Irrawaddy River

The Irrawaddy River is the principal waterway of Myanmar.

It flows through the center of the country from north to south. The river is approximately 1,350 miles long. Its drainage basin covers 404,000 square kilometers. This area accounts for 61% of the land in Myanmar. The river serves as the nation's most important commercial waterway. It supports many large cities and diverse ecosystems.

The river begins at the confluence of two other rivers. These are the N'mai and the Mali rivers. They both start in the Himalayan glaciers of Upper Myanmar. The N'mai is the larger eastern branch. It has a strong current that makes it unnavigable for boats. The Mali is the smaller western branch. It is navigable despite some rapids. Locals often call the main river by the name of the Mali.

As the river flows south, it passes through three distinct defiles. A defile is a narrow pass between mountains or hills. The first defile is 65 kilometers downstream from Myitkyina. The second defile is located below Bhamo. Here, the river cuts through limestone rocks. It is only 90 meters wide at its narrowest point. The cliffs on either side are 60 to 90 meters high.

The third defile is located about 100 kilometers north of Mandalay. In this area, the river enters the Mogok region. Between Katha and Mandalay, the river is remarkably straight. However, it bends sharply near Kabwet. This bend was caused by a sheet of lava. This volcanic field is called the Singu Plateau. It covers about 62 square kilometers.

The river's water levels change significantly due to monsoonal rains. These rains occur between mid-May and mid-October. In the summer, melting glaciers also add more water. The discharge near the delta can reach 40,393 cubic meters per second. In contrast, the low season discharge is much smaller. At Mandalay and Prome, the water level can vary by over 9 meters. This change requires ports to have separate landing areas for high and low water.

Near the end of its journey, the river forms a large delta. This is the Irrawaddy Delta. It is a nine-armed area that empties into the Andaman Sea. The landscape is low and covered in fertile alluvium. Alluvium is fine silt carried by the river. Heavy rainfall helps the delta grow. The surface extends into the sea at a rate of about 50 meters per year.

The river is home to many unique living things. There are about 200 species of fish in the basin. Some fish species are endemic, meaning they are found nowhere else. The most famous animal is the Irrawaddy dolphin. These dolphins have a rounded forehead and no beak. They live in the lower reaches of the river. They are known to help local fishers catch fish.

Humans have relied on the Irrawaddy for centuries. As early as the sixth century, people used it for trade. They also built irrigation canals to support agriculture. Today, the river is vital for fisheries and tourism. However, there are concerns about new projects. In 2007, an agreement was signed for seven hydroelectric dams. Environmentalists worry these dams could impact the river's biodiversity. This includes the endangered Irrawaddy dolphin and the Ganges shark.