Yellowstone hydrology—more than just hot water!

Indeed, landmarks like Old Faithful and Grand Prismatic Spring are among the most captivating water features on Earth! But what makes the hydrology of Yellowstone more remarkable is that these distinctive hydrothermal features share a landscape with starkly different non-thermal surface water features, like lakes and rivers.

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There are approximately 150 lakes, 278 streams, 45 waterfalls, and thousands of small wetland areas across Yellowstone National Park. The journey of water through streams and waterfalls to Yellowstone's lakes is quite distinct from the subsurface pathways of the hydrothermal groundwater system to geysers and thermal springs. In the surface water system, the majority of flowing water comes from precipitation that has fallen on the nearby landscape as rain or snow. The direction and rate of movement of the surface water is controlled by varying topography that ranges between 5,282-11,358 feet (1,610-3,462 m), which produces both raging rivers and calm streams begging to be fished.

The rain and snow on Yellowstone's landscape is expressed as surface runoff that reaches the Pacific Ocean, Gulf of California, and Gulf of Mexico because the Continental Divide runs through the park. The Continental Divide is a continuous ridge of mountain summits that separates the drainage direction between eastward Atlantic Ocean and westward Pacific Ocean flow paths. Watersheds are areas bounded by a ridge of high elevation that captures precipitation and drains into a larger river or lake. There are several important watersheds on each side of the Continental Divide in the park, including the Snake (southwest), Yellowstone (north and east-central), Madison (west), and Gallatin (northwest) Rivers.

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While many of the park's surface water features appear to be disconnected from the hydrothermal features like Grand Prismatic Spring or Steamboat Geyser, researchers continue to identify new linkages between the two systems. For example, Yellowstone Lake may seem continuous at the surface, but its dynamic lake bottom is dotted by underwater hot springs and hydrothermal vents. The composition of the lake is a mixture of meteoric (snow and rainfall) water and a small but significant fraction of thermal water heated by the underwater volcanic system. Determining the relative contribution of meteoric and deeper thermal waters is a challenging task and the subject of ongoing research. The interplay of meteoric and thermal waters in the lake creates an extremely complex water system that researchers are currently working to better understand.

Yellowstone National Park is the headwaters, or major source of water, for many rivers west of the Mississippi River. Because the surface water within the park has the potential to travel long distances to the Pacific and Atlantic oceans, the quantity and chemical composition of the water are monitored continuously at multiple locations within the park. There are streamflow gaging stations at eight sites reporting continuous stream flow discharge data, which are accessible online.

So the next time you are in Yellowstone enjoying the splendor of the park's many thermal features, remember that the Park is also home to numerous spectacular lakes, rivers, and wetlands that follow paths to both oceans and support a diversity of ecosystems. In Yellowstone, water is everywhere!

For more information about water in Yellowstone National Park, visit https://www.nps.gov/yell/learn/nature/water.htm.