Pre-feasibility site-specific investigations

Site-specific investigations in the pre-feasibility study are done only at a moderate level to select the best layout.

Hydrological investigations

• Collect rainfall, flow, and climate data from DHM stations in or near the basin.
• Set up a gauge at the headworks and measure discharge across seasons (current meter, floats, salt dilution).
• Estimate mean monthly flows and the flow duration curve by regional methods (WECS/DHM, MIP) and correlation with a nearby station.
• Estimate flood flows of different return periods (frequency analysis, regional formula), and check for GLOF and landslide dam outburst.
• Sample suspended sediment to estimate load and plan the desander.

Geological investigations

• Review regional geology maps and satellite images; do detailed surface mapping of the sites for the weir, intake, tunnel alignment, powerhouse and slope stability.
• Find structures: faults, folds, shear zones, joint sets, and landslides.
• Geophysical survey (seismic refraction, resistivity) to find overburden thickness and rock quality.
• A few boreholes and test pits at the headworks and powerhouse; identify construction materials (quarry, borrow, sand).
• Seismic hazard check.

Topographical investigations

• Topographic map (1:5,000 to 1:2,000) with contours of the project area.
• River cross-sections and profile at the weir and powerhouse.
• Alignment of the waterway and access road options.
• Benchmarks and control points for later detailed survey.