Ta Trach Reservoir

Project location: Ta Trach river in Duong Hoa commune, Huong Thuy district, Thua Thien Hue province

Construction time: Investigation and design time: 2000-2005

Construction commencement: 26-11-2005

Project managers: Luong Van Nguyen, Phan Vinh Khanh

Project tasks:

+ Controlling early flood, mitigating major flood for Huong river system.

+ Supplying water for domestic and industrial uses with Q = 2.0 m³/s

+ Creating stable irrigation source for 34,782 ha of cultivated land in Huong river delta area.

+ Adding fresh water source for downstream of Huong river to push saline intrusion, improve environment in lagoon area, aquaculture with Q = 25.0 m³/s.

+ Generating power with installed capacity N=19.5 MW

Work grade and design standards:

+ Grade: II (according to the standard TCXDVN 285:2002)

+ Design flood frequency: P_design=0.5%

+ Check flood frequency: P_check=0.1%

+ Standard for major flood mitigation with the flood in 1983 for Hue city: Reduction of water level (1.0 to 1.2m) at Kim Long.

+ Early flood control frequency: P=10%

+ Irrigation frequency: P=75%

+ Frequency for domestic and industrial water supply: P=90%

Major technical parameters of the reservoir:

+ Basin area: 717 km2

+ Design flood water level (P_design=0.5%): +50.00m

+ Check flood water level (P_check=0.1%): +53.07m

+ Normal water level: +45.00m

+ Water level before flood: +25.00m

+ Dead water level: +23.00m

+ Total storage capacity: 646 million m³

+ Storage capacity for flood mitigation with P=0.1%: 556.2 million m³

+ Storage capacity for flood mitigation with P=0.5%: 435.934 million m³

+ Dead storage capacity: 73.4 million m³

Scale and major technical parameters of the project works:

Main dam:

+ Site location: IIb, with marks ĐC1, ĐC2, ĐC3 and ĐM48

+ Dam crest elevation: +55.0m

+ Parapet elevation: +56.0m

+ Dam maximum height: 60.0m

+ Dam crest length 1.187m

+ Dam surface width: 10m

+ Type, structure: Mixed, zoned dam (central impervious block, upstream and downstream shells)

Spillway:

+ Type: Surface spillway combined with bottom outlet, chute and energy dissipator basin, constructed of reinforced concrete.

+ 5 surface outlet gates: B=5x9m, sill elevation +37.0m

+ 5 bottom outlet gates: B= (4.0x3.2)m, sill elevation +16.0m

+ Q_design (with design frequency P_design=0.5%): 4.367 m³/s

+ Maximum relief discharge (with check frequency P_check=0.1%): 6.147 m³/s

+ Spillway width: 66 m

Non-overflow dam:

+ Type: Gravity concrete dam, square trapezoidal section, vertical upstream slope, downstream slope ratio: 1:0.75

+ Dam crest width: B=7.0m

+ Dam crest elevation: +54.0m

Tunnel:

+ Site location: On hill, between main dam and spillway, through marks TN1 and TN5

+ Total length: 372.48m

+ Arch cross section D=7m

Hydropower plant

+ Number of units: 03

+ Installed capacity: N = 19.5 MW