May 6 (Reuters) - At least 15,000 people have been killed and 30,000 people are missing from the cyclone that tore through Myanmar's Irrawaddy delta last weekend, officials said on Tuesday. Here are some key facts on the area, once known as the "rice bowl of Asia".

* The delta is a triangle of fertile land, mangrove swamps and tidal estuaries at the mouth of the Irrawaddy, Myanmar's longest river and its most important trade artery.

* Stretching from scattered islands in the Bay of Bengal to the southeast port city of Yangon, the delta's base is about 150 miles (240 km) long and its western flank about 180 miles.

* It is criss-crossed by a vast network of streams that swell to become small lakes during the May-October monsoon rains. Their muddy waters empty into the Andaman Sea.

* The delta was jungle and high grass when annexed as 'Lower Burma' by Britain in 1852 after the Second Anglo-Burmese War.

The colonial rulers, in charge until independence in 1948, encouraged migration and rice cultivation in the delta, commercialising its once feudal lands.

* An estimated 3.5 million people now live in the delta's towns and villages -- 15 percent of a total population of 53 million. About five million live in Yangon, Myanmar's biggest city, on the delta's southeast edge.

* Most people in the delta are from the majority Burman ethnic group, though minorities such as Karen and Shan also live there. It is one of Myanmar's most densely populated areas.

* Over the last 150 years huge areas of mangrove forest have been cleared and converted to paddy in order to grow rice. Before independence, Myanmar was the world's largest exporter of rice, most of it grown in the delta.

* Communication inside the delta is mainly water-based. Most households own a boat, and the southern delta's major towns are all connected by steamers.

Sources: Reuters, Asean Regional Centre for Biodiversity (http://www.arcbc.org.ph/wetlands/myanmar/mmr_irrdel.htm), Changing Faces of the Ayeyarwady (Irrawaddy) Delta (1850-2000), published by the Institute of Southeast Asia Studies, Singapore (http://std.cpc.ku.ac.th/delta/conf/Acrobat/Papers_Eng/Volume%20 2/Mya%20Than.pdf) (Writing by Gillian Murdoch, Singapore Editorial Reference Unit, Editing by Ed Cropley)

AlertNet news is provided by