Rio Mesa Solar Electric Generating Facility

Wooded Desert Mesa: April Field Trip

April 2012 - Members of Basin and Range Watch visited the site of the Rio Mesa solar project on Palo Verde Mesa near Blythe, California. The area is full of life on an ancient terrace overlooking the Colorado River, and surrounded by picturesque jagged peaks. We started on the old Bradshaw Trail that heads westward from the river, and old trade route, then explored south on the few dirt roads that traverse the project site.

^Southwestern speckled rattlesnake (Crotalus mitchellii pyrrhus) crosses Bradshaw Trail in the low hills west of the project boundary at dusk.

Vast Microphyll Woodlands

Blue palo verdes (Parkinsonia florida) bloomed yellow, Desert ironwood (Olneya tesota) trees, and Catclaw acacia (Acacia greggii) formed numerous long thickets along washes, and the occasional Smoke tree (Psorothamnus spinosus) and Ocotillo (Fouquieria splendens) dotted the arid landscape. Creosote (Larrea tridentata), Wolfberry (Lycium sp.), and Big galleta (Hilaria rigida) were also common. Microphyll means "small leaves" referring to the numerous multiple small leaves along a stem, an adaptation in the desert to reducing the area from which water is lost.

^Looking south from Bradshaw Trail over desert pavement and ironwood forest towards the Palo Verde Mountains. Much of this view is the solar project site in Metropolitan Water District land.

^Tall ironwood trees on the project site would have to be bulldozed and cleared.

^Blooming palo verde.

^Large wash with microphyll woodland, and the Palo Verde Mountains. This is the southern edge of the project site.

^Large wash at the southern edge of the project site looking east into the Colorado River area.

^Palo verde trees at the edge of the Mule Mountains.

^The Mule Mountain peaks in the distance with Ironwood trees in the foreground.

^Looking eastwards off the edge of Palo Verde mesa at the project site over the Colorado River Valley and into Arizona.

^Ocotillos and creosote on the project area of the mesa.

^Dusk looking from the project site to the Mule Mountains.

^Looking across the project site with extensive microphyll woodland towards the Palo Verde Mountains.

^Biological soil crust.

^Desert ironwood.

^Smoke tree on the eastern edge of the project site, with the Colorado River in the distance.

^Unexploded ordinance may be present.

^Wash and Mule Mountains.

^A few small dirt roads branch off Bradshaw Trail. This is the area where very rare Elf owls (Micrathene whitneyi) have been reported, normally an Arizona species.

^Dusk in the ironwood washes on the project site.

^Dusk on a windy spring evening.

^We found scat of Burro deer (Odocoileus hemionus eremicus), which inhabit the ironwood thickets.

^Project site at dusk.

^Big galleta grass in a sand wash.

^ A kit fox or coyote burrow.

^Wash with palo verde.

^Desert ironwood tree.

^Pincushion flower (Chaenactis sp.).

^Desert ironwood.

^Extensive palo verde-ironwood stands on Palo Verde Mesa at the project site.

^Speckled rattlesnake moves into an ironwood thicket at dusk.

^Some palo verdes flowered during our visit.

Bird list:

  • Verdin (Auriparus flaviceps)
  • Phainopepla (Phainopepla nitens)
  • Mourning dove (Zenaida macroura)
  • Gambel's quail (Callipepla gambelii)
  • Cactus wren (Campylorhynchus brunneicapillus)
  • Loggerhead shrike (Lanius ludovicianus)
  • Red-tailed hawk (Buteo jamaicensis)
  • Osprey (Pandion haliaetus)


Reptile list:

  • Side-blotched lizard (Uta stansburiana)
  • Western whiptail (Cnemidophorus tigris)
  • Zebra-tailed lizard (Callisaurus draconoides)
  • Southwestern speckled rattlesnake (Crotalus mitchellii pyrrhus)
  • Sidewinder (C. cerastes)
  • Desert tortoise (Gopherus agassizii)


Mammal list:

  • Round-tailed ground squirrel (Xerospermophilus tereticaudus)
  • Desert kit fox (Vulpes macrotis)
  • Coyote (Canis latrans)
  • Burro deer (Odocoileus hemionus eremicus)
  • bats (Chiroptera)



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