BASHA DAM

KEY FACTS
Dam Type:	Zoned earth-rockfill with central core
Location:	Chilas on the River Indus
Height:	200 metres (660 ft.) (above river bed)
Length of crest:	3,018 feet
Reservoir Area:	27,700 acres
Catchment Area:	152,100 km2
Gross Head:	145 m (476 feet)
Average Flow:	1,970 m3/sec (69,600 ft3/sec)
Design Flood Discharge:	19,300 m3/sec (682,000 cusecs)
Total Storage Capacity:	9.0 km3 (7.3 MAF)
Live Storage Capacity:	7.0 km3 (5.7 MAF)
Total Volume of Dam:	58 million yards3
Total Volume of Fill:	44 million m3
Installed Capacity for Hydropower:	3,360 MW from 12 units
Energy Generated:	14.1 GWh
Spillway Type:	Overflow, with concrete lined chute, flip bucket and plunge pool
Spillway Gates:	6 - 16.6 x 20 metres (54.5 x 65.6 ft)

LOCATION OF BASHA DAM

The Basha Dam project site has been identified about 314 km upstream of Tarbela dam on the River Indus and about 165 km south of Gilgit City. The development of a high dam at Basha will create significant storage capacity in the Indus valley between Rakhiot bridge and Dasu-Sazin gorge. The selected axis is the first suitable site for the construction of such a dam downstream of the relatively wide and flat reach of the river dominated by the town of Chilas.

The dam site is located on a pronounced bend of the Indus River, in a section with steep rock slopes covered locally with a thin veneer of talus and acree. At the dam axis, the river is some 160 metres wide. The maximum depth of the river bed alluvium is 55 metres near the right bank. The bedrock has high strength, moderately jointed norite (a form of gabbro) and is suitable as foundation and embankment material. The material constituting the riverbed is also compact and has low compressibility. However, its location requires the laying of long distance transmission lines to connect the hydel power generated to the national grid.

THE BASHA DAM PROJECT

The project will comprise of a 660 feet high zoned earth-rockfill dam, a chute spillway with a flip bucket and plunge pool, one low-level and three mid-level outlets, intakes, water conduits on the right side and an underground powerhouse with an installed capacity of 3,360 MW. The reservoir created behind the dam would have a gross capacity of 7.3 MAF and a live storage of 5.7 MAF. The average generation of hydropower by the project is expected to be 14.1 GWh.

The dam is planned in two stages:

Stage I

Additional comprehensive technical, financial, social and environmental investigations and studies were proposed to be carried out to fully assess the feasibility. This would also facilitate the selection of an appropriate project layout to develop the hydroelectric potential of the Indus River at Basha. The activities of this stage are expected to be completed in 54 months.

Stage II

The detailed engineering design of the selected project layout will be prepared to the level required for tendering purpose in this stage. Tender documents of all major contracts will also be completed. This stage will take another 42 months, with the possibility of overlap of a period of 12 months.

APPRECIATION OF THE BASHA DAMSITE

Ample quantities of suitable material for the production of the impervious fill are available within reasonable distance of the site. The rockfill, however, will come from necessary excavations from nearby quarries. The site topography provides significant confinement of the embankment on both the upstream and downstream toe of the dam. The dam will be inherently stable and is designed to resist severe seismic loadings expected in the region. The spillway will be located on the right bank and will pass maximum floods from glaciers. A flood caused by a landslide of magnitude equal to that of 1841 could be passed by making use of a freeboard.

The four tunnels in the right abutment will be used for river diversion during the construction period and converted to intermediate and low-level outlets to meet irrigation needs in the downstream area when the reservoir level is below the spillway crest.

The good bedrock favours an underground powerhouse, which will be located in the left abutment. The transmission facilities will deliver power generated at Basha to areas of Pakistan showing generation deficit.

It is estimated that the life of Basha reservoir will be limited by sedimentation to about 80 years. In the early years of Basha's operations, the sediment inflow to Tarbela will be reduced to 40% of the present inflow. As a result, the life of Basha and Kalabagh (if executed) will be significantly prolonged. The positive impact on the two reservoirs will be felt for over a century.

RESISTANCE FROM BY LOCAL PEOPLE

There has been resistance from the local people from the onset. The main demands of the local people are:

One major concern of the Northern Areas populace is the location of the powerhouse on the left side inside NWFP. The Constitution of Pakistan has given royalty rights to the province where the power station is located and not the reservoir. This issue caused a major portion of the social problems.

In efforts to resolve the disputes, the Government of Pakistan held 4 high level meetings during 1990-92 in the Ministry of Kashmir Affairs and Northern Areas (KANA) at Islamabad. KANA constituted a Standing Committee comprising of the NWFP Government and local civil administration functionaries concerned with the issue on September 12, 1995. The Standing Committee held two meetings in 1995. WAPDA is also actively pursuing the problem in order to the remove the bottlenecks.

ENVIRONMENTAL CONSIDERATIONS

Large hydroelectric projects have a number of environmental impacts. These cause major problems that have to be encountered at the time of project conception. Basha dam was no different in this regard. In fact, given its location at a high elevation and the tough terrain, the nature of impacts becomes even more grave:

1. Resettlement of the local people is an important aspect, which becomes more serious where individual landholdings are comparatively small and the cultivable area is scarce due to mountainous terrain.
2. Project construction is bound to affect the natural environment - both flora and fauna - which is quite dense. Here the construction activities of the dam, development of roads, quarrying, etc have to be taken into account. 120 km of the Karakoram Highway (KKH) is also expected to be submerged. In order to carry heavy equipment to the dam site through KKH would require improvement in its present condition.
3. Soil erosion may deteriorate a vast area of land and also induce instability in downstream irrigation channels due to fluctuations based on the reservoir level.
4. Altered stream flow and nutrient content including sediments will cause changes in the habitat.
5. Other downstream effects are likely to impact water supply, fisheries, navigation, aesthetics and recreation.
6. Dams maintain thermally stratified reservoirs which tend to alter thermal regimes, reduce dissolved oxygen content, reduce turbidity and elevate the level of manganese, iron, ammonia-nitrogen and hydrogen sulphide. There is also tendency for loss of phytoplanktons, which are the staple diet of a number of fishes and other aquatic life.
7. Basha dam will be located in a seismically sensitive area. There are certain researches that indicate that the impoundment of water in the vicinity of faulted area poses a potential impact towards increasing the earth tremors.

THE CURRENT STATUS

According to the plan, the following activities were to be conducted in 1999 -2000 period: surveys/ studies regarding socio-economic status, consolidation of hydraulic and sedimentation data by ISRIP and consolidation survey by fixing bench marks and other reference points. Due to difficulties in accessing the site, resistance from locals and some other problems, the planned activities could not be carried out.

The Panel of Experts recommended, in the light of the PC-II performa, that the planning of the project be in two stages costing Rs. 1,636.28 million including the foreign exchange component (1988 prices). The financing of 399.2 million in local currency and US$ 25 million in foreign currency was approved in the year 2000. The budget needs to be revised for the current timeframe. The total expenditure incurred up to June 2000 on the Basha dam project was Rs. 83.552 million.

A feasibility study conducted in the 1980s has now been ranked as a pre-feasibility study. A 3-year feasibility study is in the final stages of award. Due to non-availability of foreign exchange and local financing, an amount of Rs. 900 million has been allocated for the feasibility of Basha dam of which Rs 300 million will be spent in the year 2001-02 with no foreign exchange component. Other than this amount, the government has also allocated Rs 360 billion for the construction of the dam from the year 2006 onwards.

REFERENCES

1. Montreal Engineering Company, "Basha Storage and Power Project - Feasibilty Study", Hydroelectric Ranking and Feasibility Studies for Pakistan - Phase B, October 1984.
2. Montreal Engineering Company, "Inventory and Ranking Study", Hydroelectric Ranking and Feasibility Studies for Pakistan - Phase A, November 1984.
3. Pakistan Water & Power Development Authority, "Annual Report 1999-2000", 2001.
4. Dr. Bashir A Chandio & Ms Nuzhat Yasmin, "Proceedings of the National Workshop on Water Resources Achievements and Issues in 20th Century and Challenges for the Next Millennium", Pakistan Council of Research in Water Resources, June 1999.
5. Centre of Excellence in Water Resources Engineering, Lahore, "Proceedings - Water for the 21st Century: Demand, Supply, Development and Socio- Environmental Issues", June 1997.
6. Planning Commission, Govt of Pakistan (Sep 2001), "Ten Year Perspective elopment Plan 2001-11& Three Year Development Programme 2001-04".