LADWP Vegetation Management Types

During the 1980s, the County and LADWP collaborated to develop a cooperative water management plan and in 1991 entered into the Inyo County/Los Angeles Long Term Water Agreement (LTWA). The overall goal of the LTWA is to manage ground and surface water resources, in order to provide a reliable supply of water for export to Los Angeles and for use in Inyo County while maintaining healthy groundwater dependent vegetation communities found in Owens Valley.

The LTWA contains management strategies for avoiding long term groundwater mining from aquifers of Inyo County, as well as avoiding or minimizing impacts to vegetation as a result of groundwater pumping or changes in surface water management practices. Vegetation is used as the principal indicator of environmental quality associated with ground and surface water activities in Owens Valley. As part of this effort, vegetation in Owens Valley has been classified based on the dominant species documented on vegetation inventories conducted by LADWP between 1984 and 1987. As contained in the LTWA, approximately 227,000 acres of vegetation on the valley floor have been classified as follows:

A. TYPE A CLASSIFICATION. This classification is composed of vegetation communities with evapotranspiration, approximately equal to average annual precipitation. Species in these communities include big sage (Artemesia tridentata), allscale (Atriplex polycarpa), and Mojave indigo bush (Psorothamnus arborescenes), among others. This classification includes approximately 150,347 acres.

B. TYPE B CLASSIFICATION. This classification is comprised of scrub dominated communities, including rabbitbrush and Nevada saltbush communities with evapotranspiration greater than precipitation. This classification includes approximately 10,390 acres.

C. TYPE C CLASSIFICATION. This classification is composed of grasslands/meadow vegetation communities with evapotranspiration greater than precipitation. The communities comprising this classification exist because of high groundwater conditions, natural surface water drainage, and/or surface water management practices in the area, i.e., conveyance facilities, wet year water spreading, etc. Species in this classification include saltgrass (Distichilis spicata), alkali sacaton (Sporobolus airoides), and Mexican rush (Juncus mexicanus), among others. This classification includes approximately 42,013 acres.

D. TYPE D CLASSIFICATION. This classification is composed of riparian/marshland vegetation communities with evapotranspiration greater than precipitation. The communities comprising this classification exist because of high groundwater conditions, natural surface water drainage, and/or surface water management practices in the area, i.e., conveyance facilities, wet year spreading, etc. Species in this classification include common reed (Phragmites australis), cattail (Typha latifolia), and hardstem bulrush (Schoenoplectus acutus), among others. This classification includes approximately 5,580 acres.

E. TYPE E CLASSIFICATION. This classification is composed of areas where water is provided to LADWP-owned lands for alfalfa production, pasture, recreation uses, wildlife habitats, livestock, and enhancement/mitigation projects. This classification includes approximately 18,830 acres.

Type A classification is not affected by groundwater pumping or by changes in surface water management practices since such vegetation survives on available precipitation. Areas of Type B, C, and D classification will be managed for groundwater pumping and changes to surface water to avoid causing significant decreases in live vegetation cover, and to avoid causing a significant amount of vegetation comprising these classifications to change to vegetation in a classification type which precedes it alphabetically. Type E classification is lands supplied with water. These lands will be supplied with water and will be managed to avoid causing significant decreases and changes in vegetation.