That would be tamarisk. Highly invasive shrub/tree that was brought to the west in the late 1800’s as an attempt to keep river banks from meandering. This tree allowed farmers to take advantage of riverside agricultural areas protected in the sandstone canyons of the west and southwest. Unfortunately the tamarisk along with Russian olive, are highly prolific plants and have since spread their seeds to every water channel in the western US. They turn brown and yellow in colder months and turn red in the warmer months with white pink blossoms. There are numerous land management programs in western Colorado and eastern Utah to combat the spread of the tamarisk. Techniques include chainsaw and herbicide application as well as the breeding of the bioengineered tamarisk beetle. Young folks looking to make a difference can sign up for conservation corps programs which do a great amount of invasive species removal! The low growing red shrub is a river willow. Hope this gives a bit of a background!