Grand Canyon's Underground Water System Mapped by Researchers

Scientists are mapping the Grand Canyon's hidden cave networks to understand how snowmelt supplies the park's vital springs. This research aims to protect the canyon's water from drought, contamination, and other threats. Roaring Springs, a cave-fed spring on the North Rim, provides water for park visitors, plants, animals, and ecosystems. Protecting this water source is increasingly important as the region becomes hotter and drier.

Researchers at Northern Arizona University (NAU) are investigating how these cave-fed springs function. A new grant from Grand Canyon National Park supports efforts to map these water systems. The team will also study the connection between snowmelt and the springs. Understanding where water enters the system is crucial for the infrastructure, animals, plants, and ecosystems that rely on these springs. Early findings from this project were published in *Scientific Reports*.

Most of the caves feeding Grand Canyon springs are closed to the public. They are often located far from established trails. Blase LaSala, a doctoral student in ecoinformatics, worked with Professor Temuulen Sankey to create detailed maps of several cave systems. They used a mobile lidar (light detection and ranging) scanner to produce high-resolution three-dimensional models. These models captured cave walls, ceilings, passages, and chambers in detail. Over 45 days, researchers, volunteers, and park staff documented more than ten kilometers of underground passages and rooms.

The research team transported lidar equipment weighing up to 55 pounds to remote cave entrances. Some hikes took as long as two days. Inside the caves, they climbed, rappelled, crawled, and floated through flooded sections. They recorded the caves' shapes and fracture patterns. These details reveal how water travels through different rock layers beneath the canyon. The simplest explanation for the water's origin is surface snowmelt from the Kaibab Plateau.

The more complex question is how this water travels underground to springs like Roaring Springs. The cave-fed springs are located within Redwall and Muav limestone formations. Several other rock layers sit between these springs and the surface. Previous dye tracing experiments showed water can move quickly through this underground system. Dye poured into sinkholes on the plateau traveled approximately 20 kilometers and appeared at springs in as little as one week. The exact movement of water through the subsurface remains uncertain. Factors like fractures, faults, rock permeability, and underground pathways all influence the journey.

Understanding these underground pathways is important for water quality and public safety. The Grand Canyon's largest springs are fed by karst systems, which have numerous holes, channels, and openings. Water can move rapidly through these pathways, with little natural filtration. This means contaminants can also travel quickly. Runoff from wildfire burn areas or bacteria could enter sinkholes connected to Roaring Springs Cave. This could contaminate the water supply. If contamination is detected, park officials might need to shut down pumping operations. Identifying water entry points and tracing its movement helps managers pinpoint contamination sources. This reduces the risk of future disruptions. The next phase of the project, starting in early 2026, will use airborne lidar surveys and satellite observations. Researchers will map sinkholes and examine snow accumulation and melt patterns over the last 40 years. This research will create an extensive archive of environmental data. This data will improve understanding of water systems throughout the region and globally.