IN THIS ISSUE . . .
• The History of the Arroyo Mocho
• How the Arroyo Mocho Got Its Name
• Water in the Arroyo Mocho
• Steelhead Trout in the Arroyo Mocho?
• The Arroyo Mocho – A Riparian Community
• Young Visitors from the Church of Jesus Christ of Latter-day Saints
Livermore is enclosed by three arroyos, or creeks, passing around and thru the city. All three arroyos originate in the hills in the northeastern part of Santa Clara County, or in other streams that feed into them, and flow westerly toward Pleasanton and Dublin. The Arroyo Las Positas, the shortest of the creeks and fed by the Arroyo Seco, runs north of Livermore along Highway 580. The Arroyo del Valle flows south of Livermore; it is dammed at Lake Del Valle and continues its flow thru Sycamore Grove Park toward Pleasanton. The Arroyo Mocho drains the hills the south of Livermore, and runs between Crane Ridge and Cedar Mountain, next to Mines Road, entering the City of Livermore just east of Robertson Park. It flows thru the city northwesterly along the Arroyo Mocho hiking and biking trail, past the Granada Native Garden and the Oak Knoll Pioneer Memorial Park (the site of Livermore’s first public cemetery, now also known as “Daffodill Hill” and “Boot Hill”), and under Stanley Avenue. From there, it turns west toward Isabel Ave. and joins the Jack London bike trail at El Charro Road. On the map below, the Granada Native Garden is the narrow green triangle at the bend in Murrieta Blvd, across the arroyo from Granada High School, and across the street from the Peppertree Plaza Shopping Center.
The History of the Arroyo Mocho 500 years ago, the northern part of the City of Pleasanton was a vast marsh, surrounded by a lagoon. It was fed largely by Tassajara Creek, flowing from the north. At its south end was Tulare Lake, fed from the southeast by the Arroyo del Valle, and from the east by the Arroyo Las Positas and the Arroyo Mocho, forming the lagoon encircling the marsh and lake. Originally, the Arroyo Mocho was an intermittent stream that may have flowed down several channels, carrying water, sand and gravel from the upper watershed, and depositing the sand and gravel over much of what is now the City of Livermore. By 1875, as a result of the railroad, the layout of the city, and farmland, the Arroyo Mocho was confined to the present channel location, where it turned west of Murrieta Blvd. to flow parallel to the railroad. In the early 1990’s, with the construction of the Murrieta Meadows housing devel- opment south of Olivina Avenue and west of Hagemann Drive, Zone 7 created an innova- tive flood protection plan. Two separate channels were created.
The first channel is the original, historical streambed of the arroyo. The Arroyo Mocho Trail follows this comfortable, scenic path which runs alongside Daisyfield and Summertree Streets. It is shaded with mature (but non-native) eucalyptus and native cottonwood and sycamore trees; subsequently it was planted with native toyon, coyote brush and Ceanothus. When water is available in the Arroyo, the flow splits off from the Arroyo at a grate at the foot of the iron bridge near Murrieta Blvd. (see the photo above, left), flows underneath the bridge, and re-enters the historical channel a short distance on the other side of the bridge (see the photo above, right). It parallels the Trail for about three-quarters of a mile to Rockrose St., near the intersection with Sparrow St., where it empties into the second channel (see the photo below, left).
The second channel, called the Stanley Reach Flood Bypass Channel, begins at the iron bridge near Murrieta Blvd. It was constructed to accommodate higher flood flows during periods of heavy rainfall. It runs westward parallel along the Arroyo Mocho Trail, then turns north for a short distance at Isabel Avenue before cutting sharply toward the southwest. Volunteers are currently planting the Stanley Reach with native trees and vegetation. Over time, it is hoped that the seasonal flow of water will cut a meandering path in the confines of this channel, and restore a more natural streambed. The Reach will be opened to the public within the next couple of years.
How the Arroyo Mocho Got Its Name According to Cassell’s Spanish Dictionary, “mocho” can have two connotations. One is “cut short”, or “cropped off”. According to the surveyor Sherman Day, the arroyo got its name because at its western end, about 2 miles from Livermore, it gradually sinks into the gravelly soil and seldom reaches a place where it connects on the surface with the Arroyo Las Positas or the Pleasanton marsh complex. A more somber explanation is related by the local historian Anne Marshall Homan, but attributed to the local scholar Randall Millikin. A second meaning of “mocho” is “mutilated”. According to this story, a missionary priest from Mission San Jose (Father Cueva) and the Mission San Jose’s overseer (Ignacio Higuera) mistakenly wandered into a village of the unfriendly Luechan Indians, thinking they were friendly Asirins. The unreceptive Luechans killed several of Cueva’s party, including Cueva, Higuera, and others. Soldiers from the San Francisco Presidio came to punish the Luechans and recovered the body of Higuera, which had been cut into pieces (that is, mutilated). Hence, the name “Creek of the Mutilated”.
Water in the Arroyo Mocho During the rainy season, the Arroyo Mocho was often gorged with water from occasional large rain storms in the hills and from neighbor- hood runoff. Along with the Arroyo del Valle, it could turn into a raging torrent, threatening to flood out homesteads and drown unwary people caught in its flow. In 1862, rain was so heavy that the valley was under water from Arroyo Road all the way to Pleasanton (but this was followed by a severe drought lasting the next two years). In 1907, heavy floods washed away part of the hillside on the east side of the cemetery at Oak Knoll, just downstream from the Granada Native Garden, and, according to the Livermore Herald, washed away a number of bodies, including a coffin, exposing the bones of its occupant. As the city of Livermore grew, flooding from the arroyo continued to be an annual problem. The Arroyo Mocho would jump its bank and flow down what is now South Livermore Avenue and flood First Street. This problem was lessened when, in the 1920s, Henry Kaiser started mining gravels from the arroyo, thus deepening and widening the arroyo, creating more space for water to flow. Later, in 1955, a storm drain system was constructed to handle residential runoff. This prevented the city from being flooded during a big storm in December, 1955. Finally, as described above, the Stanley Reach Flood Bypass Channel was constructed in the 1990’s, diverting water away from the residential areas in the Murrieta Meadows development. But in the summer, roughly from June thru November, the Arroyo Mocho is naturally dry, as the water it holds gradually disappears into the underlying gravelly water table. Nevertheless, it may come as a surprise that a year-long supply of water in the Livermore Valley was never a problem, as it is now. Water would still be present a few feet below ground level, allowing farmers to grow crops such as alfalfa without the help of irrigation. A Livermore resident as late as the 1950’s describes the arroyo as “a series of ponds, and it would fill up with moss, and there would be lots of toads and then these side ponds would have the tiger salamanders.”
But it is not unusual, during the summer dry season, to still see water flowing down the Arroyo Mocho as it passes the Granada Native Garden, and visitors to the Garden frequently ask where the water comes from. Summer water in the arroyo is water that has been purchased by the Zone 7 water agency from the State Water Project. The water is pumped from the Sacramento-San Joaquin Delta into the South Bay Aqueduct, then is released as needed into the Arroyo Mocho and Arroyo del Valle. The purpose of this release is mainly to help re-charge the water table under the Livermore Valley, from which the residents draw their water supplies, by percolating into the aquifer. It is from this artificial reservoir that we Livermore residents draw our water supplies during the summer. In dry, drought years, the release into the arroyo is turned off and water is pumped from the ground wells (thus continuing to deplete the water table).
Steelhead Trout in the Arroyo Mocho? – Not an Impossibility! Steelhead trout are anadromous (“a-NAD-ro-mus”), that is, they are born in fresh water, live there for 1-3 years, then migrate downstream to the ocean where they mature, then return upstream to fresh water between December and April to spawn (release their eggs and sperm, which become juvenile fish). There is very good evidence that steelhead trout once swam up the Arroyo Mocho to a suitable spawning and rearing habitat in the upper Arroyo Mocho paralleling Mines Road. They also migrated up the Arroyo del Valle, before the construction of the Lake del Valle dam, to the former Lake Tulare (in Pleasanton), which is believed to have been prime trout-rearing habitat. This ended when the arroyos in Pleasanton were drained for development, and later when the dam at Lake del Valle was built in 1968. This ended when the arroyos in Pleasanton were drained for development, and later when the dam at Lake del Valle was built in 1968. Furthermore, steelhead are currently prevented from ascending Alameda Creek or entering the arroyos because of a grade control structure below the BART tracks in Fremont, for which construction of a fish ladder is planned. In all, there were about eleven barriers that needed to be removed or modified between the San Francisco Bay and the upper Arroyo Mocho habitat in order for the steelhead to spawn there. In order to restore steelhead in the Arroyo Mocho and other streams, the Zone 7 Water Agency and other agencies have been removing concrete fish passage barriers and constructing a series of fish “ladders” to enable steelhead to return to their traditional spawning habitats. For their part, the Lawrence Livermore National Laboratory removed one barrier on the upper Mocho near the Hetch Hetchy aqueduct many years ago. Alameda County installed a fish ladder on the Mocho when they constructed flood control improvements, and the Zone 7 Water Agency recently removed a fish barrier on the Stanley Reach bypass channel. Other agencies in the Fremont area have been removing concrete bariers and constructing a series of fish ladders. But there are two remaining concrete structures in the Arroyo Mocho in the Livermore Valley, one at Stanley and Murrieta Blvd. at the old Southern Pacific Railroad Bridge (just downstream from the Granada Native Garden), and another near West Las Positas Blvd. and Highway 680, which need to be slotted so that the fish can get thru. This will restore a more natural stream channel, planted with native vegetation to enhance fish and wildlife habitat. The hoped-for completion of this work is 2018. Once it happens, all the fish will need is water!
The Arroyo Mocho – A Riparian Community At one time, the Livermore Valley was a vast grassland covered with native grasses and wildflowers. Surprisingly, the classic valley oaks were not common in the valley itself. The clay soil of the northern part of the valley was too saturated during the rainy season for oaks; the gravelly soil in the southern valley drained too quickly to leave enough moisture for oaks.
But oaks and sycamores tended to flourish along the banks of the Arroyo Mocho and Arroyo del Valle, which were flooded during the winter and spring, but where the gravelly soil drained quickly and there was a deep supply of water. Such an environment constitutes a “riparian” zone. A riparian zone is an environment in which there is a constant supply of water. This water allows a community of plants and wildlife to thrive there, when they otherwise could not survive in nearby, drier ecological zones.
Even if the riparian zone is dry during part of the year, there is enough water near the surface to enable certain plants, and the animals that depend on them, to take hold and prosper. Typical riparian plants native to California are willows, sycamores, alders, maples, ashes, cottonwood, sedges, rushes, cattails, monkey flower, dogwood and wild grape. Typical animals are beaver, raccoons, fish, turtles, crayfish, ducks, swallows, warblers and blackbirds.
Unfortunately, like much of California, most of the vegetation we see in the Arroyo Mocho is made up of non-native weeds from other continents. But we are able to identify a few California native riparian species growing among the weeds in the arroyo. These include two types of willow (sandbar willow, and red willow or arroyo willow), cottonwood, western goldenrod, mule fat (Baccharis salicifolia), sagebrush, mugwort, black walnut, blackberry, and an occasional valley oak and coast live oak probably planted by man or beast.
The Granada Native Garden itself has a “riparian” zone, winding in and out of the oak woodland and grassland communities. But it is riparian in name only, because it has no water source, only a rocky, simulated creekbed that is wet only when it gets rained on. Nonetheless, the optimistic and enterprising GNG staff has planted a few riparian plants near that zone, in the hope that they will survive on the winter rains and an occasional drink provided by the dedicated staff. With a little extra summer water and loving attention, riparian California natives might do quite well in your residential garden too!
Young Visitors from the Church of Jesus Christ of Latter-day Saints These inquisitive young students from the Church of Jesus Christ of Latter Day Saints, Livermore 3rd Ward, happened to visit the Granada Native Garden when most of the GNG staff was there. This enabled them to take advantage of a guided tour of the Garden, learning something about the Native American uses of the plants that grow there, and about the sticky wonders of gumplant!
Quote du Jour “… the walks and drives along the sycamore and willow-lined banks of the winding Arroyo Mocho would render life ten thousand times worth the living.” – San Francisco Call, 1865, a newspaper that served San Francisco
Guided Tours of the Granada Native Garden Are Available! Are you interested in seeing some of the plants that are described in this Newsletter or in past issues? One or more staff of the GNG are routinely on duty at the Garden on Mondays and Thursdays, roughly between 10:00 AM and 12:00 noon. But it isn’t very hard to arrange a guided visit at other times. If you are interested in scheduling a visit, just email Jim at JIMatGNG@gmail.com .
Correct Restoration of the GNG’s eMail Address The original email address of the Granada Native Garden has been mysteriously restored. You can again reach the GNG staff at JIMatGNG@gmail.com .