Salt cedar, also tamarisk, was introduced from Eurasia and is now widespread in the United States. Salt cedar, a member of the Tamarisk family, is a deciduous or evergreen shrub or small tree that grows from 5 to 20 feet tall. The bark on saplings and stems is reddish-brown. Leaves are small and scale-like and the flowers are pink to white and 5-petalled.
Small flower tamarisk (T. paviflora DC.) is similar in appearance ,but has 4-petalled flowers and the bark is brown to deep purple.
Both species are used as ornamentals, but have escaped and can be found growing along streams, canals, and reservoirs in much of the western United States.
For more info and how to control, check out the La Plata County Weeds Dept. Fact Sheet
Notice the long tap roots of the water sucking Tamarisk