South Thach Han Reservoir

Project location: Thach Han river in Quang Tri

Construction time: Commencement: 3/1978 - Completion: 2002.

Project managers: Le Van Khuong, Pham Khac Minh Hung, Pham Vu Liem

Project tasks: Irrigating 17,000 ha of cultivated land

Major technical parameters:

- Basin area: 1,460 km²

- Work grade: II

- Maximum water level in front of dam: +20.05 m

- Normal water level: +8.30 m

Scale and structure of project major works:

Main dam: homogeneous earth dam, crest elevation: +21.70m, length: 680m, height: 24.70m and 7 auxiliary dams with height from 2m to 14.5m.

Spillway is located in the left bank: Wide crest, ungated spillway with chute, spillway sill elevation: +8.30, spillway width: 135m, maximum discharge p=1%: 7300 m³/s.

Intake: dimension: 5x2.5m, design discharge: 32 m³/s. Lock for boats weighted under 100 ton, dimension 5x7.5 m, length: 63m, intake bottom elevation: +5m

Sand sluice: dimension: 5x2m, discharge in flood season: 88 m³/s, sluice bottom elevation: +2m, L = 83m.

Canal system:

Main canal: 17,225 km long and 6 primary canals with total length of 90.385 km, details are as follows:

+ Canals N2A, N4, N6, N2B irrigate Hai Lang area

+ Canals N1, N3 irrigate Trieu Phong area

+ Quang Tri town is irrigated by over sided canals. Actually, after completion, the project only irrigates 50% of the planned area due to many reasons.

Recently, to restore irrigation capacity of the project, HEC has selected the option of raising spillway sill by a rubber dam of 2.2m high and 140m long to additionally store 9.750 million m³ of water and repaired a part of canal system to satisfy the planned irrigation area of the project.