BOARD01713

• Board Meeting Date: 7/28/2003
• Description: CF Section - Tamarisk Control and Eradication Update
• Board Meetings - Doc Type: Memo

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Impact of Tamarisk Infestation on the
Water Resources of Colorado
May 30, 2003

4.0 Impacts and Costs of Control and Revegetation

Costs for removal vary depending on the expanse of the infestation, existence of other valuable
plant species, and terrain. For aerial helicopter spraying with herbicide the cost is around $200
to $250 per acre (Hart 2003, Lee 2002). For mechanical mulching and herbicide application the
cost ranges from $300 (see Appendix B (Tamarisk Coalition 2003)) to $800 per acre (McDaniel
2000, Taylor 1998). For hand clearing and herbicide application the cost can range form $1,500
to $5,000 per acre (Tamarisk Coalition 2002). Terrain, access, presence of other native
vegetation, etc. all dictate which approach to use. No one approach is right for all situations. The
Colorado Department of Agriculture recommends the strategy of Integrated Pest Management
that matches the right methods for each situation. Additionally, a new bio-control approach that
uses a Chinese leaf beetle is being researched by the U.S. Departments of Interior and
Agriculture and may help further to reduce costs (De Loach 2002).

Removal is only part of the cost. Restoration is the other component which is necessary to bring
back the right native plants and restore habitat. If the objective is to only kill tamarisk, other
invasive noxious weeds will likely take their place if restoration is not part of the effort.
Restoration may occur naturally where native plants are still viable or may require specialized
efforts to restore the riparian lands. In general, costs may range from $50 to $1,500 per acre.

Taking all the information developed above and using an average cost of tamarisk control and
revegetation of$750/acre, 57,000 acres of infestation in 2003, and 170,000 acre-feet of water
potentially saved within Colorado, the resulting overall cost for control and reveg:::tation is
$43,000,000 or approximately $250 per acre- foot of water resources recovered. If the average
costs for tamarisk <fontrol and revegetation are different, the costs will also change. As a
reference point, the cost of purchasing senior water rights in the Denver, Colorado area is valued
at $4,000 to $12,000 per acre- foot (Franscell 2002). Another reference point is the Colorado
River Return Project (aka the Big Straw) that would cost several billion dollars to capture
approximately 300,000 acre-feet of water per year (Bender 2003). Looking at it a little
differently, the costs of tamarisk control and revegetation prevent the future loss of water as this
invasive plant would otherwise spread to a much larger area (see Figures 3 and 12).

Beyond improving the abundance of water, the extremely important side benefits of tamarisk
control and riparian restoration are 1) water quality will be enhanced, 2) wildlife habitat will be
improved, 3) there will be greater bio-diversity among both plants and animals, and 4) there will
be improved conditions for hwnan enjoyment of the river systems. The value of this improved
viability of Colorado's river systems is difficult to measure in terms of dollars but is considered
to be highly significant.

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