depletion

Short definition from Wiktionary

Noun

1. 1
   The act of depleting, or the state of being depleted; exhaustion.
2. 2
   The consumption of a resource faster than it can be replenished.
3. 3
   The act of relieving congestion or plethora, by purging, blood-letting, or reduction of the system by abstinence.
4. 4
   gradual expense or use of natural resources over time.