Surface water readily disappears underground in some stream reaches (segments) in others, groundwater regularly feeds streamflow. Many parts of the Ventura River stream network are typically dry during much of the year. Consequently, cycles of drought and flood are the norm: as an illustration, in the main settlement of Ojai since 1906, 67 percent of the years have had less than the mean rainfall. However, even in the subhumid upper basin, rainfall is infrequent – falling on as few days in a year as in hot, arid Phoenix, Arizona – but when rain does fall it can be extremely heavy with totals of 20 inches or 510 millimetres in a week not uncommon in the middle and upper basins. Median annual precipitation is 14.12 inches or 359 millimetres in the lower watershed, 19.20 inches or 488 millimetres in the middle watershed, and 28.74 inches or 730 millimetres in the upper watershed. Rainfall varies geographically, seasonally, and from year to year. Much of the Ventura River's route is contained by the steeply sloped sides of the narrow Ventura Valley, with its final 0.7 miles (1.1 km) through the broader Ventura River estuary, which extends from where it crosses under a 101 Freeway bridge through to the Pacific Ocean. Matilija Creek is Ventura River's highest volume tributary, followed by San Antonio Creek, which joins the Ventura River from the east halfway to the ocean Coyote Creek enters the river from the west about 7 miles (11 km) from the river mouth and Cañada Larga Creek from the east a few miles downstream. The smallest of the three major rivers in Ventura County, the Ventura River's source stream is Matilija Creek, from its confluence with North Fork Matilija Creek. The river flows 16.2 miles (26.1 km) from its headwaters through to the Pacific Ocean. Income varies widely, and several areas qualify as disadvantaged or severely disadvantaged communities. The population is 58% white, 37% Hispanic or Latino, 2% Asian, and 3% other races. The population is approximately 44,140, which represents just 5.4% of Ventura County's population (as of 2010 Census). The population of the watershed is relatively small and the rate of growth low. Only 13% of the larger city of Ventura lies within the watershed, adjacent to the coast on the lower stretch of the Ventura River. The smaller of the two cities, Ojai, lies entirely within the watershed, 13-mile inland (21 km) at an elevation of 746 feet (227 m). The populated area includes two cities and a number of unincorporated communities. The watershed's southern half has agriculture as the dominant land use, with irrigated citrus and avocados as the primary crops while a significant area of land is used for cattle grazing. The northern half of the watershed lies within Los Padres National Forest. ĭeveloped land (excluding grazing) comprises only about 13% of the total land area in the watershed. Most of the watershed's primary streams and drainages are unchannelized, though the natural hydrologic patterns have been modified by two dams (the Casitas and Matilija) and three levees (the Ventura River, Casitas Springs, and Live Oak). Conditions in much of the watershed remain natural and undeveloped, with 57% of its land area in protected status. Valley floors are home to communities and farms. The Ventura River watershed encompasses 226 square miles (590 km 2) consisting of steep mountains and foothills, with altitudes ranging from 6,010 feet (1,830 m) to sea level.
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