A re-post from 2018.
My long-time readers will recall that last year I was following a local playa lake over the course of the seasons. I’m still doing that, but it has been so dry that the view has not really changed, at least from the place where I take pictures. Unless you really know what to look for, all you see is swaths of brown stuff with slightly enlarging or contracting patches of green stuff. Not really gripping blog fodder.
So I thought I’d go back to what a playa is, on the off-chance we get more precipitation and water actually, you know, shows up in the lakebed.
Playa lakes (also called “playas”, pronounced ply-uh), are shallow, generally ephemeral lakes that are found on the High Plains and South Plains in Colorado, Kansas, Oklahoma, Texas, and New Mexico. They are low spots in the landscape that catch water, sometimes for a few days or weeks, in other places all year around. They range in size from a dozen yards/meters across to over a mile across, and provided the main drainage system and aquifer recharge system for the region. Playas are generally round-ish.
Most are relatively shallow. It is hard to drown in a playa, although it can be done if someone tries hard enough.
Playas provided critical water sources for animals and birds. Because so little water flows across the plains and very few sweet-water springs bubble to the surface, the rainwater ponds served as oases in the semi-arid grasslands. As I said above, some only lasted a few weeks after springs storms dumped their rains, but others survived year-round. A few of the deepest playas had springs in them, especially on the southern plains near Lubbock and Shallowater, because the playas eroded down to the very shallow water table.
Technically, a depression has to be lined with a type of soil called Randall clay to be a true playa. This clay forms when the local soils get saturated and stay that way over an extended period of time. When dry, the clay cracks, opening gaps in the surface that reach to the sub-soil. The first rains after an extended dry spell go straight to the sub-soil, and will (relatively) quickly reach the aquifer below. Once the clays swell, it takes longer for the water to get through, and a puddle, then pond, forms in the basin around the playa. Because so many depend on rainfall and snow-melt for their water, playas are termed “pluvial.”
The plants around a playa form a sort of bulls-eye. In the center of a deep playa is open water. Then cattails and rushes and sedges, arrowhead, and other plants that need wet feet. The next ring contains sedges, goosefoot, and things that will tolerate a few dunkings but need moist soil that is not always under water. Then plants that tolerate drier soil such as little Bluestem and western wheat grass, then the native short-grasses. Depending on how much water a particular playa holds for how long, the inner basin might start with goosefoot, or western wheat grass.
People built over, built in, and plowed through playas for decades. Runoff from plowed fields and construction sites filled some in, leading to the second diagram under the playa drawing above. Today there is more of an interest in protecting them, although developers don’t always allow for things like higher-than-usual runoff when they build near “dry lakes.”
As you can tell, I find playa lakes fascinating, and not just because I wrote a book chapter about them. They are a wonderful study in species succession and retreat, and provide vital habitat for migratory waterfowl and native birds, as well as other critters. Groups like the Playa Lakes Joint Venture, Ducks Unlimited, and others are working to preserve and protect playas, working with landowners, hunters, developers, and others to preserve those playas that remain and to learn and teach more about them.