A ciénega is a specific type of wetland system found primarily 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.
These systems occur when geomorphology forces water to the surface over large areas rather than through a single channel or pool. In healthy ciénegas, water migrates slowly through wide-scale mats of thick, sponge-like wetland sod. The soils are notably squishy, highly organic, anaerobic, and black in color.
The dominant vegetation in these wetlands consists of highly adapted sedges, rushes, and reeds. On the drier margins or down-valley areas where water may move underground, succession plants such as Goodding's willow, Fremont cottonwoods, and scattered Arizona walnuts are commonly found.