The global annual
runoff into the
oceans (38,500–44,200 km3/year) is dominated by runoff into the South Atlantic from eastern South America, into the western Pacific from east Asia, and into the Indian Ocean from India, and southeast Asia. Depending on the estimate, the
Amazon alone accounts for 15–18% of the annual freshwater runoff into the oceans. File:Rivers of the world by discharge volume.png|Circle represents total global river discharge of 38,500 km³/year Total_global_runoff_rate_by_continent_and_oceans.jpg|Total global runoff rate by continent and oceans Riverfunoffoceans.jpg|Largest primary rivers by runoff Water discharge may be expressed as mean annual discharge (denoted MQ), or as annual discharge (denoted Q). The units for measuring mean annual discharge (MQ) are
m³/sec, and can be measured over a period of one or more years. The annual discharge (Q) is measured in units of
km³/year. For large rivers, these values difficult to measure (see
ADCP), and they also vary considerably from year to year. The very large variation between low and high flow is often not apparent from the average runoff volume. The discharge values shown in the tables below are mean annual discharge (units m/sec). To convert to annual discharge (units km/year) multiply by 0.031536. ==List of rivers==