to be determined. Adverse Effect of Over Dosage Colour, add manganese to water.

(a) Use of Potassium Permanganate JAR TEST ON USE OF POTASSIUM PERMANGANATE (KMn04) To determine KMnO4 Dosage and Reaction Time Table 1 : Raw Water Quality Date 06/10/03 pH 6.21 Turbidity (NTU) 97.1 Apparent Colour (Pt.Co) 521 Manganese total (mg/L) 0.224 Manganese soluble (mg/L) 0.128 Iron (mg/L) 0.132 Aluminium (mg/L) 0.038 TOC 3.90

Table 2 : Jar Test Data Date of Test 24/09/03 Beaker No 1 2 3 4 5 6 Pre-lime (mg/L) Potassium Permanganate (mg/L) 0.00 0.10 0.20 0.30 0.40 0.50 Liquid Alum Dosage (as mg/L product) 24 Flocculant AN910 (mg/L) Floc Size d3 Settled water quality SW pH 6.13 6.12 6.15 6.10 6.08 6.11 SW Turbidity (NTU) 3.76 3.82 3.58 3.55 3.68 3.65 SW Colour (Pt-Co) 24 21 22 SW Fe (mg/L) 0.12 - 0.11 0.13 SW Al (mg/L) 0.098 0.073 0.061 0.054 SW Mn (mg/L) 0.096 0.091 0.082 0.066 0.078 0.085 SW TOC (mg/L) 2.7 2.1 1.8

Table 3 : Jar Test Data Date of Test 24/09/03 Beaker No 1 2 3 4 5 6 Pre-lime (mg/L) Potassium Permanganate (mg/L) 0.30 Retention time for KMnO4 Dosing (mm) 11 9 7 Liquid Alum Dosage (as mg/L product) 24 Flocculant AN910 (mg/L) 0.10 Floc Size d3

Table 4 : Jar Test Data Settled water quality Beaker No. 1 2 3 4 5 6 SW pH 6.10 6.09 6.11 6.08 6.05 6.07 SW Turbidity (NTU) 3.08 2.85 2.72 2.75 2.73 2.71 SW Colour (Pt-Co) 20 19 18 SW Fe (mg/L) - 0.11 0.12 SW Al (mg/L) 0.056 0.055 0.057 SW Mn (mg/L) 0.016 0.017 0.020 0.032 0.046 SW TOC (mg/L) 1.9 2.0 2.1 Filtered water quality FW Turbidity (NTU) 0.341 0.348 0.335 0.329 0.389 0.350 FW Colour (Pt-Co) 6 5 FW Fe (mg/L) - 0.01 FW Al (mg/L) 0.08 0.07 FW Mn (mg/L) 0.009 0.010 0.012 0.014 0.023 0.028 FW TOC (mg/L) 1.7 1.8 2.0

Use of Potassium Permanganate - SSP 1

b) Use of chemicals (Coagulant) Appropriate Choice of Coagulant

Coagulant PAC – Filter – SSP1

Coagulant Alum – Filter – SSP1

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