If there are any depletion counters on River Delta, it does not untap during your untap phase. At the beginning of your upkeep, remove a depletion counter from River Delta.
oc
T: Add o
U to your mana pool. Put a depletion counter on River Delta.
oc
T: Add o
B to your mana pool. Put a depletion counter on River Delta.
Artist(s): Sandra Everingham