Photo: Stuart Allen's Lake Berryessa Line

The Putah-Cache Bioregion Project:

Stebbins Cold Canyon Reserve and Putah Creek

Who | What | Where | Publications


This trip, originally created for a UC Davis class, takes you from Davis to Stebbins Cold Canyon Reserve, just below Lake Berryessa, and back again. It introduces the natural environment of the Vaca Mountains through a hike up a chaparral-lined canyon, and demonstrates the importance of natural processes, especially fires and floods, in shaping the landscape and in creating habitat for wildlife. It also shows a fairly typical California water project, to illustrate the positive and negative effects of such projects on fish and wildlife.

Best Time to Visit
Length of Trip
Route From Davis to Stebbins Cold Canyon Reserve
History of Stebbins
Natural History
Landmarks on Hike
Return Trip


Cold Canyon is a lovely spot but it has its hazards. The trail has become quite rough and steep in places as a result of landslides. Poison oak is present everywhere, including right along the trail in many places. Mountain lions and rattlesnakes are present, although your probability of encountering either species is remote. You are advised to wear long pants, hiking boots, and a good hat. Do not hike alone, please. The best time to hike is early morning, when it is cool. The canyon is a surprisingly quiet place, so do not expect to see much wildlife, except a few small birds flitting through the trees or underbrush and an occasional lizard scurrying across a rock.

Bikes, dogs, and guns are not allowed on the reserve.

Best time to visit

Most of the vegetation in the reserve is deciduous. By late November, plant identification by the usual means (comparisons of leaf or fruit shapes to illustrations) will be very difficult, and the more plants you are able to identify, the more rewarding will be your experience. Fall is migration time for many species of birds, especially songbirds, and many species which breed to the north pass through this area or stay to spend the winter. Pay particular attention to the cottonwoods and other trees lining the stream bed (usually dry in fall). A visit in the spring, when the hills are green, the flowers are blooming, and the stream is flowing, is recommended.

Length of trip

It takes about 45 minutes to get from Davis to the reserve, including the suggested stops. At least 2 hours are required to hike the reserve up to the old homestead and back. Thus, at least four hours are required to complete this field trip. You will get much more out of the experience, however, if you spend more time in the reserve, looking at the plants and birding, or merely exploring to see whatever might be there to interest you; 5 hours is the recommended duration of this trip.

Trip Guide

Route From Davis to Stebbins Cold Canyon Reserve: Mileage

Odometers vary in accuracy so these mile numbers should only be regarded as approximate.

0.0 Highway 113 overpass
Start the trip on Covell Boulevard at Highway 133, heading west (towards the hills).

2.2 Stop sign at Covell and Road 98

6.6 DQ University
As you drive along in this region, look for birds. Diversity is low, but numbers may be high when birds forage in the fields. One of the more common large birds you will see, recognizable by its long tail, is the yellow-billed magpie, a species found only in the Central Valley of California.

8.0 Orchards
For the next eight miles or so, you will be driving mainly through orchards, which can be regarded as very intensively managed ecosystems of low biological diversity. The orchards are growing in the rich alluvial soils created from material washed from the foothills. What animals do you see while driving through these orchards? It is worth noting that many of the orchards are walnut trees. The base of each walnut tree has dark rough bark, while the main part of the tree has smooth gray bark. The base is actually stock from native California black walnut, while the top is English walnut, grafted on to the black walnut. The black walnut stock protects the productive English walnut from diseases and generally grows better in this climate. This provides a concrete example of the unexpected uses of native organisms, one of the reasons for protecting biological diversity.

11.7 Putah Creek Village
This new subdivision on the left side of the road is being built on formerly productive farmland, next to Putah Creek. What do the name and location of the subdivision tell us about our cultural preferences for living areas? Are there any inherent contradictions here?

11.9 Winters stop sign. Continue straight ahead on Rt. 128.

13.1 Bridge over Dry Creek
Dry Creek is a low elevation tributary to Putah Creek that flows only after it rains, sometimes with surprising volume and force. Because it is dry most of the year, the creek channel and banks have generally been neglected or channelized and houses built close by. As a result, the channel has downcut several meters and the collapse of banks is becoming a major problem, threatening the integrity of some structures and fields. Properly managed, dry creek channels can become community assets and important seasonal wildlife areas.

14.7 The Vaca Hills
At this point there is an abrupt change in topography, from the flat Sacramento Valley to the steep Vaca hills. Is there a corresponding change in the vegetation? Is the change in vegetation abrupt or gradual? How might these changes affect the number and abundance of wildlife species?

The large trees on the hillsides are mostly native oaks. The trees with dark green foliage are valley oaks (Quercus lobata) while those with a gray-blue tint to their leaves are blue oaks (Quercus douglasii). The grasses underneath are largely annual grasses native to Eurasia.

16.3 Pleasants Valley Road intersection
Remember this intersection, because you will be turning on Pleasants Valley Road when you return.

16.4 Solano Reservoir
You are now driving along Solano Reservoir on Putah Creek (left side). Solano Reservoir (a.k.a. lake) is the destination for water released from Berryessa Reservoir about eight miles upstream. The water is then diverted from Solano Reservoir to irrigate farms and provide urban water in Solano County (with a small amount going to UC Davis as well). The eight miles of connecting stream has high flows in summer when water demand is highest and relatively low flows in winter.

The high summer flows have allowed the development of one of the best trout fisheries in the region. Not only does it provide space for large numbers of domestic, catchable-size rainbow trout dumped in by the Department of Fish and Game on a regular basis throughout the summer, but it also provides habitat for a significant population of wild rainbow trout. The presence of this wild rainbow trout population, known by fly fishermen to exist for years, was documented in a study by UC Davis undergraduates, who found trout ranging in size from small juveniles to 60+ cm (24 in) adults.

The angling regulations on the creek were changed as a result of this study, allowing only limited take by anglers during the winter months, with gear restricted to artificial flies and lures. Most fly fishers in the creek engage in catch-and-release angling in any case. The summer fishery for planted fish allows a much higher take and no gear restrictions, but seems to have no detrimental effects on the wild trout fishery (so far). The popularity of the creek for angling is demonstrated by the many public fishing access points you can see as you drive along the creek.

17.9 Gravel pullout on right side of road
Look at the pattern of the vegetation around you. The riparian vegetation, characterized by big trees, borders the stream. Dry pastureland on your right is largely maintained by cattle grazing. The slopes are covered with oak woodland or chaparral. Look directly across the field and across the creek on your left and you will see a 'valley' on the hillside with thick vegetation on the left side and sparse vegetation (mostly grasses) on the right side. Why does this pattern exist? Hint: which slope (north or south facing) would be hotter in summer and receive less moisture in winter?

19.3 Burned areas
Ahead of you on the distant slopes you can see brown patches of dead trees. These are some of the few visible remnants of a major fire which burned much the area in 1988. During the summer of 1988, much of the area had a blackened, parched look to it.

The road now closely follows the creek, occupying much of the riparian zone on the right side of the creek. Riparian zones are relatively small pieces of the landscape, yet are exceptionally important as wildlife habitat. Because they are low, cool, and green, they are also favored by humans as places to build roads, live, and recreate. Riparian zones are also very sensitive to decreases in stream flow or to alterations of the stream channel because the trees and other plants require wet conditions (often created by seasonal floods) to flourish. Not surprisingly, this conflict between human needs and wildlife needs has resulted in the creation of many riparian-dependent endangered species of plants and animals.

20.9 Sierra Pacific Resorts Campground
A classic example of concentrated human use of the riparian zone. Is there much room for wildlife here?

21.1 Bridge across Putah Creek; Monticello Dam to the right

21.2 Turn left into parking area
In this area you can view the lowermost reaches of Cold Creek, which flows out of Stebbins Cold Canyon Reserve. You can either leave your car here when you visit the reserve (about half mile up the road) or park your car in pulloff at mile 21.4. In any case, walk over to the channel in front of you.

The dry channel in front of you is an example of channelization that was done to enable water to move quickly through the area. This project was finished in the summer of 1995 in response to the problems created by the immense debris flows that came out the canyon in the previous winter, one of the wettest on record. You will see evidence of these flows when you hike up the canyon. In response to the rains, huge landslides occurred in the canyon and the material was flushed into Putah creek, much of it winding up in Solano Reservoir.

The landslides are natural events in this steep, geologically active landscape. Indeed, the soil on which the regional agricultural depends arguably originated from such events accumulated over thousands of years. Unfortunately, humans can no longer allow the sediment to spread across the valley floor (old maps mark the Davis region as "swamps, impassible in winter"). As a result it fills in reservoirs and otherwise becomes a problem for us.

About 500 m upstream from where you are standing is Monticello Dam. Monticello Dam was constructed by the US Bureau of Reclamation in 1956 in order to (1) store water in Berryessa Reservoir for agricultural, urban, industrial, and military uses, (2) to reduce flooding of lands (e.g., Davis) along lower Putah Creek, and (3) provide recreational benefits. Unfortunately, in the process of allocating the water from the reservoir, Putah Creek below Solano Dam was provided with just a small amount of water during the dry season. As a result, most of the creek dried up in the summer of 1989 (a drought year), killing thousands of fish and withering riparian vegetation. Therefore, the Putah Creek Council (a local group formed to protect the creek), the City of Davis, and the University have all been involved in legal actions against the Solano Water Agency and the Solano Irrigation District to obtain more flows for the lower creek.

This is a close-to-home example of the increasing conflicts over water that exist in California, as a growing awareness of the importance of living streams with fishable and swimmable waters conflicts with the needs of the ever-growing human population of the state. The amount of water required to keep the creek flowing is surprisingly small compared to the amount of water available in the reservoir, but the monetary value of even that small amount of water is high enough so that every drop is fought over.

Just upstream of the mouth of Cold Creek is the major spawning area for wild trout in Putah Creek. If you return to this spot in December and January, you may be able to see the shadowy forms of large trout spawning in the shallows of the riffles. Their presence is marked by the distribution of fly fishers! Major efforts of anglers to improve the spawning habitat were largely negated by the floods of '95 so the future of trout spawning in this region is not known.

21.4 Pullout on right
Just past a sign with an arrow bending to the right and a recommended speed of 30 MPH you will see a large gravel area: pull off to the right here. Park your car (and lock it!) and walk across the road to the left (being sure to look both ways for traffic!) and up to a pipe gate with the caution, "Fire Access: Don't Block Gate." Proceed on past gate.

This is the entrance to Cold Canyon. About 200 meters up the trail past the gate you will come to the Stebbins Cold Canyon Reserve sign and sign-up book. Please sign in and remember to sign out again when you leave.

Reminder:be on the lookout for poison oak. After it loses its red fall foliage, poison oak can often be recognized by clusters of green berries attached to bare woody stems. Even without leaves poison oak can be nasty. If you are going to apply insect repellent to keep ticks off, now is the time to do it.

A hike through Stebbins Cold Canyon Reserve


Stebbins Cold Canyon Reserve is one of 26 reserves in the University of California Natural Land and Water Reserve System. Named in honor of Dr. G. Ledyard Stebbins, Professor Emeritus in the Department of Genetics, U.C.D., the reserve was acquired in two parcels, the first in 1979 and the second in 1984, for the purpose of preserving the land for teaching and research.

The history of human occupation of the area goes back to at least 2,000 B.C., when Native Americans, members of the Southwestern Patwin tribe, lived here. The Patwins were hunter-gatherers and used the native flora and fauna to meet all of their food, clothing, and shelter needs. As recently as 1838, Indians still lived along Putah Creek in large numbers, but by 1877 they were gone, forced out by Mexican and Spanish settlers during the period of land grant rancheros. In 1848, with the end of the Mexican American War, California was ceded to the United States. California received statehood in 1850 and in 1852 the area that included Cold Canyon was legally defined as unappropriated unreserved public land.

In 1916 the region was redefined as stock raising lands available for homesteading and in 1938 John Vlahos obtained a patent for the lands adjacent to and including Cold Canyon Reserve. The remains of his homestead, in the upper portion of the reserve, consists of two foundations, some rock walls, and a well. The smaller of the two structures is located in a cool, shady glade and served as a cold room in which to store cheese that Vlahos made from the milk of his goats. This is how Cold Canyon got its name.

In 1968 John Vlahos sold part of his land to Paul Leiter. The Leiters sold this portion of the reserve to the University in 1979 and Petro and Virginia Vlahos sold the remainder to the University in 1984.

As you approach the end of your hike up Cold Canyon, and reach the old Vlahos homestead, try to imagine life as a homesteader. Imagine what it would have been like to share your property with grizzly bears (the last one in the region was killed in Pleasant's Valley, a few miles to the west, in 1856) or mountain lions (which probably still wander through the reserve occasionally). Please be careful not to disturb any of the relics which may be still around. The Vlahos homestead has been the victim of much recent vandalism. Recall that this area served as a family's home as recently as 30 years ago and, at its present rate of decay, may not be worth much as an instructional site by the time the next generation of U.C.D. students enroll.

Natural History

Stebbins Cold Canyon Reserve has been used by humans continuously for at least 4,000 years, but it retains many of its original characteristics. The basic plant and animal communities are largely the same as they have been since the first Native Americans arrived in this area, which is why the area was deemed worthy of preservation. The reserve covers only 576 acres and yet supports 322 species of plants, 44 species of mammals, 114 species of birds, and 26 species of reptiles and amphibians!

Still, recent human activity has left a strong mark on the landscape. You are walking on the remains of a road built by John Vlahos. The hills above you are ribbed with the trails created by several hundred years of livestock grazing, most recently the Vlahos goat herd. Natural fires were suppressed for years until there was so much dead wood lying around that major fires, such as one that swept through the reserve in 1988, became inevitable. Some of the patches in the hillside vegetation were created by "hot spots" in the 1988 fire.

More subtle were the effects of the elimination of the grizzly bear as a major predator and earth mover in the area. In recent years, recreational users have created many unauthorized trails through the reserve and increased erosion of the official trails (which were improved by the CCC in 1989). The University reserve is in the middle of some large tracts of BLM land on which hunting and other activities are allowed, which no doubt spill over onto the reserve. As you walk up the trail, keep these changes in mind and think of the effects of wildlife that your own presence on the reserve is having.

As you hike the path through the reserve, you can see examples of each of the five major plant communities found here: grassland, blue oak savanna, chaparral, live oak woodland, and riparian live oak woodland.

Grassland. This community is dominated by mostly introduced annual grasses. A potential management activity in the future might be to find ways to reestablish the native, perennial bunch grasses here.
Savanna. This association is characterized by clumped to widely-spaced, fairly tall, broad-leaved trees with an understory of grasses and forbs (non-woody plants). Blue oak is the dominant tree but an occasional foothill (formerly digger) pine (Pinus sabiniana) may also be found. The foothill pine is unusual not only for its ability to live in hot dry areas, but for its branched appearance.
Chaparral. This, the most important community type in terms of coverage or area, is characterized by a dense mixture of shrubs with few emergent trees and little understory. Dominant shrub species are chamise (Adenostoma fasciculatum), scrub oak (Quercus dumosa var. macdonaldi), toyon (Heteromeles arbutifolia), manzanita (Arctostaphylos manzanita), and buck brush (Ceanothus cuneatus).
Live oak woodland. This is a medium-tall, dense to open broad-leaved evergreen and deciduous forest with a few needle-leaved evergreen trees mixed in. Dominant trees are interior live oak (Quercus wislizenii) and foothill pine. Shrubs include many of the same species listed under chaparral, plus California buckeye (Aesculus californica), California coffee-berry (Rhamnus californica) and poison oak (Toxicodendron diversiloba). For much of the year, the buckeye can be recognized by the large nuts either hanging from the tree or lying on the ground around it.
Riparian live oak woodland. A medium-tall, broad leaved evergreen forest associated with streams and springs. Dominant plants are interior live oak, Fremont cottonwood (Populus fremontii), and willows (Salix spp.). Live oak retain their leaves even in the winter, while cottonwoods are large coarse-barked trees.

You should pass through or adjacent to each of these plant associations on your hike from the entrance of the reserve to the Vlahos homestead. Imagine that you were a reserve manager: would the management strategy that you proposed for one of these associations be the same as that for all the others, or do you think that keeping each of the associations relatively intact (i.e. complete assemblage of plants and animals) would require its own strategy? If so, how might these strategies differ and why?

1. Gate. This gate once blocked public entrance to a fire road which went a considerable ways up the canyon.. No longer!

2. Landslide. Around the first bend is the first major landslide that resulted from the heavy rains of the winter of 1995. The debris flowed out of the dry canyon on your left (facing upstream). The debris flow eliminated much of the riparian vegetation in the creek below and nearly took out the highway as well. Remember that this was a natural event! In fall, 1995 only a few plants were growing from the barren soil. Cross over the slide area.

3. Lichen rock. Just after you cross the slide, you will see a large rock on your left that is covered with circular patches of greenish lichens. Lichens (a fungi-algae symbiotic organism) gradually dissolve rocks, creating soil, and are part of the whole process of constant change symbolized by the landslides.

4. Sign in area. This marks the official entrance to the Reserve. Sign in and proceed. In September, 1995, the entrance sign was used for target practice by someone with a shotgun, as was a tree back down the trail. Vandalism of this sort is all too common in protected areas but the university has made it a deliberate policy to keep this Reserve open to the public, even so. Is this a wise decision? Why or why not?

5. Slide area. About 100 m up the trail is a flat open space that resulted from another slide, in this case a chunk of the hillside on the left.

6. Rocky peak on right. As the trail starts to climb, marked by wooden erosion control bars, note the rocky peak across to the right. Usually, you can see raptors soaring around it. Mostly they are turkey vultures, but redtailed hawks are also common. Rarer are birds such as golden eagles or peregrine falcons. If you really want an ambitious hike, you can follow a fire road that climbs to the top of that ridge that starts on the other side of Cold Creek, from the highway. Toward the top that trail passes areas of chapparal recovering from a 1997 fire. On the ridge, views are spectacular - much of Berryessa and, on clear days, Sacramento and the Sierra Nevada. The soaring birds will be below you.

7. Old landslide. When the trail starts to climb abruptly with some "stairs", you will know you are crossing a landslide that occurred in 1982. Actually, it was more of a land slump because a good chunk of the hillside slid downwards with much of the vegetation still on top. Large pieces of it did become plant-free, however, but it is now hard to tell this piece from the surrounding hillsides. Development of plant cover on the new slides may take a bit longer, but it will occur.

8. Droppings on trail. The trail you are walking on is a freeway for the area's wildlife. Consequently, you often see scats of gray fox and coyotes on the trail The scats are easy to recognize because both species eat almost anything vaguely edible, so the remains of manzanita berries, insect parts, and animal hair can be seen. The fox scats are small and black and are often carefully placed - by the fox - in the middle of a rock as a territorial marker.

9. Dead limbs of bushes. As you walk along the trail, in a few places you can see dead limbs of bushes sticking out of thick growth. These are one of the few reminders of the fire that burned throughout the canyon in 1988. The chaparral plants are adapted to fire and new branches and foliage sprouted from the old rootstocks.

10. Cold Creek. The trail next crosses the dry bed of Cold Creek. In most years, this stream flows for about seven months (November-May). When it starts flowing, it is quickly colonized by aquatic insects and algae. Winter rains bring out California newts to breed in the stream. Up in the canyons pools of water are left behind when the stream stops flowing and are important sources of water for California quail, blacktail deer, mountain lions and other wildlife.

In wet years, such as 1995, water may flow down to this point in late summer. If water is present, examine the pools and note what life is present. The insects skating across the surface are true bugs called waterstriders that prey on other insects that fall into the water.

11. Cottonwood tree. As you cross the small bridge on the trail, you will have a good view of a cottonwood tree growing right in the stream channel. Cottonwoods are important riparian trees, requiring water around the roots. This is a good spot to watch birds.

12. Wildhorse Canyon. After crossing the stream, the trail climbs through dense stands of chaparral. When you emerge from the chaparral, you will have a good view of both Wildhorse Canyon in the distance and Cold Canyon close by. This wild area is owned partly by the University and partly by BLM, with a few private inholdings. Notice the pattern of the vegetation, with grasslands on some slopes, chaparral on others.

13. No entry fence. This fence was constructed to keep people from climbing this tempting open hillside. Even a small trail in this fragile land can start a major landslide. Look up the arroyo along the hillside and you can see where part of the hill slid down in 1995, creating the debris flow at your feet. Note also the blackened remains of the large foothill pine, another reminder of the 1985 fire. To the left of the pine, you can seen blackened remains of chaparral as well, in an area which has not recovered like so much of the other chaparral areas have. This is a drier hillside and fire may have burned exceptionally hot here, killing the rootstock.

14. Homestead. A short distance further the trail crosses the Vlahos homestead. The open area around you was probably cleared by Vlahos and the soil compacted by livestock, mainly goats. One indication of this are the dry prickly plants that line the trail among the grasses. This is star thistle, (Centaurea sp.) a native of Asia, that thrives on poor, overgrazed soils.

15. Cold storage area. Beyond the homestead, the trail continues into (and ends in) the shady glen containing the old cold storage shed. This area is delightfully cool and moist all summer long. Why is this? The fragrant trees providing the shade include California bay and spicebush.

The cold storage glen is one of the few areas of the reserve that was not burned by the 1988 fire. Most of the reserve only had the litter and plant understory burned by the fire, although a few trees were lost as well. The reserve was actually the site of backfires carefully set by the California Division of Forestry to prevent further spread of the fire (which burned thousands of acres before it reached Cold Canyon) and to reduce the effects of fire on the reserve. Look for fire effects as you walk down the trail. Do some plant species or communities appear to be more affected by fire than others? What are some of the plant adaptations to fire? What do you suppose some of the attendant effects on wildlife were? Do you think that fires in this ecosystem are bad for it, or do fires have their good sides, too (you may wish to think back to Yellowstone '88 and some of the more recent news of that area)?

16. Hike back down the trail. Enjoy.

Return Trip

21.7 Drive uphill until you come to Monticello Dam and Berryessa Reservoir. Stop for a view. What kinds of habitat for wildlife and fish have been lost and what have been gained. Do they balance?

Return to Pleasants Valley Road and turn right. Reset odometer.

O.1 Bridge, Solano Reservoir
This is a good place to fish for hatchery trout. For a fee, you can have a nice picnic in the county park, which is also a good place for bird watching. Ever seen a phainopepla? This is a place to see one! Watch for peacocks.

0.6. New houses on right.
Examples of the ever-expanding suburbia. What effects do such developments have on wildlife, considering the land was previously used for grazing?

1.0 Turn left on Putah Creek Road.
Watch for ostriches on right.

1.1 Bridge over Pleasants Valley Creek.
This creek has water in it year around and is the only place in the region that supports a small native fish called California roach, which is much more interesting and attractive than the name would indicate.

2.2 Solano Reservoir
In the fall and winter, this is an excellent place to see waterfowl, such as widgeon, mallards, canvasbacks, bufflehead, ruddy ducks, coots, and cormorants. The trees on the island across from you often support osprey ( a large fish-eating raptor) or bald eagles.

2.8 Solano Diversion Dam and Putah South Canal
Why is there so much water in the canal and so little in the creek below? Even the minimal releases provided below the dam keep a live stream roughly down to Winters. The stream immediately below the dam contains mainly native fishes, but the further downstream one goes, the more non-native fish (bluegill, carp, etc.) become abundant. When the creek dries up, of course, no fish are found.

4.6 Historical marker
This is a UCD experimental farm. It was settled in 1842 by John R. Wolfskill. His family fished the creek and were recorded as catching large numbers of catfish in the 1870s.

5.9 Stop sign. Turn left on Winters Road

6.1 Turn right on Putah Creek Road.
Alternately, you can cross the bridge and drive into Winters, where a number of reasonably-priced cafes will tender to your hunger. Putah Creek aficionados, naturally, seek out the Putah Creek Cafe, which features photographs and art of Putah Creek.

6.9 Road passes under Highway 505 bridge over creek.
The road closely follows the creek for a ways here. The creek in this region has historically been a dumping ground for trash but major clean-ups have reduced the problem. During the wet season you can launch a canoe here and paddle to Stevenson Road or to the campus (a long day). You will have to get over the Great Falls of Putah, however.

11.5 Open fields
Not much wildlife habitat here. Notice the line of trees marking the Putah Creek corridor. This demonstrates why stream corridors are important for wildlife: they are much of the habitat left.

13.2 Stevenson Bridge Road - turn left.

13.7 Stevenson Bridge
Look at the creek, not the graffiti.

14.5 Turn right on Russell Blvd.
Head for home.

Putah-Cache Home

Who | What | Where | Publications

These pages are copyright © University of California. UC Davis Home