A ciénega is a specific type of wetland system primarily found in Northern Mexico and the American Southwest. These wetlands are characterized as alkaline, freshwater, spongy meadows with permanently saturated soils that typically occupy the entire width of valley bottoms within otherwise arid landscapes.
Geomorphologically, ciénegas occur where land formations force water to the surface over large areas rather than through single channels or pools. They are commonly associated with springs or seeps located along stream margins and canyon headwaters. In healthy systems, water migrates slowly through wide-scale mats of thick, sponge-like wetland sod.
The soils in these environments are highly organic, anaerobic, black in color, and squishy. The dominant vegetation consists of highly adapted sedges, rushes, and reeds. On drier margins or down-valley areas where water may move underground, succession plants such as Goodding's willow, Fremont cottonwoods, and Arizona walnuts are typically found.