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Arkansas Nature|On The Water

Most People Don’t Realize An Underground River Flows Right Through Arkansas

By Carol Ann Carson | Published October 19, 2017

Whether waterfalls, bluffs, or forests, Arkansans are keen on knowing the best areas of natural beauty. You may be familiar with Mammoth Spring but did you know it connects to an underground river? This Arkansas anomaly makes for one trip that shouldn’t be missed.

Mammoth Spring is on the AR/MO state line, about 17 miles north of Hardy. It’s the largest spring in Arkansas (and 7th largest in the world).

Rainfall in southern Missouri is the spring’s main source of water. It seeps into the underground water table and flows into the main channel that becomes Mammoth Spring.

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Proven by dye tests, water that passes through the collapsed cave appears one to four days later at Mammoth Spring.

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The spring of Mammoth Spring emerges 80 feet below the surface. Since the water stays a chilly 58° and flows at nearly 10 million gallons per hour, Mammoth Spring is the perfect spot for trout fishing and canoeing.

You can glimpse the underground river at Grand Gulf State Park in Missouri — just nine miles north of Mammoth Spring. Dubbed the 'Little Grand Canyon,' a collapsed cave reveals the underground channel.

The spring has powered a grist mill in the mid 1800s, and later a hydroelectric plant that supplied electricity to the area until 1972.

When you’re busy fishing, canoeing, or exploring the restored Frisco Railroad train depot, it’s easy to miss the spring’s unusual geological source.

Did you know about Arkansas’ underground river? What other AR anomalies have you seen? Let us know in the comments below!

For a fantastic fall view in Arkansas, try this hike.

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