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and the riverbank is lined with <br />trailer resorts wherever these areas <br />are accessible by road. For the <br />present, the lower Colorado River has <br />been tamed and molded; what was once a <br />formidable barrier to human settlement <br />now supports a thriving economy based <br />on large-scale corporate agriculture <br />and tourism. <br /> <br />Figure 17. All American Canal origi- <br />nating at Imperial Dam delivers water <br />to the Imperial and Coachella Valleys, <br />CA. Photo by R.E. Tollefson. <br />Figure 18. A-ha-Quin Trailer Park <br />north of Blythe, CA. Note some mature <br />cottonwoods remaining in the back- <br />ground providing some habitat for <br />native bird species. Photo by W.C. <br />Hunter. <br />2.2 FLORAL CHANGES <br />Written accounts of explorers and <br />missionaries in the 1600's to the mid- <br />1800's leave the reader with a vision <br />of cottonwood and willow forests <br />lining the banks of the lower Colorado <br />River, except where bedrock formed the <br />channel. The ever-meandering river <br />would cut away one bank and deposit <br />new fertile soils on the opposite <br />shore, thus providing a new seedbed <br />for riparian trees. Oxbow lakes were <br />frequently formed during flood-stage <br />flows or through natural channel cutt- <br />ing by the river. <br />Slow-growing honey mesquite grew <br />in the broad alluvial floodplains of <br />the valley on the second and higher <br />floodplain terraces. The hot and dry <br />soils and seldom-flooded second ter- <br />race did not affect the status of <br />honey mesquite, as its 15-m (50-ft) <br />root could reach into a deep water <br />table. More important to honey <br />mesquite was the continuing process of <br />second terrace formation as the river <br />cut lower into the floodplain. <br />and filling of emergent wetlands in <br />areas where agriculture generally was <br />not present. <br />The present-day lower Colorado <br />River Valley supports about 200,000 <br />people, mostly in the cities of Yuma, <br />Blythe, Parker, Lake Havasu City, <br />Needles, and Bullhead City. Numerous <br />other small communities are dispersed <br />throughout the agricultural valleys.. <br />Spring floodwater, containing silt <br />and organic debris, spread new soil <br />and nutrients over the floodplain. <br />Trees, shrubs, and vines were abun- <br />dant, making travel along the river or <br />attempts to cross it difficult. Wild <br />grape (Vitis spp.), wolfberry (Lvcium <br />spp.), mistletoe (Phoradendron <br />californicum), and other berry- <br />producing plants provided a rich and <br />varied food resource for wildlife. <br />19