Briones Reservoir was constructed in 1964 to store water for the East Bay Municipal Utility District (EBMUD, commonly pronounced "E-B Mud"). This reservoir is interesting because fishing, boating, and swimming are all prohibited. However, local rowing crew teams from local universities including Cal and St. Mary's use it for training.
You need a EBMUD hiking permit to hike this route. See information down by directions.
The starting point is the Briones Overlook Staging Area. Go through the gate just past the rest room, and follow the signage to the Oursan Trail which goes left, or clockwise around the reservoir. You descend a small slope towards the lake through a nice copse of introduced Monterey pine. The vegetation opens up, and the trail turns north as it crosses the large earthen dam that holds the reservoir. The Oursan Trail passes its junction with the Sobrante Fire Road which branches off to the west towards San Pablo Reservoir.
Oursan Trail gradually gains elevation as it continues north, and open meadows are punctuated by views of Mount Diablo to the southeast, the Berkeley Hills in the near west in front of Mount Tamalpais further beyond, and the various mountains north of San Pablo Bay. This is a great place to see wildflowers in the spring. The route crosses the headwaters of Fault Creek, and follows the contour high above the reservoir. Oursan Trail then gradually begins to lose elevation while traveling through open hillsides interspersed by forests of oak and California bay.
Soon after passing its junction the Hampton Trail which heads north to the Hampton Staging Area, you will need to pay attention to the signage. The trail looks like it continues due south down towards the reservoir, but actually makes a left turn back uphill to cross the Boy Scout Creek drainage. The trail is only about 50 yards from the reservoir, but don't consider heading down to enjoy the water because doing so would involve bush-whacking down a steep slope only to reach the very steep bank. You would need a rope to get to the water, and swimming is prohibited. After following the trail around the sizable Bearinda Cove you reach a ridge covered in large oak trees with views of two parts of the reservoir. You've traveled 6.5 miles at this point, and the ridge is a scenic spot for a lunch break.
The Oursan Trail continues along the north shore towards the narrowing eastern arm of the reservoir. The open ridges here are also known for spectacular displays of spring wildflowers. There are a few stretches here which feature nice uphill stretches. The Oursan Trail here continues the pattern of open ridges with deep forests of oak and bay in the drainages. After 9.75 miles you reach the Bear Creek Staging Area.
The Bear Creek Staging Area is at the eastern edge of the reservoir. There is a port-a-potty and a small parking lot here. The rest of your trip is on the Bear Creek Trail. Pass through the staging area, and cross Bear Creek. You cross right above a small waterfall, and can be very tricky. If the creek's flow is low you can walk across the concrete spillway. If the creek has a lot of water in it you will need to walk across the wooden planks, and that can be challenging. You quickly climb out of the forested drainage into an open area. There is an introduced giant sequoia in the middle of the meadow on your left, and it looks like a mushroom-shaped juniper. These giants grow to be the largest organisms on earth in their native habitat in the southern Sierra Nevadas, but come nowhere close to approximating that majesty here. The trail here is decaying asphalt, and is sometimes referred to as the Shuetman Road.
The first mile west of the Bear Creek Staging Area is flat, but that does not last. The last 3 miles of your hike are up-and-down through a deep forest of ferns, California madrone, various species of oak, and California bay. The Bear Creek Road is slightly above you to the south (left), and the reservoir is 300 feet below you to the right. Be very careful not to stray onto the numerous fire roads that branch off the Bear Creek Trail. Signage is very prominent so this isn't difficult. Continue until you reach the Briones Overlook Staging Area.
Gate Policy: If a gate is closed upon arrival, leave it closed after you go through. If it is open, leave it open. Leaving a closed gate open may put cattle in danger. Closing an open gate may cut them off from water. Please be respectful, leave gates as found.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.