Stroll along a silvery brook at Oak Canyon in Mission Trails Regional Park.

Oak Canyon, tucked into a relatively pristine corner of Mission Trails Regional Park just west of Santee, has come alive with a thin stream of gurgling water, owing to the recent decent (if not quite up to par) seasonal rains. More importantly, the vegetable kingdom on the canyon's hillsides is engaging in a frenzy of new growth. This has led to the sudden appearance of thick carpets of green grass and brassy displays of annual and ephemeral wildflowers. Last month California poppies, nightshade, lupine, wild hyacinth, and encelia were in bloom. This month, who knows? It's certain, however, that the peak of the bloom won't last much longer.

The Oak Canyon area is popular with hikers and mountain bikers, though bike riders are confined to dirt roads running along the canyon rim. Only hikers are allowed on the trail running through the most scenic, narrow section of the canyon. The starting point for all is the Old Mission Dam, on the paved Father Jun�pero Serra Trail, 0.8 mile west of Mission Gorge Road in Santee. (Note that the segment of Father Jun�pero Serra Trail south of the dam and connecting to the Mission Trails visitors' center is one-way northbound for car traffic.) The Old Mission Dam, built in the early 1800s, was considered a major engineering feat of its day. A six-mile-long flume carried water from this dam to Mission San Diego in Mission Valley.

From the parking area at the dam site, walk west (downstream) past the dam and across the turbid waters of the San Diego River by way of an iron footbridge. Once you get across the river floodplain, double back east for 0.2 mile, and then go left on a well-worn pathway following sycamore- and oak-lined Oak Canyon. Stay left (assuming you are on foot) at all forks in the trail in order to keep following the canyon bottom. In the next mile, you'll wend your way along the banks of the trickling creek, passing small cascades and rock-bound pools.

When the pathway intersects a dirt road ahead, turn left, follow the road about 100 yards, and go right on a path continuing up Oak Canyon. About one-quarter mile farther you'll come to a picturesque mini-chasm of water-polished rock, with a deep, narrow pool. This is about as far as it's worth going. The Route 52 freeway passes high over the canyon not far ahead, and beyond that is land controlled by the Miramar Marine Corps Air Station, currently off limits to hikers.

For an expeditious return, retrace your steps. Or you can choose to lengthen your exploration in several ways by following trails ascending Fortuna Mountain to the west, or rambling through the "grasslands" area east of Oak Canyon.