Hot Springs Recharge Zone

The Hot Springs Recharge Zone is the source of most of the water that emerges from the thermal springs at the base of Hot Springs Mountain.

Imagine it as massive, underground funnel into which snow and rain collects before filtering thousands of feet beneath the surface of the Ouachita Mountains.

 

The high, forested ridges of the Ouachita Mountains, in and around Hot Springs National Park, create the recharge zone that continuously replenishes the hot springs.

NPS/MSmith

Recharge Zone Characteristics

The Hot Springs Recharge Zone has to have special conditions in order to collect rain and snowmelt, funnel it down deep under the surface, and the push the heated waters quickly back to the surface.

The Recharge Zone needs to

• be a permeable area of intact forest that allows water to soak into the ground.
• receive enough precipitation so that a significant amount of water can flow into the underground system that produces approximately 700,000 gallons of water a day.
• have enough elevation to provide hydrostatic, or head pressure, to push the water column downwards between 4,500 and 8,000 feet deep and quickly back up to the springs.
• contain rocks layers that are fractured enough to provide pathways for the water to travel miles underground.

 

The Hot Springs Recharge Zone is currently estimated to be 22 square miles, much of which lies outside of the boundaries of Hot Springs National Park

NPS

Area of the Recharge Zone

Studies have identified characteristics of rock layers, elevation, and groundwater flow patterns to help clarify the area the Hot Springs Recharge Zone.

The results of research:

• elevations exceeding 660 feet define the Hot Springs Recharge Zone.
• Bigfork Chert, Arkansas Novaculite and Hot Springs Sandstone are highly permeable rock formations, due to their fracture patterns, and are the primary recharge zone rock layers.
• The fractured rocks form a highly interconnected waterflow system that stretches for miles around Hot Springs National Park.

Scientists have mapped these characteristics over a 22-square mile area, much of which lies outside of the bounds of Hot Springs National Park.

Visitors may see the recharge zone area as the high, forested ridges of the local ZigZag Mountains.