Physical and Temporal Isolation of Mountain Headwater Streams in the Western Mojave Desert, Southern California¹

Abstract

Streams draining mountain headwater areas of the western Mojave Desert are commonly physically isolated from downstream hydrologic systems such as springs, playa lakes, wetlands, or larger streams and rivers by stream reaches that are dry much of the time. The physical isolation of surface flow in these streams may be broken for brief periods after rainfall or snowmelt when runoff is sufficient to allow flow along the entire stream reach. Despite the physical isolation of surface flow in these streams, they are an integral part of the hydrologic cycle. Water infiltrated from headwater streams moves through the unsaturated zone to recharge the underlying ground‐water system and eventually discharges to support springs, streamflow, isolated wetlands, or native vegetation. Water movement through thick unsaturated zones may require several hundred years and subsequent movement through the underlying ground‐water systems may require many thousands of years – contributing to the temporal isolation of mountain headwater streams.

Implications of scale-independent habitat specialization on persistence of a rare small mammal

“…The Amargosa River is one of four rivers in the Mojave Desert and runs approximately 235 km from Nevada into the southern Death Valley region of California. The main source of water for the river is seeps and springs, which historically formed wetland and riparian communities that occurred throughout the watershed (Izbicki, 2007). Over the last 100 years though, groundwater pumping and land clearing has resulted in significant loss or alteration of these communities.…”

Solar Energy Development and Aquatic Ecosystems in the Southwestern United States: Potential Impacts, Mitigation, and Research Needs

“…Direct disturbance to intermittent and ephemeral waters would result from site grading and from modifying flow pathways to avoid the erosion of facility infrastructure. Consequently, significant changes in surface water flow could affect the transport of sediment, nutrients, minerals, and organic matter that maintains habitat and geomorphological processes in downstream reaches (Webb et al 2000;Izbicki 2002Izbicki , 2007Larned et al 2010;Smith et al 2011). Although species in arid environments are generally adapted to temporary drying, the abundance and composition of animal communities would be altered in streams experiencing significant changes in the timing, duration, velocity, and magnitude of surface flow (Stanley et al 1994;Lake 2003;Sada et al 2005;Archer and Predick 2008;McCluney and Sabo 2011;Datry 2012).…”

Integrating probabalistic and targeted compliance monitoring for comprehensive watershed assessment

“…Limiting the sampling frame to exclude first and second order streams was necessary because the majority of low order streams are ephemeral and only flow for very short periods following moderate to heavy rain. This is common for headwater streams in the arid western United States, which are often hydrologically isolated from downstream areas and are dry for most of the year (Izbicki 2007). The majority of indicators in this program (e.g.…”