Lower Subansiri Dam and its Salient Features

Lower Subansiri Dam and its Salient Features

I already have discussed about the Subansiri Dam in my earlier blog. The project is being constructed with Rs 7500 crore and 30 per cent work had been completed. The actual construction of the dam will begin this year as the American engineering company, involved in the world’s biggest hydel project–the three gorge dam of China–is being commissioned for the project.

Subansiri Lower Hydel Project is the biggest undertaken in India so far and is a run-of-river scheme on Subansiri. The estimated annual energy generation from the project is 7421 mu in a 90 per cent dependable year.

SALIENT FEATURES

Reservoir

FRL                                                                 :           EL 205 M

Min Reservoir Level                                         :           EL 190 M

MDDL                                                             :           EL 181M

Gross Storage at El 205M, 190 M, 181M        :           1365/923/720 m cum

Area under submergence at FRL                       :           33.50 Km2

Dam Type                                                        :           Concrete Gravity

Top Elevation                                                   :           EL  210 M

Height of dam above River Bed Level              :           116 m

Spillway

Spillway opening number                                  :           9 Nos

Size                                                                  :           11.5 m x 14 m

Spillway discharge capacity                               :           37500 Cumecs

Power House                                      

Installed Capacity                                             :           2000MW (8X 250 MW)

Annual Energy Generation                                 :           7422 MU

SAFETY AND STABILITY OF DAM

NHPC has ensured safety & stability of dam by adopting following design measures

1.      The Stability of dam has been ensured for all statutory load        combinations by providing larger base width.

2.      Maximum base width for the dam is kept 170 m for 125m high dam (1.35 times of Dam height) whereas it is normally kept as 0.8 times of     Dam height.

3.      The dam has been designed for seismic parameters as approved by NCSDP.

4.      50m deep concrete cut off wall with cumulative length of 370m envisaged for the safety of Dam foundation.

5.      Concrete apron provided at the Toe of the Dam.

6.      Concrete cladding with cable anchors (30-35m long) provided for stability of dam abutements.

Flood Protection

•         Subansiri Lower Dam will have 09 spillways to pass the probable maximum flood of 37500 cumecs. 

•         The Project would help in flood control by regulated discharge of water in river. During flood period the reservoir will be operated 15 m below the FRL having flood cushion 442 M.Cum.

DOWNSTREAM FLOW

·        To maintain a minimum discharge of 300 Cumecs during lean period by running one machine for 24 hours.

·        Power generation capacity of Subansiri Lower Project is based on design of generators installed at Project i.e. 250 MW with configuration of 8 number of units to meet the peaking requirement as per Techno Economic Clearance.

·        Being a policy matter, this is to be decided by CEA/MOP depending upon the power requirement of the beneficiary states.

·        Machines are operated as per the requirement received from the Load dispatch centre.

·        Nevertheless, NHPC will have no objection to operate one machine on part load for 24 hours if agreed by CEA/MOP, ASEB and other beneficiary states

N.B. All the information’s are collected from various sources.