3 rd NATIONAL DAM SAFETY CONFERENCE 18 and 19 February, 2017 SIMULATION OF JUNE 2013 FLOOD AT TEHRI DAM Niraj Agrawal DGM (Design) THDC India Limited Rishikesh 1
BROAD CONTENTS • Background of the Project • Data Availability • Methodology • Results & Discussions • Conclusions 2
Type : Rock and Earth fill Height of dam : 260.5 m Base : 1128 m Width at top : 25.5 m Length at the top : 575 m THDC India Ltd.
TEHRI DAM ( STAGE-I) 1000 MW PSP TEHRI DAM ( STAGE-II) 1000 MW UPPER RESERVOIR FRL. EL. 830.0 M LOWER RESERVOIR MDDL. EL. 740.0 M KOTESHWAR DAM 400 MW MIN.LEVEL EL. 606 M FRL. EL. 612.5 M TEHRI HPP KOTESHWAR HPP ~ 22 KM L-SECTION OF TEHRI HYDRO POWER COMPLEX (UPPER AND LOWER RESERVOIRS) 4
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Water Spread : 42 Km 2 Gross Storage : 3540 M CM Live Storage : 2615 M CM M ax. Flood Level : EL 835 m Full Reservoir Level : EL 830 m M DDL : EL 740 m THDC India Ltd.
CHUTE SPILLWAY Head : 220 M Type : Conventional Stilling Basin Type M ax Discharge : 5500 cumecs Width : 39.5m at top 50m at toe Regulating Gates : Radial 15.5m high/ 10.5m wide Aerators : 3 nos on Glacis Stilling Basin : 140 x 50 m 22m deep pool 55 m high walls D/s River Bed : Protection by Concrete Blocks
THDC India Ltd.
RIGHT BANK SHAFT SPILLWAYS Head : 220 M Type : Vertical Shafts Nos : 2 (Un-gated) Intakes : Funnel type (34m dia) Discharge : 3900 cumecs Vertical Shaft : 12m dia Junction with : T angential with 6.0m tunnel opening De-aeration System : Through a Separation Chamber and de-aeration shaft opening above M WL Velocity at toe : 45 m/s
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LEFT BANK SHAFT SPILLWAYS Head : 220 M Type : Vertical Shafts Nos : 2 (Gated) Intakes : Tunnel type (80m long) Discharge : 3800 cumecs Vertical Shaft : 12m dia Junction with : T angential with 5.5m tunnel opening De-aeration System : Through a Separation Chamber and de-aeration shaft opening in a De- aeration tunnel Velocity at toe : 45 m/s THDC India Ltd.
THDC India Ltd.
INTERM EDIATE LEVEL OUTLET • BOTTOM M OST OUTLET IN THE PROJECT AT EL 700M . • BEING USED FOR INITIAL FILLING OF RESERVOIR • TO BE USED FOR IRRIGATION RELEASES • TO BE USED FOR EM ERGENCY EVACUATION • T ANGENTIALL Y JOINING T-3 SHAFT SPILLWAY • LINING COATED WITH POL YUREA
THDC India Ltd.
Designed For PM F Of 15540 Cumecs
FLOODS ON 16 th ,17 th & 18 th JUNE 2013 • Peak Discharge at Haridwar due to River Alakhnanda = 15000 Cumecs • Water level at Haridwar at 4pm = 295.90 m (1.90 m above danger level) • Actual Peak Discharge of River Bhagirathi at Tehri at 6am = 7500 Cumecs (262500 Cusecs) • Releases from Tehri Dam = 500 Cumecs (17500 Cusecs) • Prevented Flooding of Rishikesh & Haridwar by about 2.5-3.0 m
Actual observed discharge of Ganga at Rishikesh and anticipated discharges after superimosing Tehri actual inflows with 10 hrs time lag 18000 15728 D 16000 15284 i s 13923 14000 c h 12357 a 12000 11083 r 10736 10049 g 9823 10000 9376 9201 9061 9236 e 8224 8161 8549 8549 7464 i 7405 8000 8049 7799 7087 6947 6889 n 7299 6536 6537 6242 6799 6549 5949 5774 6124 6299 6299 5637 5437 5089 6000 C 5599 5474 4608 u 4169 3700 3999 4179 4259 4419 4799 4649 4179 3949 3750 3590 m 4000 3307 3420 e 2231 2523 3150 2700 c 2110 2280 2000 s 0 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 16.6.13 17.6.13 18.6.13 Date and Time Actual inflow at Rishikesh (Cumecs) Anticipated inflow at Rishikesh if actual inflows at Tehri superimposed with 10 hrs time lag (Cumecs)
Actual observed discharge of Ganga at Haridwar and anticipated discharges after superimosing Tehri actual inflows with 12 hrs time lag 24000 21519 22000 20331 D 19772 i 20000 s 18009 c 18000 16292 h 16140 15748 15420 15246 16000 a 15145 15008 14917 r 13938 14457 14340 14000 g 13153 12925 12909 12307 13008 13037 e 12951 12088 11949 12713 11704 12321 12321 12208 11190 12000 11091 11001 11722 11483 11251 11167 11063 i 9909 9692 9419 10284 10000 9939 n 9633 9651 8455 9112 9166 9023 8939 8503 8222 8004 79197705 8000 C u 5451 6000 m e 4843 3689 4000 c 3446 2363 s 2241 2000 0 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 16.6.13 17.6.13 18.6.13 Date and Time Actual inflow at Haridwar ( Cusecs) Anticipated inflow at Haridwar if actual inflows at Tehri superimposed with 12 hrs time lag (Cusecs)
Actual observed inflow and outflow at Tehri 8000 7535 7090 7000 D i 6229 s 6000 c 5413 h a 5000 r g 4292 4104 e 3879 3782 3782 4000 3639 3634 i 3336 3292 3186 n 3037 3037 3037 2980 2862 2888 3000 2487 2440 C 2112 2112 u 1925 1808 m 2000 e 1175 c 958 s 1000 471 593 355 355 425 425 425 425 425 425 350 355 355 355 355 355 355 355 355 355 355 350 350 350 350 350 350 350 350 350 350 350 0 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00 16.6.13 17.6.13 18.6.13 Date and Time Outflow from Tehri Reservoir (Cumecs) Inflow Tehri (Cumecs)
DATA AVAILABILITY Rainfall Data: • June 2013: Daily peak discharge of River Bhagirathi at Discharge Data: Maneri and River Bhilangana at Ghansali. 16 th , 17 th & 18 th June: Hourly discharge at Maneri and • intermittent discharge at Ghansali. • Reservoir Elevation-Capacity Curve Reservoir Data: 16 th , 17 th & 18 th June: T • wo hourly reservoir level reading • Outflow from reservoir 20
METHODOLOGY • 90 m resolution SRTM data was analyzed in Arc-GIS 9.3 for extracting the geomorphologic features of the catchment. • Whole catchment has been divided Fig 3 : Total Catchment Fig 4 : Bhagirathi upto Dharasu into three sub- catchment based on the physiographic features and data availability. Fig 5 : Bhilangana upto Ghansali Fig 6 : Area between Dharasu and Ghansali 21
METHODOLOGY • For classification of snow fed and rain fed area, Land sat data of the catchment for the month of June 2013 has been analyzed in Erdas Imagine 2011. • Result was matched with the true color imagery of the area and the previous study Fig 7 : Whole Tehri Catchment report. Fig 9 : Bhagirathi Catchment Fig 8: Bhilangana Catchment upto Dharasu upto Ghansali 22
HORTON’S RATIOS • Hortan’s stream order ratio, area ratio and length ratio are calculated as follows: • (R B ) = N ω -1 / N ω , (R A ) = A ω / A ω -1 & (R L ) = L ω / L ω -1 S. No. R B R A R L A Ω L Ω Remarks Bhagirathi 4.99 5.92 2.97 5050.00 152.00 Bhilangana 4.00 4.70 3.00 833.00 61.20 W1 2.75 3.00 2.34 10.73 5.41 W2 3.17 3.73 2.76 108.03 25.21 W3 2.50 3.45 2.98 9.15 5.73 W4 3.50 4.72 3.37 46.15 11.58 W5 2.50 4.11 3.57 11.45 7.89 W6 3.00 4.68 3.76 16.27 9.04 W7 2.74 3.29 2.52 69.68 18.04 W8 3.95 4.53 2.89 259.04 35.86 W9 3.50 4.43 3.57 21.34 10.26 W10 3.83 4.86 3.30 41.81 11.94 W11 3.00 4.28 3.20 13.20 7.35 W12 2.25 3.70 2.35 7.78 4.25 W13 2.50 3.03 2.65 16.99 7.16 W14 2.00 2.65 2.79 12.65 5.90 W15 3.33 4.02 2.49 43.95 10.53 W16 3.00 3.49 1.95 14.24 7.42 W17 5.23 6.39 3.66 472.89 49.27 23
GIUH Model: GcIUH Model: 0.43 (V/ L ω ) q p = 0.871/ ᴨ i q p = 1.31 R L 0.4 -0.38 (R B / R A ) 0.55 (L ω / V) t p = 0.44 R L t p = 0.585 ᴨ i 0.4 ᴨ i = L Ω 2.5 / (i r * A Ω * R L * α Ω 1.5 ) α Ω = S Ω 0.5 / (n* b Ω 0.667 ) GIUH-Nash Model: The concepts of GIUH and the Nash IUH models are used to derive the GIUH based Nash model. The complete shape of the GIUH can be obtained by linking q p and t p of the GIUH with the scale k and shape parameter n of Nash IUH model. 24
EFFECTIVE RAINFALL HYETOGRAPH: Distribution of Daily Rainfall to Hourly Rainfall: • Rainfall records of SSRG of Chandrabhaga experimental watershed near the T ehri dam was taken from NIH Roorkee. • Similar distribution pattern was followed to distribute the daily rainfall records within the catchment to hourly data. Fig 10 : Mass curve of hourly & daily rainfall Abstraction & Infiltration Losses: • 10 mm initial abstraction loss. • 2.5mm/ hr infiltration loss. 25
EFFECTIVE RAINFALL HYETOGRAPH: Average Rainfall Over the Basin: For the Bhilangana sub-catchment and the region between Dharasu and Ghansali, the rainfall record of T ehri station is taken as the average rainfall. For Bhagirathi catchment, Thiessen polygon method is used to get the average rainfall from the records of Dunda, Uttarkashi and Gangotri Fig 11 : Location of raingauge stations station. 26
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