<P> Like many other seasonal Indian rivers, the Mahanadi too is a combination of many mountain streams and thus its precise source is impossible to pinpoint . However its farthest headwaters lie 6 kilometres (3.7 mi) from Pharsiya village 442 metres (1,450 ft) above sea level south of sihawa town in Dhamtari district of Chhattisgarh . The hills here are an extension of the Eastern Ghats and are a source of many other streams which then go on to join the Mahanadi . </P> <P> For the first 80 kilometres (50 mi) of its course, the Mahanadi flows in a northerly direction and drains the Raipur district and touches eastern portions of Raipur city . It is a rather narrow river at this stage and the total width of its valley does not exceed 500--600 metres . </P> <P> After being joined by the Seonath, the river flows in an easterly direction through the remaining part of its journey . It is joined by the Jonk and Hasdeo rivers here before entering into Odisha after covering about half of its total length . Near the city of Sambalpur, it is dammed by the largest earthen dam in the world, the Hirakud Dam . A composite structure of the earth, concrete and masonry, the dam measures 24 kilometres (15 mi) including the Dykes . It spans two hills; the Lamdungri on the left and the Chandili Dunguri on the right . It also forms the biggest artificial lake in Asia, with a reservoir holding 743 square kilometres (287 sq mi) at full capacity, with a shoreline of over 640 kilometres (400 mi). </P> <P> After the formation of Chhattisgarh State, the major portion of Mahanadi basin now lies in Chhattisgarh . Presently, only 154 square kilometres (59 sq mi) basin area of Hasdeo River in Anuppur District lies in Madhya Pradesh . </P>

Where do the rivers mahanandi godavari krishna and kaveri drain into