1860s TO 1920
This report focuses on Colorado River development from roughly the middle of the 19th century until the present. Prior to this period there was a rich and extensive history of exploration, irrigated agri- culture, and related means for coping with drought and aridity. Span- ish explorers led by Coronado in 1540, as well as other expeditions and individuals, referred to the river as the “Colorado” in reference to the reddish silt that—before construction of storage dams—was sus- pended in the stream’s lower reaches. Irrigation in the southwestern United States dates back several centuries to the Hohokam of south- ern Arizona, who cultivated fields in what is now the greater Phoenix metropolitan region. Spanish settlers, especially in present-day northern New Mexico, later established acequia (ditch) systems for irrigation in the 1700s; many of these are still in use. For purposes of this report, discussions of contemporary water management and sci- entific issues related to the Colorado River basin date back to the 19th-century origins of Anglo-American irrigated agriculture, and to the growth of urban water demand initiated by Los Angeles in the early 20th century. Well before this period, there was an extensive prehistory of water use in the basin, which is chronicled in a substan- tial body of archaeological and ethnohistorical research (see Brooks, 1974; Dart, 1989; Fish and Fish, 1994; Meyer, 1984). Although a review of long-term social processes dating back several centuries is beyond this report’s scope, this body of knowledge could be a valu- able resource in helping water managers better cope with hydrocli- matic variability. It could be used, for example, in scenario construc- tion, water conservation practices (e.g., reviewing past water harvest- ing techniques), and forecasting by analogy (see Glantz, 1988).
From the mid-19th century through 1920, the Colorado River ba- sin saw both Anglo-American exploration and the inception of large- scale irrigated agriculture. In the 1860s the upper Colorado River basin constituted one of the last great unexplored regions of North America. Explorer and scientist John Wesley Powell led two impor- tant expeditions through this region, the first in 1869 down the Colo- rado River through Grand Canyon, and the second 2 years later. Boosted by a popular self-penned account of Powell’s expeditions, by
the late 19th century the Colorado watershed—or at least that encom- passing the Grand Canyon and Utah’s Canyonlands—had attained almost mythic status in the minds of many Americans (Powell, 1895; Stegner, 1954; Worster, 2000).
The period from the mid-1860s to 1920 witnessed the diffusion of many new irrigation systems throughout the Colorado River basin. In the 1860s Mormon farmers were cultivating fields with water from the Virgin River and, in central Arizona, major irrigation diversions from the Salt and Gila rivers were under way by the end of the dec- ade. In the 1870s farmers began diverting lower Colorado River wa- ter for irrigation near Blythe, California, and in the 1880s farmers near Grand Junction, Colorado, were using upper Colorado River flows to nourish crops. These early diversions were relatively minor compared with later development but they established an important precedent that demonstrated future economic and agricultural possi- bilities (Hundley, 1975; Kleinsorge, 1941; Raley, 2001; Zarbin, 1984, 1997).
Plans for the first major diversion of the Colorado River began in the late 1890s. During this period the California Development Com- pany launched an ambitious plan to divert Colorado River water from near the Mexico-U.S. border and convey it more than 50 miles west to a remote part of Southern California known to 19th-century geogra-
phers as the “Colorado Desert.” Company boosters changed the re- gion’s name to the more inviting “Imperial Valley” and set out to cre- ate an agricultural empire encompassing several hundred thousand acres. Imperial Valley irrigation offered enormous possibilities be- cause (1) much of the valley was below sea level, (2) as much as 3 million acre-feet of water could be taken annually from the Colorado River to support irrigation, and (3) in ancient times a channel of the Colorado River—the “Alamo River”—had carried water into the val- ley. This latter factor proved particularly important because the Alamo Canal of the California Development Company largely fol- lowed the ancient channel formed by the Alamo River—thus necessi- tating little new (and expensive) excavation. A downside to the pro- ject (at least in the eyes of many investors and farmers) was that the company’s Alamo canal extended through Mexican territory for 50 miles before crossing the international border back into the United States (De Stanley, 1966; Hundley, 1992; Starr, 1990).
By 1900 the California Development Company was delivering water to the Imperial Valley and thousands of settlers were flocking to the region. In 1904 the upper end of the Alamo Canal was recon- figured to counter problems with silt accumulation; unfortunately for the company, in 1905 this canal’s newly built wooden headgate was overwhelmed by heavy floods. For the next 2 years the entire flow of the Colorado River descended into the Imperial Valley, drowning crop land and creating a large new waterbody—the Salton Sea— which still exists today. In 1907 the canal heading was finally closed off through laborious efforts of the Southern Pacific Railroad and the flooding stopped, but not before the California Development Com- pany lay in financial ruin. After the company’s remaining assets passed to the newly formed Imperial Irrigation District in 1911, local farmers began soliciting federal government support for (1) a flood control dam across the Colorado River to prevent a recurrence of the 1905-1907 disaster, and (2) construction of an “all-American” canal that could deliver Colorado River water to the Imperial Valley with- out passing through Mexico. Intense lobbying for what eventually became the Boulder Canyon Project Act was under way by 1920 (De Stanley, 1966; Hundley, 1975; 1992; Starr, 1990).