Mapping & Inventory

In 2007, the Tamarisk Coalition completed an inventory of tamarisk infestations on all the major rivers and their main tributaries in Colorado for the Colorado Water Conservation Board (CWCB). This included Russian olive data where appropriate. The purpose of this work was to:

1. establish and implement an inventory protocol that would be economical to perform,
2. provide a relatively accurate understanding of the extent of the tamarisk problem in Colorado,
3. develop water and wildlife habitat impacts,
4. estimate the cost of restoration. 

An accurate assessment of impacts and costs are essential for future decisions on the tamarisk issue.

This inventory and mapping effort was preceded by the following two actions:

1. Governor Bill Owens issued Executive Order D-002-03 in 2003 directing state agencies to coordinate efforts for the eradication of tamarisk on public lands, and 

2. In response to this directive, the Department of Natural Resources in cooperation with the Department of Agriculture completed the 10-Year Strategic Plan on the Comprehensive Removal of Tamarisk and the Coordinated Restoration of Colorado’s Native Riparian Ecosystems, January 2004. 

The direct and indirect actions that have resulted because of the completion of the tamarisk inventory and mapping by CWCB are:

1. In 2006, CSU sponsored a more complete tamarisk research conference.

2. Palisade Insectary has become the region’s lead facility for research and monitoring of the biological control insect, tamarisk leaf beetle.

3. Colorado's Department of Local Affairs is funding comprehensive tamarisk planning efforts for the Colorado, Gunnison, and Dolores watersheds. Similar planning efforts have been completed for the Arkansas, Purgatoire, and San Juan watersheds. These planning efforts rely heavily on the completed inventory and mapping efforts.

4. Western Governors Association and Tamarisk Coalition are working with USDA to utilize provisions of the Farm Bill to aid agricultural lands on tamarisk control.

5. Colorado’s Congressional delegation strongly supported the passage of the Saltcedar and Russian Olive Control Demonstration Act which was signed by President Bush on October 11, 2006. This act will support large-scale demonstrations, research, and the development of long-term management and funding strategies.

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 shapefiles and site specific characteristics data, has been transformed into a digital GIS database which is now available on the USGS invasive species website:  www.niiss.org .

Results

The inventory of Colorado’s rivers and their major tributaries is summarized in Table 2.  Information 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.

Individual Watershed and Area Mapping Reports are available below:

• 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

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.