Castac Lake Valley

2014: CASGEM basin prioritization – Very Low

2018: Draft basin priority – Very Low. Groundwater levels comments:

• 1) CASGEM/WDL/GWIDS: No data or data insufficent to determine GWL status. Source: DWR
• 2) Overdraft and Subsidence, see lawsuit Pg 4 #10: In recent years, however, population growth and agricultural demands have led to increased pumping and declining groundwater levels… Source: Willis v Los Angeles County Waterworks et al

Subsidence comments:

• 1) “Most groundwater pumping in the valley occurs in the Antelope Valley groundwater basin, which includes the rapidly growing cities of Lancaster and Palmdale. Groundwater-level declines of more than 270 feet in some parts of the groundwater basin have resulted in an increase in pumping lifts, reduced well efficiency, and land subsidence of more than 6 feet in some areas.” Source: USGS – Scientific Investigations Report 2014?5166 Groundwater-Flow and Land-Subsidence Model of Antelope Valley, California
• 2) Estimates of pumping in 2005 are in the 110-120K AF. 2012 was 90K AF. Court Adjudicated (pending?); Prior to 1972, groundwater provided more than 90 percent of the total water supply in the valley; since 1972, it has provided between 50 and 90 percent. ; Nearly four feet of land subsidence at Edwards Air Force Based between 1926 and 1992. From 1990 to 2000, nearly 0.4 feet of subsidence (Sneed and Galloway, 2000). Fissures range from one inch to over one foot wide and can be as long as 700 feet.. Ground deformation has affected the use of the lakebed as a runway for aircraft and space shuttles (Phillips, et al., 2003). Source: Aquifer-System Compaction and Land Subsidence: Measurements, Analyses, and Simulationsthe Holly Site, Edwards Air Force Base, Antelope Valley, California 

2018 Final Basin Prioritization: Unchanged at Very Low.