About two million people in northern Nigeria have been displaced after authorities opened the floodgates on two dams, an official says.

尼日利亚一位官员称，当局打开北部地区两座大坝的水闸，使大约两百万人民无家可归。

The flooding began suddenly when the gates on the Challawa and Tiga dams were opened, a spokesman for the Jigawa governor said.

The dams are in Kano state, but about 5,000 villages in neighbouring Jigawa state have been affected¹, he added.

Several states in northern Nigeria have been hit by floods this year.

It is not yet clear whether residents received a warning or if anyone was injured or went missing in the flooding, reported the Associated Press news agency.

The floodgates（水闸，水门） are normally opened every year during the rainy season.

Nigeria's meteorological（气象的） agency had previously² forecast low rainfall in the north, warning that more than 12 million people could face food shortages as a result, according to the AFP news agency.

In a normal year, the water released from the dams flows into fields, irrigating³ crops of corn, rice and vegetables during the brief growing season.

Jigawa and Kano are part of the Sahel region, a belt of semi-arid land south of the Sahara desert.

In neighbouring Niger, millions are facing food shortages after a prolonged（延长的，拖延的） drought caused crops to fail. That was followed by severe flooding last month. Millions are now facing food shortages.