Tamarisk – Can Water be Saved?? 35 th Annual Colorado Water Workshop, WSC July 22, 2010 Tim Carlson Research & Policy Director

Tamarisk is a non-native phreatophyte that can dominate riparian lands

Distribution Tamarisk covers approximately 1.6 million acres of riparian lands within the western United States Courtesy of Fred Nibling, Bureau of Reclamation

Tamarisk has a Reputation for consuming large amounts of water

BOR & USGS Tamarisk Assessment Peer reviewed Papers 7-States Colorado River Basin Tamarisk Assessment ET Peer Panel Is there an opportunity to save water? 2 Studies, 2 Different Approaches

BOR & USGS Report7-States Report CW & Willows use same amount of water ~ 3’/yr. On upper terraces of floodplain, tamarisk will use more water than native xeric plants (e.g., bunch grasses, sage, rabbitbrush, etc.). Difficult to measure savings. Demonstration projects advocated. Impacts to wildlife – Mixed. CW & Willows use same amount of water ~3’/yr. On upper terraces of floodplain, tamarisk will use more water than native xeric plants (e.g., bunch grasses, sage, rabbitbrush, etc.). Difficult to measure savings but savings can be modeled. Demonstration projects advocated. Impacts to wildlife – Mixed.

Tamarisk Induced Changes in Channel Structure and Associated Habitats Figure 1

Water Savings – You do the ET Math 1.Cottonwoods and willows 2.Upland shrubs and grasses 3.Measure water savings -- difficult 4.Model water savings (e.g. GSFLOW) 5.Demonstration Projects Colorado River near CO/UT border

Canyon de Chelly, AZ

CWCB Tamarisk Mapping for Colorado 2006

Close-up of flowers Courtesy of Dr. Phil Westra, CSU Other Impacts

Wildfires Rio Grande in Albuquerque 4/2002

Purgatoire River – east of Trinidad, CO Sedimentation

Water value $/ac-ft Always senior, even in extreme drought Value of water lost by Tamarisk ?? Almost always senior, except in a drought Water Rights Available for Purchase Normal water year Usually called, except in wet years Always called, except in extremely wet years Water rights Seniority Water Market Value, Seniority, & Availability Question: What is the value of water Preserved in the groundwater & surface water systems ?

Climate Change

INVASIVES ?? Courtesy of Fred Nibling, US Bureau of Reclamation

or Natives??

Near Garden City, Kansas