Simplify the following text for a Grade 7 native English-speaking person.
Original: In extreme events , water from the Finke River flows into the Macumba River , and thence into Lake Eyre , a total distance from headwater streams of around 750 km .
Simplified: In a big flood water from the Finke River can flow into the Macumba River , and then into Lake Eyre , a total distance of about 750 km .