Ice Age

River Delta

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.

River Delta doesn't untap during your untap step if it has a depletion counter on it.
At the beginning of your upkeep, remove a depletion counter from River Delta.
{T}: Add {U} or {B}. Put a depletion counter on River Delta.