The Putah-Cache Bioregion Project:
Putah Creek: Four Versions At UCDCourtesy of Peter Moyle, Ph.D.
This trip will acquaint you with parts of the campus you may not have seen, and with what happens to riparian (=stream side) and aquatic habitats in an area intensely used by humans. The background section gives a short history of Putah Creek, while the trip guide gives directions and information about the trip stops.
Originally created for a UC Davis class, the field trip guide includes questions you may want to consider in your travels. It may make you think about concepts that are important in our culture but rarely given much thought, such as "nature", "wildlife", "natural environments," and "pristine ecosystems."Background
The portion of Putah Creek that flows past UC Davis is the lowermost reach of a creek that drains a large watershed. The creek's origins are in springs on Cobb Mountain, part of the Mayacmas Mountains (on the western edge of Napa and Lake counties). It flows through Middletown in the upper watershed and eventually empties into Berryessa Reservoir, filled in 1957. Below the reservoir, there are about eight miles of cold 'tail water' that forms an excellent trout stream before the water is diverted at Putah Creek Diversion Dam for use in Solano County and at UC Davis.
Below the diversion dam, the creek flows (usually) through a channel confined by levees through Winters, past Davis, and then into the Yolo Bypass. The bypass is a flood control channel that drains into the Sacramento River. If a single theme stands out in the history of lower Putah Creek, that theme is change. Lower Putah Creek has been modified from a free-flowing, un-managed waterway to a regulated stream following an unnatural channel and supporting many exotic (introduced) species of plants and animals. The creek once supported over 22,000 acres of lush riparian forest between the foothills and the Sacramento River, but now supports only a small fraction of that.
The Patwin people were our predecessors as the human inhabitants the region. The Native Americans lived here for centuries, modifying the landscape through the use of fire and exploitation of the large animals. However, much larger changes to the landscape came about only after the Patwin were eliminated by disease, dislocation, and murder. In the early 1800s Spanish and Mexican peoples settled here, in the period of land grant rancheros. The Spanish released semi-wild longhorn cows into the region and soon huge herds were trampling the landscape. With the coming of statehood in 1850, land ownership, which had been a rather risky and tumultuous proposition, became organized and land went mostly to newly-arrived settlers, who plowed the land and diverted the streams for irrigation.
Isaac Davis and his son, Jerome, were early settlers who owned a large farm on Putah Creek. In 1867, Jerome Davis sold a large tract of land to promoters from the California Pacific Railroad and he set the stage for rapid land speculation and the development of "Davisville" as a train stop. In the early years, Davisville was periodically flooded by high flows from Putah Creek.
In 1872 efforts began to divert Putah Creek away from the city. These efforts resulted in the dredging of a new channel, the "south fork" of the creek, which is the present-day creek channel on the south edge of the campus. The levees on both sides of the creek bed are the remains of this early dredging operation, which was enlarged by the Army Corps of Engineers' Putah Creek Project in 1943-49. As a result of the straightening of the channel, the stream cut downward, creating a channel that is 10-20 feet lower than the original stream bed. This down-cutting was largely halted by the elimination of most flood flows by the closing of Monticello Dam in 1957. The former flood flows are now stored in Berryessa Reservoir. The stabilized creek now supports diverse populations of native and alien fishes, as well as small runs of salmon and other sea-run fish.
The narrow, cement-lined canal that meanders through the University Arboretum follows the original creek bed but has no natural flow; it is more a slough or pond than it is a creek. The channel is labeled the Arboretum Waterway, although the wide section in front of Mrak Hall is called Spafford Lake after Ed Spafford. He was the vice chancellor who was instrumental in setting up the Putah Creek Riparian Reserve. On the west side of Highway 113 (which has cut through the old creek channel) the original creek channel is visible as a depression that wanders past the sheep barns and through a fenced area of trees and thistles (Spieth Reserve).
Actually, it is a bit of a miracle that the creek contains any water at all today. During the 1987-1992 drought, the south fork nearly dried up several times, with water on campus maintained in a few pools by effluent from UCD aquaculture facilities and the sewage treatment plant. The flow had been cut off by the Solano Irrigation District, which controls the water flowing from Monticello Dam and Berryessa Reservoir. Some flows were reluctantly restored only after "pressure" was applied by the Putah Creek Council, a coalition of environmentalists, creekside landowners, and concerned citizens. At once point the Putah Creek Council actually purchased water to keep the creek (and its inhabitants) alive! The university and a private company (Alhambra Company) also donated water to keep the creek alive.
The result of this struggle was a trial in March and April 1996, to resolve a suit filed by the Putah Creek Council, the City of Davis, and the University. The judge awarded the creek more water but the decision has been appealed. The battle for Putah Creek's limited water is thus far from over and mirrors battles taking place statewide, with citizen groups fighting to keep streams from being totally diverted for irrigation and urban development.
You should avoid poison oak, a shrub standing a meter or more high in the Putah Creek Reserve. Poison oak has shiny oak-like leaves in clusters of three; in fall many of them are likely to be bright red. If you contact poison oak and are allergic to it, you will break out in a painful rash which could last weeks.
It is possible, though not likely, that ticks carrying Lyme disease are present in any brushy area (no cases of Lyme disease have yet been reported from Yolo County). It may be prudent to apply any insect repellent containing at least a 25% concentration of DEET to exposed skin of arms and legs or to spray it on the legs of your pants before going into any brushy or wooded area. This will keep the ticks from attaching to you (an unpleasant experience even if they don't carry Lyme disease). However, the entire trip can be completed without stepping off a road or wide path. Staying on the pathways also reduces the likelihood of negative encounters with mountain lions (a lion has actually been seen along the creek in recent years), grizzly bears, and attack mice.
The Putah Creek Riparian Reserve was set aside by the University in July, 1983, with the aim of preserving a portion of once-abundant riparian habitat. The reserve protects some Central Valley riparian forest, provides wildlife habitat, and greatly increases opportunities for study, observation, and enjoyment of riparian plants and animals.
Riparian ecosystems in California are of major importance to 25% of the native land mammals, many breeding and migrating birds, 83% of the amphibians, and 40% of the reptiles. Many of these animals can be found along Putah Creek along with remnants of the native fish fauna such as hitch, Sacramento blackfish, Sacramento pikeminnow, Sacramento suckers, and threespine stickleback. In winter and spring, chinook salmon, steelhead rainbow trout, and Pacific lamprey may move up from the Sacramento River to spawn in the creek. The most common fishes, however, are introduced species such as largemouth bass, bluegill, green sunfish, mosquitofish, white catfish, channel catfish, and common carp. However, native fishes significantly increase in numbers during years when flows are high.
The creek here is wide and pond-like most of the year and is 2-3 meters deep. As a consequence it supports a large population of fish and is a popular fishing area. You can see many areas along the bank where the plants have been worn away by anglers standing on the bank. Beavers build dams in the flowing areas upstream and downstream of here and live in burrows in the banks. Quiet observers can see beaver in this area in the evening (beaver are most active at night) and occasional otters.
Looking toward the creek from the sign, you will see vegetation dominated by large trees. The most conspicuous of these are valley oaks (Quercus lobata), distinguished by their furrowed bark and lobed leaves and the large Fremont cottonwoods (Populus fremontii),with their spade-shaped leaves. To the left of the sign, in the Picnic Ground, is a single large American hackberry (Celtis occidentalis). The plants at your feet are largely annual grasses and thistles introduced from Europe, probably as seeds attached to the hair of livestock. Such plants have largely replaced bunch grasses and other native plants.
Off to your right are two large dead oaks. Note that they are full of holes drilled by woodpeckers. Such holes are important and scarce nesting areas for a number of native birds. Unfortunately, the ones you see here are largely occupied by European starlings, an alien species. This is the small glossy bird with short pointed wings, a sharp beak, and a raspy squeak as its call.
You should also notice holes in the ground dug by California ground squirrels and without much effort you should see the bushy-tailed beasts themselves. Because of their enthusiastic burrowing, ground squirrels are regarded as agricultural pests, but they also are a principal food of the hawks, owls, and grey foxes in the area and are an example of a native species that has thrived in the presence of humans. If it is warm and sunny during your visit, you will hear the grass rustling nearby and be able to observe western fence lizards scurrying about in pursuit of insects. Gopher snakes are also common here, chasing the lizards and mice that are so abundant. A common mouse in the reserve is the house mouse, a native of Europe.
The most visible native birds here are yellow-billed magpie (found only in the Central Valley), black phoebe (perched on branches hanging over the water), herons (great blue and green-backed), coots, mallards and other species of waterfowl, and, overhead, turkey vultures, redtailed hawks, and black-shouldered kites. If you are lucky, you will see a rare, dark-colored Swainson's hawk (see next stop for discussion).
Walk through the picnic ground until you come to a road that goes down to the creek. Follow it to the creek. The water may be low because of diversions upstream. Look across the creek and you will be able to see where the normal water level is by the marks on the banks and trees. The water here is green and slimy looking, but it is full of life. The small guppy-like fish you can see in shallow water are mosquitofish, introduced into California for mosquito control.
Across the creek you will notice the dark green tamarisk bushes, a species native to Asia which thrives along western streams with flow regimes altered by humans. On the top of the bank across the creek you can see a large eucalyptus tree (native to Australia). This tree was damaged by the severe freeze in 1990, during which time Putah Creek was frozen over for a couple of weeks. If the landscape around you seems to have a shabby, worn appearance, consider all the stress it has been under for the past few years, including increased student and recreational use. Last winter was one of heavy rain, so the grasses have grown thickly in many places. Keep in mind that, despite its appearance, this is the main refuge for wildlife in this area. If you see any trash, pick it up and put it in the dumpster by the road.
In the landscape before you, what is natural and what is not natural? Is the distinction between native and alien (introduced) organisms a useful one for determining how to manage the reserve?
Continuing with your tour, go east (to your left as you look at the creek) until the paved road bends to the north and becomes Brooks Rd. In about a quarter of a mile you will encounter, on your left, a large area enclosed by a chain-link fence. On the fence are small brown signs which read "Putah Creek Campus Reserve." This is the Spieth Reserve. Entry is restricted to those conducting research on the reserve, so your observations will be confined to those which you can make from the perimeter of the reserve.
Park your bike and walk around the south and east edges of the reserve. You may notice that there is a shallow gully or swale in the reserve: this is the former channel of Putah Creek (now the so-called North Fork). How does the vegetation here differ from that along Putah Creek Riparian Reserve? Do you see any difference(s) in the wildlife here vs. that seen at the first stop? Can you associate the difference(s) in wildlife with differences in vegetation or habitat?
The vegetation at the south end of the reserve is dominated by tree of heaven (Ailanthus glandulosa), a native of China, although there are many valley oaks and black walnuts throughout the reserve. Look for the pomegranate (Punica granatum) trees along the fence at the northeast corner of the reserve; these are natives of the Mediterranean region.
As you look at the reserve, you will notice that many of the trees here have died; these dead trees are referred to as snags. Snags are an important component of wildlife habitat; they provide perches for raptors and flycatchers, and cavities for hole-nesting birds such as woodpeckers and bluebirds. Unfortunately, here too the starling often evicts native species when it nests.
You may see a Swainson's hawk here on Spieth Reserve, recognizable by its dark wings and body. The Swainson's hawk is a large raptor (bird of prey) which has suffered a serious population decline due to loss of nesting habitat; it has been declared a threatened species. Here in Davis, however, and especially on the U.C.D. campus, the Swainson's hawk continues to breed in fair numbers. Recently, there have been nests on the Putah Creek Riparian Reserve near Pedrick Rd., one here on Spieth Reserve, and even one at the top of a redwood tree just east of Wellman Hall! The Swainson's hawk spends the winter in Mexico and is usually on its way south by October, so you might stand a better chance of seeing one of the other raptors which use Spieth Reserve: redtailed hawk, American kestrel, black-shouldered kite, or turkey vulture.
One of the more important functions of the Speith Reserve is that it is a refuge for native ant species. These ants thrive in dry habitats. In the Putah Creek Riparian Reserve the dominant ant is a species introduced from Argentina, which drives native ants to extinction if there is sufficient moisture for it to survive. This is also the common ant in your kitchen, a true alien invader.
What is it about the habitat provided by the Spieth Reserve which attracts such a large number of raptors? Does it surprise you that an area of this size can support so many species? This reserve is an example of passive management: a fence was put up to restrict access and things were left alone. Is there anything that you would do (i.e. any active management strategy) to make this area even more attractive to wildlife? Would you install ponds, as has been proposed, to provide water for wildlife (consider the effects on ants)? How about burning it, because natural fires were common in this region before the arrival of Europeans?
Continue down Brooks Rd. until it bends to the left and goes through the former creek bed. Off to both sides you will see sheep and cows, in what was once Putah Creek. The only native vegetation left consists of a few old valley oaks. The native herbivores, mainly blacktail deer and tule elk, have been replaced by cattle and sheep.
How does the quality of the wildlife habitat here compare to that inside Spieth reserve? Are all components of the vegetation i.e. grasses, shrubs, trees, equally affected by the presence of livestock? Do you see as many animals here as you did at your last stop (excluding sheep and cows!)? Do you expect that the valley oaks inside the pens will be able to reproduce themselves? This area is slated to become part of the Arboretum someday. What would you recommend be done with it?
Continue around the livestock holding pens to the right; the road becomes Garrod Rd. and crosses the freeway. After you cross the freeway, (which bisects the old creek bed) notice the strip of grassland on your right with the power poles in it. This strip supports numerous ground squirrels and (in some years) a bird that lives with them in their burrows, the burrowing owl. If you are lucky, you will see several of them sitting in the sun on the edge of their burrows, ready to hide if disturbed.
Follow Garrod Rd. past the Veterinary Medicine Hospital until it bends back to the left but instead of following the bend, follow the dirt road along the fence line (keeping on the left side of the fence) until you can look down into the old creek bed again. This is what all the original bed of Putah Creek would have looked like if the University had not decided to create an arboretum, complete with an elongate pond (Spafford Lake) filled with pumped water and campus run-off. The Arboretum was established in 1939, with an annual budget of $200.
Now go back to the road and continue until you see the Peter J. Shields Gazebo on your right. If you wish, stroll through the Ruth Storer Drought Garden (brochures for $1.00 at the gazebo), the Carolee Shields Moon Garden, and the Peter J. Shields Oak Grove, set in large expanse of green lawn. Reflect on the fact that green lawns first became popular in England, where grasses grow readily in the damp, maritime climate. A more natural landscape for this area is that across the pond: the brown, leaf-strewn ground beneath the oaks. How does our culture influence our taste in landscapes?
It would be best if you would walk the length of the Arboretum, stopping now and then to look at the signposts naming the vegetation and giving its origin. What can you say about the origins of most of the shrubs and trees in the arboretum? What might these origins suggest to you about the value of the Arboretum as habitat for native vertebrates?
Observe the creek channel here and think back to its appearance at the APO picnic grounds. The water here is stagnant, with inflow coming from runoff and water provided by the University. The inflowing water is often contaminated with fertilizers and other matter and the large population of domestic ducks also fertilize the water. As a result the water is green with algae, resembling the sloughs and backwaters that were once common in the Central Valley.
Only fish that are tolerant of warm water with little oxygen in it can thrive here: common carp, Sacramento blackfish, and mosquitofish. Turtles are abundant; there are many species of alien turtles (former pets) and the native western pond turtle. An effort is being made to eliminate the non-native turtles (by live trapping) and to encourage the breeding of the native turtle. Is this a good idea? Why or why not?
The most abundant vertebrate in the arboretum is the mallard, or hybrids between wild mallards and domestic mallards. Because of minimal natural predation and the food provided by humans, duck densities here can reach high levels. These densities, along with the lack of water flow through the arboretum, contribute to several waterfowl diseases, the most important of which is fowl cholera. This disease was introduced to North America from Europe by way of domestic ducks and was first noticed in San Francisco Bay in 1944. Fowl cholera has been responsible for the deaths of many ducks in the Arboretum, and is of special concern when, during the winter months, wild ducks join the residents and run the risk of becoming infected and transmitting the disease (a bacterial infection) to wild populations elsewhere. For this reason, excess numbers of ducks are occasionally culled from Mrak Pond.
If you look carefully, you may see coots, pied-billed grebes, ruddy ducks, and other native waterfowl mixed in with the mallards. Look carefully for small green backed herons stalking the edge of the water, patiently waiting to spear small fish.
As you walk through the Arboretum look up in the trees. Do there seem to be as many birds as you saw at Putah Creek? Do you see any raptors? Do you see any signs that ground squirrels, lizards, and mice are as abundant? Finish your walk by the pavilion overlooking the creek, by the bridge that crosses over to the Art/Music/Theater building. Read the informational sign about the arboretum to understand its purpose. Cool off by sitting at one of the tables in the neighboring redwood grove. Is this a natural environment?