Shallow Subsurface Evidence for Postglacial Holocene Lakes at Ivanpah Dry Lake: An Alternative Energy Development Site in the Central Mojave Desert, California, USA

Abstract

Dry lakes, or playas, in the American Southwest have become important locations for alternative energy solar electric generation systems. Many of these playas have not been investigated for past environmental conditions prior to their development, causing alterations to the shallow sediment profile and altering subsurface chemical and physical data important to recent geologic and hydrologic histories of these areas. Recent studies of these features commonly have focused on surficial data with little or no subsurface geologic data to delineate wet and dry cycles of playa lakes. Many of the playa margins are covered with a surficial layer of alluvial and/or aeolian sands varying in thickness, which could interfere with correct interpretations of data gathered only on the surface material on these lands. Over the past 13,000 years Ivanpah Dry Lake has had at least three episodes of lake highstands up to ~10m in response to climate changes, based on data in this study with the oldest episode dates to ~13,000 cal yrs BP. This study has a link to other sites as many other playas are slated for energy development and could endure subsurface data alteration during site reworking and occupation, resulting in a loss in their collective historical geologic and hydrologic records if more complete studies of important sites are not carried out before developments begin.

Commentary and Review of Modern Environmental Problems Linked to Historic Flow Capacity in Arid Groundwater Basins

“…Case examples 3 and 4 uses data collected mainly by the author and a few water isotope samples from Newton and Allen [24]. Case example 2 uses raw data collected by Waring and Sims and Spaulding and reinterpreted in relation to modern flow capacity [25,26]. Case examples 1 and 5 uses information developed in studies by Miner et al, Duffy and Al Hassan [27], and Hamann et al [13,17,28].…”

“…Sims and Spaulding reported that transitional lakes existed in Ivanpah Valley in two Holocene and one Pleistocene-Holocene transitional period [26]. The deepest and longest was a lake unit that was dated at a high stand at ca.…”

“…Glancy and TRC [69,71] report much more saline groundwater near the playa environment with sodium-chloride and sodium-sulfate signatures with TDS in the 5000 to 20,000 mg/L TDS range. Sims and Spaulding measured soil salinity at Ivanpah Playa [26]. Shallow soil cores for salinity and trace element analysis were collected along a transect on and off the Ivanpah Playa (Figure 6; Table 3).…”

“…TRC reported saline groundwater was from the dissolution of playa evaporite salts but did not discuss issues of aquifer flow capacity [71]. 2, from Waring, 1920) plotted against soil chemistry data from soil cores collected at and above Ivanpah Playa (Table 3, from [26]). On playa samples for groundwater and soils (see Figure 6) show a clearly related evaporite dissolution signature.…”

“…Phreatic playa-lake sediments of high salinity that formed when water tables were at land surface are probably the source of salinity in groundwater beneath Ivanpah Playa (Figure 7, Table 2). There were other more recent but smaller and shorter duration Holocene lakes at Ivanpah Playa [26] that may have both precipitated and leached salts, creating a complex transition from phreatic to vadose playas at various times. A vadose playa has existed primarily at Ivanpah Playa for most of the last two thousand years.…”