When last we left the playa lake I’ve been watching and sort of quasi documenting for just over a year, it was dormant. Two and a half inches of snow had disappeared into the knee-high bunchgrasses surrounding the main basin, and the longer reeds and sedges of the inner basin absorbed all the moisture that might fall. A coyote had sniffed around the school during class hours, drawn by the shelter of the wind, and by the smaller mammals that also sought out protection and heat. Otherwise the world lay still, quiet, sleeping. But slowly, in fits and starts, green returned to the land.
That doesn’t look too green, does it? There’s a lot of standing dead material that has accumulated since last summer, when everything was in full growth and wet.
That’s because the native plants are C-4 grasses, warm season grasses that start greening up in mid to late-April and May, to take advantage of the onset of the spring rains. They are very efficient at not losing moisture, unlike C-3 plants and grasses such as Kentucky bluegrass, wheat, and other cool-season grasses. Maize, or as US residents call it, corn, is a C-4 grass that requires a certain number of heat days in order to thrive, and is planted relatively late. Winter wheat is a C-3 plant. That said, maize in this region is past the edge of its minimum moisture and needs to be irrigated. Winter wheat can be grown dry-land relatively well, and people graze livestock on it in winter, then let it grow starting in March or so.
Once you get below the dead stuff, er, senescent material, excuse me, you start seeing some greening up. I suspect the inner playa has more, but I didn’t go out there because 1) snakes, 2) lack of permission from land owner, 3) wasn’t wearing march-through-muck shoes.
So, what does it take to put water in the playa? One of two things. Either a week of continuous rain, to the point that the soil is saturated and any additional runs off and fills the basin, which has also become saturated so that instead of soaking in, the water collects. More often, what happens is a frog-strangling, goose-drowning, cow-floating thunderstorm that drops an inch or so of rain in a half hour, so much rain so fast that it can’t sink in and instead runs off, into the playa, which begins to fill. The clay in the bottom swells and closes, holding the water, and presto, insta-lake. The problem that engulfed one of the new subdivisions last year started with a three and a half inches in an hour rain that did just that. What the playa needs in order to fill is what is called Hortonian Overland Flow, water that doesn’t soak in but instead runs across the land and collects in low places.
Thus far, although we have decent soil moisture, the county around this playa has not had excessive rainfall yet this season, unlike, oh, the area down south that had a massive tornadic storm park on top of it for six hours and drop so much rain that, in between tornadoes, people were looking out the windows to see if an ark was bobbing past.