Mapping & Inventory

Colorado River Basin

As a component of the Colorado River Basin Tamarisk and Russian Olive Assessment, the Tamarisk Coalition created comprehensive databases and maps characterizing tamarisk and Russian olive infestations throughout the entire Colorado River Basin. To request a disk of the map information, please email Stacy Kolegas at skolegas@tamariskcoalition.org.

State of Colorado

In 2007, the Tamarisk Coalition completed the Colorado Tamarisk Mapping and Inventory Report. Protocols were developed to do an inventory of tamarisk infestations on all the major rivers and their main tributaries in Colorado for the Colorado Water Conservation Board (CWCB).

This summary is supported by the detailed inventory and mapping data-DVDs created for the state of Colorado. If you are interested in obtaining any of this information and data, please contact us. Additionally, this information in the form of shape files and site specific characteristics data, has been transformed into a digital GIS database which is now available on the USGS invasive species web site:  www.niiss.org

Individual Watershed and Area Mapping Reports are available:

• Arkansas Watershed Mapping Summary
• Colorado River Mapping Summary
• Dolores River Mapping Summary
• Gunnison River Mapping Summary
• Montezuma County Mapping Summary
• Purgatoire River Mapping Summary
• Republican River Mapping Summary
• South Platte River Mapping Summary
• Uncompahgre River Mapping Summary
• White River Mapping Summary

The inventory of Colorado’s rivers and their major tributaries is summarized in the Colorado Tamarisk Mapping and Inventory Summary Report.  Table 2 on p. 15 is organized by watershed and includes: total area of infestation, average density or canopy cover, estimated current water and future water losses associated with the tamarisk and Russian olive infestations as well as estimated costs for control and revegetation.

These water losses and cost estimates are based on the most recent research and statistical analysis available through the USDA, NOAA, USGS, CSU, National Invasive Species Council, Tamarisk Coalition, and others. The following represents a summary of these findings -

Of the riparian acreage in Colorado infested with non-native woody vegetation, 95 % is dominated by tamarisk, although some rivers (White and Republican) have infestations that are predominately Russian olive. These infestations stress water resources and degrade wildlife habitat. Totals for the state are:

1. The total area of Colorado’s riparian land infested with tamarisk is approximately 92,000 acres with an average density of 38%.

2. The total area of Colorado’s riparian land infested with Russian olive is approximately 5,000 acres with an average density of 24%. It is important to note that throughout Colorado’s river systems, Russian olive normally coincides with tamarisk, but generally at a much smaller level of infestation.

3. Current water losses are based on the amount of water tamarisk and Russian olive, both water-loving or phreatophytic plants, are currently using under observed densities, minus the water that would be used by native plants. The most significant water losses occur as tamarisk and Russian olive occupy upland areas within the floodplain that would normally support only dry-land, xeric vegetation such as grasses, sage, rabbit brush, etc. Based on the percentage of upland tamarisk and Russian olive infestations in Colorado, the estimates of current water losses above and beyond what native vegetation would use are approximately 98,000 acre-feet per year.

4. Future water losses assume an infilling of the existing infestation areas that will likely occur over the next several decades based on similar conditions observed in other states (NM, UT, and NV). Future water losses from infilling only (no expansion from existing infested areas) are estimated to be approximately 270,000 acre-feet per year. For comparison, the Denver Water Board used 210,000 acre-feet of water in 2005 to serve over 1,100,000 people.

5. Costs for tamarisk and Russian olive control and revegetation are based on current work being performed by the National Invasive Species Council on an economic model that incorporates Integrated Pest Management practices with planning, design, control, revegetation, monitoring, and maintenance activities.  Estimated costs for the rivers and their major tributaries in the Colorado study area are approximately $96,000,000.

6. If tamarisk control and revegetation occurs on any of these river or tributary sections, some of the water lost to the atmosphere through evapotranspiration will be preserved and will remain within the groundwater and/or surface water regimes.

7. The costs of water retained within the hydrologic system of approximately $1,000 per acre-foot should be compared to the value placed on the purchase of senior water rights because tamarisk is always using water even during a drought. For Colorado, these rights often exceed $10,000 per acre-foot.

8. The method used to develop this inventory information is predicted to identify 85 to 90 percent of tamarisk within Colorado. The remaining percentage represents small pockets of infestations that are scattered throughout the region. Because these outlying infestations are not included in the cost development, approximately a 20% contingency should be added to these cost values to account for their identification and remediation.

Southeastern Utah Tamarisk Partnership (SEUTP)

In March 2006 a partnership was formed to plan collaborative riparian restoration efforts in Southeastern Utah’s Colorado River Watershed. Much of this area is heavily infested by non-native, invasive vegetation, principally tamarisk (Tamarix spp., aka salt cedar) and Russian olive (Elaeagnus augustifolia).

The Tamarisk Coalition aided in the completion of tamarisk and Russian olive inventory efforts for this area through the utilization of GIS technology, high-resolution aerial photography and on-the-ground mapping.

An active group holding monthly meetings in Moab, Utah, SEUTP has wasted no time in making great strides towards the goals outlined in their strategic management plan. The group has identified 21 desired projects for 2008 that are in various stages of action and 7 projects to initiate in 2009.