upstream

Aramco did not comment on the letter when contacted by BBC Sport but has previously said it has "one of the lowest upstream carbon footprints in the industry".

Biologists from the California Department of Fish and Wildlife have spotted fall-run Chinook salmon in tributaries miles upstream from where Iron Gate Dam was removed.

It followed an appeals court ruling that cleared the way for city officials and water managers to reduce flows upstream, keeping some water behind a dam and sending other supplies to farms.

The team also had to leave their kayaks at a base camp they set up when it became impossible to head further upstream, hiking through the jungle using machetes for five days.

The canoes and kayaks continued upstream until the group reached an impassable spot where the river was cascading through rocks.