Complex sentence: On the border it merges with the Papurí River and becomes known as the Uaupés, continuing to flow east until it flows into the Rio Negro at São Joaquim, Amazonas.
Split into simpler sentences: On the border it merges with the Papurí River and becomes known as the Uaupés. Discoveries and Explorations, Charles G.D. Roberts, 1905 The river continues on east until it flows into the Rio Negro at São Joaquim, Amazonas.