Ill. Admin. Code tit. 35, § 302.658
The HNC applies at all times except during periods when flows are less than the harmonic mean flow (Qhm), as determined by:
Qhm = N / SUM(1/Qi)
Where:
| Qhm | = | harmonic mean flow, |
| N | = | number of daily values for streamflows, and |
| Qi | = | daily streamflow value on day i. |
(Source: Amended at 47 Ill. Reg. 4437, effective March 23, 2023)