Observed and urbanization-adjusted annual maximum peak discharge and associated urban fraction and precipitation values at USGS streamgage:
05527950 MILL CREEK AT OLD MILL CREEK, IL
| Water year | Segment | Discharge code | Cumulative reservoir storage (acre-feet) | Urban fraction | Precipitation (inches) | Observed peak discharge (ft3/s) | Adjusted peak discharge (ft3/s) | Exceedance probability |
| 1960 | 1 | 7 | 1739 | 0.132 | 0.606 | 778 | 1050 | 0.187 |
| 1962 | 1 | -- | 1739 | 0.141 | 0.234 | 439 | 632 | 0.581 |
| 1963 | 1 | 2 | 1739 | 0.146 | 1.422 | 70 | 141 | 1.000 |
| 1964 | 1 | 2B | 1956 | 0.151 | 1.160 | 120 | 215 | 0.965 |
| 1965 | 1 | -- | 1956 | 0.156 | 0.558 | 423 | 602 | 0.618 |
| 1966 | 1 | 2 | 1956 | 0.161 | 0.495 | 500 | 697 | 0.497 |
| 1967 | 1 | -- | 1956 | 0.165 | 1.405 | 395 | 562 | 0.665 |
| 1968 | 1 | 2 | 1956 | 0.170 | 0.518 | 146 | 246 | 0.954 |
| 1969 | 1 | -- | 1956 | 0.175 | 1.460 | 720 | 945 | 0.254 |
| 1970 | 1 | -- | 1956 | 0.180 | 1.917 | 744 | 969 | 0.236 |
| 1971 | 1 | -- | 1956 | 0.185 | 0.548 | 583 | 781 | 0.403 |
| 1972 | 1 | -- | 1956 | 0.189 | 0.890 | 921 | 1180 | 0.139 |
| 1973 | 1 | -- | 1956 | 0.194 | 1.360 | 510 | 685 | 0.511 |
| 1974 | 1 | -- | 1956 | 0.199 | 1.299 | 840 | 1070 | 0.182 |
| 1975 | 1 | -- | 1956 | 0.204 | 0.919 | 319 | 449 | 0.797 |
| 1976 | 1 | -- | 1956 | 0.209 | 1.594 | 1050 | 1310 | 0.094 |
| 1990 | 1 | -- | 1956 | 0.257 | 0.651 | 486 | 614 | 0.605 |
| 1991 | 1 | -- | 1956 | 0.263 | 1.582 | 931 | 1110 | 0.163 |
| 1992 | 1 | E | 1956 | 0.269 | 0.969 | 336 | 434 | 0.812 |
| 1993 | 1 | -- | 1956 | 0.275 | 2.581 | 1090 | 1280 | 0.101 |
| 1994 | 1 | -- | 1956 | 0.282 | 0.604 | 988 | 1160 | 0.146 |
| 1995 | 1 | -- | 1956 | 0.288 | 1.370 | 696 | 830 | 0.355 |
| 1996 | 1 | -- | 1956 | 0.294 | 1.325 | 1020 | 1180 | 0.137 |
| 1997 | 1 | -- | 1956 | 0.300 | 1.816 | 1000 | 1150 | 0.148 |
| 1998 | 1 | -- | 1956 | 0.307 | 0.689 | 609 | 719 | 0.472 |
| 1999 | 1 | -- | 2022 | 0.313 | 1.344 | 1160 | 1320 | 0.093 |
| 2000 | 1 | -- | 2022 | 0.319 | 1.223 | 1060 | 1200 | 0.130 |
| 2001 | 1 | E | 2022 | 0.333 | 0.535 | 405 | 476 | 0.768 |
| 2002 | 1 | -- | 2022 | 0.347 | 1.255 | 581 | 658 | 0.545 |
| 2003 | 1 | E | 2022 | 0.360 | 0.679 | 138 | 168 | 0.983 |
| 2004 | 1 | -- | 2022 | 0.374 | 1.475 | 831 | 902 | 0.288 |
| 2005 | 1 | -- | 2022 | 0.388 | 0.617 | 436 | 477 | 0.767 |
| 2006 | 1 | -- | 2022 | 0.402 | 1.197 | 465 | 499 | 0.744 |
| 2007 | 1 | -- | 2022 | 0.415 | 1.570 | 770 | 804 | 0.380 |
| 2008 | 1 | -- | 2022 | 0.429 | 1.332 | 1070 | 1100 | 0.171 |
| 2009 | 1 | -- | 2022 | 0.443 | 1.266 | 1730 | 1750 | 0.038 |