Each week day, for two weeks, Paulo will be posting a diary entry on the web, and responding to a selection of your e-mails. His diary begins on Monday 23 June.

Along the banks of the S�o Francisco river lays a large country called Brazil. Less famous but not less important than its huge and northern cousin Amazon River, Velho Chico - the Old Frank, as Brazilians call it - is often referred to as the river of the national union.

In 1865 the British explorer captain, later sir, Richard Francis Burton, understood that a great destiny was written for those 3000 kilometres of water.

Despite his prejudices - commonly found also in other Victorian explorers - Burton was a very effective observer when he pointed more than 150 years ago that along the banks of the S�o Francisco would pass a nice deal of the Brazilian history and development during the 20th Century. He identified that it could provide "large and unexploited wealth for the poor classes in Europe".

Dams and plantations

During his journey he found fertile lands and abundant wildlife, much mineral wealth (including diamonds and gold) and along a river that would one day be navigated by steamship. He pointed to small villages that would become great cities off the back of this proposed new trade route.

Click here to see a map of the route Paulo will be following Enlarge image

Part of his prophecy became true: nowadays Old Frank provides water for some of the main hydro electrical projects in the country.

It irrigates plantations that produce high quality fruits for export in what was once arid soil. Its banks are exploited by the tourist industry, among other economical activities developed in its valley.

But the environment has suffered as a result. The dams required for the hydroelectric power plants have submerged some of the noteworthy places Burton visited - including his "Brazilian Niagara", the great Paulo Affonso rapids at the end of his journey.

Journey through history

Pesticides used in agriculture and industrial waste in the major cities areas have also had an effect. And the wealth generated by Old Frank's waters is highly concentrated and restricted to an oasis of prosperity, surrounded by a desert of poverty and misery.

For a Brazilian journalist who has heard about the S�o Francisco from childhood, and as an adult, amazed by its astonishing landscapes, following Burton's footsteps is a unique challenge.

Burton tried to see what those waters would bring within the next decades. I am interested in what they have brought and in what is still to come for this and the next centuries.

A version of this article will appear in the August edition of the BBC's On Air magazine.