The Kern National Wildlife Refuge was established in 1960 by executive order as a wintering area for migratory waterfowl and other wetland dependant species. Of the 11,249 acres that comprise the Refuge, approximately 5,000 to 6,500 acres consists of seasonal wetlands, irrigated moist soil units, and riparian habitat. In addition, uplands total about 3,600 acres and are made up of grassland, alkali playa, and Valley sink scrub habitats.
Water is a critical component of wetland management, including not only quantity but also timing and availability. Early in the history of the Refuge, water was supplied by deep wells or purchased annually from local water districts, but eventually both became cost prohibitive. It wasn't until 1992, when Congress passed the Central Valley Project Improvement Act that the refuge was provided with a reliable annual water supply.
All wetlands are seasonal in nature. Fall flood-up begins in mid-August and reaches a peak of nearly 6,500 acres of flooded marsh habitat by January. Habitat is maintained through February after which a slow draining of the wetland begins. Selected units are irrigated during the late spring and early summer months to encourage plants to grow to provide food for wintering and migrating birds the following fall.
Moist Soil Units
Wetland habitats are divided into moist soil and seasonal units. Moist soil areas, which comprise approximately 2,300 acres, are covered by shallow water depths (less than 6" deep). They are maintained by irrigation in the late spring and summer to encourage food plant growth. Swamp Timothy, watergrass, and sprangletop typically grow in moist soil areas. Once every five years, moist soil units undergo a removal of all vegetation and a re-working of the soil to improve aeration and fertility.
Seasonal marsh units generally maintain water depths ranging form 4 feet to only a few inches and generally do not receive a summer irrigation. Cattail, hard-stem bulrush, burhead weed, alkali bulrush are plants typically found in these units.
The Refuge also contains some drier areas. Riparian areas are lush, filled with plants and trees that provide protective cover and nesting sites for many wildlife species. Willow and cottonwood trees provide shade and feeding areas for migrating birds, as well as year-round habitat for a host of aquatic animals.
Uplands are not irrigated and primarily get their water form rain. These closed units, which occupy the northeast and northwest portions of the Refuge, have been set aside for threatened and endangered species such as the San Joaquin kit fox, Tipton kangaroo rat, and the blunt-nosed leopard lizard.
Salt Cedar is a deciduous shrub native to Southern Europe into Mongolia, Tibet, Central China, and North Korea. It was first introduced in the United States in the early 1800s and has since become a major problem in many arid areas of the arid regions of the southwest. Prior to 1980, this invasive species was seen on the Refuge as isolated plants. Floodwaters from the 1982-1983 flood year spread the highly viable seeds throughout the Refuge. Currently 25% of the Refuge is covered with salt cedar. Control methods range from mechanical removal coupled with herbicide treatment and foliar herbicide treatments.