Survey of Existing Dams 1 096 Environmental Engineering

Survey of Existing Dams 1. 096 Environmental Engineering Clinic Week 2 - February 13, 2004 Teresa Yamana

Objective • To gain insight into our assessment of the Merowe Dam in the areas of: – Sedimentation – Small Scale Impacts • Archeology • Public Health • Resettlement

Three Gorges Dam, China Yangtze River www. cbc. ca/news/features/threegorges_quickfacts. html

Dam Overview • Purpose – Flood prevention – Power generation • Cost: $24. 7 billion • Expected Completion: 2009 • Height: 175 m • Reservoir – Area: 1080 km 2 – Volume: 39. 3 bcm • Power Capacity: 18, 200 MW

Sedimentation in Reservoir • 40 year sedimentation observation data • Store clean water during dry season, sluice muddy water in flood season • Scouring and silting to reach balance • Initial sediment discharge rate 30 -40% • Storage remaining after 100 years – Flood storage: 86% – Regulated storage: 92%

Downstream Effect of Sedimentation • Erosion of riverbed, leading to decrease in water level between 0. 5 - 8. 0 m • Requires minimum 5000 m 3/s discharge at Yichang shiplock • Caving banks • Shallow bendways impede local navigation • Mitigate damage of flood and waterlogging in Dongting Lake area

Small Scale Impacts • Archeology – 1300 Archeological sites to be submerged – Cultural relics from various dynasties – 200 ancient tombs – International effort to excavate • Public Health – Unlikely increase in schistosomiasis – Likely increase in malaria, other local water related diseases • Resettlement – 844, 124 residents – Relocate 130 villages

Aswan Dam, Egypt - Nile River www. usgs. gov/features/ satellite_images. html

Dam Overview • Purpose – Flood prevention – Power generation • Cost: $1 billion • Completed: 1970 • Height: 111 m • Reservoir – Area: 6000 km 2 – Volume: 169 bcm • Power Capacity: 21, 000 MW

Sedimentation in Reservoir • Majority of sediment inflow trapped in tail end of reservoir • Dead storage capacity of 31. 6 bcm for 500 years • Feasibility study being conducted for uses of sediments • Lack of sediments downstream means farmers use 13, 000 t fertilizer

Small Scale Impacts http: //www. pbs. org/wgbh/nova/ UNESCO Courier, Dec. 1964. • Archeology – Twin temples of Pharoah Ramses II relocated by UNESCO

Small Scale Impacts • Public Health – Schistosomiasis associated with stagnant water from Dam • Resettlement – 90, 000 Nubians displaced • In Egypt, 28 miles away • In Sudan, 370 miles away

Tarbela Dam - Indus River, Pakistan www. pakwapda. com/htmls/ water-dams. html www. dams. org

Dam Overview • Purpose – Part of Indus Basin Irrigation System – Irrigation – Power generation • Cost: $1. 85 billion • Completed: 1993 • Height: 148 m • Reservoir – Area: 259 km 2 – Volume: 11. 5 bcm • Power Capacity: 3478 MW

Sedimentation in Reservoir • Sediment inflow 0. 106 bcm/yr • Useful life 85 years • Concern about sediments blocking power intakes in case of earthquake – Underwater protection to low-level outlets • Sediment management – Sluicing tunnels to remove sediment – Management measures to reduce sediment deposition – Not feasible to reduce sediment inflow

Small Scale Impacts • Resettlement – 120 villages submerged – 96, 000 people – Replacement land in Punjab or Sindh, or cash compensation for home – Widespread dissatisfaction

References • Three Gorges Dam – Chinese Academy of Sciences and the Research Inst. For Protection of Yangtze Water Resources. Environmental Impact Statement for the Yangtze Three Gorges Project – Nova. Damming the Past www. pbs. org/wgbh/nova/zeugma/ • Aswan High Dam – Marc Lavergne. The Seven Deadly Sins of Egypt’s Aswan High Dam – Asit K. Biswas. Aswan Dam Revisited – Hassan Osman. Hydro Development in Egypt - Lessons from High Aswan Dam – The Aswan High Dam http: //geography. about. com/library/weekly/aa 012698. htm • Tarbela Dam – World Commision on Dams. Pakistan: The Tarbela Dam and Indus River Basin www. dams. org/kbase/studies/pk/pk_exec. htm – Pakistan Water and Power Development Authority http: //www. pakwapda. com/htmls/water-dams. html