Alviela River (Portuguese: Rio Alviela, Portuguese pronunciation: [aɫviˈɛlɐ]) is a river in Portugal. It is 51.16 kilometres (31.79 mi) long.[3] The Alviela spring is one of the deepest in the world and is locally connected to a cave complex that represents the most significant fluvio-karstic phenomena in Portugal, one which supports several bat colonies with more than 5,000 bats in total.[4]

Alviela
Physical characteristics
Source
• location	Olhos d’Água do Alviela, Alcanena
• elevation	135 m (443 ft)
Mouth	Tagus
• location	near Vale de Figueira[1]
• elevation	23 m (75 ft)
Length	51.16 km (31.79 mi)
Basin size	180 km2 (69 sq mi)[2]-331 km2 (128 sq mi)[1]
Discharge
• maximum	17 m3/s (600 cu ft/s)[2]
Basin features
Tributaries	Ribeira dos Amiais, Ribeira de Carvalhos, Ribeira da Gouxaria
Tagus Basin

The river has its origin in a karst spring. Ribeira dos Amiais, a losing stream, infiltrates through the Sumidouro da Ribeira dos Amiais, a ponor, only to return to the surface 250 m further on through a canyon.[5]

• 
  Ribeira dos Amiais, tributary of Alviela
• 
  Sumidouro da ribeira dos Amiais, were the water from the stream infiltrates

References