physical

• valley -

  • narrow cross section = dam supports water + lower construction costs
  • deep valley needed behind dam = reservoir has smaller surface area = reduce loss from evaporation
• rock type -

  • impermeable rock = advantageous as reduced water loss from reservoir by percolation and withstands pressure
• stability -

  • area free from earthquakes and subsidence is required as area needs to support weight of large dam
• source -

  • area must has snowmelt / rainfall to provide the river to ensure a consistently high volume in the reservoir