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This
subsection includes the alluvial fans and basin floor in Chuckawalla Valley,
between the Eagle Mountains on the north-northwest end and Palo Verde Valley
on the east-southeast end. It has a very hot arid climate.
MLRA 30g.
Lithology and Stratigraphy. Quaternary alluvial, lacustrine, and eolian deposits predominate in this subsection.
Geomorphology. This section is on very gently to moderately sloping alluvial fans, nearly level basin floors, and dry lake beds. The elevation ranges about 400 to 1800 feet. Fluvial erosion and deposition and eolian deflation and deposition are the main geomorphic processes.
Soils.
The soils are mostly Torrifluvents, Torripsamments, Torriorthents and Haplocambids
on younger fans and basin-fill, and mostly Haplocalcids, Petrocalcids,
Haplargids, Argidurids, and shallow Haplodurids on older fans. There
are Typic Torripsamments in eolian sand. The soils are well drained,
except on poorly drained playas. There are Haplogypsids and Haplosalids
on poorly drained playas lacking vascular plants. Soil temperature
regimes are hyperthermic; and soil moisture regimes are aridic.
Vegetation. The predominant natural plant communities are Creosote bush series and Creosote bush - white bursage series. Mixed saltbush series is common and Mesquite series occurs on basin floors. Blue palo verde - ironwood - smoke tree series occurs in washes and on some sand dunes.
Characteristic series by lifeform include:Climate. The mean annual precipitation is about 3 to 4 inches; it is all rain. Mean annual temperature is about 65° to 75° F. The mean freeze-free period is about 275 to 325 days.
Grasslands: Alkali sacaton series, Desert sand - verbena series, Indian ricegrass series, Pickleweed series, Saltgrass series.
Shrublands: Allscale series, Bush seepweed series, Brittlebush series, Brittlebush - white bursage series, Catclaw acacia series, Creosote bush series, Creosote bush - white bursage series, Desert-holly series, Fourwing saltbush series, Iodine bush series, Mixed saltbush series, Ocotillo series, Teddy-bear cholla series, White bursage series.
Forests and woodlands: Blue palo verde - ironwood - smoke tree series, Mesquite series.
Surface Water. Runoff is rapid from mountains and alluvial fans and slow from basin-fill. The drainage is internal, toward Palen Dry Lake or Ford Dry Lake, but runoff generally sinks below ground before reaching these dry lakes. Streams have no water in some years and are dry most of each year in other years. There is temporary ponding on playas, or dry lake beds, in some years.
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