Land Subsidence in the Southwestern Mojave Desert, California, 1992–2009 In cooperation with the Mojave Water Agency (MWA), the U.S. Geological Survey (USGS) has been monitoring land subsidence in the southwestern Mojave Desert of California using satellite Interferometric Synthetic Aperture Radar (InSAR) combined with ground-based techniques. Maps of land subsidence constructed from the InSAR data have proven to be an economical means to evaluate subsidence—with the goal of identifying small problems before they become large ones. The maps of subsidence over the considerably large (nearly 5,000 square miles [mi2]) MWA management area (fig. 1) enabled researchers to detect small magnitude, localized areas of subsidence near five lakebeds. Introduction and Background integrated with results from other USGS/ MWA cooperative groundwater studies into the broader scoped USGS Mojave Groundwater has been the primary source of domestic, Groundwater Resources Web site (http://ca.water.usgs.gov/ agricultural, and municipal water supplies in the southwestern mojave/). This fact sheet combines the detailed analyses from the Mojave Desert, California, since the early 1900s. Increased three subsidence reports, distills them into a longer-term context, demands on water supplies have caused groundwater-level and provides an assessment of options for future monitoring. declines of more than 100 feet (ft) in some areas of this desert (fig. 2 inset) between the 1950s and the 1990s (Stamos and others, 2001; Sneed and others, 2003). These water-level InSAR Reveals Localized Subsidence near Dry Lakebeds declines have caused the aquifer system to compact, resulting InSAR data and field observations reveal land subsidence in land subsidence. Differential land subsidence (subsidence during 1992–2009 in five localized areas near dry lake beds— El occurring at different rates across the landscape) can alter Mirage Lake, Harper Lake, Troy Lake, Coyote Lake, and Lucerne surface drainage routes and damage surface and subsurface Lake (fig. 2). Average subsidence rates at Harper, Troy, and Coyote infrastructure. For example, fissuring across State Route 247 Lakes, were smallest at about 0.3–0.4 inch per year (in/ yr), El at Lucerne Lake (fig. 2) has required repairs as has pipeline Mirage Lake had a slightly higher rate at nearly 0.5 in/yr, and infrastructure near Troy Lake. Lucerne Lake had the highest rate of about 0.6 in/yr. Only two Land subsidence within the Mojave River and Morongo of the areas—Troy Lake and Lucerne Lake—indicated increased Groundwater Basins of the southwestern Mojave Desert has subsidence rates starting in the late 1990s or early 2000s, which may been evaluated using InSAR, ground-based measurements, reflect changes in agricultural land use and (or) a population increase geology, and analyses of water levels between 1992 and 2009 that require more water use, whereas the other three areas subsided (years in which InSAR data were collected). The results of the at fairly steady rates. analyses were published in three USGS reports— Sneed and others (2003), Stamos and others Figure 1. National Agriculture Imagery Program (NAIP) imagery (2007), and Solt and Sneed (2014). from 2012 overlain with dry lakebeds, Mojave Water Results from the latter Agency management area, and other features two reports were 15 in the Mojave Desert, California. Coyote 40 Dry Lake Mojave Valley Troy Calico Mtns Dry Lake Black Mtn Rodman Mtns Barstow Newberry Mtns s tn Johnson M rd 247 O ern Valley 395 Harper Luc e Valley Dry Lake 58 Lucerne e Dry Lake t i s n n a t r M M G Lucerne N O JA Valley VE ntains RI Mou Mojave VER rdino 58 Victorville erna an B El Mirage S Desert Dry Lake R E V I R NA A A T N ins A unta S Mo iel abr U.S. Department of the Interior G 15 Fact Sheet 2017–3053 an U.S. Geological Survey Printed on recycled paper S July 2017 395 Troy Lake Coyote Lake July 2004 - November 2009 July 2004 - November 2009 32G2 Harper Lake July 2004 - November 2009 22R5 ~2 inches 26R1 ~2 inches 30N1 subsidence subsidence 10E1 ~1.5 inches 28R2 subsidence 32G2 Coyote 15 Harper Lake Lake 28R2 58 30N1 26R1 P583 HAR7 BSRY 58 Barstow 22R5 Troy 40 Lake ER 15 247 10E1 IV P588 R E V 40 A J O El Mirage M 0 Lake 20 P582 SCIA 10P2 40 23C3 60 395 Lucerne 25G1 (site ID: 342943116555201) Lake 80 Victorville 25G1 100 AVRY 36F1 level, in feet Water P470 below land surface 120 36F5 140 P606 1950 1960 1970 1980 1990 2000 2010 El Mirage Lake Lucerne May 2005 - May 2009 Valley LDES Lucerne Lake 10P2 July 2004 - November 2009 SDHL 23C3 GMAG ~1.5 inches subsidence 25G1 36F1 247 CTMS 36F5 15 ~3 inches Figure 2. Study area and boundaries of selected groundwater subsidence 62 basins, the Mojave Water Agency management area, and other features. Insets show typical subsidence extents near dry lake beds—l Mirage Lake, Harper Lake, Troy Lake, Lucerne Lake, and Coyote Lake—and a hydrograph of water EXPLANATION Mojave River Groundwater Basin C levels near Lucerne Lake. Subsidence generally occurred A Morongo Groundwater Basin L I near the eastern edge of Harper Lake, western edge of Troy F Mojave Water Agency management area O Lake, near the southern edges of Coyote Lake and El Mirage R Approximate location of fissures N Lake, and south of Lucerne Lake. IA P588 Continuous GPS site and name 0 5 10 15 MILES 36F5 Well and name (symbol colors match 0 5 10 15 KILOMETERS 36F1 hydrograph colors) El Mirage Lake Harper Lake 395 Observations Observations Troy Lake • More than 6 inches (in.) of subsidence occurred at a fairly • More than 6 in. of subsidence occurred at a fairly steady rate of Coyote Lake July 2004 - November 2009 July 2004 - November 2009 steady rate of nearly 0.5 in/yr during 1995–2009. about 0.4 in/yr during 1992–2009. 32G2 • Water levels generally declined by small to moderate amounts • Water levels generally declined in shallow wells to historically Harper Lake in shallow and deep wells during the 1990s and 2000s. low levels since the 1950s, although deep wells generally July 2004 - November 2009 22R5 • Historical groundwater levels (prior to the 1980s) are not recovered after reaching historically low levels in the 1980s. known, although simulations indicate water-level declines • Clay layers ranging from 8 to 89 ft in thickness are present in the since the 1930s (Stamos and others, 2001). shallow and deep parts of the aquifer system. 26R1 ~2 inches ~2 inches • Clay layers ranging from 5 to 295 ft in thickness are present in Results 30N1 subsidence subsidence 10E1 the shallow and deep parts of the aquifer system. • Concurrent and residual compaction in the shallow parts of the ~1.5 inches 28R2 Results aquifer system are likely because water levels were declining subsidence • Concurrent and residual compaction throughout the aquifer and thin and thick clay layers are present. 32G2 Coyote 15 system are both likely because water levels were declining • If compaction has occurred in the deep parts of the aquifer Harper Lake and thin and thick clay layers are present. system, it likely is residual because water levels (at depth) Lake • Historical (simulated) and current (measured) water-level were recovering and both thin and thick clay layers are 28R2 present. 58 30N1 26R1 declines suggest that water levels were likely at or near P583 HAR7 historically low levels, indicating that at least some of the • At least some compaction that may have occurred in the compaction is permanent. shallow parts of the aquifer system is permanent because BSRY 58 water levels have persistently declined. 0 30 Troy Barstow 22R5 40 0 50 40 Lake 2 50 60 4 2 290 70 ER 15 247 10E1 IV P588 4 80 R 6 300 E V 40 90 A 310 J 8 6 O 190 El Mirage M 0 320 8 200 Lake Subsidence, in inches 10 20 330 P582 SCIA 210 10P2 40 12 340 Subsidence, in inches 10 23C3 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 220 60 Water level, in feet below land surface Water 12 230 395 Lucerne 25G1 (site ID: 342943116555201) EXPLANATION 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 level, in feet below land surface Water Lake 80 Lowest recorded Victorville Subsidence Well no. (site ID) and depth well water level 25G1 100 EXPLANATION InSAR 10P2 (343712117361701)—320 feet 43.77 feet Lowest recorded AVRY 36F1 level, in feet Water P470 below land surface 120 Subsidence Well no. (site ID) and depth well water level 36F5 Estimated 23C3 (343555117351202)—700 feet 329.6 feet 140 subsidence InSAR 28R2 (350039117112101)—223 feet 82.4 feet P606 1950 1960 1970 1980 1990 2000 2010 El Mirage Lake Lucerne Estimated 30N1 (350050117204901)—500 feet 223.18 feet May 2005 - May 2009 Valley subsidence LDES Troy Lake Lucerne Lake 10P2 July 2004 - November 2009 SDHL Observations GMAG 23C3 • About 5 in. of subsidence occurred at an average rate of 0 20 ~1.5 inches about 0.3 in/yr during 1993–2009. 30 subsidence 25G1 2 40 36F1 247 CTMS • Subsidence rates increased from about 0.15 in/yr during 50 4 36F5 1993–99 to nearly 0.45 in/yr during 2004–09. 60 70 15 ~3 inches • Water levels fluctuated seasonally but declined persistently 6 80 Figure 2. Study area and boundaries of selected groundwater subsidence 62 to historically low levels in shallow and deep wells since the 90 basins, the Mojave Water Agency management area, and 8 1950s. 100 other features. Insets show typical subsidence extents near • Clay layers ranging from 3 to 100 ft in thickness are present in Subsidence in inches 10 110 dry lake beds—l Mirage Lake, Harper Lake, Troy Lake, the shallow and deep parts of the aquifer system.