Playas Are Important Source of Water

Those of us who grew up on the High Plains probably heard our fathers or grandfathers talk about mud holes or buffalo wallows. Nowadays, they’re called playas, and those seasonal ponds are an important feature of the high plains landscape. They are the most numerous wetland in the region, more than 80,000 of them, and they’re an important source of water — both for people, and wildlife.

In recent decades, many researchers, representing a variety of disciplines, have been studying these wetlands.

“There’s a number of researchers that are focused on playas,” says University of Kansas geologist Bill Johnson. “What’s really important now, for a lot of people, relates to what everybody’s interest is rooted in — what’s their connection with the groundwater?”

Johnson has been investigating playas more than 30 years. He says scientists have evidence playas are a primary source of recharge to aquifers such as the Ogallala — that vast but diminishing source of groundwater so vital to life on the semi-arid plains.

Playas are shallow, round water catchment areas found at the lowest point in a watershed. These basins have a layer of clay soil that enables recharge, says Ken Rainwater, who directs the Water Resources Center at Texas Tech.

“Even though soils in the playa bottoms are clay, they dry out and desiccate with big cracks between rainfall events. So when you have your first flush of water coming into the playa, when there is enough rainfall, it’s real easy for water to go down through those cracks and head down through the clay toward the aquifer below.”

As the clay absorbs water, it expands, sealing the cracks, and filling the basin with water from rainfall and runoff, and providing water, food and shelter for birds and other wildlife.

But just as we’re learning their importance, so are we learning that playas are under stress. Ken Rainwater says many have lost capacity to not only recharge groundwater but also to filter and clean water going down into the aquifer because they’re clogged with sediment — sediment transported from cultivated fields by rain runoff. Establishing native grass buffers around a playa helps to filter out soil and agricultural contaminants present in runoff, preventing sediment accumulation and allowing the playa to send clean water to the aquifer.

“We’re not trying to go get anybody in trouble; we’re not trying to tell people you are doing things that are wrong. We’re just trying to understand how these complex processes on our planet work so that maybe we can have a better future,” says Rainwater.

Learn more about how playas recharge the aquifer.