Kaplan turbine suitability in Nepal

The Kaplan turbine suits low heads (about 2–40 m) with large discharge. Its suitability in Nepal is limited, because most Nepalese hydropower sites are in steep hills with medium to high heads.

Points against wide use

• Nepal's rivers fall steeply, so most projects have heads of 50–600 m, which suit Francis and Pelton turbines.
• Low-head sites lie mainly in the Terai and inner valleys, where the land is flat; a barrage there floods farmland and may affect India downstream (border rivers).
• Nepalese rivers carry heavy sediment in the monsoon; Kaplan runners have high blade tip speeds and are prone to abrasion and cavitation.
• Kaplan units are large and heavy for their output; transporting them on hill roads is hard, and civil works (deep setting) are costly.

Where Kaplan is suitable

• Canal-drop and barrage plants: e.g. the Gandak hydropower station on the Gandak canal and potential sites on the Koshi, Karnali and Narayani in the plains.
• Low-head, high-flow ROR schemes on large rivers in the Terai and Chure foothills.
• Kaplan's flat part-load efficiency is useful where river flow varies a lot between seasons.
• Small low-head schemes can use simpler propeller or bulb turbines.

So Kaplan has a niche role in Nepal; Francis and Pelton dominate, but Kaplan is the right choice for low-head, high-discharge sites in the southern plains.