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Lawa HPP

  Lawa HPP is located on the upper reaches of the Jinsha River at Sichuan-Tibet border. The proposed dam site is on the reaches of Lawa gully mouth at Lawa Township, with Lawa Township of Batang County in Sichuan Province on the left bank, Zhubalong Township of Markam County in Tibet Autonomous Region on the right bank, Yebatan HPP at its upstream, and Batang HPP at its downstream, and is the fourth of the proposed seven cascade developments in the hydropower development plan for Sichuan-Tibet reaches of the Jinsha River. Through comprehensive technical and economic comparison, Lawa HPP is proposed to have a NPL of 2702.00m, a reservoir storage of 1.992 billion m3, an effective storage of 720 million m3, and seasonal regulation capacity. The proposed installed capacity is 1900MW, with four sets of 475MW Francis turbo-generator units. According to the comprehensive comparison of upper, middle and lower dam site alternatives and four dam axis alternatives, the middle one is proposed at this stage, and the lower one as the backup. The alternative of RCC gravity dam at middle dam site + underground powerhouse on the right bank is tentatively determined as the project layout.  In the alternative of RCC gravity dam at middle dam site, the proposed dam would have a crest length of 478.20m, maximum height of 235.00m, and 22 monoliths. Ski-jump energy dissipation is adopted, with three 16m×16m (W×H) overflowing surface bays and two 5m×7m (W×H) mid-discharge orifices. Dam-type intake is employed for the headrace system, with four 9.0m-inner-diameter headrace tunnels (penstocks). Four branches and two main tunnels (inner diameter 15.0m) are proposed for the tailrace system, and the surge shaft would be of simple tailrace gallery type. GIS switch station and outgoing line platform are arranged on the surface. A construction diversion scheme of tunnel diversion, once river closure and year-round water retention by cofferdams is adopted, and the upper and lower cofferdams would be non-overflow earth-rock type against 20-year flood. The construction duration up to power generation of the first batch of units would be 102 months, and the total construction duration 108 months.