Drought severity shall be determined by the Director using the Keetch-Byram Drought Index (KBDI) during the vegetative growing season between May 1 and October 31 and the Palmer Drought Severity Index (PDSI) during the dormant vegetative season between November 1 and April 30.

Added at 14 Ok Reg 1236, eff 5-12-97

Amended at 16 Ok Reg 2125, eff 6-25-99

Amended at 24 Ok Reg 1768, eff 6-25-07