Background
Yolo County’s Reclamation District 108 boasts one of the richest water delivery networks along the Sacramento River. Yet, like other water districts, there are valid concerns regarding erosion, sedimentation, and nutrient build-up in the system. US Bureau of Reclamation goals, under the Central Valley Project Improvement Act (CVPIA) and CALFED mandates, are to sustain and restore wildlife habitat and improve water quality, mainly in the Sacramento and San Joaquin Rivers. In fact, what greatly impacts the quality of water and of habitat are the vast acreages of agricultural land beyond the river corridor and the irrigation supply and drainage canal system.

These lands are key to greater water quality demands, future waterfowl populations in the Central Valley Flyway, and many other species dependent on disappearing valley habitats. The Yolo County RCD in cooperation with Reclamation District 108 and funding from the Bureau of Reclamation joined forces to achieve these goals on demonstration sites within Reclamation District 108.

The levee revegetation program was an opportunity to demonstrate that establishing native grasses, rushes, and sedges on levee banks and drainage ditches is a viable alternative to the traditional management of these areas by spraying and disking. By establishing specific vegetation in these locations, the anticipated effects are improved water quality, increased wildlife habitat, reduced soil erosion, and noxious weed suppression. The program included three different planting scenarios--the Lateral 14A Canal bank, the "backside" (field side) of its levee, and an agricultural drainage ditch.

Implementation
Under this program, RD 108 staff reshaped and compacted over one-mile of canal bank to a 3:1 slope between 1999 and 2000, which they and RCD staff and a labor crew seeded and plugged with native grasses and wetland species, including: Creeping wildrye, Barber sedge, Baltic rush, and Shining willow. The most successful planting configuration featured Creeping wildrye on most of the bank and only the more labor-intensive and water-dependent sedges and rushes on the bottom of the bank to provide wave erosion protection.

The backside levee section of the project was planted with a “dry land mix” of native grass that consisted of Purple needlegrass, Slender wheatgrass, and Blue wildrye. This mix was chosen because these grasses can withstand short inundation and also thrive in the drier conditions that exist on the backside levee. Deer grass plugs were planted at the bottom of the northern portion of backside levee in fall 1997 as well. In early 1999, the Reclamation District also treated the backside levee and ditch bank slopes with Clopyralid to better suppress Yellow starthistle.

A mix of native grasses was planted along both sloping sides of the 0.4 mile stretch of drainage ditch. The mix was broadcasted at 25-31 pounds to the acre and consisted of four parts Meadow barley and one part Creeping wildrye. These species were used on the ditch banks because both can withstand winter inundation. In addition to the grass seeding, RCD staff and laborers planted plugs of Baltic rush, Deer grass, Creeping wildrye, and Barber sedge at various levels along the drainage ditch banks.

Costs and Benefits
As part of the program, the RCD contracted researchers to evaluate the actual wildlife benefits of the new plantings, the potential water use of the selected native plants, and the costs of undertaking levee vegetation management with native plants as compared to standard "clean" techniques. Several duck nests were found in the grass planted areas along the ditch bank and back levee, indicating an immediate benefit in terms of nesting cover for waterfowl. No significant pest insect species were observed by the RCD monitoring specialist as well. Water use of native wetland plants is potentially high, but that must be weighed against the benefit of the bank stabilization they provide. In terms of economics, overall costs of vegetation management (including installation) appear to run in the same range as those of periodic levee repair and reshaping, depending on the initial planting success.

A copy of the project's Final Report and analysis is available in our Resource Library folder.