Habitat Restoration
Habitat restoration is very different today than it once was. In the 1980s and 1990s, it was common to plant thousands of trees and riparian shrubs. Today, most of those plantings sites are weed-fields, scour channels or sediment dumps. However, OCWD is still required to plant 10,000 mulefat tree seedlings in the Prado Basin annually as partial mitigation for conserving water behind Prado Dam. Mulefat is a focus for planting because it is a large woody shrub with intricate branching that affords the least Bell’s vireo songbird multiple sturdy nest opportunities. Most of the rest of today’s restoration efforts attempt to reestablish river functions that allow natural revegetation. Where invasive weeds are removed and kept off the flood plain, natural succession occurs quickly and native riparian elements re-plant and flourish. The major problematic invasive species on the Santa Ana River over the past three decades has been a giant grass or reed, Arundo donax. The Santa Ana River was estimated to contain about 10,000 acres of Arundo, but the Santa Ana Watershed Program has removed 3,000 acres of that total and continues working downstream from the upper river.
The Battle to Eradicate Arundo Donax
The widespread Arundo invasion in the Santa Ana River led many people and agencies to support environmental restoration. Arundo took over half of the flood plain, forming impenetrable thickets 30 feet tall covering 8,000 to 10,000 acres. Arundo donax resembles skinny bamboo and became so pervasive, so quickly, that it roused people to action. Arundo provides no redeeming wildlife value and carries fire. It obstructs flood flows and causes expensive beach clean-ups. Compared to native habitat, it consumes nearly three times the water and provides poor stream shading, impacting water quality. Arundo consumes an estimated 56,200 acre-feet (1 AF= 325,900 gallons) of water annually from the Santa Ana River alone.
Purposely Introduced
Arundo is a genus of tall perennial grasses that includes six species native to the warmer regions of Europe. Giant reed is the largest member of the genus and one of the largest living grasses. Native to the Mediterranean region, it was purposely introduced to California in the 1820s when it was planted along the banks of drainage canals in the Los Angeles area for erosion control. The reed also was used as thatching for roofs and fodder for domestic animals. Arundo reproduces vegetatively, with new stalks sprouting from roots and pieces of stalk that break under high flows and replant themselves downstream. Arundo is reported to grow up to three inches per day under optimal conditions.
OCWD and SAWA: Partners in the Santa Ana Watershed for Arundo Removal
OCWD works closely with many partners in the Santa Ana Watershed, including the Santa Ana Watershed Protection Agency (SAWPA) and the Santa Ana Watershed Association (SAWA). Primarily responsible for managing the wildlife resources in Southern California’s largest coastal river system, SAWA serves 4.5 million residents in portions of San Bernardino, Riverside, Los Angeles and Orange counties. SAWA's governing board is comprised of one voting member each from OCWD, Inland Empire Resource Conservation District (RCD), Riverside-Corona RCD, San Jacinto RCD and the Army Corps of Engineers. OCWD manages Orange County’s vast groundwater basin and refreshes its supply with resources from the Santa Ana River. To that end, the District has great interest in maintaining the highest quality water from the Santa Ana River system and monitoring the activities occuring in the upper watershed. SAWA’s mission is to protect and nurture the natural environment of the Santa Ana River. OCWD operates under the philosophy that excellence in water management and stewardship of natural resources go hand-in-hand. The District’s close partnership with SAWA demonstrates this commitment.
Local agencies and organizations with interests in the Santa Ana River recognized the urgent need for Arundo control. Support for its eradication has come from every sector. However, the level and consistency of funding needed to effectively tackle the Arundo issue made it difficult to get significant results prior to the passage of State Proposition 13 in 2002, when $9 million was made available for these important efforts. Arundo grew largely unchallenged on the Santa Ana River for so long that it became the dominant species. By the 1990s, the cost of ridding this watershed of the species was growing by millions of dollars annually.
The Santa Ana River Watershed Program is attempting to counter-balance human-induced changes on the river through control of invasive species, habitat restoration, wildlife management emphasizing endangered species, and public education and involvement. SAWA implements the program in partnership with federal, state, county and municipal agencies, as well as organizations and private interests. Work accomplished on the ground through SAWA is done by the partnering agencies, mostly the RCDs, or under contract with SAWA. Funding for Arundo control and the associated activities has come from grants and mitigation funds.
Fighting Back...and Winning!
Several techniques and tools have been used to remove Arundo, including removal by hand or using loppers, chainsaws, brush cutters, tractor-mounted mulching mowers, arm-mounted tractor/cutters and other approved power equipment. Care is taken to minimize impacts to native habitat that could result from the transport of personnel and equipment and from removal activities.
The methods used for treating Arundo depend on the makeup of the stands. Pure stands of invasive, non-native plants can be tackled with heavy equipment, but hand-removal is the only method allowed in mixed stands or if sensitive species are in the area. Where removal is by hand, stockpile areas are established in order to chip the stalks after surgical, biologist-supervised removal from sensitive habitats. Where access is poor, small piles of cane no higher than three feet can be left to dry above the high-water line. In most areas the material is chipped and scattered on site or removed to be used as mulch elsewhere.
For stands of invasive plants mixed with willows (Salix species), cottonwoods (Populus fremontii), and mule fat (Baccharis salicifolius), no removal or spraying of native vegetation is allowed. All native plants and animals are protected from damage by equipment, personnel, and all other Arundo control activities. Native shrubs and trees may be trimmed to provide access and to protect them from incidental spraying with herbicide, but only under close supervision by a qualified field biologist. The field biologist for each removal site approves the equipment to be used and meets at least daily with the work crew to coordinate avoidance of sensitive species. Endangered nesting birds are not approached closer than 100 meters; their territories are revisited for Arundo removal after nesting is completed.
On the Santa Ana River, Arundo control starts with biomass reduction and removal. Where possible, the canes are chipped in place to pieces smaller than six inches. The roots are left in place to avoid the major excavation required to remove them. New growth is allowed to reach four to six feet tall and then sprayed with a systemic herbicide, “Rodeo” (glycol is the active ingredient), which is taken in through the herbage to the roots. Over sufficient years of re-treatment, the huge root masses eventually dry out and become unable to support new plant growth. Any unabsorbed herbicide degrades to water and other harmless ingredients within 48 hours. As re-sprouting diminishes and Arundo eradication approaches in an area, the need for riparian revegetation is assessed, but the forest usually reclaims treated areas naturally over time. Achieving total eradication of Arundo in some parts of the Santa Ana River Watershed will take decades.
As of July 2007, SAWA raised nearly $30 million and has more than 3,000 acres of Arundo treated and under management. Native riparian forest once again dominates most of those acres and at least 11,250 acre-feet of water is back in the river annually. The alien invasion was once so expansive that the most widely held belief was that Arundo eradication on the Santa Ana River was not possible. We are in the midst of disproving that belief.
Contact Richard Zembal at rzembal@ocwd.com.