10 June 2012
Last updated at 13:50 GMT
North Wales Police said it was a precautionary measure.
It comes a day after around 1,000 residents and holidaymakers were moved to safety after flooding of homes and caravan parks in mid Wales.
North Wales Police, which is leading the latest operation, said the whole village in Pennal was affected.
The force said it followed a slight breach in the dam of a local reservoir - believed to be due to a landslide - which has caused a small amount of water to escape.
The residents are being transported to a leisure centre in Machynlleth, just over the border in Powys.
Council workers, the local water board, North Wales Fire and Rescue Service and officers from North Wales Police are at the scene working to stabilise the situation.
Supt Andy Jenks -Gilbert said: "The water is flowing over the top of the reservoir stone wall into a quarry below which has the Afon Pennal running through it.
"A crack has been discovered in the wall, causing a small amount of water to escape.
"Should the wall be completely breached, the contents of the reservoir will go into the river which flows through the village of Pennal, which is around half a mile from the reservoir.
"Police officers are evacuating residents in the area and would ask visitors and locals to avoid the village at this current time."
It comes as the clean-up operation continues in Ceredigion and parts of Powys.
Villages were flooded by 5ft (1.5m) of water with record high river levels in parts of Aberystwyth on Saturday.
First Minister Carwyn Jones praised the "impressive bravery" of emergency services.
Mr Jones added: "Working in truly harrowing conditions, they ensured up to 1,000 people were moved to safety."
In a statement, he said he was shocked at the damage and ministers would work with agencies to ensure normality returned to communities as quickly as possible.
Andy Francis, of Mid and West Wales Fire and Rescue Service, told the BBC: "There's mass scale damage to caravan parks and indeed, more importantly really, to private dwellings throughout the area.
"A lot of flood water's gone through them, leaving a huge amount of damage, and a residual danger as well from the biohazards, from sewerage, and other contaminants that have entered the waters."
Meanwhile, Ceredigion council has also issued advice to householders starting the clean-up operation.
There have not been any reports of anyone seriously hurt.
Debris Environment Agency Wales said one flood warning remains on the River Teifi, at Lampeter and Llanybyther. It is providing flood alert updates online.
It has also published river level reports showing the highest water level was recorded at Llangorwen in Aberystwyth at 2.05m (6ft 7in) on Saturday afternoon. Typically it is up to 72cm. However it has been previously recorded at 1.81m (5ft 9in).
Main roads throughout Ceredigion are now open and passable with care apart from the B4353 between Ynyslas and Tre'r Ddol which remains closed.
A section of the A487 north of Ceredigion remains closed at
Derwenlas, according to the council which issued a statment on Sunday
afternoon saying the "situation has improved considerably".
Worst affected Caravan parks and villages near Aberystwyth were inundated by floodwater when twice as much rain fell in 24 hours than normally falls in the area in the whole of June.
The areas worst affected in the early hours of Saturday were Talybont, Dol-y-bont, Llandre, and Penrhyncoch - all in Ceredigion.
Machynlleth, in Powys, was also flooded and roads in surrounding areas were closed.
Dyfed Powys Police said they believed 1,000 people had been evacuated in total from Ceredigion and parts of Powys.
'Unprecedented' Police said a bridge in Talybont and another in the village of Goginan had been damaged - but although inspections were planned, neither were thought to be in immediate danger of collapsing.
The Environment Agency Wales said the flooding had been an "unprecedented event".
Water levels have been receding, however people have been urged to stay away from rivers and flooded areas.
A spokesman said minimal rainfall was forecast for Wales on Sunday so was not expected to impact further on river levels.
Agency officers are also assisting Dyfed Powys Police and Ceredigion Council with the clean-up operation.
Officers are continuing to inspect flood banks and defences in the affected area to make sure they have not been damaged by flood waters.
For latest information listen to BBC Radio Wales, BBC Radio Cymru and the BBC News Channel.
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600 villagers moved from Pennal, Gwynedd in flood precaution
A village in Gwynedd is being evacuated over concerns about a flood risk at a reservoir's dam.
Around 600 people from Pennal are being moved to a local
leisure centre after concerns of a slight breach in a local reservoir's
dam.North Wales Police said it was a precautionary measure.
It comes a day after around 1,000 residents and holidaymakers were moved to safety after flooding of homes and caravan parks in mid Wales.
North Wales Police, which is leading the latest operation, said the whole village in Pennal was affected.
The force said it followed a slight breach in the dam of a local reservoir - believed to be due to a landslide - which has caused a small amount of water to escape.
The residents are being transported to a leisure centre in Machynlleth, just over the border in Powys.
Council workers, the local water board, North Wales Fire and Rescue Service and officers from North Wales Police are at the scene working to stabilise the situation.
Supt Andy Jenks -Gilbert said: "The water is flowing over the top of the reservoir stone wall into a quarry below which has the Afon Pennal running through it.
"A crack has been discovered in the wall, causing a small amount of water to escape.
"Should the wall be completely breached, the contents of the reservoir will go into the river which flows through the village of Pennal, which is around half a mile from the reservoir.
"Police officers are evacuating residents in the area and would ask visitors and locals to avoid the village at this current time."
It comes as the clean-up operation continues in Ceredigion and parts of Powys.
Villages were flooded by 5ft (1.5m) of water with record high river levels in parts of Aberystwyth on Saturday.
First Minister Carwyn Jones praised the "impressive bravery" of emergency services.
Mr Jones added: "Working in truly harrowing conditions, they ensured up to 1,000 people were moved to safety."
In a statement, he said he was shocked at the damage and ministers would work with agencies to ensure normality returned to communities as quickly as possible.
Andy Francis, of Mid and West Wales Fire and Rescue Service, told the BBC: "There's mass scale damage to caravan parks and indeed, more importantly really, to private dwellings throughout the area.
"A lot of flood water's gone through them, leaving a huge amount of damage, and a residual danger as well from the biohazards, from sewerage, and other contaminants that have entered the waters."
Meanwhile, Ceredigion council has also issued advice to householders starting the clean-up operation.
There have not been any reports of anyone seriously hurt.
Debris Environment Agency Wales said one flood warning remains on the River Teifi, at Lampeter and Llanybyther. It is providing flood alert updates online.
It has also published river level reports showing the highest water level was recorded at Llangorwen in Aberystwyth at 2.05m (6ft 7in) on Saturday afternoon. Typically it is up to 72cm. However it has been previously recorded at 1.81m (5ft 9in).
Main roads throughout Ceredigion are now open and passable with care apart from the B4353 between Ynyslas and Tre'r Ddol which remains closed.
About 1,000 people were moved to safety and 150 rescued
Worst affected Caravan parks and villages near Aberystwyth were inundated by floodwater when twice as much rain fell in 24 hours than normally falls in the area in the whole of June.
The areas worst affected in the early hours of Saturday were Talybont, Dol-y-bont, Llandre, and Penrhyncoch - all in Ceredigion.
Machynlleth, in Powys, was also flooded and roads in surrounding areas were closed.
Dyfed Powys Police said they believed 1,000 people had been evacuated in total from Ceredigion and parts of Powys.
'Unprecedented' Police said a bridge in Talybont and another in the village of Goginan had been damaged - but although inspections were planned, neither were thought to be in immediate danger of collapsing.
The Environment Agency Wales said the flooding had been an "unprecedented event".
Water levels have been receding, however people have been urged to stay away from rivers and flooded areas.
A spokesman said minimal rainfall was forecast for Wales on Sunday so was not expected to impact further on river levels.
Agency officers are also assisting Dyfed Powys Police and Ceredigion Council with the clean-up operation.
Officers are continuing to inspect flood banks and defences in the affected area to make sure they have not been damaged by flood waters.
For latest information listen to BBC Radio Wales, BBC Radio Cymru and the BBC News Channel.
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