River IL

Idlewild Slough

Illinois • 37.9361, -89.9612

Reviewed mapped path Updated Dec 30, 2025

Checking mapped path coverage…

USGS and NOAA data is for informational purposes. Source notes

Length

6 mi

10 km

Elevation

373′ → 349′

24 ft drop

Stream Order

Major River

Slope

0.08%

4.1 ft/mi

Drainage

583,786 mi²

1,512,000 km²

Avg Flow

-- cfs

4.0 mph velocity

Path to Mouth

127 mi

205 km to ocean

Classification

Tributary

Mid-reach

Elevation Profile

Water Quality

Data from EPA Water Quality Portal (USGS, EPA, state agencies).

Detailed hydrology

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Data from USGS & NOAA for informational purposes only. Read source and safety notes