Eradication of the saltcedar shrub is a promising water conservation strategy.

Saltcedar (also known as tamarisk) was introduced into the western United States in the early 1880s for windbreaks and erosion control. It had near-perfect attributes. It lived 50 to 100 years, its growth was as dense as any shrub or tree, and it reached heights of six to 26 feet. It spread readily, sending out roots or submerged stems during flooding or by scattering prolific numbers of seeds. The plant was well adapted to arid climates and it was flood-tolerant. If fire struck the local landscape, it could adapt by sending out long taproots that could reach into deep water tables.

Over time, these same attributes have proved to be problematic. Deep roots interfere with natural aquatic systems. According to the National Park Service, a single large saltcedar can consume up to 300 gallons of water per day, an unwelcome feature in dry western areas. Once established, saltcedar is capable of growing a foot per month. It displaces native plant communities, causing native wildlife habitat to decline, and increases the frequency, intensity and impacts of fires and floods.

How Big Is The Problem?
As the human population grows and strain increases on limited western water supplies, the saltcedar problem becomes more evident. Columnist George Will of the Washington Post wrote, “Tamarisks, also known as saltcedars, are especially thirsty trees that slurp as much as 500,000 acre-feet (about 163 billion gallons) a year from the Colorado—almost twice Nevada’s allocation from the river.” That’s enough water to supply about 1 million households each year.

The Colorado River is a crucial source for Metropolitan Water District customers. With seven states and Mexico competing for its waters, every drop counts, particularly in drought periods. Metropolitan’s conservation programs have traditionally focused on advancing water-saving technologies and encouraging changes in human behavior. The time may be right to expand the West’s “conservation portfolio” to include non-native plant mitigation, and saltcedar is a prime candidate. As the numbers above demonstrate, its removal could provide a bountiful water “harvest.”

The Bureau of Reclamation estimates saltcedar coverage in the 17 western states at 500,000 to 1.5 million acres. The estimated value of the resulting water loss runs between $133 million to $265 million.

Long-Term Commitment Needed For Control
In order to derive lasting benefits, saltcedar management will require a long-term commitment to prevent re-infestation. A combination of mechanical, chemical and biological methods would offer the most effective control. Ongoing removal of existing growths and seedlings, along with continued monitoring, is essential to prevent re-growth.

The Bureau of Reclamation is supporting a coordinated eradication effort that encourages resource managers to control saltcedar as a means to restoring stream flows and augmenting supplies. A “follow-up” effort would then restore native species —such as cottonwoods and willows —along the shorelines of reservoirs, lakes, rivers and floodplains. In addition to water conservation, these steps should improve wildlife habitat and reduce hazardous fuel loads.

Like any ecological initiative, proposals to eradicate saltcedar raise questions that are viewed from diverse perspectives. The proposed use of beetles to consume saltcedar plants could have unintended negative impacts. Some people have raised questions about the removal expense and there is a debate over whether or not there is really a water savings when replacing tamarisk with native plants; others consider saltcedar eradication a promising prospect for effective water conservation in the Southwest, and that after scrutinizing the costs and benefits, we may find it’s a worthy multi-agency project with broad public benefits. I believe it’s worth a try—based on the magnitude of savings and success with another water guzzling invasive plant, Arundo donax (giant cane). The Santa Ana River Project invested $1 million in Arundo removal and saved $5 million in water costs. In my book, that’s a great return!

Coordinated Efforts
Metropolitan is among a growing list of supporters for California Assembly Bill 984, which would require the California Department of Water Resources to cooperate in a saltcedar eradication program in the Colorado River Basin, replacing the foreign plantings with native varieties including willows and cottonwoods.

By removing saltcedar at manageable locations, we can realize additional water savings. Or, think about it this way—through the harvest of a thirsty plant we can realize an increase in our water “yield.”

Glen Peterson is vice president of the Association of California Water Agencies (ACWA) and also serves on the Board of Directors for the Metropolitan Water District of Southern California, representing Las Virgenes Municipal Water District.