The Irrawaddy River begins where the streams of the Nmai and Mali join. Both of these rivers begin in high and remote mountains near the border with Tibet. In this area rain falls at all seasons of the year, but mostly in the summer. The valleys and lower hill ranges are covered with an evergreen rainforest. At elevations above there are forests of oak and pine. Above , are forests of rhododendrons. Above there are evergreen conifer forests.