Survey of Existing Dams 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

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: 18,200MW

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 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 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 Archeology –Twin temples of Pharoah Ramses II relocated by UNESCO UNESCO Courier, Dec

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 water-dams.html

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 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 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 Tarbela Dam –World Commision on Dams. Pakistan: The Tarbela Dam and Indus River Basin –Pakistan Water and Power Development Authority